CHARACTERISATION OF NEW ZEALAND Recently QMAP Fiordland has investigated the NEPHRITE JADE USING ITS GEOLOGICAL southern-most part of the Cretaceous Western AGE AND STRONTIUM ISOTOPIC Fiordland Orthogneiss (WFO) suite and its COMPOSITION relationships to adjacent Paleozoic metasedimentary rocks. In central-west Fiordland, C. J. Adams1,H.J.Campbell1 & R. Beck2 10-20km to the north of the area mapped, previous 1GNS Science, PO Box 30368, Lower Hutt, New work indicates granulite facies (ca. 10-12kbar) Zealand. WFO is juxtaposed against Paleozoic amphibolite 2 27 Chelmsford Street, Invercargill, New Zealand. facies (ca. 7-9 kbar) metasedimentary rocks across (argon*gns.cri.nz) the Doubtful Sound Shear Zone (DSSZ). A more complex variety of gneisses and field relationships New Zealand pounamu (nephrite jade) occurs in characterise the southern-most part of the WFO several ‘fields’ in the South Island, mainly in suite. Breaksea Island, much of northern Resolution northern Southland and North Westland. The usual Island and the area between Breaksea Sound and occurrence is in metasomatic reaction zones the Coal River mouth are underlain by distinct forming tremolite of unusual texture, where coarse banded clinopyroxene-garnet and gabbro/dolerite/harzburgite undergoing plagioclase-garnet-clinopyroxene gneisses that are serpentinitization is adjacent to siliciclastic widely retrogressed to hornblendite and metasediments (and metavolcanics). plagioclase-hornblende gneiss. Igneous textures have been completely destroyed during For the probable Early Permian gabbro/dolerite metamorphism and deformation. These rocks are pounamu precursors, Rb-Sr age and Sr-isotope data collectively referred to as the Breaksea Gneisses. suggest a primitive origin, with initial 87Sr/86Sr Eastern Resolution Island, inner parts of Breaksea ratios, c. 0.7032. Sound, much of Wet Jacket Arm and the Acheron However, the Permian-Triassic metasediment Passage are underlain by a homogenous dioritic 87 86 precursors have more elevated initial Sr/ Sr orthogneiss in which igneous textures are widely ratios, whose values confirm their suggested terrane preserved despite granulite facies metamorphism origins: <0.7050 (Caples), 0.7050-0.7065 (Dun and development of garnetiferous anorthosite Mountain-Maitai), >0.7090 (Torlesse). Pounamu leucosomes. These rocks are referred to as from in situ occurrences in the Livingstone Malaspina Gneiss since they are contiguous with Mountains, northern Southland (Dun Mountain- WFO mapped in Doubtful Sound of the same name. Maitai terrane) and Arahura River, North Westland Dikes of Malaspina Gneiss cut layering in the 87 86 (Torlesse terrane), have initial Sr/ Sr ratios close Breaksea Gneiss indicating that the former is the to the metasediment values noted above. The younger unit. Significant deformation, gabbro and dolerite Sr contributions to pounamu metamorphism and recrystallisation appear to have formation thus clearly play a very minor role. separated emplacement of these two members of Sr isotopic ratios may thus provide a useful the WFO suite, but the magnitude of their age characteristic of the New Zealand nephrite jade difference is not known. ‘fields’. Since Torlesse and Caples terrane rocks Breaksea Gneisses are juxtaposed against Paleozoic occur within Alpine and Otago Schists of quite rocks across both broader ductile shears similar to different ages, it is possible that metamorphic age the DSSZ and younger brittle faults. variations may also play a finer-scale role in Reconnaissance thermobarometry of unretrogressed determining Sr-isotopic compositions. Breaksea Gneiss indicates peak metamorphic ORAL pressures of ca. 15-16kbar accompanied by growth of omphacitic clinopyroxene, probably before emplacement of the Malaspina Gneiss, making THE GRANULITE FACIES WESTERN these the highest grade rocks discovered to date in FIORDLAND ORTHOGNEISS IN Fiordland. Intrusive contacts between the younger SOUTHWEST FIORDLAND Malaspina Gneiss and adjacent rocks are still widely preserved indicating that the DSSZ does not A. Allibone1, I. Turnbull2,L.Milan3,S.Carroll3, enclose the entire circumference of the WFO in &N.Daczko3 southwest Fiordland. Trondhemitic leucosomes 1 School of Earth Sciences, James Cook University, with locally abundant peritectic garnet define a Townsville, Q4811, Australia narrow thermal aureole a few 100 metres wide 2Institute of Geological and Nuclear Sciences, along the intrusive margins of the Malaspina Gneiss Private Bag 1930, Dunedin in Paleozoic psammites and amphibolites, unnamed 3Department of Earth and Planetary Sciences, older gabbro, and the Cretaceous Supper Cove Macquarie University Orthogneiss. Rare xenoliths confirm the intrusive (rodinian*msn.com) relationship between Malaspina Gneiss and the adjacent units. Reconnaissance thermobarometry

50thKaikoura05 -1- Kaikoura 2005 indicates pressures of ca. 10-12kbar during aureole cathodoluminescence. The spar cements were development in Wet Jacket Arm. Amphibolite precipitated during shallowest burial (likely no facies assemblages remain outside the aureole more than about 200 m), involving mild pressure- indicating that equilibration to granulite facies dissolution of skeletons, and during subsequent assemblages only occurred within the immediate uplift when dissolution of aragonitic shells vicinity of the Malaspina Gneiss suggesting provided a later stage of equant and micro-equant reaction kinetics were an important control on the cement. Most of the limestones retain moderate extent to which granulite facies assemblages porosity in outcrop. developed in country rocks intruded by the WFO. The skeletal composition is consistent with ORAL deposition of all three limestones in a similar high energy, current swept seaway environment (Ruataniwha Strait) at inner shelf depths. LATE NEOGENE BARNACLE-RICH Deposition was associated with rapidly LIMESTONES, MATAPIRO-OMAHU, transgressing seas coupled with low terrigenous HAWKE’S BAY: THEIR LIFE FROM sediment supply, forming relatively thin DEPOSITION TO UPLIFT transgressive systems tract (TST) carbonate deposits. Highstand systems tract (HST) deposits 1,2 2 2 R.A. Baggs ,C.S.Nelson, P.J.J. Kamp ,K.J. are represented by the intervening, thicker, mid- 2 2 Bland & S.D. Hood shelf mudstones, which accumulated over longer 1 CRL Energy Ltd. P.O. Box 290, Greymouth durations than the limestones. Four major 2 Dept of Earth Sciences, University of Waikato, cyclothems (TST + HST) are identified for the Private Bag 3105, Hamilton mapped succession, the depositional settings being (rachelbaggs_nz*hotmail.com) primarily controlled by glacio-eustatic sea level fluctuations near the opening of the Ruataniwha A new GIS-based 1:40,000 scale geological map Strait into Hawke Bay in the Nukumaruan, during a has been produced for the Matapiro-Omahu region, period of slow basin subsidence followed between the Tutaekuri and Ngaruroro Rivers, west eventually by uplift and exhumation of the whole of Napier city in eastern North Island. The rocks succession. occupy the southern part of the regional Matapiro Syncline, are of late Pliocene-early Pleistocene age ORAL (Nukumaruan), are contained within the Petane Group, and comprise a cyclothemic succession of FISH, FRUSTULES, FRUITS, A FLOWER - formations of terrigenous mudstone and limestone, AND LOTS OF LEAVES: AN with some conglomerate. INVESTIGATION INTO THE BIOTA OF AN The three limestone units, in ascending order the EARLY MIOCENE MAAR LAKE Tangoio Limestone, Matapiro Limestone and Puketautahi Limestone, tend to stand proud in the J.M. Bannister1 &D.E.Lee2 landscape and provide good mappable horizons, 1Departments of Botany & Geology, University of while the intervening mudstones are poorly Otago, PO Box 56, Dunedin exposed. The Tangoio Limestone is restricted to the 2Department of Geology, University of Otago, PO eastern limb of the Matapiro Syncline and grades to Box 56, Dunedin fossiliferous greywacke gravels (Sherenden (jmb*clear.net.nz) Conglomerate Member) towards the west. The pebbly Matapiro Limestone is distributed Preliminary findings from a finely varved diatomite throughout the southern part of the syncline, while deposit formed during the Early Miocene in a maar the Puketautahi Limestone caps the hills on the lake near Middlemarch, Otago are presented. The western limb. varves are alternately dark and light and the light Sedimentological and petrographic analyses of the coloured layers are made up almost entirely of three limestones indicate that they are all barnacle- diatom frustules with some freshwater sponge dominated with an increasing proportion of bivalve spicules. The diatom flora is overwhelmingly material up through the units, and with small dominated by a single species, Encyonema jordanii amounts of bryozoans, echinoderms, benthic (Grunow) Mills. The sponge(s) probably encrusted foraminifera, and occasional serpulids and red plant material such as stems of water plants and algae. Skeletal grains are commonly microbored. dead leaves. Limited excavations in the upper few The rocks are mainly skeletal grainstones, less metres of the deposit have yielded several entire commonly skeletal packstones, and carbonate fish skeletons up to 15 cm long that belong to a new contents average 70-80%. Cements involve a species of galaxiid. The diatomite contains variety of calcite spar fabrics, including syntaxial numerous fruits and seeds in different states of rim, isopachous fringe, meniscus and equant types, preservation; these are mainly small and difficult to usually non-ferroan and with non- to dull identify, but some of the larger fruits may be

50thKaikoura05 -2- Kaikoura 2005 myrtaceous. One 20 mm diameter flower, on the Law of the Sea (UNCLOS) surveys by three Fouldenia staminosa Bannister, D.E.Lee and Raine, countries – France, New Zealand and Australia – 2005, was preserved complete with anthers from with potential extended continental shelf claims in which excellently preserved pollen was collected the region. The UNCLOS factor allowed 9 cruises and preparations made for both light and electron to focus on the region in the past 9 years, collecting microscopy. Identification of pollen and spores approximately 30,000 km of seismic reflection from the matrix on the same bedding plane as the (5,000 deep crustal), 263,700 sq km of swath flower produced a list of more than 55 pollen types, bathymetry, and 70 dredge samples. Feedback including new taxa (Bannister et al. 2005). through sharing or publishing data and joint Angiosperm leaves are numerous; those collected participation allowed efficient planning and from the layers of diatom frustules are better deployment of academic and UNCLOS cruises. preserved than those from darker, more organic Two models for South Fiji and Norfolk basin layers and we surmise that mucus from the vast evolution arise from current studies: at the level of numbers of diatoms has assisted in preservation of the Three Kings Ridge – Norfolk Basin – southern the leaf material. Some leaves have both upper and South Fiji Basin both involve Pacific trench roll- lower surface cuticles present and cuticle back and southward propagating spreading, but one preparations for over 150 individual leaves also uses two subduction systems and arc-continent representing several families and genera, some with collision. Linked spreading of the Norfolk Basin close affinities to extant genera, have been made. and South Fiji Basin is invoked in both models, but The leaves appear to be mainly from forest trees the veracity and geodynamics of the link are not and lianes with moderately thick cuticles; as yet no investigated. A growing body of petrological and herbaceous leaves or examples of leaves with thin radiometric evidence and the tectonics of the New cuticles have been found. Leaf venation is not Zealand continental margin point to tandem Early always visible but various methods for clearing Miocene spreading of the South Fiji Basin and leaves to expose venation, and methods of leaf Norfolk Basin despite published magnetic preservation, have been developed. A database interpretations that would confine South Fiji Basin incorporating cuticular features and leaf spreading to the Oligocene. The Franco-NZ architecture is being compiled together with a NOUCAPLAC-1 cruise, the last cruise relevant to reference collection of cuticles from extant trees UNCLOS in this region, included a scientific and lianes from both New Zealand and Australia. objective to investigate the South Fiji Basin– Norfolk Basin link in the critical area bounded by Bannister, J.M., Lee, D.E., & Raine, J.I. 2005: the Loyalty Ridge, the Cook Fracture Zone, the Morphology and palaeoenvironmental context of Bounty spreading centre and the Julia Lineament Fouldenia staminosa, a fossil flower with associated with swath mapping, magnetics and seismic pollen from the Early Miocene of Otago, New reflection. Initial results show a complex Zealand. New Zealand Journal of Botany 43: 515-525 bathymetry where a possible link between the Bounty spreading centre and the Cook Fracture ORAL Zone involves ridge propagation, overlapping spreading centres, rift blocks and overprinting TECTONIC EVOLUTION OF THE SOUTH volcanoes. The link to the Julia Lineament was not FIJI BASIN: UNCLOS HELPS TACKLE adequately tested due to sparse coverage. Closer to REGIONAL TECTONICS the Loyalty Ridge, a thick, faulted sedimentary basin was found. D. Barker1,R.Herzer1,N.Mortimer2,W.Roest3, POSTER A. Mauffret4 & Y. Lafoy5 1 GNS Science, P.O. Box 30368, Lower Hutt, New Zealand INITIAL WAVEHEIGHT OF LANDSLIDE 2 GNS Science, Private Bag 1930, Dunedin, New TRIGGERED TSUNAMIS: APPLICATION Zealand OF A SIMPLISTIC EMPIRICAL APPROACH 3 IFREMER, Géosciences Marines, 29280 Plouzané, BP 70, France P. Barnes & A. Pallentin 4 Lab. Tectonique Univ. P. et M. Curie, 4 Place National Institute of Water & Atmospheric Jussieu, 75256 Paris Cedex, France Research, Private Bag 14901, Wellington. 5 ServicedelaGéologieetdesMines(SGM), (a.pallentin*niwa.co.nz) DIMENC, Nouméa, New Caledonia (d.barker*gns.cri.nz) The seafloor associated with New Zealand’s active margin is locally susceptible to slope failure. In Marine surveys to study the evolution of remnant areas of frequent large earthquakes, steep slopes, arcs and backarc basins north of New Zealand have and high sediment load, submarine landslides are been complemented by United Nations Convention extremely common. Large failures, particularly in

50thKaikoura05 -3- Kaikoura 2005 shallow water, may be capable of generating POSTER damaging tsunami waves. Whilst there have been few studies to model landslide tsunami in New TOWARDS A CLIMATE EVENT Zealand (e.g., Magill, 2001; Walters et al., STRATIGRAPHY FOR NEW ZEALAND submitted), NIWA is developing a growing OVER THE PAST 30,000 YEARS database of submarine landslide distribution and geomorphologies derived from high-resolution D.J.A. Barrell1, B.V. Alloway2,J.Shulmeister3, multibeam bathymetry data. These data offer an 4 opportunity to evaluate landslides as a potential R.M. Newnham and other contributors to the source of tsunami waves. NZ-INTIMATE Project (P.C. Almond; P.C. Augustinus; N. Bertler; C. Briggs; L. Carter; Studies by other workers (Watts et al., 2003) C.H. Hendy; N.J. Litchfield; D.J. Lowe; B. involving simple laboratory experiments of slope Manighetti; M.S. McGlone; A.S. Palmer; H. failure, derived empirical relationships between Rother; P. Shane; R.P. Suggate; landslide geometry, water depth, various slope P.J. Tonkin; M.J. Vandergoes; P.W. Williams)5 parameters, and the initial tsunami wave height 1GNS Science, Private Bag 1930, Dunedin. generated from the draw down of the ocean surface 2GNS Science, P.O. Box 30-368, Lower Hutt. over a submarine landslide failure. Whilst there are 3Department of Geological Sciences, University of severe limitations in such an approach, and Canterbury, Christchurch. consequently very large uncertainties in the tsunami 4School of Geography, University of Plymouth, wave heights at the source, these relationships have Plymouth PL4 8AA, United Kingdom. been applied to real field examples on continental 5Contact details of all authors can be found at margins (e.g., McAdoo et al. 2000, McAdoo & www.paleoclimate.org.nz Watts, 2004, de Lange & Moon, 2004). Although (d.barrell*gns.cri.nz) simplistic the approach offers a method of rapidly approximating the potential tsunami wave heights A poster summarizing representative evidence for from a large landslide population. environmental conditions and climate change in In this study we apply these empirical relationships New Zealand during the past 30,000 years is an to evaluate tsunami wave heights generated at the initial contribution to the INTIMATE (INTegration source of landslides, by analyzing the of Ice-core, MArine and TErrestrial records) geomorphology of a subset of nearly 300 landslide initiative of the INQUA (International Union for failures recognised in Cook Strait and the Bay of Quaternary Research) Paleoclimate Commission. Plenty. The landslides studied are from a wide The aim of this international initiative is to improve range of water depths, from about 100 m to > 2000 2 knowledge of the nature, timing and regional-to- m, and the majority has surface areas of < 5 km . global extent of climatic and environmental The method involves the measurement, within an changes that have occurred since the Last ESRI ArcGIS framework, of a number of the Glaciation. landslide scar parameters from bathymetric DTMs, The poster depicts key New Zealand onshore and including maximum width, length, thickness via the offshore records that include the Last Glacial head scarp height, slope angle, and water depth. Maximum and/or the Last Glacial-Interglacial The height of the initial tsunami waves were Transition from a variety of latitudes and calculated using an empirical relationship elevations. Inset maps show New Zealand’s developed for translational slides. oceanographic setting, extent of glaciers, and The results of the calculations indicate initial draw- distribution of vegetation zones at approximately down tsunami wave heights of up to 6 m at the 22,000 calendar years ago and at modern times source of the landslides. Tsunami experts at NIWA (incorporating the inferred vegetation distribution at suggest the uncertainties on the wave heights may c. 1250 AD, before deforestation associated with be as much as a factor of three. In the absence of human settlement). The calendar-age timescale is dating of individual landslides, we constructed based on a combination of volcanic ash (tephra) relationships between frequency (annual rate of and radiometric dates. Ice core records from return) and initial wave height, by estimating a Antarctica and Greenland are shown for range of return times that might conceivably cover comparison with New Zealand records. the entire populations studied. We correlated these High-resolution records are derived from sediment- relationships with an estimate of initial wave height filled volcanic craters in Auckland (total carbon, for the giant Ruatoria Landslide, and we note carbon isotopes and pollen), wetlands in northeast differences between the Cook Strait and Bay of North Island, central North Island and western Plenty populations. Our study is strictly limited to South Island (pollen), marine sediments off eastern the initial wave heights at the landslide sources and North Island (oxygen isotopes), and stalagmites in does not consider the propagation, amplification, caves in northwest South Island (carbon and and attenuation of the waves approaching the coast. oxygen isotopes). In addition, the poster includes a

50thKaikoura05 -4- Kaikoura 2005 range of lower resolution or fragmentary records of years ago. These ruptures were located on, or up to climatic events, based on glacial landforms and 6 m west of, the bedrock fault that juxtaposes deposits (central Southern Alps, South Island), river Mesozoic- and Tertiary-age rocks (respectively east terraces and deposits, loess deposits (eastern North and west of the fault). Relative upthrow has been to and South Islands), and aeolian quartz silt in non- the west in the late Quaternary. This represents a quartzose, loess-like, andesitic tephric deposits of reversal from a net westerly downthrow that western North Island. accumulated during the late Tertiary as shown by The poster reflects work-in-progress and aims to the Mesozoic versus Tertiary rock relationships assist comparison of the New Zealand across the fault. paleoclimatic records with those from the wider The two most recent surface ruptures had single- Australasian region and elsewhere. The immediate event, west-side-up, vertical separations of c. 0.5 m goal is the establishment of an Australasian- (penultimate) and c. 1.5 m (most recent). INTIMATE climate event stratigraphy by the New Slickenside-lineations, and other slip indicators, Zealand and Australian paleoclimate communities, show an oblique right-lateral – reverse sense of late for presentation at the 2007 INQUA Cairns Quaternary rupture, with a horizontal (H) Symposium. component greater than the vertical (V) component (ratios of displacement in the range of 1H:3V to POSTER 1H:1V). In addition, a zone of “small-scale” late Quaternary faults and folds, with single-event LATE QUATERNARY DISPLACEMENTS ON vertical separations of up to 0.7 m, extends up to at THE WAITANGI FAULT, AVIEMORE DAM, least 150 m west of the Waitangi Fault. SOUTH ISLAND, NEW ZEALAND The fault displacement characteristics documented from the field investigations were subsequently 1 2 D.J.A. Barrell ,R.J.VanDissen,K.R. used to derive earthquake performance assessments 2 2 Berryman & S.A.L. Read for the dam, and to evaluate dam safety under direct 1 GNS Science, Private Bag 1930, Dunedin. fault rupture loadings. 2GNS Science, P.O. Box 30-368, Lower Hutt. (d.barrell*gns.cri.nz) ORAL

Aviemore Dam was constructed across the Waitaki THE DEVELOPMENT OF ANTARCTIC River valley in the mid-1960s. The dam straddles GLACIAL HISTORY OVER THE LAST the steeply WSW-dipping Waitangi Fault. At the FIFTY YEARS time of construction, no evidence of late Quaternary movement was documented on the P. J. Barrett fault. However, in the mid-1990s, dam safety Antarctic Research Centre, Victoria University of review investigations unearthed evidence of late Wellington, P O Box 600, Wellington. Quaternary deformation, and this led to the detailed (peter.barrett*vuw.ac.nz) paleoseismological investigations that provided data for displacement characterisation of the fault Fifty years ago it was thought that the Northern and subsequent evaluations of dam safety under Hemisphere had experienced 4 glacial episodes direct fault rupture loadings. over the last two million years, and no-one The primary paleoseismology investigation method supposed the Southern Hemisphere would be much was the excavation of 10 trenches, the largest of different. That view was changed radically in 1973 which was up to 10 m deep and 180 m long, across with the first Antarctic offshore drilling by the faults and folds within 1 km of the dam, Glomar Challenger in the Ross Sea. The cruise, accompanied by geological mapping of surface which was led by Denny Hayes and Larry Frakes exposures and landforms. Detailed logging of the and included three New Zealanders, Derek Burns, trench walls (typically 1:20 scale) documented the Peter Webb and me, cored through glacial geometry of Late Quaternary deposits and the sediments that dated back 25 million years. The locations, amount and sense of slip of the most cruise that followed, Leg 29, led by Jim Kennett recent fault displacements. Over 30 samples were and Bob Houtz, cored a series of deep ocean sites to dated to constrain the timing of past fault the north that covered the Cenozoic Era. This movements, using, where possible, at least two yielded the first oxygen isotope curve, from which duplicate methods of luminescence, and they concluded there was Antarctic cooling and sea complemented in a few instances by radiocarbon. ice in the latest Eocene, and the formation of an ice The investigations documented two, and possibly sheet like today’s in the middle Miocene. three, surface rupture fault movements on the The Leg 29 results could not, however, resolve the Waitangi Fault in the last c. 23,000 years, with the relative contributions of ice volume and most recent movement between 13,100 and 14,100 temperature to the isotope signal, and gave no

50thKaikoura05 -5- Kaikoura 2005 indication of the style or extent of Antarctic offshore on fast sea ice. Water depths ranged from glaciation. Therefore further drilling was planned 153 m to 295 m and core recovery for the 1680 m both through DSDP in other parts of the Antarctic drilled was 95%. The cores are a high quality margin (Antarctic Peninsula and Prydz Bay) and nearshore marine sedimentary record for the period through the use of a land-based drilling system from17to34Maagoandarewell-datedfrom from the fast ice of McMurdo Sound, where NZ-led volcanic ash, biostratigraphy, Sr isotopes and efforts had identified a sedimentary basin suitable magnetostratigraphy. for drilling close to the edge of the Transantarctic Key findings are: Mountains (and the East Antarctic ice sheet). i. Provenance studies indicate the Transantarctic This drilling (www.geo.vuw.ac.nz/croberts ), along Mountains had achieved most of their present with recent high-resolution deep-sea isotope height by 34 Ma. Apatite fission track studies records, has now led to the following history. show Cenozoic denudation began at ~55 Ma, but Around 34 Ma an ice sheet reaches the coast on CRP core studies show that most of the 1500 m both sides of Antarctica. Subsequent ice sheets of subsidence on the western margin of the advanced and retreated on Milankovitch Victoria Land Basin took place from 34 to 29 frequencies, causing variations in eustatic sea level Ma, slowing down to almost none by 17 Ma, and of the order of 50 m through Oligocene and early none since that time (Wilson et al., Geology, Miocene times. Low beech forest persisted around submitted). This changes the established view of the coast throughout this period. the West Antarctic Rift System. • Around 14 Ma the ice sheet developed a ii. The stratigraphy is largely cyclic repetitions of persistent core with margins close to its present shallow glacimarine facies, with well-dated limits and largely frozen to its bed. During the cycles of glacial advance and retreat around 24 warm Pliocene coastal Antarctica was warmer Ma showing that the Antarctic ice sheet by several degrees, but there is no firm evidence responded to orbital forcing at that time, much as that the East Antarctic ice sheet collapsed. the Northern Hemisphere ice sheets have done in • From 2.5 Ma to the present the Antarctic ice the Quaternary (Naish et al., Nature, 2001). sheet has responded to sea level variations iii. Pollen records show the cooling of the Victoria induced by Northern Hemisphere ice sheets, but Land coast from a temperate climate (>34 Ma) to only on a scale of ~15 m of sea level equivalent. a cool temperate climate (34 to ~17 Ma) • Future drilling by the ANDRILL consortium (Prebble et al, Palaeogeography, will investigate Quaternary behaviour of the Palaeoclimatology, Palaeoecology, in press). Ross Ice Shelf, and Antarctic climate during the This record shows no hint of the late Oligocene middle Miocene transition, in the McMurdo warming inferred from deep-sea isotopes by area (http://andrill.org/ ). Zachos et al (Science, 2001). An alternative explanation for the apparent warming has now ORAL been provided by Pekar et al (Palaeogeography, Palaeoclimatology, Palaeoecology, in press). THE CAPE ROBERTS PROJECT: iv. Rapid sedimentation and multiple dating TECTONIC AND CLIMATIC HISTORY OF techniques on CRP core have provided a new THE VICTORIA LAND COAST, potential calibration point for the Oligocene- ANTARCTICA OVER THE LAST 34 MA. Miocene boundary at 23.7 Ma (Wilson et al., Geology, 2002). 1 2 P. J. Barrett & Cape Roberts Science Team v. A 2-m-thick shell bed within 43 m of Quaternary 1 Antarctic Research Centre, Victoria University of strata in CRP-1, and dated at 1.1 Ma, records a Wellington, P.O. Box 600, Wellington. “super-interglacial” period (MIS 31) when the 2 55 scientists from Italy, United States, New Antarctic coast was ice-free and significantly Zealand, Germany Australia, United Kingdom and warmer than today (Scherer et al., Nature,in The Netherlands) review). (peter.barrett*vuw.ac.nz) Detailed results from individual drill holes can be found in 10 issues of the journal Terra Antartica From 1997 to 1999 the Cape Roberts Project between 1998 and 2001. (http/www.geo.vuw.ac.nz/croberts) drilled 3 holes off the Victoria Land coast at 77.0ºS and 163.7ºE. POSTER The project was a cooperative venture between scientists, administrators and Antarctic support personnel from 7 countries. The aim was to investigate the early history of the East Antarctic ice sheet and the West Antarctic Rift System, using a 55 tonne drilling system set up 13 to 16 km

50thKaikoura05 -6- Kaikoura 2005 CRETACEOUS-EOCENE TRANSGRESSION Greenland Group. Volcanic quartz is zoned with MARKED BY CHANGES IN SEDIMENT straight extinction and was most likely derived PROVENANCE AND GLAUCONITE from the Cretaceous Mt Somers rhyolites and not FORMATION, BROKEN RIVER TO the underlying Mandamus Igneous Complex due to WAIPARA/IRONCREEK FORMATIONS a lack of coarse quartz crystals. The provenance analysis suggests local derivation Kari Bassett & David Kapoutsos of sediments while fluvial deposition occurred Dept. of Geological Sciences, University of followed by more distal derivation once transported Canterbury in the nearshore marine setting. The glauconite (kari.bassett*canterbury.ac.nz) analysis indicates extremely low sedimentation rates with autochthonous/para-autochthonous Detailed provenance analysis and glauconite glaucony formation in nearshore marine settings, morphology of the Broken River and overlying possibly even estuary environments. Ironcreek/Waipara greensand Formations were POSTER conducted at 4 localities: the Mandamus-Dove River confluence, Waipara River, Avoca, and Castle Hill basin. The basal Broken River SEDIMENTOLOGY OF THE MAHOENUI Formation is a fluvial boulder conglomerate GROUP, KING COUNTRY REGION interbedded with sandstones, mudstones, and coal dated as Haumurian (L. Cretaceous) by pollen. The T. Bear, P.J.J. Kamp & C.S. Nelson transgressionismarkedbyagradualdrowningof Department of Earth Sciences, University of the fluvial conglomerates with glauconite appearing Waikato, Private Bag 3105, Hamilton. in the beds immediately overlying the (tlkb2*waikato.ac.nz) conglomerates in all localities. These estuary deposits contain a mixture of nascent, micaceous, The Mahoenui Group is of Early Miocene age and evolved/mature types of glaucony, previously (Otaian Stage) and accumulated in the King described as Types A and B by McConchie and Country region of western North Island. It Lewis (1978). In transgressive successions, represents a discrete depocentre that formed during glauconitization commonly post–dates coarse the early Otaian and became structurally inverted grained sedimentation in nearshore areas. during the late Otaian or early Altonian. The Upsection, evolved/mature glaucony dominates, in present area of outcrop is probably less than the some beds formed in situ (autochthonous) and in original extent of the depocentre, as its southern other beds transported from nearby (para- margin is buried beneath younger formations, and autochthonous) to line foresets. The age of the its eastern margin is erosionally truncated within greensand units is Mangaorapan - Whaingaroan the Hauhangaroa Range. The western margin was (Early Eocene Late Eocene). The extremely low bounded by the Tongaporutu-Herangi structural sedimentation rate from Cretaceous to Eocene is high, which was being deformed (uplifted) during necessary to form the evolved/mature type of sedimentation. The Mahoenui Group conformably glauconite. overlies the Oligocene Te Kuiti Group in the Clast counts from the basal conglomerates indicate northern and eastern parts of the basin where this derivation from very local sources, the underlying contact is exposed, and marks dramatic and sudden Torlesse greywackes and/or the Mandamus Igneous deepening from shelfal to bathyal depths, Complex. Quartzose sandstones plot in the interior corresponding to a lithological change from craton province in QFL plots for both Broken River carbonate to siliciclastic sediments. Mahoenui and Waipara/Ironcreek Formations. Sandstone Group is unconformably overlain by late Early lithics are probably derived from Torlesse Miocene (Altonian) Mokau Group in the north and greywacke. Alkali feldspars dominate over west, and by the middle Miocene (Lillburnian) plagioclase indicating a probable felsic plutonic Otunui Formation in the south and east. source. SEM-cathodoluminescence on quartz Mahoenui Group comprises a flysch succession in grains indicates a mixture of plutonic and the south (Taumarunui Formation) and a massive metamorphic quartz with minor volcanic input. mudstone facies in the north (Taumatamaire Plutonic grains are identified by microcracking Formation). Facies analysis of the Taumarunui features, and are possibly derived from western Formation confirms earlier oil company Province batholiths such as the Karamea or investigations that it comprises turbidities and Separation Point Batholiths. Polycrystalline/dark intervening hemipelagic mudstone, that would have CL quartz grains indicate a relative high-grade accumulated as broad submarine fan deposits at metamorphic source such as the Haast/Otago bathyal depths. The scale of the fans is larger than Schist, while dark CL monocrystalline quartz grains the largest of the outcrops, some of which are indicate a low to medium metamorphic grade, hundreds of metres long. Surprisingly, there is no possibly the Alpine schist, Otago Schist, or evidence of a regressive shelf or slope succession at

50thKaikoura05 -7- Kaikoura 2005 the top of the group, which was probably thin and fluid/melt body of unknown thickness but limited eroded during the inversion phase prior to lateral extent. We present preliminary results from accumulation of younger units. The Taumatamaire a recently completed active source seismic Formation comprises mainly massive mudstone. experiment (MORC) that seeks to address the issue Along the western margin (Herangi High) the of what constitutes Mantle OR Crust beneath the mudstone is interspersed with several limestone TVZ. members (Awakino Limestone; Black Creek Building upon the results of NIGhT, the MORC Limestone); the carbonate sediments were sourced experiment was designed to provide a enhanced along the contemporary rocky shoreline of the data set to examine the character of the 30 km deep Herangi High underlain by Murihiku basement, and PmP2 reflector. Nine dynamite shots of between dispersed across a very narrow east-facing shelf and 500 and 1300 kg were detonated into a 120 km long down the slope into the basin. array across the northern end of Lake Taupo. The Paleocurrent measurements derived from flute casts shot geometry and the deployment of 714 receivers and tool marks indicate that the flysch facies were (600 IRIS Texans, 96 geophones on multi-channel sourced from the south, and the depositional system systems, and 18 3-component seismometers) with probably prograded to the north. Muddy sediment an average spacing of ~200 m provides a ten-fold and carbonate were locally derived from basement increase in spatial resolution relative to the NIGhT exposed along the Herangi High, but this was data. Reflections from the 15 km deep PmP1 probably a minor source. The sandstone beds are horizon are present in the MORC data, however the cemented with calcite, and glauconite comprises a dominant features are arrivals from PmP2 at a surprisingly high proportion of their content (10%). depth of ~ 30 km. The occurrence and amplitude of Mica is an accessory mineral, suggesting that the PmP2 reflections are strongly dependent on schistose or gneissic terrane (in South Island) both the shot position and receiver offset. Initial contributed sediments to the basin. ray-tracing of the PmP2 reflections suggests the interface is of limited lateral extent and located POSTER directly below the active (eastern) part of the main TVZ rift. For stations with both PmP1 and PmP2 MANTLE OR CRUST? FIRST RESULTS arrivals it is possible to directly compare the FROM A DETAILED ACTIVE-SOURCE relative amplitude of these two phases. At large SEISMIC EXPERIMENT ACROSS THE offsets the amplitude of PmP2 reflections are at TAUPO VOLCANIC ZONE least 5 times those of PmP1 phases, which are modelled as being from a < 6.0 km.s-1 to 6.8 km.s-1 Adrian Benson1, Tim Stern1 &Stephen velocity boundary (Stratford & Stern, 2004). These Bannister2 results indicate the PmP2 reflections must be due to 1School of Earth Sciences, Victoria University of a large change in the velocity and/or physical Wellington, PO Box 600, Wellington. properties of rocks at 30 km depth. 2 Institute of Geological and Nuclear Sciences, PO Further work to characterise the crust-mantle Box 30-368, Lower Hutt. structure beneath the TVZ will include ray-trace (adrian.benson*vuw.ac.nz) and tomographic modelling of the combined MORC and NIGhT datasets, the production of a Seismic studies of the central North Island have stacked low-fold seismic section, and detailed consistently shown the Taupo Volcanic Zone to be analysis of the AVO properties of the PmP2 and a region of attenuated continental crust underlain by other reflectors. mantle of anomalously low seismic velocity (~7.4 km.s-1). However, the nature of the crust-mantle ORAL boundary beneath the rift and, in particular, the position of the Moho remain contentious. Active SEAFLOOR STRUCTURAL GEOMORPHIC source data acquired during the 2001 NIGhT EVOLUTION IN RESPONSE TO experiment detected two prominent reflectors at SUBDUCTION PROCESSES, POVERTY BAY depth: a ~ 15 km deep horizon (PmP1) and an INDENTATION, NEW ZEALAND unusually strong set of reflections from an interface at ~30 km (PmP2). These NIGhT data have given K. L. Bodger1,J.R.Pettinga1 andP.M.Barnes2 rise to divergent models of the lower-crust and 1Dept. of Geological Sciences, University of upper-mantle. Harrison & White (2004) place the Canterbury, Christchurch base of the crust at 30 km (= PmP2) and infer that 2National Institute of Water and Atmospheric the 15 km interval between PmP1 and PmP2 is Research (NIWA), Greta Point, Wellington under-plated and/or intruded lower crust. Stratford (k.bodger*geol.canterbury.ac.nz) & Stern (2004) suggest that the Moho lies between 15 and 20 km depth and interpret the PmP2 The >4000 km2 Poverty Bay Indentation, in the reflections as being from the top of an intra-mantle northern sector of the Hikurangi subduction margin,

50thKaikoura05 -8- Kaikoura 2005 consists of a well-developed canyon system, small margin at a mid to deep crustal level. Correlation accretionary wedge, landslide scars and debris flow between the surface expressions of these deposits. Outboard of the Hikurangi trench the processes and the underlying tectonics will be subducting plate incorporates the Hikurangi the next stage in this project. Plateau, a section of anomalously thick Mesozoic POSTER age oceanic crust (10-15 km) studded with seamounts and guyots (flat-topped seamounts). Morphologically the Hikurangi margin changes TRACE ELEMENT GEOCHEMICAL markedly from south to north of the Poverty Bay EVIDENCE FOR A LACUSTRINE Indentation. To the south, the margin is ENVIRONMENT OF DEPOSITION OF LATE characterised by a thick trench-fill turbidite section ARCHAEAN FORTESCUE GROUP and a wide, low-taper accretionary wedge with STROMATOLITIC CARBONATES, numerous thrust ridges and slope basins. To the WESTERN AUSTRALIA north of the indentation the margin is narrow, 1 2 relatively steep, and characterised by non-accretion R.Bolhar & M.J. Van Kranendonk 1 and tectonic erosion associated with reduced Department of Geological Sciences, University of sediment supply, seamount/guyot subduction, and Canterbury, Christchurch, NZ 2 gravitational failures. The transition between the Geological Survey of Western Australia, 100 characteristics of the two sectors is evident in the Plain St., East Perth, Western Australia, 6004 study area with the developed accretionary wedge (robert.bolhar*canterbury.ac.nz) and gentler slopes in the southern half contrasting with the steep slopes and numerous failures to the The late Archaean Fortescue Group (2.78-2.63 Ga) north of the canyon system. in the Pilbara Craton, Western Australia, records a High quality bathymetric images of the Poverty transition in depositional environments from Bay Indentation and adjacent regions of the subaerial in the lower part of the group, to marine Hikurangi subduction zone acquired by NIWA in the upper part of the group. Stromatolitic using a SIMRAD EM300 multibeam system carbonates (i.e. microbialites that formed by provide excellent seafloor morphologic resolution precipitation of minerals due to metabolic activity covering the entire continental slope from 50 – or decay of microbial communities and/or 3500 m water depth. These images have been associated organic matter) occur throughout the converted into a Digital Elevation Model (DEM) stratigraphic section at various levels, and their allowing three-dimensional analyses of the trace element geochemistry is used to make seafloor. inferences about the ambient water from which these carbonates were precipitated. In particular, Initial DEM interpretations suggest that: rare earth elements (REE) and Yttrium were i. seamount impact significantly influences the analysed to address whether structure/tectonic evolution, and submarine i. Fortescue carbonates display a marine geomorphology of the inboard slope of the geochemical signature or show compositional Hikurangi subduction zone, including the similarity to modern-day lacustrine waters and generation of large-scale gravitational collapse their deposits and features; ii. to identify temporal trends in the geochemistry ii. large gully systems located at the shelf – slope that may be consistent with a transition from boundary are source areas for mega-debris flows deposition in a subaerial/lacustrine to marine recognised in mid-slope basins; environment. iii. there exists a complex interaction between the Detailed inspection reveals that Fortescue evolving thrust-driven submarine ridges, ponded microbialites lack trace element characteristics that slope basins and the structural geometry and are diagnostic of carbonates deposited in a marine evolution of the near-surface fault zones environment. In particular, the Fortescue Group (imbrication); and samples lack distinct La (expressed as La/[3Pr- iv. the submarine canyons may initiate complex 2Nd] in shale-normalised diagrams) and Gd patterns of fault zone segmentation and [Gd/(2Tb-Dy]shale anomalies and supra-chondritic displacement transfer within the accretionary Y/Ho ratios, which are well-developed in seawater slope. carbonates formed throughout Earth history, from v. The addition of high quality 3.5 kHz single- at least 3.4 Ga. The late Archaean microbialites channel and multi-channel seismic reflection also lack depletion of the light REE relative to the data complements the morphological and middle and heavy REE when shale-normalised, in structural surface interpretation. In particular, contrast to seawater and marine carbonates, which this allows investigation into the impact of thrust are typically HREE enriched. Importantly, no fault loading and seamount subduction on the temporal trends in the geochemistry that is

50thKaikoura05 -9- Kaikoura 2005 consistent with a marine deposition can be Mariner Group (Mindyallan and Idamean stages). identified as a function of the relative stratigraphic These conglomerates are marine and interbedded height of the carbonates in this study. with turdidites and fossiliferous mudstones. The It is concluded, on the basis of the trace element fluvial Carryer Conglomerate is probably late geochemical evidence presented herein, that late Idamean or younger. Thus the first appearance of Archaean stromatolitic carbonates of the Fortescue coarse fluvial deposits is 1-2 million years later in Group record deposition in a lacustrine NVL than in NZ. environment, to the top of the group. Our study There is considerable evidence that the Ross demonstrates that trace element geochemistry is a Orogeny was the result of oblique convergence and powerful tool to constrain depositional that the tectonic-plutonic maximum progressed environments of ancient (and modern) carbonate from south (near polar) to north. In this context, rocks. To our knowledge, our study is the first to back-arc basin closure and arc accretion most document the geochemical characteristics of probably progressed from south to north. The data carbonates formed through microbial activity in an above suggest that the NZ portion of the back-arc ancient lake setting, with important implications for basin and arc lay to the south of the NVL portion, the development of early life. possibly east of southern Victoria Land. POSTER Comparisons of post-Ross-Delamerian sedimentation of Latest Cambrian-Ordovician age in mainland Australia and Antarctica with that in THE ORIGIN OF NEW ZEALAND: New Zealand show significant differences. CAMBRIAN INTRA-OCEANIC ARC Australian and Antarctic Ordovician rocks are very ACCRETION TO THE GONDWANA thick and almost entirely detrital, whereas the NZ MARGIN CONSTRAINS THE LOCATION OF Ordovician includes thick developments of PROTO-NEW ZEALAND carbonate rocks (Arthur Marble, Takaka terrane). Only in Tasmania are Ordovician carbonates well J.D. Bradshaw,M.Gutjahr,S.D.Weaver&K. developed but Tasmania is now generally N. Bassett considered to have been a crustal block separate Department of Geological Sciences, University of from Australia. Together, these data suggest that Canterbury, Christchurch, New Zealand the attachment of the NZ portion of the arc to the (john.bradshaw*canterbury.ac.nz) continental margin may have been short-lived and that the proto-NZ block was rifted away from the Data from New Zealand (NZ) and northern Victoria Gondwana margin in the early Ordovician and Land (NVL, Antarctica) indicate strongly that the became an isolated crustal block within the broader Cambrian Devil River intra-oceanic arc accreted to Lachlan belt. In contrast the Buller terrane closely the Gondwana margin in the Middle to Late resembles the western Lachlan fold-belt. Cambrian. The close similarity of NZ arc rocks ORAL and immediate post-arc sediments to those of northern Victoria Land (Antarctica) firmly place the two regions in the same tectonic framework and LABORATORY MODELLING OF imply paleogeographic proximity. The arc & back- SEISMICALLY TRIGGERED arc setting in NZ and NVL contrasts with accepted MOUNTAINSIDE COLLAPSES models of fore-arc collision for Cambrian orogenesis in Tasmania and southern Australia. F. Buech1, T.R. Davies1,J.R.Pettinga1 &J.B. 2 Combined sedimentological, paleontological, Berrill 1 2 geochemical and geochronological data from NZ Dept. of Geological Sciences, Dept. of Civil and NVL show that by the Middle to Late Engineering, Cambrian, the accreted arcs were partially buried University of Canterbury, Private Bag 4800, by the deposits of major fluvial systems derived Christchurch. from sources both within the arc and within the (f.buech*geol.canterbury.ac.nz) Gondwana continent. In NZ, sandstone clasts of Precambrian Gondwana origin first appear in Strong seismic events can initiate slope failure channelised marine conglomerate in the youngest leading to devastating mass movements of a wide part of the Tasman Formation ( Boomerangian range of sizes and types. Earthquake-induced rock stage) and are joined, in the succeeding marginal avalanches represent one of the most damaging of marine to fluvial Lockett Conglomerate all seismic hazards. This research project focuses (Mindyallan stage), by continental-arc plutonic on the kinematic response of mountain slopes to clasts. In NVL, rare clasts of continental-arc strong seismic shaking. We are designing a plutonic rocks occur in Boomerangian and older physical laboratory model at small scale (1:10,000) rocks, but conglomerates with arc plutonic clasts that will simulate controlled seismic waves become abundant only in the upper part of the propagating through a three-dimensional mountain

50thKaikoura05 -10- Kaikoura 2005 model. The relative position of the mountain to the are attributed to prehistorical surface ruptures on direction of the incoming seismic wave field, the nearby Alpine fault. These forest disturbance topographic modification and local resonance events were synchronous (± 2 yr at 2
) with effects are likely to be important factors for regional rockfall events dated by lichenometry triggering deep-seated failures within the mountain using Rhizocarpon subgenus Rhizocarpon.Using leading to catastrophic mountainside collapses and the names of previous workers these are, ± 5 yr, the characteristically bowl-shaped source scars. 1715 Toaroha, 1615 Crane Creek, and 1580 A. D. Seismic waves interfering with local geological and Waitaha events. topographical conditions will produce site-specific This cluster of magnitude Mw ~7 earthquakes ground motions within the mountain edifice. The occurred in a brief time span of only 135yr. The measurement of ground motion at different Waitaha event was the smallest, with a surface positions of the small-scale mountain surface will rupture limited to the central Alpine fault. Crane provide information on the effect of slope Creek was the largest event with a surface rupture topography on strong seismic ground motion. The that probably extended from the Nelson Lakes to combination of the physical laboratory modelling the central Alpine fault. The Toaroha event data with a numerical analysis will then be used to consisted of two surface ruptures, one from north- evaluate dynamic internal stress fields developed, central and the other on the southern Alpine fault. to infer the location of potential deep-seated failure surfaces, and to estimate possible volumes of seismically triggered mass movements. In addition to the laboratory modelling a seismic field experiment will provide an indication of the degree to which the small-scale model data can be extrapolated to comparable full-scale field situations. Detailed geotechnical field investigations of coseismic landslide sites within the Southern Alps of New Zealand (e.g. Acheron, Craigieburn rock avalanche) will provide information about specific rock fabrics and morphological parameters and will be used as a reference to improve and calibrate the physical laboratory and numerical modelling. This research project is a combination of physical laboratory and numerical modelling techniques with seismic field tests and geotechnical investigations to deepen the understanding of coseismic landslide initiation within bedrock mountain edifices. It can be seen as a first attempt to set up a deterministically-based methodology for evaluating mountain slopes susceptibility to failure during strong earthquakes and for predicting the impacts of future coseismic landslides. POSTER

RECENT ALPINE FAULT EARTHQUAKES

William B. Bull This figure shows trends in seismic shaking based Geosciences Department, University of Arizona, on spatial variations in the abundance of rock-fall 1040 E 4th Street, Tucson, AZ, USA blocks dating to times of the three most recent University of Canterbury, Natural Hazards prehistoric Alpine fault earthquakes. An index Research Centre value of 10 or more is about equivalent to a (Bill*ActiveTectonics.com) Mercalli seismic shaking intensity of 7 or more. Tree-ring analyses and lichenometry precisely date ORAL a recent cluster of three Alpine fault earthquakes, and describe their seismic shaking intensities. Marked suppressions of annual growth rings of New Zealand cedar (Libocedrus bidwillii)at seismically sensitive Oroko Swamp and Alex Knob

50thKaikoura05 -11- Kaikoura 2005 EXPLORING CONSTRAINTS ON UNCOVERING THE FACE OF THE ANTIQUITY OF TERRESTRIAL LIFE IN EASTERN NEW ZEALAND MARGIN – A NEW ZEALAND VIEW FROM THE OCEAN

H.J. Campbell1 &C.A.Landis2 Lionel Carter1 & Jarg Pettinga2 1 GNS Science, PO Box 30-368, Lower Hutt, New 1NIWA, Private Bag 14-901 Kilbirnie, Wellington, Zealand New Zealand 2 Department of Geology, University of Otago, PO 2University Canterbury, Private Bag 4800, Box 56, Dunedin, New Zealand Christchurch, New Zealand (h.campbell*gns.cri.nz) (l.carter*niwa.cri.nz)

The New Zealand land surface appears to be less than 25 million years old. Our knowledge of New Zealand’s eastern margin, It therefore follows that the modern terrestrial biota including the active Hikurangi and passive Bounty is not descended from archaic ancestors residing on sectors, is surprisingly recent. Even though the proto-New Zealand (Zealandia) when it broke away broad outlines of these sectors were charted as early from Gondwana. Rather, it has evolved from as 1910, it was not until 1958 that Hikurangi accidental arrivals since New Zealand became Trench and Bounty Trough were formally emergent. For all that, the modern biota is indeed recognized. Being the pre-plate tectonic era, the derived from lands of Gondwanan heritage. forces behind these major oceanic forms were unclear. Hikurangi Trench was regarded as either a Our first statement is a bold assertion. It is based on compressional or tensional feature, whereas Bounty systematic investigation of the geological evidence Trough was seen as the consequence of large-scale for ‘islands’ during latest Oligocene to earliest uplift of the bordering Chatham Rise and Bounty Miocene time. These ‘islands’ were first portrayed Platform. by Charles Fleming in 1959 and have subsequently become established in most treatments of New Marine studies began in earnest in the mid-1960s. Zealand geological history and paleogeography Systematic surveys were undertaken by the Navy since formation of the Geological Society 50 years and government research groups, but more ago. significant was the oceanographic and geophysical transects run by the USNS Eltanin. This network of Our studies have shown that the geological survey lines provided the first regional view of the evidence for the existence of islands during latest eastern margin. Single channel seismic lines, in Oligocene to earliest Miocene time is either non- particular, highlighted the architecture of acoustic existent or so wanting that we can confidently basement and sediment fill, as well as prominent conclude that any islands that may have existed morphological features. In Bounty Trough, the were small and short-lived. Here we critically discovery of a canyon-channel system hinted at the evaluate four inferred mid-Cenozoic islands in: long-distance transfer of South Island sediment to Fiordland, Central Otago, Northwest Nelson and the deep ocean via turbidity currents. Likewise, the central North Island. presence of a prominent axial channel and 2km- As part of this analysis, we have identified eight thick sedimentary fill in southern Hikurangi factors that appear to have influenced Trench, indicated similar trench-fill processes paleogeographic map reconstructions. supplemented by the mass wasting of trench walls. This research has grown from exploration of However, the margin’s place within a plate tectonic regional planar surfaces in the New Zealand model had yet to be appreciated. landscape and particularly the Waipounamu Intellectual and technological advances of the Erosion Surface as expressed in Otago and the 1970s started to shift emphasis from descriptive to Chatham Islands, and is supported by the ChEARS process-oriented research. The shelf circulation and Marsden Project. eustatic oscillations of sea level were shown to be All available geological evidence suggests that key drivers of Quaternary sedimentation on and off Zealandia broke away from Gondwana c. 85 Ma the margin. The imprint of sea level change on a and then slowly sank 1,000 to 3,000 metres over a tectonically active seabed was identified on the period of c. 60 million years, culminating in Hikurangi margin, yielding landmark papers on complete submergence c. 23 Ma (Waitakian). sequence stratigraphy and sediment mass transport. Shortly following this, plate boundary collision Industry seismic data, especially that collected on became vigorous resulting in tectonic emergence of the reconnaissance voyages of MOBIL’s Fred H. New Zealand. This process is ongoing. Moore, mapped the eastern margin in unprecedented detail. By 1978, results from marine ORAL and terrestrial research were sufficient to finally bring New Zealand into the plate tectonic fold; no doubt giving satisfaction to pioneers and early

50thKaikoura05 -12- Kaikoura 2005 converts to plate theory. Thus, the foundation was pervasive background of cm-scale, planar or wispy laid for a suite of studies, fuelled by committed alternating muddy and sandy silts, consistent with scientists and research facilities, and aided by deposition from rhythmically fluctuating bottom rapidly developing technologies that included deep currents. In the Plio-Pleistocene, the sand:silt ocean drilling, satellite navigation, multichannel lithological rhythmicity occurs in synchroneity with seismic profiling, remote sensing from space, Milankovitch-scale climate cycling; periods of seabed mapping systems and computer-based inferred faster current flow (sand intervals) mostly facilities to handle the ever-expanding stream of correspond to warm climatic intervals. data. It is a measure of these efforts, that eastern The drifts vary in thickness from 300 m near the margin science has achieved significant early Miocene shoreline, where they were international recognition. But that status should not accumulating in limited shallow water invite complacency. Much of the margin remains accommodation, to 2000+ m under the modern untouched. Thus, the scene is set for another 50 shelf edge. Mounded drifts first occur at 15 Ma years of discovery. (Middle Miocene), their appearance perhaps ORAL reflecting more vigorous intermediate water flow consequent upon worldwide climatic deterioration between 15 and 13 Ma. A further change from large CANTERBURY DRIFTS, SW PACIFIC (more than 10 km wide) to smaller (1-3 km wide) OCEAN RECORD OF INTERMEDIATE mounded slope drifts occurs at 3.1 Ma, marking DEPTH WATER FLOWS SINCE 24 MA further cooling, the inception of discrete SAMW flows, and initiation of the Subantarctic Front. The 1 Robert M. Carter natural gamma ray record from Site 1119 contains a 1 Marine Geophysical Laboratory, James Cook history since 3.9 Ma of the waxing and waning of University, Townsville the New Zealand mountain ice cap. Back to ~0.7 (bob.carter*jcu.edu.au) Ma, this record closely mirrors the climate history of Antarctica, as manifested in the Vostok and The Canterbury Drifts were deposited in water EPICA ice cores, at 0.1 to 0.6 ka resolution. depths between 400 and 1500 m by northward Beyond, and back to 3.9 Ma, the gamma record flowing, cold, intermediate depth water masses - reflects southern mid-latitude ice-volumes, and Subantarctic Mode Water (SAMW), Antarctic perhaps Antarctic polar plateau temperature, at a Intermediate Water (AAIW), and their predecessor resolution of 1.3 ky. current flows. Drift accumulation started at 24 Ma, ORAL fed by terrigenous sediment derived from the newly rising Alpine Fault plate boundary in the west, which has built a progradational shelf-slope sediment prism up to 130 km wide at rates of eastward advance of up to 5.4 km/My. These regionally extensive, intermediate-depth sediment drifts can be examined in outcrop (Bluecliffs Silt and younger equivalents), in marine drillcore (ODP Site 1119) and at the modern seabed.

The drifts comprise planar-bedded units up to

several metres thick. Sand intervals have either reverse graded or sharp, erosive bases and normally graded tops. Bioturbation is moderate and the sands occur within a

50thKaikoura05 -13- Kaikoura 2005 THE “SO-CALLED MARSHALL v. the contact between the Mt. Brown Beds and PARACONFORMITY1”HISTORICAL overlying deeper marine siltstones (Motunau SIGNIFICANCE OF UNCONFORMITIES IN and Greta beds) (deepening-surface, and basin THE KAIKOURA SYNTHEM, EASTERN formation, caused by Pliocene transtensional SOUTH ISLAND tectonism; north margin of Canterbury Basin only). Robert M. Carter Since its first description by Hutton (1885), detailed Marine Geophysical Laboratory, James Cook study by Speight & Wild (1918), and naming by University, Townsville Carter & Landis (1972), the significance of the (bob.carter*jcu.edu.au) Marshall Paraconformity has been controversial. Haast, Hector and Park and many later geologists Between the 1860s and the early part of the 20th failed to see or make comment on an unconformity century, exploration geologists Julius von Haast, at this horizon, McKay and Marshall argued James Hector, Frederick Hutton, Alexander strongly against its presence, Jenkins (1975) and McKay, James Park, Pat Marshall, Robert Speight, Findlay (1980) denied its wider significance, and Charles Cotton and J. Allan Thomson engaged in a Lewis (1992) inferred a partly tectonic origin. High lively debate about the classification of New resolution dating of the ~4 to 33 My-long gap Zealand “Cretaceo-Tertiary” strata. In eastern across the surface (Fulthorpe et al., 1994; Graham South Island, these strata were deposited in the et al., 2004; Nelson et al., 2004), and Canterbury Basin, and are now classified in the palaeoceanographic interpretation (Carter et al., successive Matakea (rift-fill), Onekakara 2004), have confirmed its regional significance. (transgressive ramp), Kekenodon (carbonate The Marshall Paraconformity is the sedimentary platform), Otakou (regressive progrades and drifts) pivot around which turns the entire Kaikoura and Hawkdun (piedmont gravel) Groups of the history of the New Zealand Plateau. Kaikoura Synthem. Pivotal to the historical debate was the identification of, and significance accorded to, claimed unconformities at different stratigraphic Nelson, C.S. et al., 2004: Strontium isotope dating of the New Zealand Oligocene. New Zealand Journal of levels. Illuminated by hindsight, and armed with Geology & Geophysics 47: 719-730. modern sedimentary knowledge and age-dating techniques, some of the arguments used to justify ORAL particular past stratigraphic interpretations seem arcane. Notwithstanding, all but one of the MINING-INDUCED DEBRIS FLOW EVENTS “unconformities” claimed by historic geologists IN THE GREYMOUTH COALFIELD have a broader stratigraphic significance, albeit in ways that mostly differ from their 19th century Murry Cave interpretation. Resource Solutions In ascending stratigraphic order, the unconformities Western Exploration Ltd & Resource Solutions, (and their modern interpretation) include: PO Box 3523, Wellington i. that which separates the base of the Kaikoura (cavem*paradise.net.nz) Synthem from underlying Rangitata Synthem strata (post-Rangitata or pre-Kaikoura In Mid 1998, miners working the United Mine in unconformity; basin creation by Cretaceous the 10 Mile area of the Greymouth Coalfield rifting), noticed changes in Doherty Creek which they had ii. the contact between the Waipara and Oamaru to cross to access the mine. The Creek would run series of Hutton (1874, 1885) (the Amuri and dirty during fine weather and small rushes of debris occurred, one of which washed away the coal bins Weka Pass Limestone junction, now termed the th Marshall Paraconformity; creation of the for an adjacent mine. On the 24 of August 1998 a Southern Ocean and the Antarctic Circumpolar huge amount of water, trees, mud and rocks rushed Current); down the creek blocking access to the mine. No significant rain had occurred in the preceding iii. the contact between the Oamaru and Pareora period. The miners’ observations suggested that Series of Hutton (1899) (the Weka Pass- the material was coming from Solid Energy’s Bluecliffs Formation contact; seaward downlap Strongman # 2 underground mine which was of Otakou Group clinoforms), working at the head of Doherty Creek iv. the “Weka Pass rail cutting” unconformity rd On the 23 of September 1998 the United Mine (Hutton, 1887), claimed to be at the Grey Marls- workers heard an horrendous roar from the head of Mt. Brown Beds contact, but actually lying Doherty Creek and when they emerged they found within the Mt. Brown Beds (Southburn Sand; a large wall of debris damming the creek above the chanellisation within the regressive shoreface mine access. Again the weather was fine at the succession), and time. On the night of 24th of September it rained

50thKaikoura05 -14- Kaikoura 2005 and on the following morning the miners arrived at Zealand Oil and Gas in 1985 as a test production work to find the debris moving. Just after they well using the Rockdrill 20 rig. The well was a retreated down the road, the debris dam failed and limited success in that hydrocarbons were the resulting debris flow destroyed the road end and discovered and some oil was recovered to surface access to the mine. during testing. The well was subsequently What went wrong? The Strongman#2mineisin suspended pending a re-entry and a new well was rugged terrain with coal outcropping against an drilled to test the projected up-dip extension to the escarpment. The licence conditions required a play. The updip well, Niagara 2 was poorly located reasonable range of environmental protections. and thus not a success and NZOG subsequently Mining best practice and the mine plan and called surrendered the permit. for an outcrop barrier, however, the mine plan also Ocean Harvest obtained the permit in late 2000 and called for high extraction under shallow cover. undertook a review of the potential for Niagara 1. Problems soon occurred with surface subsidence The existing data was reviewed by Western developing from early 1996. Extensive extraction Exploration who concluded that the poor of the outcrop barrier was also initiated in 1996. production performance of the well was most likely This lead to the collapse of the escarpment and the due to formation damage resulting from drilling generation of debris flows in Doherty Creek. These with an excessively overbalanced mud over the debris flows ultimately destroyed access to mines production zones. M Pearson (Pers comm) of operating in the area. The ongoing instability Kappa SEA reviewed and re-interpreted and precluded restoration of access as the safety of available test production data in 2002 and workers could not be guaranteed nor was it possible confirmed the formation damage assessment. The to design a new cost effective means of access that kappa assessment also considered 40 bbl/day to be would survive any future debris flows from the a realistic production target. degraded catchment. Since 2002, Western Exploration and Ocean The court cases that arose out of the debris flow Harvest have been exploring cost effective damage have now all been settled but the solutions for undertaking a re-entry of the well. subsidence, escarpment damage and associated Because of uncertainty over the potential of the mine fires at Strongman Mine is having an ongoing well, mobilisation of a full-scale oil rig could not be environmental impact. Just as important is the justified because of the impact this would have on damage done to the reputation of coal mining on project economics. Alternatives such as the Failing the Coast, and of the mining industry as a whole as DMX used to undertake the P&A of Blenheim 1 a socially and environmentally aware industry. were explored but lack of trained crew precluded The consequence has been for a far greater level of that option. Eventually a suitable rig was obtained scrutiny of other mining projects such as Pike and crew trained to undertake the re-entry in 2005. River. To some extent this degree of scrutiny is The re-entry was more successful than anticipated beneficial because it can be too easy for mine with oil and gas flows to the surface immediately developers to “accentuate the positive” and after the bridge plug had been drilled through and minimise the potential downsides. Industry additional flows once the main production zone was acceptance of the rigorous examination of the reached. A post re-entry review suggested that the issues by independent analysts may help to offset 40 bbl/day production target is a minima and the concerns of those currently concerned at the production of up to 80 bbl/day plus enough gas for impact of mining in NZ. small scale on site power generation is possible. POSTER The design of the Niagara 1 well impacts on the development programme. In particular the 5” production casing and the barefoot completion A LONG TIME COMING: WILL NIAGARA 1 below the casing shoe constrains our ability to BE THE SOUTH ISLAND’S FIRST install suitable artificial lift equipment. A COMMERCIAL OIL WELL? production design has been formulated and is presently being tested. In addition, existing seismic 1 2 Murry Cave & Selwyn Love will be reprocessed and additional seismic 1 Resource Solutions acquisition is planned. Depending on the results a Western Exploration Ltd & Resource Solutions, PO new well may be drilled to intersect the producing Box 3523, Wellington formation within the fault bound Niagara structure. 2 Ocean Harvest (cavem*paradise.net.nz) ORAL

Niagara 1 is located in the Aratika Forest, between Lake Brunner and Greymouth on the West Coast of the South Island. The well was drilled by New

50thKaikoura05 -15- Kaikoura 2005 POTENTIAL FOR A 6000 YEAR RECORD OF to improved assessments of the hazard that the ALPINE FAULT EARTHQUAKES FROM Alpine Fault poses to New Zealanders. HOKURI CREEK, SOUTH WESTLAND POSTER U.A. Cochran & K.R. Berryman Institute of Geological & Nuclear Sciences, PO SEDIMENTOLOGY AND Box 30-368, Lower Hutt TEPHROCHRONOLOGY OF LAST- (u.cochran*gns.cri.nz) GLACIAL LAKE SEDIMENTS AND PEAT FROM SOUTH WESTLAND A large surface-rupturing earthquake on the Alpine Fault is one of New Zealand’s most significant J. Cole-Baker1,C.H.Hendy2,D.J.Lowe1 natural hazard scenarios. Current estimates of & P.J. Cooke1 recurrence interval for Alpine Fault rupture events 1Dept. of Earth Sciences, 2Dept. of Chemistry rely on calculation from slip rates and single event University of Waikato, Private Bag 3105, Hamilton displacements or from age determination of the last (jrc1*waikato.ac.nz) three or four earthquakes. A 16 m thick sequence of lake and wetland sediments immediately adjacent We undertook a high resolution study of cores from to the Alpine Fault in Hokuri Creek, south two lakes in South Westland aimed at determining Westland has the potential to dramatically improve the nature and timing of abrupt climate change these estimates. The sequence spans the last c. 6000 during the Last Glacial–Interglacial transition. years and consists of c. 25 silt-peat couplets. Cores were collected from Skiffington Swamp and Couplets are thought to represent repeated cycles of Galway Tarn in South Westland and the sediments ponding and drainage with silt units deposited in characterised by measuring magnetic susceptibility, ponded open water and peat deposited under percent organic carbon (by loss on ignition), grain wetland conditions. For at least part of its history, size and mineralogy. Pollen assemblages had been the lake outlet crossed the Alpine Fault thereby analysed previously (Vandergoes and Fitzsimons, causing drainage to be fault-controlled. It is likely 2003). Both sites contain a visible tephra layer that every time the Alpine Fault ruptured to the identified as the Aokautere Ash (Kawakawa surface in the last 6000 years, it affected the Tephra, 22.6 14C ka or c. 26.5 cal ka) based on hydrology of this waterbody. Preliminary counts stratigraphic position and existing geochemical indicate the rate of couplet formation (one every analysis. This layer provides an excellent 240 years) is consistent with existing recurrence chronostratigraphic reference point. Several other interval estimates. Horizons containing soft peaks in glass shard concentration were identified sediment deformation features provide additional during microscope analysis and concentrated with evidence of strong earthquake shaking. heavy liquid techniques for geochemical analysis Initial field observations suggest the Hokuri Creek by electron microprobe. This showed that all lake sequence has the potential to provide a c. 25 samples were consistent with the Kawakawa event paleoseismic record – one of the longest Tephra. obtained globally. We present a progress report on Existing pollen data for both cores (Vandergoes and the research required to identify and extract Fitzsimons, 2003; Vandergoes, unpublished data) paleoseismic information from this sequence. exhibit a grass pollen peak interpreted to represent Paleoenvironmental analysis is currently underway the Last Glacial Maximum (LGM), followed by a to better define major silt-peat couplets and their reduction in grass and a later rise in tall trees as the mechanism of formation. Plant macrofossils and climate ameliorated. Our analysis showed a diatom microfossils are used to characterise distinctive and abrupt increase in the combustible depositional environment. Radiocarbon dating of organic carbon content of both cores, occurring leaves and reed material provides a basic after the decline of the grass peak and just before chronology for the sequence. However further age the rise in tall-tree pollen. A possible interpretation controlwillberequiredtoestablishanevent of this change is the retreat of ice from near the site chronology. Further work on the paleogeography of and rapid re-vegetation of exposed outwash plains the valley will also be required to understand the by grasslands. This led to a reduction in loess input relationship between drainage patterns and the as vegetation covered and stabilised the exposed fault. source areas. Grain size data were less conclusive. The ultimate aim of the research is better definition Both cores showed a higher degree of variability in of Alpine Fault earthquake recurrence and an the latter part of the LGM, with a period of coarser improved understanding of the fault’s mid to late grain size commencing just before, and finishing Holocene activity. In particular, obtaining data with just after, the sudden increase in organic matter which to assess variability in earthquake recurrence seen in the loss on ignition results. Galway tarn would enable significant refinement of probabilistic showed a very distinct period of finer grain size seismic hazard models. Such information will lead prior to this coarse period, seeming to coincide with

50thKaikoura05 -16- Kaikoura 2005 the LGM grass peak. This period of fine sediment sediment by-passes the shelf and is directly deposition is also present in the Skiffington Swamp deposited into the troughs and canyons east of results but is less distinct. Galway Tarn samples South Island. In core MD97-2120, arrival of were found to have a very high phytolith content, characteristic silt-sized grains is offset by over 50 which may have contributed to the less distinct cm at both Termination II (MOIS 6/5) and grain size results. The mineralogy of the Termination I (MOIS 2/1), this equates to Skiffington Swamp core was examined by optical approximately 10,000 years based on the existing microscope using point counting methods. A peak
18O records, i.e., the sediment did not arrive in the in micaceous mineral content (as a percentage of Bounty Trough until interglacial warming was at its total mineral grains) was found corresponding with maximum. the end of the LGM. A rapid reduction in mica The modern west coast system is slightly different content was found to correlate well with the rise in as it lacks the trapping capacity of the lakes and the organic content as shown by the loss on ignition proximity of the Southern Alps is much closer. results. This is interpreted to represent a reduction Approximately 10 times more sediment is injected in mica supply as outwash areas were re-vegetated into the west coast system than into the Bounty after glacier retreat. Trough. New core sites (TAN0409-173 and -174) off the Vandergoes, M. J.; Fitzsimons, S. J. 2003: The Last Hokitika and Haast Canyons in the Tasman Sea, are Glacial-Interglacial transition (LGIT) in South being investigated to determine how much greater Westland, New Zealand: paleoecological insight into the sediment loading is and what the delivery rate is mid-latitude Southern Hemisphere climate change Quaternary Science Reviews 22: 1461-1476. compared with the east coast sediment system. We suggest this high sediment loading would be POSTER exacerbated during glacial times and during the climate transitions. MUDDY WATERS ~ OFFSHORE RECORDS The west coast cores will enable us to assess how OF ONSHORE RESPONSES TO ABRUPT abrupt climate changes will be expressed in the CLIMATE EVENTS sediment record, given the delivery rate should be faster and lacking the ‘holding’ capacity of the Penelope J. Cooke1, Chris H. Hendy2, lakes. Knowing this will contribute to climate Campbell S. Nelson1 & Helen L. Neil3 change modelling and our understanding of the 1Dept. of Earth Sciences, University of Waikato, climate system. Private Bag 3105, Hamilton POSTER 2Dept. of Chemistry, University of Waikato 3NIWA, Private Bag 14901, Wellington (p.cooke*waikato.ac.nz) HOW GOOD IS THE FOSSIL RECORD? NEW ZEALAND MIGHT HAVE THE Most palaeoclimate proxies recorded from marine ANSWER sediments, are in fact of a marine origin, e.g.,
18O, 1 2 1
13C and alkenones, and therefore record the R. A. Cooper ,P.A.Maxwell,J.S.Crampton, 1 1 3 oceanic systems’ responses to the changing climate. A. G. Beu ,C.M.Jones,B.A.Marshall 1 However, the terrigenous sediment which has GNS Science, PO Box 30368, Lower Hutt, New accumulated in large quantities in the offshore area Zealand 2 around New Zealand, started life onshore. Erosion Bathgates Road, R.D. 10, Waimate, South of the South Island of New Zealand contributes Canterbury, New Zealand 3 almost 0.7% of the total riverine sediment loading Museum of New Zealand Te Papa Tongarewa, PO to the oceans per year and is inferred to have been Box 467, Wellington, NZ much greater during glacials, particularly during (r.cooper*gns.cri.nz) transitions between climate states. Hence the timing of events, which generate the sediment are Estimates of past biodiversity, speciation rates and likely to be offset from the records of the same extinction rates based on the fossil record, have events in marine proxies. built-in assumptions about completeness of the The arrival of terrigenous sediment into the marine fossil record. Biodiversity change and evolutionary system is likely to be delayed by its transit from the rate metrics have become increasingly sophisticated site of origin to the marine system. Sediment in recent years, but there has been no corresponding supplied to the Bounty Trough off eastern South improvement in estimates of completeness. This is Island is first trapped by the large natural lakes because completeness of fossil populations is which retain about 15% of the sediment yield to the extremely difficult to measure. It is widely east of the Alps. Configuration of the Canterbury recognised that a major contributor to Shelf during glacials is such that the delivery of this incompleteness is size bias – the preferential loss of

50thKaikoura05 -17- Kaikoura 2005 small sized species from the fossil record. Using the potential for exploitation/over-use and theft of exceptionally good fossil record of New Zealand genuine pounamu. Recent and Cenozoic Mollusca, we use a novel Research is underway to characterise different approach to estimate the magnitude of the bias pounamu source regions by defining their “genetic against small body size and the effect of this bias fingerprint”. The geological age and radiogenic on completeness of the fossil record. Our database isotopic composition of Aotearoa/New Zealand of 3907 fossil species represents an original living pounamu is distinguished from other nephrite jade pool of 9086 species, from which 36% have been occurrences overseas, due to relatively young removed by size culling, 27% from the smallest cooling ages. Strontium isotope ratios distinguish size class (<5mm) alone. In contrast, non-size pounamu from different source areas within related losses comprise only 21% of the total. Aotearoa/New Zealand (whakapapa), with Exhaustive collection and preparation techniques, signatures reflecting the host terrane rocks (their not used for most of the samples, demonstrates that family) and their position in a sequence of the loss of small taxa can be reduced by nearly a metamorphic events (their generation). The half. This implies that just over half of the size- research will provide a tool for archaeological related loss is due to non-preservation and just research, trademark and resource protection. under a half is due to non-collection. Mineral resource assessments normally aim to define the total volume/tonnage present, which is generally assumed to be finite, applying drilling and geostatistical modelling. Pounamu resource assessment requires a different approach, as its intrinsic value is insufficient to warrant modern exploration methods (e.g. drilling, geophysics). Pounamu is only known to occur at a restricted few in-situ (hard-rock) localities. It is primarily found in transported (alluvial) detrital river and glacial outwash deposits, where collectable material has short term variability due to erosion and transport Fig. 1. Left, more than half of living mollusc species are processes. A new methodology is being developed culled out and not found in fossil collections, due mainly to their small size (size culling, 36%), but also to other aiming to define causes (21%). Right, size culling removes more than half i. the total resource present, of the smallest size class alone. ii. the relative rate of change in the availability of ORAL that resource through erosion and other geological processes, iii. active areas where new material is likely to be POUNAMU RESOURCE ASSESSMENT & exposed (e.g. by erosion), and CHARACTERISATION iv. appropriate extraction rates for sustainable S. C. Cox1,C.J.Adams1,T.Popham2,3, use. The methodology will provide a holistic A. Goodall2 &H.J.Campbell1 overview of the resource in different regions 1GNS Science, Private Bag 1930, Dunedin. of Aotearoa/ New Zealand, and may be 2Te R nanga o Ng i Tahu. 3Geology Department, applicable to other transient or restricted University of Otago natural resources that occur within (s.cox*gns.cri.nz) geologically active environments (e.g. supplies of driftwood on beaches). Pounamu is a M ori collective term for semi- POSTER precious stone scientifically referred to as nephrite, semi-nephrite, jade or bowenite (tangiwai) that is composed predominantly of metamorphic tremolite QMAP AORAKI: THE NEW 1:250 000 in a felted, fibrous texture. It is Aotearoa/New GEOLOGICAL MAP OF CENTRAL SOUTH Zealand’s icon mineral material. Ownership and ISLAND management of this important taonga (treasure) has been vested in Te R nanga o Ng i Tahu as part of a S. C. Cox &D.J.A.Barrell Treaty of Waitangi settlement process. Increasing GNS Science, Private Bag 1930, Dunedin. demand from the tourist, jewellery, fashion and (s.cox*gns.cri.nz) sculpture industries, as well as cultural renaissance, has placed pressure on the pounamu resource. This A revised 1:250 000 geology map of the central had led to nephrite importation, allegations that South Island, QMAP Aoraki, is in the final stages foreign material is being marketed falsely as New of compilation and nearing publication. Aoraki is Zealand pounamu, and wider concerns over the the only South Island QMAP sheet that spans from

50thKaikoura05 -18- Kaikoura 2005 offshore west coast to offshore east coast. It Southern Alps lack of evidence of activity, rather overlaps in part with the original 1:250 000 Mt than showing evidence of inactivity. Cook, Hokitika, Hurunui & Christchurch geology POSTER maps compiled in the 1960s (Gair 1967, Warren 1967, Gregg 1964, Suggate 1972). Aoraki’s improvements over the earlier maps include the LATE CRETACEOUS EUSTASY AND THE detail of greywacke and schist mapping, more EAST COAST BASIN - THE GOOD NEWS! extensive mapping of Quaternary deposits in hill and mountain country, and the recognition and James S. Crampton1,PoulSchiøler2 & detail of numerous new faults and folds, many Lucia Roncaglia3 demonstrably active. As with other QMAPs, the 1Institute of Geological & Nuclear Sciences, PO primary emphasis is compilation of existing data, Box 30368, Lower Hutt. from published (e.g. maps, papers) and unpublished 2Geol. Surv. Denmark & Greenland, Ø. Voldgade (e.g. reports, theses) sources. Additional mapping 10, DK-1350 Copenhagen, Denmark. as part of QMAP aimed to fill data gaps, ensure 3Danish Oil & Natural Gas A/S, Agern Alle 24-26, uniform levels of data detail, or resolve major DK-2970 Hørsholm, Denmark. conflicts of interpretation. The map has been (j.crampton*gns.cri.nz) compiled at 1:50 000 scale into a Geographic Information System (GIS), but with sufficient Distinguishing tectonic from supposedly eustatic generalisation for legible presentation at 1:250 000 Upper Cretaceous sequences is highly problematic scale. for New Zealand successions that are structurally New mapping has added much improved and/or stratigraphically complex and remote from understanding of the Rakaia (Torlesse) terrane. well-studied Northern Hemisphere localities. The Greywacke/schist mapping emphasises textural problem is largely one of resolution in zonation (t.z.) rather than the mineral zonation chronostratigraphic correlation, and conclusions (chlorite, biotite, garnet) of the earlier maps, may vary depending on philosophies and although the new map also depicts mineral approaches to correlation. A complementary study isograds. Alpine schist fabrics and isograds vary (Schiøler et al., this volume), based on palynofacies considerably along the plate boundary, and schist analysis and zonal correlations, found little units are not parallel to the Alpine Fault. Bedding evidence for Late Cretaceous eustatic signatures in trends in t.z.1 greywacke are emphasised with the East Coast Basin. Here we take a different formlines. A regional swing in bedding strike (from approach that employs multidimensional graphic 320° to 030°) commences around 60 km SE of the correlation using constrained optimization Alpine Fault, mimicking the oroclinal bend of (CONOP) to derive a high-resolution correlation Mesozoic terranes in the southern South Island. for 15 Coniacian-Maastrichtian sections in the East Bedding faces mainly west or southwest, with Coast Basin. The resulting composite section, based locally eastward-facing, overturned, sections up to on 398 well-constrained lowest- or highest- 10 km thick. Steeply plunging folds become occurrence bioevents, yields 183 event levels and progressively tighter and with shorter wavelength an average chronostratigraphic resolution of approaching the Alpine Fault. En echelon approximately 142 Kyr. The age of the composite is northeast-striking, reverse-dextral oblique-slip calibrated using seven dated bioevents; two of these faults dipping 40-60° NW are common in the events are tied to geochemical or paleomagnetic central Southern Alps. Steeply plunging folds are datums. transected, overthrust and rotated by late Cenozoic CONOP cannot resolve unconformities that occur displacement on these faults. across all sampled sections. We suggest, however, Relatively few changes have been made to the that such unconformities are represented by large mapping of Cretaceous to Pliocene sediments, a event-clusters at single composite levels, and 13 tribute to the quality of Cenozoic stratigraphy and such event-clusters are identified. Of these, 10 lie paleontology in the 1960s. However, the QMAP within hiatus intervals recorded from the New Aoraki units and legend contain more Jersey coastal plain and interpreted as eustatic lithostratigraphic information, reflecting the sequence boundaries; the probability of this Cretaceous-Cenozoic transgression and regression coincidence arising by chance alone is c. 8%. in more detail than on the earlier maps. Quaternary Although provisional, these results suggest that map units on QMAP Aoraki include scree, high resolution quantitative stratigraphy can colluvium & landslide debris, in addition to the provide a potent tool for the resolution and global glacial and fluvial deposits emphasised by earlier correlation of stratigraphic sequences. Furthermore, maps. Faults and folds are depicted as active only our findings add support for recent studies that have where there is good geomorphic evidence of late argued for the presence of Late Cretaceous eustatic Quaternary deformation. Other structures, sea-level changes. particularly those outcropping in the mountainous

50thKaikoura05 -19- Kaikoura 2005 occurrence of black shales and a hydrocarbon source rock interval. Did a similar event occur in New Zealand? Hydrocarbon generation modelling (Field & Uruski et al. 1997) suggests there was generation of hydrocarbons from mid-Cretaceous rocks on the East Coast North Island, but we do not know specifically what the sources for these hydrocarbons were. Crampton et al. (2001) placed the CTB within the Arowhanan Stage at Mangaotane Stream, Raukumara Peninsula. The Mangaotane section of grey, red and green mudstones, with minor sandstones, was re-collected in detail for the present study and samples were analysed for carbon isotopes and total organic carbon (TOC). A carbon isotope signature consistent with that at the CTB in other parts of the world was found within the Arowhanan, but RockEval results indicate that the event at Mangaotane Stream did not produce high enough TOCs to form a good source rock. We cannot rule out the possibility that there are CTB black shales elsewhere on the East Coast or in the New Zealand region. The absence at Mangaotane Stream might be due to factors in its local setting such as rate of terrigenous input, paleobathymetry or oceanic paleocurrents. Our results confirm the correlation of the Arowhanan with the CTB (Cooper 2004), provide a SW Pacific datapoint for modellers of Cretaceous paleoclimates, and indicates that the CTB event in New Zealand was, at least in detail, different to that at classic Northern Hemisphere sections.

Crampton, J.S., Raine, I., Strong, P., Wilson, G. 2001: Integrated biostratigraphy of the Raukumara Series Inferred U. Cretaceous eustatic unconformities (Cenomanian-Coniacian) at Mangaotane Stream, (shaded) and sequence boundaries, and significant Raukumara Peninsula, New Zealand. New Zealand event-clusters in the East Coast Basin: filled Journal of Geology and Geophysics 44: 365-389. triangles = clusters that coincide with New Jersey Cooper, R.A. (ed.), 2004: The New Zealand Geological unconformities; open triangles = clusters that do Timescale. Institute of Geological and Nuclear not. Sciences Monograph 22, 284pp. ORAL Field, B.D., Uruski, C.I., and others, 1997: Cretaceous- Cenozoic geology and petroleum systems of the East Coast Region, New Zealand. Institute of Geological WHERE IS THE CENOMANIAN-TURONIAN and Nuclear Sciences Monograph 19. 301pp. BOUNDARY IN NEW ZEALAND, AND IS POSTER THERE A HYDROCARBON SOURCE ROCK ASSOCIATED WITH IT? CHRONIC HEALTH IMPACT OF FLUORIDE J. Crampton1,B.Field1 & T. Hasegawa2 DUE TO VOLCANIC DEGASSING ON 1GNS Science, Box 30368, Lower Hutt, New AMBRYM, VANUATU Zealand 1 1 2 2Department of Earth Sciences, Faculty of Science, R. Crimp ,S.Cronin,D.Charley, 3 4 Kanazawa University, Kakuma-machi, Kanazawa C. Oppenheimer &P.Bani 1 920-1192, Japan Institute of Natural Resources, Massey University, (j.crampton*gns.cri.nz) Palmerston North, New Zealand 2Department of Geology, Mines & Water Resources, Port Vila, Vanuatu. An oceanic anoxic event around the time of the 3 Cenomanian-Turonian boundary (CTB) in many Department of Geography, University of parts of the world resulted in widespread Cambridge, Cambridge, United Kingdom

50thKaikoura05 -20- Kaikoura 2005 4Institut de Recherche pour le Développement, significance for researchers investigating the risks Noumea, New Caledonia associated with possible prolonged degassing of (r.j.crimp*massey.ac.nz) any of New Zealand’s Central North Island volcanoes. Fluoride is a common constituent of volcanic ash ORAL and has been implicated in human and animal morbidity and mortality, for example the Laki Fissure eruptions in Iceland (1783-1784, 1947, and WHERE ARE THE GIANT TUFF CONE AND 1970). The 1995-1996 Ruapehu eruptions also IGNIMBRITES OF AMBRYM? A MORE resulted in thousands of sheep deaths which CONVENTIONAL STORY OF MAFIC similarlywereattributedtoacutefluoride VOLCANISM AT AMRBYM VOLCANO, poisoning. VANUATU. The island volcano Ambrym has several open vents, including Marum and Benbow, within a Shane J. Cronin & Károly Németh centrally-located caldera. These have been semi- Massey University, Institute of Natural Resources, continuously active for at least two to three hundred PO Box 11 222, Palmerston North, NZ years. The predominant southeast trade winds (S.J.Cronin*massey.ac.nz) direct volcanic plumes toward the west where the majority of the population of over 9000 resides. Ambrym is located in the central part of the Wind variability, particularly during the cyclone Vanuatu volcanic arc and forms a triangular shaped season, ensures that no area of Ambrym is entirely island around 60 km long on its NE-SW axis. The immune from volcanic emissions. NW-SE oriented rift zone accommodates most of In January 2005, the Ambrym plume was emitting the historic eruptions from this arc-basaltic volcano and a series of older overlapping edifices make up SO2 at 14 000 - 20 000 tonnes/day, with a fluoride output estimated to be up to 1 100 tonnes/day. The the northern portion. A 12 km-wide caldera continuous degassing from Ambrym’s vents leads dominates the centre of the island, containing two to acid rain and ash fall causing damage to food active tuff/scoria cones (Benbow, Marum) and crops and vegetation. In terms of acute human many smaller open vents. Semi-continuous ash falls health impacts, respiratory and gastric symptoms and periodic lava flows inundate the caldera and are commonly reported following particularly choke stream networks down-slope with intense periods of activity. This study focuses on remobilised pyroclastics. Since the mid 90’s the chronic human health impacts that prolonged Ambrym has been regarded as a type-locality for a exposure to volcanogenic fluoride may have on the “giant tuff cone”, that formed by enormous local population. phreatomagmatic eruptions, which accompanied disruption of an edifice to form the large caldera. The plume fluoride appears to be very efficiently This theory, however, is entirely built on field scavenged by rainfall, which the island residents observations of a layer-cake stratigraphy collect for drinking and cooking purposes. constructed from a mosaic of sections. Current field Drinking water samples collected in January 2005 studies revisiting these sites and others, show that typically contained between 3-10 ppm F, with this mosaic is false, and many of the sections streams, shallow ground wells and coconuts having cannot possibly be related to one another either similarly high F contents. To put this in genetically or chronologically. Our studies indicate perspective, the World Health Organisation that the island is a composite structure, formed of recommends < 1.0 ppm F in the drinking water of many generations of coalescing monogenetic populations living in tropical environments. volcanic fields. The type localities of the “giant tuff In humans, ingested fluoride is deposited primarily cone” (dacitic) pycroclastic flow deposits in the in bones and teeth. Dental fluorosis – evidenced by northern shoreline of the island we interpret to be white or brown discolouration of teeth - is the first either (1) mafic phreatomagmatic fall and surge visible sign of over-exposure to fluoride and occurs sequences (in places hydrothermally altered) or in where levels of fluoride in drinking water are 1-2 other cases (2) stacks of lahar and fluvial sediment ppm. The Dean’s Index is a visual scale for the derived from the caldera outflow and forming classification of fluorosis and was used to assess valley-fills. These successions are typical of many over 250 children in West Ambrym. Of these new sites described around the volcano which children, 53% and 8% respectively, fell into the two imply several generations of a frequently active highest categories of Moderate and Severe. The mafic volcano, with coalescing fields of lava, base- dental results and water analyses suggest that surge deposits and falls (often with accretionary skeletal fluorosis, a condition involving weakening lapilli), along with abundant deposits of fluvially of bones, which in its severest form is crippling, is reworked pyroclastics. There is no evidence for a a potential health issue. As fluorosis has been climactic (or for that matter dacitic) explosive linked with Ruapehu’s eruptions, this study is of caldera-forming event, which concurs with

50thKaikoura05 -21- Kaikoura 2005 investigations in the 60’s and 70’s. The active providing an opportunity to document biological central vents shows a combination of and sedimentological response to climatic changes prheatomagmatic to magmatic explosive and in a proximal setting during the Paleocene to effusive events that are seemingly strongly Middle Eocene (~65–46 Ma). controlled by the hydrogeology and architecture of From the mid-Waipara River Section, a detailed the island. Marum and Benbow are well-developed suite of 265 samples has been collected from tuff cones with deep and complex craters, where pit Paleocene, Paleocene/Eocene boundary, and Early crater formation as well as phreatomagmatic to Middle Eocene successions of the Conway and explosive eruption induced crater subsidence play a Loburn Formations, Waipara Greensand and major role in their formation. Flank eruptions Ashley Mudstone. All samples are incorporated in a forming monogenetic fields commonly started with detailed tape and compass survey map, and the central eruptions such as in 1913, suggesting a collections are documented in six lithologic strong coupling mechanism of central and flank columns that represent a geographic and eruptions. Magma rise in the centre of the island, stratigraphic progression from the westernmost followed by intense degassing and drainage of (oldest) to the easternmost (youngest) location degassed magma along lateral dykes is inferred by (Morgans et al., 2005). Integrated studies of us to be the major means by which the central 12- sedimentology, foraminifera, dinoflagellate cysts, km wide caldera slowly formed. This caldera calcareous nannofossils, spores/pollen, and carbon formed over a long-term stable shallow magma isotopes are being completed. storage system. Hence we suggest, that the theory Biostratigraphic results suggest the top of the of the “giant tuff cone” is not necessary to explain Conway Formation youngs in an eastward direction the volcaniclastic facies associations of Ambrym, from uppermost Cretaceous in the Waipara South and the formation of its caldera. This volcano Branch section to lower Paleocene in the mid- should hence never be used as a comparative Waipara River section. A near-complete ~120 m example for large-scale explosive thick Paleocene record is sampled, with diverse phreatomagmatism – as has been done on several calcareous and organic-walled microfossil occasions since the mid 90’s. This conclusion also assemblages in the Early and early Late Paleocene. highlights that the volcanic hazard of Ambrym is Calcareous faunas are absent throughout most of rather dominated by the potential interaction of the Waipara Greensand (Late Paleocene) and age magma and water along the NW and SE rift edge control is primarily from dinoflagellate cysts. Initial and the style of eruptions in the central vent rather bulk organic 13C isotope results suggest the late than potential major caldera forming events that Paleocene carbon isotope maximum (~59.5–56 Ma) may disrupt the island and impact upon the region. is present in the upper Waipara Greensand ORAL (Stormont Member), along with a geochemical signature that is characteristic of the Waipawa (Black Shale) Formation. The Paleocene/Eocene EARLY PALEOGENE BIOSTRATIGRAPHIC boundary, or initial Eocene thermal maximum (~55 RECORD FROM THE NERITIC MID- Ma), is tentatively recognised in the uppermost WAIPARA RIVER SECTION, NORTH Waipara Greensand, however further palynological CANTERBURY and 13C isotope analyses are needed. While continuous in-situ earliest Eocene (Waipawan) E. M. Crouch, H.E.G. Morgans, B.D. Field, sediments are not presently exposed, a detailed C.M.Jones,J.I.Raine,C.P.Strong& Early to Middle Eocene (Mangaorapan– G.J. Wilson Heretaungan) Ashley Mudstone record indicates GNS Science, PO Box 30368, Lower Hutt most of the Early Eocene climatic optimum (~53– (e.crouch*gns.cri.nz) 50 Ma) is represented. Detailed studies of early Paleogene South Pacific sedimentary records are limited, but are critical in Morgans, H.E.G., Jones, C.M., Crouch, E.M., et al., providing proxy data for validating general 2005: Upper Cretaceous to Eocene stratigraphy and circulation models and understanding natural sample collections, mid-Waipara River Section, North Canterbury. Institute of Geological and Nuclear processes that led to major perturbations in carbon Sciences science report 2003/08. 101 p. cycling and global climate. Some of the most complete South Pacific early Paleogene records are ORAL from distal pelagic successions in the Clarence Valley, Marlborough, but corresponding well- exposed records from proximal settings are currently limited. The mid-Waipara River Section, North Canterbury, has a well-exposed and near continuous early Paleogene shelf succession,

50thKaikoura05 -22- Kaikoura 2005 VEGETATION AND CLIMATE CHANGE AT assemblages examined. A Late Paleocene sample THE PALEOCENE-EOCENE TRANSITION contains common gymnosperms and appears to be terrestrial, although marine dinocysts have E.M. Crouch, J.I. Raine & E.M. Kennedy previously been recorded from a similar horizon. GNS Science, PO Box 30368 Lower Hutt. Above this, a prominent ~3 m grey mudstone (e.crouch*gns.cri.nz) contains abundant cysts of the marine dinoflagellate genus Apectodinium, indicating an early Waipawan Plant microfossil (spore/pollen) assemblages from age. Marine conditions persist in the overlying New Zealand Paleocene–Eocene (P–E) sedimentary mudstone layers examined, with an uppermost sections show a general change from predominantly glauconitic sandstone unit containing dinocysts gymnosperm-rich Paleocene floras (zone PM3) to indicative of the Mangaorapan Stage. Pollen Casuarina-dominated angiosperm-rich floras in the indicative of warm climates are present by the early Early Eocene (zone MH1). Modern relatives of the Waipawan (prominent mudstone unit), and fossil plant taxa and vegetation analogues indicate Casuarina pollen (zone MH1) is abundant in the this change is related to significant climatic upper glauconitic sandstone unit. warming, although the precise timing and extent of POSTER more subtle vegetation change during the P–E transition remains poorly documented. Previous studies (e.g., Tawanui section, Hawkes Bay, and “100 KM PER MILLION YEARS” A Moeraki-Hampden section, Otago) suggest that the HIGHLY-DYNAMIC DEPOSITIONAL main vegetation change in the Paleocene–Eocene MODEL FOR LATE MIOCENE ROCKS IN occurred in the upper Waipawan Stage (earliest TARANAKI BASIN Eocene) and post-dated the significant climatic and carbon cycle perturbation at the P–E boundary (~55 Martin Crundwell &MalcolmArnot Ma). Plant microfossil records are currently being Geological and Nuclear Science Limited, PO Box studied from a silica-sand quarry at Mt Somers, 30-368, Lower Hutt, NZ South Canterbury, and in the Kumara-2 core, (m.crundwell*gns.cri.nz) central Westland, to elucidate the timing and scale of vegetation change during the P–E transition. New biostratigraphic dating techniques challenge Gymnosperm pollen and Proteaceae and small traditional exploration paradigms and suggest a triporate angiosperm pollen are abundant in the highly dynamic depositional model is more lower part of the Kumara-2 core (1739-50 m), and a appropriate for late Miocene rocks in Taranaki Late Paleocene age is suggested. Coastal marine Basin, with multiple deep-water sedimentary sediments are present from ~1733-38 m, with systems of considerable thickness, developed on abundant cysts of the marine dinoflagellate genus local geographic scales, over timescales of orbital Apectodinium recorded in the middle of this unit. proportions (40-100 kyr). Although the general Coincident with the base of the marine horizon, pattern and tempo of late Miocene sedimentation pollen indicative of warm climates (e.g., are clearly dictated by climate forcing, suborbital- Cupanieidites orthoteichus, Spinizonocolpites scale variations in sedimentary patterns and rates of prominatus) are first recognised and become a deposition reflect a complex history of shelf recognisable component of the spore/pollen progradation, tempered by sediment supply and assemblage. Spores/pollen are absent from a accommodation, and tectonic controls within and channel fill sand at 1722-33 m, but above this unit adjacent to the basin. The observed dynamism in the assemblage is diverse, angiosperm pollen are sedimentation is consistent with the tectonic abundant and Casuarina pollen (zone MH1) development of the eastern Taranaki Basin margin markedly increase in the upper part of the studied (e.g. King and Thrasher, 1996), and with detailed core. Abundant Apectodinium dinocysts in the outcrop based stratigraphic studies undertaken by coastal marine unit suggests this interval lies very GNS (e.g. King et al., 1993; Browne and Slatt, close to the P–E boundary, and it appears this 2002), and also with many of the problems marine incursion may be related to a thermal associated with hydrocarbon reservoir sequences expansion of ocean waters and slight sea-level rise (e.g. poor correlation and dating, rapid facies at the time of extreme warming at the P–E variations, and variable reservoir characteristics). boundary. Compound-specific organic carbon In this presentation, we outline some of the new isotope analyses are currently being completed to biostratigraphic tools that have been developed confirm the presence and position of the P–E specifically to address correlation problems boundary. associated with late Miocene rocks in Taranaki Within the sand dominated Broken River Basin. Examples from Pukearuhe-1 and outcrop Formation-Homebush Sandstone section at Mt studies are given, of extremely high estimated rates Somers, fine-grained mudstone layers were of sedimentation, based on weight standardized sampled where possible and palynomorph counts of planktic and benthic foraminifers,

50thKaikoura05 -23- Kaikoura 2005 millennial scale dating of deep-water sediments, normalising terrain areas to a standard area unit of using a non-linear age interpolation method, and 10,000 km2. facies analysis, based on minimum paleodepth data. Comparison of the relative landslide When applied in combination, the new magnitude/frequency curves shows an order of biostratigraphic tools provide a robust temporal and magnitude difference in the rate at which landslides paleoenvironmental framework that enables the occur in the lowest and highest hazard terrains. temporal and spatial relationships of late Miocene The relative landslide magnitude/frequency curves depositional systems to be interrogated at a level of determined for each terrain allow probabilistic resolution similar to seismic. Although developed landslide hazard maps for New Zealand to be for late Miocene depositional systems in Taranaki generated. Probabilistic landslide hazard maps for Basin, the new biostratigraphic tools can be applied New Zealand are used to show either the largest to late Miocene rocks in most New Zealand landslide that is expected to occur in a given terrain sedimentary basins, and the methodologies adapted for a stipulated time interval (e.g. 100 or 475 years) for other stratigraphic intervals. or alternatively the return period for a stipulated 3 3 ORAL landslide-area (e.g. 10,000 m ; 100,000 m or 1,000,000 m3).

A PROBABILISTIC LANDSLIDE HAZARD ORAL MODEL FOR NEW ZEALAND THE VOLCANOLOGY AND 1 1 1 G.D. Dellow , M.J. McSaveney ,M.W.Stirling GEOCHEMISTRY OF THE 13.8 – 22.5 KA 1 & K.R. Berryman ROTOAIRA ERUPTIVE SEQUENCE, 1 GNS Science, PO Box 30-368, Lower Hutt, New TONGARIRO VOLCANIC CENTRE, NEW Zealand. ZEALAND (g.dellow*gns.cri.nz) Louise R. Doyle1, Phil Shane1 &IanNairn2 A probabilistic landslide hazard model for New 1Department of Geology, University of Auckland Zealand has been developed, by producing 245 Summit Road, Rotorua landslide-area magnitude/frequency curves. (l.fowler*auckland.ac.nz) Calibrating the magnitude/ frequency curves using landslide catalogue data allows the absolute and This study focuses on the 13.8 – 22.5 ka Rotoaira relative frequency of landslide-areas of a stipulated eruptive sequence, the youngest of which is the magnitude or in a stipulated time interval to be Rotoaira Lapilli (13.8 ka). Three units make up the determined for a selected terrain. distal deposits of the Rotoaira eruptive sequence, Landslide-area data for New Zealand have been Tongariro Volcanic Centre, and are bracketed by subdivided into landslide terrains based on geology, the rhyolitic 11.9 ka Waiohau and 22.5 ka Oruanui slope angle and landslide density. For each tephras. Rerewhakaaitu tephra (14.7 ka) lies landslide terrain the landslide-area data (from an between the youngest and the middle deposit of the inventory of New Zealand landslides) is plotted as a Rotoaira sequence. All three units are separated by magnitude/frequency curve in log/log space. The paleosols. Glass, mineral and whole rock slope of the magnitude/frequency curve in log/log geochemistry has been carried out on lapilli-sized space approximates a straight line for the larger pumices from the distal, medial and proximal magnitude landslide-area data in each terrain. The deposits of the three units of the Rotoaira eruptive slope of the magnitude/frequency curve varies for sequence. Each unit has a distinct geochemical different terrains indicating that the landslide composition. Glass data indicate many of the clasts hazard varies across the different terrains. The are heterogeneous and each eruptive episode has a slopes of the magnitude/frequency curves for the wide range in SiO2 (58-78 wt %) and K2O (1.6-4.0 New Zealand landslide terrains range from 1.25 to wt %) composition suggesting magma mingling. 2.94 and are similar to the range of values reported Disequilibrium features in thin sections are further in the literature for landslide magnitude/frequency evidence of magma mingling. Temporal variations data (1.75-3.30). in composition are apparent. The oldest deposit of The magnitude/frequency curves are calibrated with the eruption sequence (PR1) is less evolved than respect to time using a nine-year catalogue of the younger deposits (SiO2=62 wt %), the middle landslide occurrences in New Zealand. This allows deposit (PR2) has SiO2=66wt%andthefinal the absolute landslide-area magnitude/frequency eruption deposit has bimodal chemistry of SiO2=64 curve for each terrain to be determined. To directly wt % and SiO2=71 wt %. Temporal variations are compare the landslide magnitude/frequency curves also evident within the youngest deposit of the in each of the terrains, we calculate the relative eruption sequence (PR3). The oldest stratigraphic landslide magnitude/frequency curves by layer has SiO2=69 wt %, the middle layer has an increased SiO2 composition (SiO2=72 wt %) with a

50thKaikoura05 -24- Kaikoura 2005 wider range. The youngest layer has a bimodal volcaniclastic, metagreywacke sandstones and composition with distinct modes at SiO2=64 wt % siltstones (Western Terrane Group) offshore from and SiO2=73 wt%. This may indicate several small continental Gondwana. Cretaceous crinoids occur pockets of magma were being sequentially tapped in basement cover rocks in North, South, and Pitt during the eruption. Individual clasts from two of Islands. Early Triassic Nelsonian and Malakovian the three eruptions contain compositions similar to Holocrinus is the sole survivor of the Permian- Taupo Volcanic Zone rhyolites. This could imply Triassic extinction event, recorded only from the that bodies of rhyolitic magma resided farther south Murihiku Terrane. Etalian taxa include Tethyan than the existing calderas. Fe-Ti oxides Dadocrinus, and endemic Maoricrinites; demonstrate a wide range of temperatures (787- Aoteacrinus occurs in both the Murihiku and 1194°C) and oxygen fugacities (NNO-0.98 to Rakaia Terranes. The Middle to Late Triassic +0.98). All three eruptions show a range in sustained a great biodiversity of benthic genera temperature and the thermal variability is consistent including Tethyan Holocrinus, Tollmannicrinus, with the geochemical variability. Whole rock data Encrinus, Tyrolecrinus, Silesiacrinus, have been used to compare the Rotoaira eruptive Angulocrinus, Eckicrinus, Singularicrinus, sequence to other eruptions from Tongariro as well Chelocrinus,thecomatulidParacomatula,and as eruptions from Ruapehu. The data show that the cosmopolitan Seirocrinus and Isocrinus, variously Rotoaira sequence is more Mg- and Fe-rich than co-occurring in Southland, Catlins, Nelson, and younger Tongariro eruptions. Correlation between Awakino facies of the Murihiku Terrane. The distal, medial and proximal deposits has been Triassic-Jurassic second order extinction event was attempted using glass geochemistry to fingerprint the last to impact greatly upon the evolution of New the deposits in order to determine the vent location. Zealand crinoid taxa, decimating populations, but The data suggest that North Crater is the source of appears favourably disposed towards the Isocrinida. at least one episode of the Rotoaira eruptive Jurassic Tethyan migration is exemplified by sequence, located on the northern side of Tongariro benthic Apsidocrinus, Chariocrinus, Hispidocrinus, massif. North Crater is also suspected to be the and dominant cosmopolitan pseudo-pelagic source vent for other two eruptions in the Rotoaira Pentacrinites,andSeirocrinus occurring only in the sequence. Murihiku Terrane. These and a new genus are radiated remnants of a depleted biodiversity. ORAL Anomalous to the ongoing re-colonisation of New Zealand by larval dispersion is that cosmopolitan MORPHING IN AND OUT AND ROUND- sessile millericrinids are almost non-existent. ABOUT Cretaceous Austral Province benthic Eugenicrinites, Bourgueticrinus, Dunnicrinus, Michael K. Eagle Apiocrinites, Austinocrinus, Balanocrinus, Geology Department, University of Auckland, Isselicrinus, Neilsenicrinus,comatulidSemiometra, Private Bag 92019, Auckland. and pelagic Poecilocrinus demonstrate a continued Natural History Department, Auckland Museum, incursion of Tethyan, and later cosmopolitan Private Bag 92018, Auckland. faunas. (meagle*auckland.ac.nz) The K/T extinction event had little immediate impact upon genera, with Apiocrinites, Isselicrinus, The biodiversity and paleobiogeography of New Neilsenicrinus,andIsocrinus transcending the Zealand and New Caledonian Mesozoic crinoids boundary. A main Tertiary evolutionary thrust involve gradual change of species over time, involving isocrinids, bourgueticrinids, migratory larvae, and an ability to occupy many millericrinids and comatulids radiated from marine niches. New Zealand Mesozoic crinoid Cretaceous and Palaeocene genera to occupy New remains are preserved rarely as calcite or ferric Zealand waters today. Extant members of the morphs, mainly as leached-out external moulds – Crinoidea have remained virtually unchanged in nearly always as disarticulated elements, mainly general overall structure and morphology. Extant columnals. Post-Palaeozoic columnals are generally species are not an ancient remnant, but the straightforwardtoclassifywithina‘natural’ consequence of many ‘revival’ episodes over time. taxonomic system to family, genus, and not uncommonly, species level (due to limited ORAL morphological diversity), or as “morphospecies”. Triassic crinoids occur in both the Rakaia and Murihiku Terranes of North and South Islands in neritic volcarenite sequences deposited at different times in fore-arc basins within an island arc. Jurassic crinoids are confined to the Murihiku Terrane of both islands, in an accretionary prism of

50thKaikoura05 -25- Kaikoura 2005 STRUCTURAL GEOLOGY AND common and evenly distributed between the GEODYNAMIC MODELING OF LINKING Wairau and Awatere faults, less abundant between FAULTS IN THE MARLBOROUGH FAULT the Awatere and Clarence faults and rare between ZONE, SOUTH ISLAND, NEW ZEALAND the Clarence and Hope faults; 4) NE striking fractures and faults parallel to the main J.D. Eusden1,P.O.Koons2,J.R.Pettinga3 Marlborough Faults decrease in number from the &P.Upton1&2 Wairau to the Hope fault; 5) a roughly N striking 1Dept. of Geology, Bates College, Lewiston, pivot or hinge zone delineates a strike change from Maine, U.S. 080° (translational) to 065° (transpressional) for 2Dept. of Geological Sciences, University of Maine, the main Marlborough faults; 6) this pivot zone is Orono, Maine, U.S. marked by at least two diamond-shaped fault- 3Dept. of Geological Sciences, Canterbury bounded blocks up to 40 km in length; 7) one block University, Christchurch, New Zealand is bounded by the Clarence-Eliot faults with (deusden*bates.edu) another somewhat less well defined block between the Clarence and Awatere faults; 8) west of the We present the preliminary results of a combined pivot zone the cross faults are topographically field-based and 3-d geodynamic modeling study on entrenched and connect between the main cross faults that link the major faults in the Marlborough faults whereas east of the pivot they Marlborough Fault Zone, South Island. Our goal is are shorter, discontinuous and have subdued to understand the kinematic mechanisms for geomorphic expression. transfer of strain between the main dextral oblique- POSTER slip structures, which are, from northwest to southeast, the Wairau, Awatere, Clarence, Elliot and Hope Faults. There has been a gradual temporal A SEISMIC-GRAVITY STUDY OF THE southeastward migration in the loci of strike-slip SOUTHEASTERN BOUNDARY OF THE displacement across these faults in the late WANGANUI BASIN Quaternary, with the Hope Fault currently carrying the highest slip rates. This is a response to the Erik Ewig , Tim Stern & Kiran Hudson southeastward development of the Marlborough School of Earth Sciences,Victoria University of Fault System over time. Wellington, PO.Box 600 Wellington (erik.ewig*vuw.ac.nz) We have combined lineament analyses on DEMs and air photographs with structural measurement in Located between the axial ranges of the North the field to unravel the structural geology, fault Island and the south Taranaki Basin, the Wanganui kinematics and tectonic geomorphology of the Basin is a region of broad crustal down-warp with Marlborough Fault Zone. The 3-d modeling will allow for an integration of the surface and predominantly reverse faulting. The Basin is of subsurface structures to depths of circa 30 km. This Pliocene-Pleistocene age, with sediments directly over Mesozoic basement. Sediments in the basin study will reveal the nature of strain partitioning in dip gently towards a central depocentre and are cut the Marlborough Fault Zone as well as plate-scale by NE-NNE-trending faults that are generally interactions between the strongly coupled downthrown towards the centre of the basin. The overriding Australian and subducting Pacific plates. depocenter of this basin has migrated south- The active cross faults dissect the regions between southwest with time, driven at least in part by the the main Marlborough faults into large uplifted Quaternary uplift and doming of the central North blocks. Kinematic mechanisms for the uplift Island. include: 1) block rotation within a dextral-reverse Offshore, the basin has been surveyed with a duplex where opposite corners of the duplex will number of oil industry and CRI-funded undergo either extension/collapse or multichannel seismic surveys. Onshore, the basin is collision/thrusting; or 2) up-dip partitioning along known only from scattered geophysical surveys and the main Marlborough faults which at the free a few exploration wells. Part of this study is surface are dominated by dextral strike-slip motion directed to learn about the southeastern corner of but in the hanging wall are a product of distributed the Wanganui Basin and the transition to the reverse oblique slip displacement. Tararua Ranges. We report three new active-source DEM and air photograph analyses show the seismic lines and three reprocessed existing active following: 1) north striking cross faults up to 40 km source seismic lines. All these lines show clear in length extend between the main Marlborough evidence of faulting. The majority of the faults are faults and have a sigmoidal S-shape indicating that high angle reverse faults. Because of the rapid they have been affected by dextral shear; 2) NNE deposition of sediments, and shifting sand dunes, striking fractures and faults are parallel to bedding these active to recently active faults could be form lines in the Torlesse; 3) these fractures are classified as blind thrusts. However, there are also a

50thKaikoura05 -26- Kaikoura 2005 few normal faults visible especially in the coastal encompasses that in which the Waipawa Formation Levin area. The reverse faults agree well with the was deposited, the distinctive geochemical notion of crustal downwarp in a region of signature of the formation is not evident in any of geodetically-determined, mild compression. Three the quarry samples. Despite an oily smell and possible explanations for the normal faults are a) a sulphurous efflorescence, all samples have low local second order effect due to dextral strike slip TOC and light bulk 13C values (less than 1% and - motion along the major faults, b) tensional forces 26‰, respectively). Based on these features, the have been or are still active in this area or c) entire sequence is correlated with the siliceous flexural bending stresses superimposed on an mudstone facies of the Whangai Formation. In overall compressive stress field. contrast, the typically high TOCs and heavy 13C We have started to create models to test for the values (> -24‰) of the Waipawa Formation are origin of the –150 mgal Bouguer/isostatic gravity found in petroliferous mudstone exposed in Black’s anomaly that dominates Wanganui Basin. The Quarry, 1.5 km to the east. Dinoflagellates confirm anomaly can only partially be explained by the a Paleocene age. Although a stratigraphic thickness sediment fill and it is one of the most compelling of 40 m is suggested, it is difficult to confirm due to geophysical observations in the Wanganui area, if poor bedding and numerous faults. The formation not the whole North Island. Initial 3D models show here is immature (Tmax 421–427 °C) and TOC and that the gravity anomaly associated with the basin HI values of 10–11% and 426–445 mg HC/g TOC, is generally consistent with a downwarp model of respectively, indicate good potential for both oil the entire crust. However, the downwarp of the and gas generation. At Whatuwhiwhi, the well- Moho has to be significantly greater than the bedded Haumurian–Teurian Waiari Formation downwarp of the sediment-basement interface to fit includes a lower chert-dominated facies and an the observed gravity anomaly. Hence we propose a upper mudstone-dominated facies. The former has a model of lithospheric shortening where thickening Whangai-type geochemical signature whereas the increases with depth. latter has a Waipawa-type geochemical signature. However, a lack of palynomorphs and almost POSTER completely exhausted petroleum potentials (S2 < 0.15 mg HC/g rock) indicate that the Waipawa-like WHAT SOURCE ROCK POTENTIAL DOES interval has been thermally altered by nearby THE WAIPAWA FORMATION HAVE Miocene intrusives to an extent that makes BEYOND THE EAST COAST BASIN? AN correlation with the Waipawa Formation uncertain. OUTCROP-BASED CASE STUDY FROM The heavy isotopic signature may be a result of this NORTHLAND thermal alteration. The results of this study indicate that good quality B.D. Field, C.J. Hollis, E.M. Crouch & R. Sykes Waipawa Formation source rock is likely to be GNS Science, PO Box 30 368, Lower Hutt present in the sedimentary succession offshore (b.field*gns.cri.nz) northeastern Northland. However, its thickness is uncertain and it is likely to grade laterally and The Paleocene Waipawa (Black Shale) Formation vertically into comparatively organic-lean siliceous is a known source of oil in the East Coast and north facies of the Whangai Formation. Seismic facies Taranaki basins. It is likely to be a significant mapping and paleoenvironmental reconstructions source rock in adjacent basins in Northland and are recommended to better define the extent and Canterbury and the Great South Basin. In order to quality of this important source rock. determine the extent and character of the formation POSTER in northern Northland, we studied Waipawa-like dark-grey mudstones exposed in Price’s and Black’s quarries in the allochthonous sequence at DISTRIBUTION AND SEISMIC Ohia, west of Taipa, and a shore platform exposure CHARACTERISATION OF GAS HYDRATES in the autochthonous sequence at Whatuwhiwhi, IN FIORDLAND, NEW ZEALAND Karikari Peninsula. The Ohia and Whatuwhiwhi exposures are inferred to record distal and proximal Fohrmann, Miko1; Gorman, Andrew R.1; deposition, respectively, off the northeastern Pecher, Ingo A.2, Jarvis, Kevin D. G.3 margin of Northland within the so-called North 1 Department of Geology, University of Otago, P.O. Slope Basin. Box 56, Dunedin, New Zealand 2 The quarry outcrops are highly deformed, making Institute of Geological & Nuclear Sciences (GNS), P.O. Box 30 368, Lower Hutt, New Zealand determination of stratigraphic orientation and 3 thickness difficult. Dinoflagellate biostratigraphy Fugro-Jason Australia, 69 Outram Street, West shows that the sequence in Price’s Quarry is Perth, WA 6005, Australia overturned and ranges in age from Late Cretaceous (fohmi830*student.otago.ac.nz) to late Paleocene. Although this age range

50thKaikoura05 -27- Kaikoura 2005 We have compiled the distribution of gas hydrates of the Chatham Rise, New Zealand, is being on the Fiordland margin based on the occurrence of examined. Ostracods are crustaceans in which the BSRs in an extensive database of seismic reflection softanatomyisencapsulatedinabivalved, data, acquired by academic, government and calcareous carapace. Valves of this microscopic petroleum research cruises over the last 30 years. organism are commonly preserved in deep-sea Bottom simulating reflections (BSRs) are thereby sediments and as result, ostracods present the most found in an area of approximately 2200 sq km on complete biogeographic and stratigraphic record of the continental slope south-west. Main any metazoan in the deep sea. This fact provides an characteristics of the BSRs include: opportunity to examine whether more complex, 1. predominately negative polarity compared to benthic deep-sea marine organisms were also the seafloor reflection, which infers to a affected by the extinction event and if so, to then decrease in acoustic impedance, provide an additional insight into what environmental factors led to the significant loss of 2. the reflections follow the morphology of the biodiversity. The results of this project will also seafloor, thereby crosscutting strata, and make a contribution to our understanding of 3. strong variations of amplitudes with offset ostracod diversification through time with (AVO), indicating the presence of free gas particular reference to significant Late Pliocene- below the reflection. In addition, the existence Pleistocene events described for bradleyinid and of free gas is supported by a reduced interval trachyleberid species especially from the Southern velocity distribution below the BSR, with Ocean. Significant problems relating to taxonomy velocity decreases of up to 30% compared to and taphonomy have and continue to hinder the overlaying layers. progress. Because seismic reflection data is the only available Samples studied are from the ODP core 1125 data source in the Fiordland region (other a priori located about 600km east of the South Island at information like well information is not available) a 1359 m depth on the northern side of the Chatham simultaneous AVO inversion algorithm is used to Rise. The samples are from the top of the core obtain rock property attributes of P-impedance, down to approximately 42 mbsf, covering the last vp/vs, and density, respectively. This information is 2.5 Ma, i.e. late Pliocene to Recent. There is a used to verify the quantities of gas hydrate and their significant variation between samples in terms of potential as a gas reserve in this region. grain size, ostracod population (total number of POSTER specimens and diversity) and the disproportionate number of juvenile valves. Some groups are well represented, including Bradleya, Taracythere, MID-PLEISTOCENE EXTINCTION OF Krithe and Apatihowella, which form the main DEEP-SEA OSTRACODA? cluster of target species for this project. The occurrence of Bradleya pygmaea in core 1125 F.J. Gaiger &K.Swanson (1359 m) is significant because it has been recorded Geological Sciences, University of Canterbury, in Pliocene abyssal/bathyal sediments elsewhere in Private Bag 4800, Christchurch the Southwest Pacific, and was also recovered in (fjg17*student.canterbury.ac.nz) uppermost Quaternary sediment from that Plateau. It is, however, no longer living on the Campbell The last identified global marine extinction event Plateau, which implies steepening thermal gradients (‘the Stilostomella extinction’) occurred about 600- and an associated shoaling as significant influences 900ka during the mid Pleistocene climate transition. on both the latitudinal and depth distribution of It is not only the most recent deep-sea extinction, Podocopid ostracods. but also least studied because recovery of sediments ORAL of that age and environment of deposition are still most effectively achieved by examination of relatively few, widely distributed cores. This extinction affected benthic foraminifera, in particular 82 species and 17 genera, including one complete family (Stilostomellidae – 21 species). A second family (Pleurostomellidae – 24 species) also suffered significant extinction, however two species of that group have been recovered in sediments which post-date the mid-Pleistocene event. In an attempt to determine whether benthic ostracods (Podocopida) have also been affected by the ‘Stilostomella event’ as an ongoing MSc thesis project, a single ODP core from the northern flank

50thKaikoura05 -28- Kaikoura 2005 TRACKING CRUSTAL DIFFERENTIATION al., 2003), this additional time could reasonably be AND ASSIMILATION PROCESSES AT ARC supposed to relate to a crustal process. Extremely VOLCANOES: A URANIUM SERIES good negative correlations between Sr and O ISOTOPE PERSPECTIVE isotopes are consistent with crustal assimilation of low 18O, hydrothermally-altered wallrocks. While R. George1,S.Turner1,R.Price2,C.Cook2 &B. the correlation between these two parameters and Finney3 (230Th/232Th) appears to be less coherent, it is 1GEMOC Key Centre, Earth and Planetary striking that these activity ratios broadly increase Sciences, Macquarie University, Sydney with increasing Sr isotope ratios and decreasing 2School of Science and Technology, University of 18O. The assimilant could therefore be Waikato, Private Bag 3105, Hamilton hydrothermally-altered arc crust of relatively recent 3Department of Earth Sciences, University of age of less than 100 kyr. Bristol, Queens Rd, Bristol, BS8 1RJ, UK ORAL (rgeorge*els.mq.edu.au)

Parent-daughter isotope systems that decay on time THE SURFACE IMAGE OF AN ACTIVELY scales appropriate to the rates of processes GROWING – INVERTED? – REVERSE themselves have proved powerful tools in tracking FAULT: THE OSTLER FAULT IN THE the histories of many arc-related processes from MACKENZIE BASIN (SOUTH ISLAND, NEW fluid release during plate subduction to dynamic ZEALAND) melting of the mantle wedge. However, the rates inferred for mantle processes can only be F. C. Ghisetti considered real if the effects of continental crustal Dept. of Geology, University of Otago, PO Box 56, interaction are demonstrably minimal. In order to Dunedin, New Zealand try and deconvolve mantle and crustal processes in (francesca.ghisetti*stonebow.otago.ac.nz) this context we consider two contrasting case studies. A reappraisal of the geometry and structural Ruapehu volcano, New Zealand:Onanequiline evolution of the Ostler fault within the Mackenzie diagram the Ruapehu samples form a subtle basin is under way. A new geological map of the positive array that extends from Taupo rhyolites fault zone (scale 1:50,000) is almost complete, and and is intermediate between them and Kermadec two seismic reflection lines across the fault will be lavas. It is conceivable from this data that a simple acquired by A. Gorman in the early months of 2006 model of mixing between mantle-derived melts and (Otago University Research Grant). The Ostler fault Taupo crustal melts may explain the Ruapehu is a 50 km long, N-S reverse fault, dipping 30º-50º disequilibria. However, other reservoirs may be W. Previous studies have documented the involved. For example, the range of calculated segmented nature of the fault, average rates of disequilibria derived from elemental Th/U ratios in deformation 1 mm/yr, and the occurrence of two averaged metasedimentary xenoliths, Torlesse and seismic events in the last 6 ka. According to Waipapa basement averages could also be involved. Kleffmann and Stern (in preparation) the Ostler Thus an alternative, although speculative, model is fault bounds the edge of a strong gravimetric that Ruapehu samples reflect melts sourced from gradient of residual Bouguer anomalies, with a the lower to middle crust (as sampled in the minimum < -200 µN/kg west of the fault. This xenolith suite), mixed with those generated at setting is interpreted in terms of a buried marine shallower levels (represented by Taupo-like Tertiary basin, controlled by earlier normal faults. magmas). Irrespective of the exact details of likely The deep geometry of the fault is largely components, the key aspect of these systematics is unresolved, but stratigraphic and structural features that for the first time, there is sufficient information revealed by surface mapping need to be considered available to show that an inclined array on the in any interpretation. equiline diagram for a single volcanic suite is A >1000 m thick sequence of terrestrial mudstones, unequivocally the product of open system siltstones and gravels (Pliocene?-Pleistocene?) is processes: mixing between mantle or lower to mid- exposed in the fault hanging wall only. Internal crustal melts and shallow upper crustal architecture reveals a growth geometry of beds components. tilted 30º-60º W, unconformably overlain by coarse Okmok volcano, Aleutian arc: At face value, 238U- gravels (120 ka?). Above, six orders of river 230Th disequilibria in young volcanics from Okmok terraces are preserved, with the three highest orders suggest time scales of 50 kyr or less for some correlating to the 35, 22-17 and 14 ka moraines. combination of mantle-crustal processes to take Terrace distribution indicates shifting of fault- place. Given good evidence in the arc as a whole transverse drainages, relatable to episodic uplift of for fluid transfer from the subducted plate to take the upthrown block during progressive northward less than 10 kyr to reach the arc volcano (George et propagation of segment ruptures in the late

50thKaikoura05 -29- Kaikoura 2005 Pleistocene-Holocene. The 22-17 ka terrace records The Revolver Pluton (Rp) of c.200 km2 is the on its carved surface the inversion of flow direction largest unit. It is a LoSY, coarse grained biotite (from east- to west-directed) of an early granite with distinctive pink alkali feldspar paleodrainage, forced by backtilting of the hanging megacrysts. LA-ICP-MS zircon U-Pb dating of Rp wall. The Ostler fault consists of sub-parallel, from Revolver Bay yields an age of 132.4 ± 1.0 splaying segments within a deformation zone up to Ma, in agreement with an unpublished TIMS zircon 2 km wide. Faults are marked by fresh scarps ( 20 age of Tulloch (reported in Mortimer at al., 1999). m high), which truncate suspended drainage Granodiorite from the northeast sector of Rp, here systems. N-S anticlinal deformation of the hanging named the Long Scarp Granodiorite (Lsg), gives a wall is traced by deformation of the 125 and 22-17 coeval age of 132.0 ± 0.9 Ma and may represent a ka terraces, with the fold crest truncated by systems marginal facies of Rp. Treble Mountain Granite of N-S, W-dipping normal faults. (Tmg, Turnbull, pers. com.) is a medium to coarse A preliminary interpretation that incorporates the grained biotite granite that intrudes Rp on the west surface geology and the available geophysical side of Isthmus Sound, and yields an age of 130.4 ± information is that the Ostler fault is a footwall 0.9 Ma. Tmg locally exhibits severe hydrothermal shortcut to an inverted normal fault that bounds the alteration and hosts epithermal base-metal vein eastern margin of a Mesozoic (?) - Tertiary basin mineralisation which was worked in the historic hidden below the thick Plio-Pleistocene cover. Tarawera Mine. Trevaccoon Diorite (Tdi, Turnbull, Compressional inversion of the early normal fault pers. com.) is a hornblende gabbro that outcrops and shortening of the basin infilling since Miocene along the western shore of Long Sound north of times has resulted in the progressive elevation of Lady Bay and has an age of 128.7 ± 1.0 Ma. A the fault hanging wall during deposition of the Plio- younger granite, here named Upper Blacklock Pleistocene terrestrial sequence, and in the Granite (Ubg), occurs between Rp and Lsg. Ubg is propagation of a number of reverse fault splays that petrographically similar to Rp, but can be cut the continental sequence at surface. This distinguished on the basis of its geochemistry and interpretation will be tested by the planned seismic age of 124.7 ± 1.0 Ma. Hornblende-rich HiSY profiles, adding to our understanding of diorite to gabbro, here named Only Island Diorite compressional deformation off the Alpine Fault. (Oid), outcrops south from Only Island where it intrudes Ubg. The composition and age of 122.1 ± ORAL 0.9 Ma of Oid suggest it is a higher level, unmetamorphosed equivalent of the Western EARLY CRETACEOUS UPPER CRUSTAL Fiordland Orthogneiss. MAGMATISM IN SOUTHWEST The presence of 15% inherited 149-136 Ma zircons FIORDLAND: GEOCHRONOLOGICAL AND in all units except Oid suggests a shared deeper GEOCHEMICAL HIGHLIGHTS source region comparable in age to Median Suite rocks dated by Muir et al. (1998) in eastern 18 M.R.Gollan1,J.M.Palin1,K.Faure2,&C.Harris3 Fiordland. Oxygen isotope values (whole rock O 18 1 Department of Geology, University of Otago, = 6-9, quartz O = 8-10) for all units other than P.O.Box 56, Dunedin, New Zealand Tmg are consistent with such a source and, together 2 Institute of Geological and Nuclear Sciences, with the rarity of older inherited zircons, limit P.O.Box 31 312, Lower Hutt contamination by the surrounding Ordovician 18 3 Geological Sciences, University of Cape Town, metasediments ( O whole rock = 12-18). Tmg 18 Rondebosch 7700, South Africa quartz and feldspar O are strongly depleted (malcolmgollan*ihug.co.nz) indicating that hydrothermal alteration was caused by circulation of meteoric water. This supports the Southwest Fiordland contains an important record interpretation that plutons in the region were of Early Cretaceous plutonism, which is not intruded at shallow crustal levels (<10 km). complicated by a polyphase metamorphic overprint as in central and northern Fiordland. Recent Mortimer et al. (1999) J. Afr. Earth Sci. 29: 257; Muir et mapping as part of the IGNS Qmap Fiordland al. (1998) J. Geol. Soc. London 155: 1037; Tulloch & programme (work in progress) has identified Kimbrough (2003) Geol. Soc. Am. Special Paper 374: multiple Paleozoic through Mesozoic plutons 275; Wood (1960) Sheet 27-Fiord, Geol. Map of NZ, composing the previously undivided Kakapo DSIR. Granite of Wood (1960) in southwest Fiordland ORAL (Turnbull, pers. com.). Field, petrographic, geochemical, and geochronologic data reveal a transition from early Cretaceous LoSY to HiSY magmatism (cf. Tulloch & Kimbrough 2003) in the area around Preservation Inlet.

50thKaikoura05 -30- Kaikoura 2005 EMPIRICAL SCALING RELATIONS FOR could be useful as a first-order approximation SEISMIC FAULTS of T. In case D is also known, T can be better estimatedbyusingrelation[1]. Álvaro González1, Javier B. Gómez1 2 & Amalio F. Pacheco Bilham, R. and Bodin, P. (1992) Science 258, 281-284. | 1Dept. de Ciencias de la Tierra. Universidad de Marrett, R. (1994) Geophys. Res. Lett. 21, 2637-2640. | Zaragoza. 50009 Zaragoza (Spain). Nicol, A. et al. (1997) Nature 390, 157-159. 2Dept. de Física Teórica y BIFI. Universidad de Nicol, A. et al. (2005) J. Struct. Geol. 27, 541-551. Zaragoza. 50009 Zaragoza (Spain). (Alvaro.Gonzalez*unizar.es) Turcotte, D. L. (1992) Fractals and Chaos in Geology and Geophysics. Cambridge Univ. Press. We are trying to clarify the scaling relations Villamor, P. and Berryman, K. R. (1999) Primer between several parameters of seismic faults: the congreso nacional de ingeniería sísmica, Murcia (Spain), vol. 1, 153-163. fault length (L), slip rate (S), recurrence interval of large earthquakes (T) and coseismic displacement Wallace, R. E. (1970) Geol. Soc. Am. Bull. 81, 2875- (D). To do this, we have compiled a data set of 2890. about 600 ground-breaking faults (extensional, Wesnousky, S. G. (1999) Bull. Seismol. Soc. Am. 89, compressional and strike-slip) from all continents. 1131-1137. For each fault, the parameters included in the ORAL database have not been estimated one from another. We have tested four relations proposed previously, and found a new one: PETROLOGY OF NEWLY DISCOVERED SUBMARINE VOLCANIC ROCKS FROM 1. Wallace (1970) suggested that T = D / (S – C), THE TONGA-KERMADEC ARC: INITIAL where C is the creep rate. This parameter is RESULTS frequently zero, and is rarely known. Excluding it, the relation becomes T D/S, Ian J. Graham1,IanE.M.Smith2, and holds for most faults for which T, D, and S Richard J. Arculus3 Susan McDonnell4 were available in our database. Cornel E.J. de Ronde1 &IanC.Wright5 2. The previous formulae suggest that T is 1 -1 Institute of Geological & Nuclear Sciences Ltd, proportional to S . This was previously PO Box 31-312, Lower Hutt, New Zealand verified for a smaller data set by Villamor and 2Auckland University, Private Bag 92019, Berryman (1999), and also holds in ours. Auckland, New Zealand 3. As previously found in smaller data sets 3Australian National University, Canberra, ACT (Bilham and Bodin, 1992; Nicol et al., 1997; 2601, Australia Wesnousky, 1999; Nicol et al., 2005), longer 4Department of Geology, Donovans Road, UCC, faults tend to have faster slip rates. In our Cork, Republic of Ireland composite data set, S is roughly proportional to 5National Institute of Water & Atmospheric L2. Research, PO Box 14901, Wellington, New 4. From relations [2] and [3], T should be Zealand roughly proportional to L-2, and our data show (i.graham*gns.cri.nz) that this is the case. This is important to seismic hazard assessment: it implies that The NZAPLUME III research cruise to the northern earthquakes on large faults can not only be Kermadec – southern Tonga arc during September- larger, but also more frequent, than those of October 2004 mapped and dredge-sampled eight short faults. Turcotte (1992) also proposed that newly discovered volcanic centres along the arc- T was proportional to a negative power of L, front, including Monowai, now known to have a although Marrett (1994) pointed out that this caldera complex immediately to the north of the power could be positive for large faults, and previously mapped cone. These centres, which Nicol et al. (2005) assumed that T and L do not typically include one or more calderas with correlate to each other, at least in extensional multiple associated volcanic cones, have an average faults. spacing of 47 km, slightly greater than the average spacing of 41 km for the entire Kermadec arc (i.e., 5. Finally, a new scaling relation has been found for the whole data set: S is proportional to the from Whakatane in the south to Monowai to the ratio L/T. Interestingly, this relation (as [1]) is north). All of the newly discovered volcanic centres dimensionally homogeneous (both its sides are show evidence of hydrothermal venting and, in the measured in the same units), and less scattered case of Monowai, recent eruptive activity. than relations [2] and [4], where T is also The dredged lavas have calc-alkaline compositions involved. Because L and S are among the ranging from high-alumina basalt to rhyolite, easiest parameters to determine, this relation confirming the occurrence of evolved lava

50thKaikoura05 -31- Kaikoura 2005 compositions associated with caldera structures times. Although sedimentation rate has increased along the entire Kermadec arc. Three of the there is no consistent trend towards increasing mud volcanic centres exhibit the full compositional or sand. In all sites, marine ostracods and infaunal range from basalt to rhyolite, three are basalt- bivalves were decimated in European times and andesite, and the remaining two entirely rhyolitic. largely disappear from the record, coincident with In contrast to published results for the southern increased abundance of large diatoms and Kermadec arc, there is no evidence for thecamoebians. The foraminiferal microfossil compositional bimodality, with the data set record is the most complete and documents a containing sub-equal proportions of basalt, basaltic progressive switch from calcareous-dominated andesite, andesite, dacite, rhyodacite and rhyolite. faunas to the agglutinate-dominated faunas of Despite the variety of volcanic edifices sampled, all today. of the volcanic centres yield tight geochemical All observed changes are similar to those correlations for major and trace elements, which are documented in transects passing from the marine interpreted to indicate simple mixing or environment up an estuary and suggest that fractionation processes. There is a suggestion, yet increased freshwater runoff from the mushrooming to be fully established with trace element or urban areas of Auckland city is the primary driver, isotopic modelling, that three of the four southern- not sediment or pollutants. This is further supported most centres, spanning some 200 km of arc-front, by the observation that changes occur during late are genetically related. Polynesian to early European times in the upper ORAL Waitemata Harbour, versus late European times (post 1950) in the Tamaki Estuary when impervious surfaces increase dramatically. If increased freshwater is indeed the culprit, carrying out remedial measures will be problematic.

Volcanic Latitude SiO2 wt% Centre °S ORAL Minimum Maximum Mean ‘V’ 25.19 47 69 57.4 VOLCANIC GEOLOGY OF THE ORTON ‘U’ 25.44 50 71 58.6 BRADLEY FORMATION Monowai 25.95 49 62 52.9 ‘T’ 26.39 50 73 65.2 S.J. Hampton &J.W.Cole ‘S’ 26.81 69 72 71.5 Dept of Geological Sciences, University of ‘R’ 27.20 72 74 73.3 Canterbury, Private Bag 4800, Christchurch (sjh163*student.canterbury.ac.nz) ‘P’ 27.86 50 65 58.3 ‘O’ 28.59 56 61 57.6 The Orton Bradley Formation was deposited during All 47 74 60.4 the period 9.5 – 8.6 Ma. It is part of the Mt Herbert Volcanic Group of central Banks Peninsula, Canterbury, which is considered to be the intermediate stage of volcanism between Lyttelton INCREASED FRESHWATER RUNOFF Volcano (11 – 9.7 Ma) and Akaroa Volcano (9.3 – FROM THE GROWTH OF URBAN 8 Ma). Prior to the emplacement of the Mt Herbert AUCKLAND - THE GREATEST CAUSE OF Volcanic Group, sector collapse occurred on the ESTUARINE FAUNAL CHANGE southeast side of Lyttelton Volcano. This collapse

1 1 1 was probably the result of persistent rifting, similar H.R. Grenfell , B.W. Hayward ,A.T.Sabaa, to that of Valle del Bove, Mt Etna. The sector M. Morley1 & M. Horrocks2 1 collapse destroyed the existing crater rim, and Geomarine Research, 49 Swainston Rd, St Johns, provided a pathway for renewed / migrating Auckland. volcanism in central Banks Peninsula. 2Microfossil Research, 31 Mont Le Grand Rd, Mt Eden, Auckland. This collapse structure would have produced a large (h.grenfell*geomarine.org.nz) horseshoe-shaped amphitheatre with a hummocky surface, and would have controlled the deposition / Microfossils and molluscs from 13 upper emplacement of later volcanic and fluvial activity. Waitemata Harbour and Tamaki Estuary cores The upper sector of the breach contained alluvial provide a record of human impact on sheltered fans, and a topographic low, steep source, coastal marine to estuarine environments around amphitheatre, which constrained the initial the fringes of growing Auckland City. Polynesian Homestead Lava Member (new name) flows at the forest clearance had only minor impact compared base of the Orton Bradley Formation. Mud deposits with the increasing tempo of changes in European formed in localised depressions, on top of the topographically controlled lava flows. A period of

50thKaikoura05 -32- Kaikoura 2005 hydrovolcanic eruptions then took place to form the are restricted to xenoliths incorporated in the Mt Bradley Volcaniclastic Member, a low angle Cenozoic lavas that have been emplaced along tuff ring formed by both ‘wet’ and ‘dry’ base much of the length of this margin, and which can surges. ‘Wet’ base surges occurred when there was preserve unique age and process information that excess water supplied at the vent, whereas ‘dry’ may be valuable in interpreting continent evolution. base surges occurred when water was limited, or Earlier work in southeastern Australia in particular, used in previous eruptions. Magma / water has demonstrated the potential of the Re-Os interaction was shallow, promoting rapid chilling isotopic system for constraining the timing of and fragmentation. Eruption through a shallow events recorded in the lithospheric mantle of the standing body of water is supported by the presence Paleo-Pacific Gondwana margin, with implications of middle mud deposits, the majority of blocks over for continent structure and evolution (Handler and bombs, preservation of delicate cuspate edges on Bennett, 2001). glass fragments, large U-shaped channels, and We will present new Os and Nd isotopic data for fluvial deposits and erosion surfaces between lithospheric xenoliths from Marie Byrd Land and eruptive packages. Hawaiian style eruptive activity Victoria Land, Antarctica, together with previously marked the cessation of phreatomagmatic activity, published Re-Os data and model ages from along and formed a thin lava flow. This flow blocked the PaleoPacific Gondwana margin in southeastern drainage, allowing the development of a lake, and Australia and central Marie Byrd Land (McBride et formed the upper mud deposits. al., 1996; Handler and Bennett, 2001; Handler et A second phase of effusive and phreatomagmatic al., 2003), and discuss their implications for the activity then occurred, producing the interfingering development of the margin. The results suggest Packhorse Lava Member (new name)flowsand preservation of Proterozoic lithospheric mantle Tablelands Volcaniclastic Member. Packhorse Lava along the sampled length of the margin. Striking Member flows overcame the topographic controlled observations include: the similarity of the oldest upper sector collapse and flowed further to the PaleoProterozoic Os model ages found beneath the southeast. On exiting the steep sided collapse flows Delamerian Fold Belt of southeastern Australia and fanned out, but were constrained to the east by the beneath West Antarctica; preservation of a ca. 500 growing edifice of Akaroa Volcano. The succession Ma age from central Marie Byrd Land; and the was then capped by Mt Herbert and flank-fed suggestion that a significant melting event may Akaroa lava flows. have affected the mantle beneath both southeast Australia and Marie Byrd Land ca. 900 – 1100 Ma. POSTER The timing of this speculated MesoProterozoic mantle event(s) coincides with the age of a EVOLUTION OF THE PALEO-PACIFIC significant peak in the U-Pb detrital zircon age GONDWANA MARGIN: ISOTOPIC spectra of the vast turbidite deposits of the Paleo- CONSTRAINTS FROM WEST ANTARCTIC Pacific Gondwana margin (Wysoczanski and XENOLITHS Allibone, 2004).

1 1 M.R. Handler , R.J. Wysoczanski , Handler MR and Bennett VC (2001) Tectonics 20: 177- 2 3 4 J.A. Gamble ,V.C.Bennett & J.H. Berg 188. 1 Institute for Research on Earth Evolution, Handler MR, Wysoczanski RJ and Gamble JA (2003) JAMSTEC, Kanagawa 237-0061, Japan Chemical Geology 196: 131-145. 2 Dept of Geology, University College Cork, McBride JS, Lambert DD, Greig A and Nicholls IA Ireland. (1996) Geology 24: 631-634. 3RSES, Australian National University, Canberra Wysoczanski RJ and Allibone, AH (2004) Journal of 0200, Australia. Geology 112: 401-416. 4Geology & Environmental Geosciences, Northern Illinois University, USA. ORAL (monica*jamstec.go.jp)

West Antarctica and eastern Australia formed part of the contiguous Paleo-Pacific Gondwana margin during Late Proterozoic to Mesozoic times. Key aspects of the regional evolution of this margin, including the nature and age of the component terranes, remain contentious due to the poor exposure of crustal sequences resulting from the extensive ice and sedimentary basin cover in West Antarctica and eastern Australia, respectively. Samples of the deep crust and lithospheric mantle

50thKaikoura05 -33- Kaikoura 2005 SEQUENCE STRATIGRAPHY AND the falling (RST) and low (LST) sea level parts of a ARCHITECTURAL ELEMENTS OF THE relative sea level cycle, resulting in highly GIANT FORESETS FORMATION, asymmetric sequences. While the Giant Foresets NORTHERN TARANAKI BASIN, NEW Formation is considered to have minor potential in ZEALAND terms of containing sandstone-dominated stratigraphic traps, it does afford the opportunity to Rochelle J. Hansen & Peter J.J. Kamp study in detail how deep-water clastic systems Department of Earth Sciences, The University of respond or evolved in response to the various Waikato, Private Bag 3105, Hamilton factors that control depositional architectures, (rjhansen*waikato.ac.nz) particularly in a rapidly prograding muddy continental margin system. The modern continental margin, northern Taranaki POSTER Basin, is underlain by a thick, mud-dominated, Pliocene and Pleistocene succession (Giant Foresets Formation, GFF) clearly imaged in seismic THE MEDIAN TECTONIC LINE INITIATED reflection datasets. A study focusing on the AS A LATE CARBONIFEROUS geometry and internal reflection character of the CONTINENTAL TRUNCATION ZONE Giant Foresets Formation has revealed structural, sedimentological, and eustatic controls on its H.J. Harrington accumulation. 16 Hobbs St., O’Connor, Canberra ACT 2602; Isopach maps prepared for northern Taranaki Basin (harringt*pcug.org.au) show shifts through time in the location of sediment accumulation of the Mangaa Formation and Giant For a 50th anniversary meeting a little preliminary Foresets Formation. During the Early Pliocene history might be permitted in an abstract. In 1941 (Opoitian Stage) deposition was focused in the two topics were important in the Geological Survey southern part of the Northern Graben. The tea-room in Wellington, one being Fyfe’s Line and progradational front moved into the vicinity of the other the Alpine Fault. The evidence for the Arawa-1andTaimana-1ontheWesternPlatform Alpine Fault was properly published in writing, but during the early-Late Pliocene (Waipipian and that for Fyfe’s Line was not, and so it gradually lost Mangapanian Stages), forming large mounded prominence. The Alpine Fault continued to be slope fans. Through the latest Pliocene discussed with fervour after Wellman announced at (Mangapanian - lower Nukumaruan Stages) the the Pan-Pacific Science Congress in 1949 that there progradational front moved rapidly to the north and had been major strike-slip on it. He was brief and west through and across the Northern Graben to hesitant, and did not publish in writing until 1953. form a distinct shelf-slope depositional front. Fyfe’s Line was re-recognised, completely During the Pleistocene (upper Nukumaruan Stage – independently in 1967, by Landis and Coombs who Recent), the progradational front straightened out named it the Median Tectonic Line (MTL). reaching the present position of the shelf-slope In the 1930s Benson, Bartrum, Keble and King break. Even during the Pleistocene, broad correlated the graptolite zones of the Western subsidence persisted in the Northern Graben, Province of New Zealand with those of the trapping a proportion of the sediment flux being Bendigo-Ballarat goldfields in Australia. Rocks delivered to this part of the basin. similar to those between Brook Street and Dun The Late Pliocene part of the GFF, particularly Mountain were recognised far to the north at where it prograded on to the Western Platform, Gympie by mining engineer T.R. Hacket in the displays classic clinoform profiles, with over 1860s (Mike Johnston, pers. comm. 2005) and were steepening having resulted in mass-failure of again recognised in 1972 by Harrington. He paleoslopes. Major degradation of the shelf edge attempted to draw a schematic map (the poster) and slope occurred during the Early Pleistocene, showing the Brook Street rocks passing through reflecting a change in the calibre and flux of Lord Howe Rise and Norfolk Ridge to Australia. A sediment sourced to the continental margin. severe problem appeared immediately. It is that in eastern Australia there is a space of 1400 km Detailed examination of part of the GFF not between Bendigo-Ballarat and Gympie, but in New significantly affected by mass-failure indicates that small-scale channel levee and overbank deposits Zealand there is a space of only 40 km between the dominate slope deposition, while basin floor Takaka Terrane and the western side of Brook Street. The gap of 1400 km in Australia is deposits are characterised by slope-disconnected occupied by the eastern half of the Lachlan Foldbelt muddy and silty basin floor fans, with little lateral and the whole of the New England Orogen. Most continuity between systems. In a sequence of those rocks are missing in New Zealand. The stratigraphic context, many of the dominant working hypothesis offered to explain that situation components of each seismic unit (slumps, fans, and is that the missing rocks were removed tectonically channel-levee complexes) were deposited during

50thKaikoura05 -34- Kaikoura 2005 and that the MTL marks a Late Carboniferous (subtidal to extreme high water spring level) of the continental truncation zone. The date of truncation, 97 richest foraminiferal assemblages. The most c. 305 Ma, matches the date of opening of the precise estimates are for marginal high tidal salt extensional Sydney-Bowen and Cooper Basins marsh assemblages and the least precise are from (Harrington, BMR Bull. 231). low tidal and subtidal assemblages from near the The Brook Street–Gympie volcanic arc was out in centre of the inlet. These paleoelevation estimates the ocean, far out, because it contains no record of combined with sediment thicknesses, age the intense Permian glaciation on the continent. It determinations (from tephrostratigraphy and is possible to argue that Late Devonian and radiocarbon dates), the New Zealand Holocene sea Carboniferous arc split in the Early Permian into level curve, and estimates of compaction, identify active and remnant arcs separated by an interarc the Holocene land elevation changes and basin in which the non-continental Maitai earthquake-displacement events in each core. sediments were deposited. The two arcs had wide By combining the records from all cores, we outer arc-flanks one of which is preserved between recognise the following major, earthquake-related Gympie and the Esk Basin, and another in the displacements: ~7200 cal yrs BP (>-0.6 m Caples Terrane. displacement); ~5800 cal yrs BP; ~4200 cal yrs BP The Carboniferous truncation zone had thin (~ - 1.5 m); ~3000 cal yrs BP (-1.4 to -1.8 m); Permian passive margin sediments on it. It became ~1600 cal yrs BP (~ -1.7 m); ~600 cal yrs BP (~ -1 an arc-continent suture zone when the oceanic m); 1931AD Napier Earthquake (+1.5 m). The six, Brook Street volcanic arc system docked with it in large (possibly subduction interface) subsidence the Early and Mid Triassic. Sediment sources then events in the last 7200 years have had a return time changed dramatically. The key to that is best of 1000-1400 years. Identified displacement events preserved in Queensland where a major foreland have a range of sedimentary expressions, from an volcanic basin, the Esk Basin, 400 km long and eroded and burrowed hiatus surface, to an abrupt with associated plutons, formed immediately to the lithologic switch from mud to sand, or peat to west of the suture. Resedimented ashfalls from the shelly mud, or in some places no change in Esk andesitic and felsic volcanoes, and from sediment character whatsoever. volcanoes in younger basins to the south, formed ORAL the main sediments in the Murihiku-Maryborough portion of the interarc basin. In New Zealand the Mid and Late Triassic rocks of the Rakaia Sub- CRETACEOUS OCEANIC RED BEDS terrane were further from the ashfalls and so (CORB’S) IN NEW ZEALAND: EVIDENCE received mainly continental material. FOR A GLOBAL PHENOMENON?

POSTER D.C.H. Hikuroa1 &J.S.Crampton2 1Department of Geology, University of Auckland, MICROFOSSIL RECORD OF SEVEN LARGE New Zealand 2 EARTHQUAKES IN THE PAST 7500 CAL. Institute of Geological & Nuclear Sciences, Lower YRS IN SOUTHERN HAWKE’S BAY Hutt, New Zealand (d.hikuroa*auckland.ac.nz) 1B.W. Hayward, 1H.R. Grenfell, 1A.T. Sabaa, 1R. Carter, 1M.S. Morley, 2U. Cochran, During the Cretaceous, New Zealand occupied a 3J.H. Lipps, 4P.R. Shane position on the Pacific margin of Gondwana. In the 1Geomarine Research, 49 Swainston Rd, St Johns, Aptian it was located at a latitude of 75°S – 85°S Auckland. and, by the end of the Maastrichtian, was at a 2Institute of Geological and Nuclear Sciences, P.O. latitude of 55°S – 65°S. The Cretaceous System Box 30 368, Lower Hutt. spans a major transition in the geological history of 3Department of Integrative Biology and Museum of New Zealand, marking the end of prolonged Paleontology, University of California, Berkeley, subduction on the Pacific margin of Gondwanaland, California, 94720, United States. and by the end of the Cretaceous, complete 4Department of Geology, University of Auckland, separation of New Zealand from all other Private Bag 92 019, Auckland. Gondwanan fragments. (b.hayward*geomarine.org.nz) Early Cretaceous strata occur as structurally complex, uppermost sections of a thick, Mesozoic Foraminiferal and diatom assemblages in eleven ‘basement’ sequence. Unconformably overlying cores (3-7.5 m deep) from brackish Ahuriri Inlet in the ‘basement’ rocks are structurally relatively southern Hawke’s Bay, New Zealand, provide a uncomplicated late Early to Late Cretaceous record of 8.5 m of subsidence followed by 1.5 m of ‘cover’ formations, comprising three characteristic uplift in the last 7500 cal years. Modern Analogue successions. (1) Thick (up to 4000 m) non-marine Technique was used to estimate paleotidal elevation sequences; (2) thick (up to 3000 m) relatively

50thKaikoura05 -35- Kaikoura 2005 complete successions of Albian to Santonian qualification played no part in his appointment in marine, terrigenous, clastic rocks; and (3) relatively Otago. thin (<500 m) non-marine to marine transgressive Hector came to Dunedin at quite the most important successions of Conaician to Maastrichtian time in its history since the 1848 settlement and any terrigenous clastic strata. CORB’s in New Zealand consideration of him must include some are found in (2), the Albian to Santonian marine acknowledgement of the political and social successions, at a number of localities in the environment of his arrival. Brief consideration can Raukumara Peninsula and Wairarapa in the North be made of a few salient events which impacted Island, and Marlborough in the South Island. The upon Dunedin, even before the official North Island CORB’s are found in mudstone- proclamation of the Tuapeka gold field in June, dominated sequences, the Marlborough CORB’s in 1861. Events and public contemplation of this mudstone-sandstone sequences, and all range in age period that were particularly pertinent to Hector’s from uppermost Cenomanian to Coniacian. They arrival were the exploration and opening up of the occur as either 0.5 – 6 m thick red mudstones or as country. Transitory as it may have been, the same 10 – 20 m thick intervals of interbedded red, green, brief period witnessed two peculiarly coincident and olive-grey mudstone. events in Otago - the rise and fall of the gold and The presence of CORB’s in New Zealand, at such a the entrance and exit of James Hector. distance from other known CORB deposits located Hector’s arrival in Otago also had significant in the Northern Hemisphere, has major implications peripheral consequences. It was through Joseph D. for their formation and suggests the driving forces Hooker’s introduction that he met John Buchanan; were likely a global phenomenon. in Dunedin, Hector renewed his field and personal ORAL acquaintance with John W. Sullivan, with whom he had worked in Canada; Hector brought with him the ill-fated mining chemist C.S Wood, who was THE ESTABLISHMENT OF JAMES obliged to take his skills, with his terminal illness, HECTOR IN OTAGO to Melbourne so soon after; and, of course, over all this was the image and influence of that Geologist A.G. Hocken & D.E. Lee of Empire, Sir Rodney Murchison, Bt. Department of Geology, University of Otago, PO Box 56, Dunedin. ORAL (agh*ihug.co.nz) RADIOLARIAN-BASED INDICATORS OF In September, 1860, the Otago Provincial OCEANOGRAPHIC CHANGES, OFFSHORE Government approached its Home Agents in EASTERN NEW ZEALAND, OVER THE Edinburgh to find a Provincial Geologist. The LAST 500,000 YEARS Agents sought the advice of Sir Roderick Murchison, who was then Director of the British C.J. Hollis1,V.Lüer1, 2,H.M.Neil3, Geological Survey as well as President of the Royal B. Manighetti3 &G.H.Scott1 Geographical Society, in London, and Alexander 1 GNS Science, PO Box 30-368, Lower Hutt Keith Johnston, Geographer to the Queen. 2 Geosciences, University of Bremen, Bremen Murchison had led the recommendation of Hector 28359, Germany to the British North American (Palliser) Expedition 3 NIWA, Private Bag 14-901, Kilbirnie, Wellington (1857-1859) where he had shown outstanding (c.hollis*gns.cri.nz) ability as a geologist and natural historian, an explorer, an enthusiastic leader in physically Radiolarians are a diverse group of difficult country, as well as in personnel microzooplankton that construct ornate tests of management, written reports and cartography. opaline silica which are commonly preserved in Thus Murchison’s recommendation of Hector for marine sediments. The group is widely used in Otago was eminently predictable. Hector paleoceanographic studies, but has been considered that the £600 annual salary offered was underutilised in the South Pacific. We have inadequate and submitted that, for £800, he would undertaken quantitative analysis of radiolarian purchase and ship all the equipment and assemblages in Pleistocene-Holocene sediment instruments. As a condition of his appointment, cores from three sites north of the Chatham Rise: Hector negotiated with Charles S. Wood, of the IMAGES site MD97-2121 and ODP sites 1123 and Bristol School of Mines, as assistant and the matter th 1124. The radiolarian assemblages consist of a was closed in London on 27 December, 1861 mixture of subtropical, subantarctic and transitional when the Minute of Agreement was signed. species, typical of temperate waters. Some 300 Whilst Hector’s medical training was radiolarian species or higher level categories have acknowledged as part of his appointment to the been identified and most samples contain over 80 British North American Expedition, that taxa. In this study we compare late Pleistocene

50thKaikoura05 -36- Kaikoura 2005 faunal changes within these cores with local Eocene Lower Marl, which consists of alternating modern radiolarian distributions in surface beds of marl and micritic limestone. sediments to determine how climatic changes over Correlation with similar successions in middle and the last 500 ka may have affected oceanographic northern Clarence River valley (Hollis et al. 2005a, conditions and sea surface temperatures in this b) indicate that lithofacies changes reflect region. We utilise preliminary sea surface climatically induced variation in ocean circulation, temperature (SST) determinations using the modern oceanic productivity and terrigenous sediment analogue technique (MAT) and a modern dataset of supply across a bathyal carbonate ramp. While 31 core-top assemblages. Paleocene erosion, glaucony, and condensed For the coastal region represented by MD97-2121, sedimentation occurred in proximal settings the last deglaciation (15-10 ka BP) was (Kaikoura, mid-Clarence valley), a thick succession characterised by progressive warming from 15°C to of biosiliceous sediment was deposited in distal 17°C and decreasing biosiliceous accumulation. settings (northern Clarence valley). This implies The interaction of the subtropical East Cape vigorous ocean circulation and enhanced coastal Current and subantarctic waters jetting northward upwelling during a period of relatively cool through Mernoo Gap may have promoted climatic conditions. Early Eocene deposition of biosiliceous productivity in this near-coastal region thick marl-rich sedimentary successions throughout in glacial times. There is little evidence from the sub-basin suggests sluggish circulation and radiolarians for cooling of surface waters during the reduced upwelling during a period of warm climatic intervals correlated with the Antarctic Cold conditions. Distinctive marl-dominated intervals Reversal or Younger Dryas. However, a warming that can be correlated across the sub-basin represent pulse is identified close to the termination of the episodes of extreme warming, notably the Initial Younger Dryas, c. 11.5-10 ka. Peak warmth of Eocene Thermal Maximum (55 Ma) and the Early 17°C at 9-4.5 ka is associated with the Holocene Eocene Climatic Optimum (53-50 Ma). These Climatic Optimum. intervals are characterised by light carbon isotope For the oceanic regions represented by ODP 1123 signatures, short-lived occurrences of warm-water and 1124, MAT estimates are coarse, reflecting a calcareous nannoplankton, planktic foraminifera lack of close analogues to the assemblages at these and radiolarians, and acmes of some warm-water sites in the local core-top dataset. Nevertheless, taxa. A significant increase in terrigenous flux glacial-interglacial cycles are well-defined with suggests that the extreme warmth caused increased SSTs falling to 14°C in glacials and rising to 17°C precipitation and weathering in the terrestrial in interglacials – similar to the modern seasonal hinterland. range. These results are consistent with general circulation models for Eocene greenhouse conditions (560 ppm POSTER CO2) that place New Zealand within a transition zone between a warm, subtropical, oligotrophic THE GREENHOUSE BEHIND THE LAB: gyre to the north and a cool, eutrophic, cyclonic WHAT KAIKOURA’S LIMESTONE TELLS gyre to the south. Within this regime, additional US ABOUT THE CONSEQUENCES OF warming is predicted to cause southward expansion GLOBAL WARMING of the subtropical gyre and increase precipitation over the New Zealand landmass. C.J. Hollis1,C.P.Strong1,G.J.Wilson1, 2 2 G.R. Dickens &M.Nicolo Hollis, C.J.; Dickens, G.R.; Field, B.D.; Jones, C.J.; 1 GNS Science, PO Box 30 368, Lower Hutt Strong, C.P. 2005: The Paleocene-Eocene transition at 2 Dept of Earth Sciences, Rice University, Houston, Mead Stream, New Zealand: a southern Pacific record TX 77005, USA of early Cenozoic global change. Palaeogeography, (c.hollis*gns.cri.nz) Palaeoclimatology, Palaeoecology 215: 313-343. Hollis, C.J.; Field, B.D.; Jones, C.M.; Strong, C.P.; Muzzle Group strata exposed in a narrow gully Wilson, G.J.; Dickens, G.R. 2005 (in press): behind the University of Canterbury Kaikoura Field Biostratigraphy and carbon isotope stratigraphy of Station record deposition at the southern margin of uppermost Cretaceous-lower Cenozoic in middle the Marlborough sub-basin under a greenhouse Clarence valley, New Zealand. Journal of the Royal Society of New Zealand 35 (3):39p. climate between 70 and 50 million years ago. Upper Cretaceous micritic limestone of the Mead ORAL Hill Formation is unconformably overlain by a 7 m thick interval of Paleocene-Eocene Teredo Limestone, consisting of highly bioturbated glauconitic sandstone. This basal member of the Amuri Limestone is overlain by >20 m of lower

50thKaikoura05 -37- Kaikoura 2005 QUATERNARY TEPHRA BEDS PRESERVED and Waikato Basins, central western North Island. ON CHATHAM ISLAND: THEIR The group consists of six 3rd to 4th order (1 to 5 IDENTIFICATION AND SIGNIFICANCE IN Ma) sequences. Each of sequences 2 to 6 includes a INTERPRETING ASSOCIATED DEPOSITS major transgressive limestone unit at their base. AND PALEOVEGETATION The field characteristics and petrology of these limestones are little known in the Waikato Basin Kat Holt (from Port Waikato to Kawhia) in contrast to their Institute of Natural Resources, Massey University, correlatives to the south in King Country Basin Palmerston North, N.Z. (includes Te Kuiti/Waitomo area). Current study of (k.holt*massey.ac.nz) these northern limestone units is providing new insights into the evolution of the Waikato Basin The Chatham Islands preserve the easternmost during the Oligocene. occurrences of terrestrial Quaternary deposits of the The earliest Oligocene Elgood limestone of New Zealand microcontinent. These include dune sequence 2, the lowermost of the Te Kuiti Group sands, loess, extensive blanket peats, and rhyolitic limestones, commonly onlaps onto Mesozoic tephras derived from the TVZ in mainland New basement rocks (e.g. Port Waikato). This limestone Zealand. At least three separate rhyolitic events are is tight, flaggy, well-cemented, c.10-12 m thick, preserved as macroscopic tephra beds at many and comprises pure biosparites, and occasionally different locations around Chatham Island. biomicsparites. Skeletons are dominated by The youngest of these is the well known and well calcareous red algae, bryozoans, benthic dated Kawakawa Tephra, which is ubiquitous about foraminifera, and echinoderms, suggestive of the Island, occurring in peat, sand, colluvium and shallow-shelf water depths. The mid-Oligocene loess deposits, providing an excellent marker for Awaroa Limestone of sequence 3, onlapping onto LGM studies on the Island. Ahirau Sandstone, is restricted to the Kawhia The c.340 ka Rangitawa Tephra is present at three region, has a flaggy appearance, and is commonly or more sites around the Island. At one of these 10-18 m thick. Rocks are dominated by bryozoan, locations it occurs less than two metres below the benthic foraminiferal, and echinoderm biosparites Kawakawa Tephra, indicating either extended suggestive of mid-shelf water depths. The mid-Late periods of non-deposition or periods of erosion at Oligocene Waimai Limestone of sequence 4 onlaps thesesitesontheIslandduringthemidtolate Kotuku Siltstone and is distinctly tabular cross- Quaternary. bedded. Rocks include a spectrum of biosparites through to rarer biomicrites. Bioclasts are In addition, devitrified tephra beds at three different dominantly bryozoans, echinoderms, and benthic localities have been recognised using foraminifera typical of mid-shelf water depths. The ferromagnesian mineral content and geochemistry late Oligocene Raglan Limestone of sequence 5 is of ilmenite grains. At present, their ages are still commonly c.10 m thick, locally up to 20 m, and is unknown, but zircon grains preserved within these restricted to northern Raglan Harbour area. This tephras are to be fission track dated which will aid limestone transgressed onto Patikirau Siltstone, and in identifying them. is a slabby, intensely bioturbated, planktic The occurrences and stratigraphic significance of foraminiferal biomicrite indicative of accumulation the various tephras will be discussed in relation to at outer-shelf water depths. The latest Oligocene- the landscape evolution and vegetation history of earliest Miocene Otorohanga Limestone or its Chatham Island. equivalent of sequence 6, the uppermost limestone ORAL of the Te Kuiti Group, onlaps the Waitomo Sandstone and is restricted in occurrence to Gibson’s Beach. The limestone is a flaggy, dense, PETROLOGY OF TRANSGRESSIVE COOL- well-cemented, pure limestone c.8 m thick. Rocks WATER LIMESTONE SEQUENCES IN are bryozoan, echinoderm, benthic foraminiferal NORTHERN TE KUITI GROUP, WAIKATO dominated biomicsparites indicative of mid to BASIN, NEW ZEALAND outer-shelf water depths. Data suggest that during the Oligocene Waikato S.D. Hood, A. Tripathi, C.S. Nelson Basin experienced six major transgressive events & P.J.J. Kamp characterised by siliciclastic sediment starvation Department of Earth Sciences, University of and the establishment of carbonate factories at Waikato, Private Bag 3105, Hamilton commonly inner- to mid-shelfal depths. Sea level (s.hood*waikato.ac.nz) changes were probably mainly tectonically driven with a superimposed glacio-eustatic component. The mainly Oligocene Te Kuiti Group is a broadly The calcite cementation of these limestones is transgressive mixed-siliciclastic cool-water consistent with burial-induced cementation carbonate succession occurring in King Country associated with pressure-dissolution of skeletal

50thKaikoura05 -38- Kaikoura 2005 material at subsurface depths of several 100s of theoretical boundary between stability and rupture metres. domains. The first results of the tests give internal friction angles ranging from 22º to 25°, and POSTER undrained cohesion values from 0 to 30 kPa. Using these mechanical parameters in the stability MECHANICAL PARAMETERS AND equation (finite elements modelling and Mohr- SEDIMENT RHEOLOGY IN THE Coulomb rupture criteria) will help to understand SUBMARINE MATAKAOA AVALANCHES, the role of external parameters (e.g., variations in EAST CAPE REGION sea-level, seismic accelerations, lithostatic loading) in the triggering of failures in the Matakaoa 1 1 2 C. Joanne ,T.Lebourg,G.Lamarche, landslides. The modelling of slope instabilities will 1 1 J.-Y. Collot ,S.Migeon help to constrain the modalities of emplacement of 1 UMR Géosciences Azur, 06235 Villefranche-sur- the multiple phases observed in the Matakaoa Mer, France submarine avalanche complex. 2NIWA, Private Bag 14-901, Wellington. (joanne*geoazur.obs-vlfr.fr) ORAL

Swath bathymetry and seismic reflection data THE FIRST PTEROSAUR BONE FROM THE acquired over the 45 km-long, ~30 km-wide LATE CRETACEOUS OF THE SOUTH Matakaoa re-entrant provide evidence of active ISLAND, NEW ZEALAND erosion and mass failure processes. Slope gullies, large failure scars and channels incise the >1000 m Craig M. Jones, thick, seaward dipping sedimentary section of the Institute of Geological and Nuclear Sciences, northern margin of the East Cape region. Seismic (c.jones*gns.cri.nz) reflection profiles from the East of the re-entrant show single catastrophic debris avalanche of low New Zealand’s record of Mesozoic terrestrial recurrence, whereas profiles acquired along the re- vertebrates is very limited; almost all of the entrant axis provide evidences of repetitive debris specimens have come from the Late Cretaceous flows resulting from regular failures of the recent shallow marine sediments exposed in sediments cover. Deep-seated anticlines and the Mangahouanga Stream, Southern Hawkes Bay. proximity of the active subduction front of the Most were collected and described by Dr. Joan Hikurangi Margin suggest structural and tectonic Wiffen and others. Included in the known fauna are controls on this complex system of debris Pterosaurs which are represented by a scapula? and avalanches and debris flows that extend northward the distal end of an ulna. over more than 200 km. Recently the author discovered an uncatalogued Undisturbed piston cores, collected at three sites bone in the reference collection of the Institute of between 600 and 1500 m water depth, provided Geological and Nuclear Sciences (GNS, formerly samples for geotechnical testing. The coring sites the New Zealand Geological Survey). are located on both east and west sides of the re- The specimen is a large, hollow, very thin-walled entrant. The east of the re-entrant corresponds to a distal? portion of a long bone. It is poorly preserved stable, undisturbed platform, whereas the west side with few identifiable anatomical features. The sediment-cover presents evidence of instability. surfaces on the end of the bone are damaged or These sites were chosen to highlight possible worn. It is tentatively identified here as the distal? variability in mechanical behaviour according to end of an, as yet, unidentified pterosaur wing long morpho-structural features. bone. The referral of the specimen to the Order Sediment mechanical parameters are calculated in Pterosauria is based on its large size (20 mm order to model slope instabilities and to test trigger minimum shaft diameter), hollow shaft (now mechanisms. Triaxial tests are conducted under infilled with sediment), and very thin walls (1 mm high values of isotropic consolidation stresses, thick). The shaft has a flattened, ovoid cross- varying from 300 to 2000 kPa, so as to simulate section. stresses existing at depths of 30 to 200 m where the The specimen was collected by C.A. Fleming in avalanche rupture surface is imaged on seismic May 1955 from the “Black Grit”, Mikonui Stream, profiles. The tests allow us to determine the near Haumuri (Amuri) Bluff, just south of shearing resistance, axial strain and stress deviator, Kaikoura. This unit (equivalent to the Tarapuhi Grit and to calculate mechanical parameters as the of Warren and Speden 1977) has recently been cohesion and the effective internal friction angle. redated, using improved dinoflagellates The shearing resistance is required to constrain the biozonations, as lower Middle Campanian boundary conditions of the sediments rheology for (Crampton et al 2000). stability models (i.e. limiting axial stress and strain at the rupture). It is also possible to determine the

50thKaikoura05 -39- Kaikoura 2005 It is probable that the specimen was collected by This composite formation occurs to the east of Fleming during a field excursion organised during the Windon Melange, however small fault the 11th Annual Geological Survey Staff blocks have been found between the Windon Conference, held at Kaikoura between the 10th and Melange and the Dun Mountain Ophiolite. th th 16 May 1955. The excursion, on Thursday the 12 3. The Patuki Melange of Nelson and the Windon May, planned to visit Haumuri Bluff between 2 and Melange of Southland can be considered to be 4pm and then pass by Mikonui Stream on the way of identical origin. back to the meet the bus at Oaro. This particular 4. There is no visible evidence for an original conference is also of note historically; as it was relationship between the Greenstone during this conference the inaugural meeting of the (Croisilles) Melange and the Windon (Patuki) New Zealand Geological Society was held Melange. (Hayward 1980) 5. The Dun Mountain Ophiolite, although block This specimen is the first pterosaur bone recorded faulted and internally sheared is not melanged, from the South Island of New Zealand. It also away from major bounding fault zones. represents the earliest verifiable collection of a Mesozoic terrestrial vertebrate in New Zealand, Where these terranes are out of their normal order, predating Dr. Joan Wiffen’s dinosaur discoveries a model of flexural strike slip due to the Cenozoic by more than 20 years. Unfortunately it was not dextral movement in the South Island is proposed recognised for what it was for almost 50 years. for their emplacement. This modal has already been proposed to explain repeated lithologies near West Dome (Cawood, 1986) and here the idea will be J. Crampton, T. Mumme, I. Raine, L. Roncaglia, P. expanded to include the Livingstone Mountains and Schiøler, G. Turner and G. Wilson, 2000. Revision of the Piripauan and Haumurian local stages and the Red Hills in Nelson, with cooperating structural correlation of the Santonian-Maastrichtian (Late evidence. It has also been observed that the active Cretaceous) in New Zealand. New Zealand Journal of part of the boundaries between these units has Geology and Geophysics 43:309-333 shifted several times. G. Warren and I. Speden, 1978. The Piripauan and The different strengths of serpentinite and Haumurian Stratotypes (Mata Series, Upper ultramafic rock are manifested in the distribution of Cretaceous) and correlative sequences in the Haumuri strain along the Dun Mountain Ophiolite. This has a Bluff District, South Malborough (S56). New Zealand significant effect on the current pattern of New Geological Survey Bullentin 92. 60p Zealand’s geology. One of the more significant B. Hayward. 1980 The first 25 years – A brief history of examples is a bend in the Dun Mountain Ophiolite the Geological Society. Geological Society Newsletter and neighbouring terranes of approximately 45o No 50: pg6-14. near the Red Hills in Nelson. POSTER POSTER

THE RELATIONSHIP BETWEEN THE GONE BUT NOT FORGOTTEN - CAPLES AND DUN MOUNTAIN TERRANES CASUALTIES OF THE LAST GLOBAL EXTINCTION Dushan Jugum & Richard J. Norris Geology Department, PO Box 56, University of Shungo Kawagata1, Bruce W. Hayward1, Otago, Dunedin Hugh R. Grenfell1 & Ashwaq T. Sabaa1 (dushan*geology.co.nz) 1Geomarine Research, 49 Swainston Rd, St Johns, Auckland Geochemical and structural data will be presented (s.kawagata*geomarine.org.nz) to help interpret the melanged boundary between the Caples and Dun Mountain Terranes. The extinction of a group of elongate, cylindrical Preliminary data indicates that: deep-sea benthic foraminifera occurred during the 1. The Windon Melange extends from the East mid-Pleistocene Climatic Transition (MPT), Eglinton to Windley Rivers in Southland between 1.2 and 0.55 Ma. This extinction was first (approx. 54 Km) and its geochemistry and recognised ~25 years ago and until recently its full lithology are distinct from the Dun Mountain impact was undocumented. Our studies in eighteen Ophiolite. The Windon Melange is fault ODP cores from the North Atlantic, South Atlantic, bounded and is located to the east of the Dun Caribbean, Mediterranean, Southern Ocean, North Mountain Ophiolite. Indian, South China Sea and South-west Pacific, 2. There is no reason to separate the Harris show that at least 82 species and 17 genera became Saddle and the West Burn Formation of the extinct during this period of major global climate Caples Terrane as they share stratigraphical and oceanographic change. A further 4 species and location, lithology and igneous geochemistry. 3 genera declined dramatically during the MPT, but

50thKaikoura05 -40- Kaikoura 2005 survived through in low numbers in geographically- Alpine Fault was active in both North and South restricted refugia. One complete family Islands up to ca 5 Ma (major North Island faulting (Stilostomellidae – 21 species), characterised by an has long been widely noted and joined commonly unusual tooth structure in its necked aperture, to the Alpine Fault); its trace is now precisely became extinct at this time; and a second family located as the CVR’s boundary, & could become (Pleurostomellidae – 24 species), also characterised widely adopted. by unusual elliptical or hooded apertures, was Offshore Northland has been shown to have killed off except for two species that appear to have moved southeast between 15 & 5 Ma to become the just survived through. A further 30 species in the East Coast - in many publications dating back large Nodosariidae family also died out and most of between 10 and 38 years. these too, had unusual cribrate or narrow, Whakatane was moved southeast at 2 cm/year constricted apertures. for 400 k.yr (evidence 10+ years old). Prior to the MPT, many of the extinct species had Clockwise North Island Rotation since 15 Ma – a cosmopolitan distributions at middle bathyal to 30 year-old average of 65o has been supported upper abyssal depths (600-3000 m), although a recently, but the effects of rotation are seldom minority had geographically-limited distributions. considered in general papers. Our studies indicate that ~20% of the global diversity of benthic foraminifera at these depths Three North Island “Tectonic Events” (ca 10 (excluding the diverse unilocular taxa) became m.yr apart since 25 Ma) have been named, but extinct during the MPT. This was an extinction rate ignored, for ca 10 years; they allow changes in of ~30% of the middle bathyal-upper abyssal compression & tension to be dated accurately and fauna/myrs, which is an order of magnitude greater linked to (e.g.) important changes in the local class than the background extinction rate for deep-sea of volcanism. benthic foraminifera of ~2-3%/ myrs. A Single Subduction System, initially off Northland, moved & rotated progressively via ORAL Coromandel offshore, to become the Hikurangi Subduction System with only one change in the “CM/YR” IS NOW AVAILABLE – WHAT OF rotation rate at a tectonic event. No new data are THE NEXT 50 YEARS? necessarily needed to reach such conclusions as these. A 1963 diagram, based solely on then David Kear published (pre- radiometric) data, nevertheless 34 West End, Whakatane illustrated the creation of the CVR from nothing. (kear*xtra.co.nz) The North Island predominates in these examples, but the 2005 fieldtrip programme emphasises an In its first 50 years, our Society exceeded all accelerating interest in Marlborough’s plate expectations and world geology underwent its tectonic history - reflected in several recent greatest revolution. Belief in the Alpine Fault led to convincing papers. Compatibility of evidence from that in Continental Drift, which sparked off a new the two islands, at specific points backwards in era of Plate Tectonics with a new unit for its time, will be a key objective for the second 50 years movements of “cm/yr”. There seems general – Alpine Fault movement, large rotation, tectonic acceptance of these concepts in NZ, regarding other events, subsurface termination of subduction, parts of the world. Let us hope that the next 50 effects on non-geologic factors etc. However the years will bring comparable acceptance regarding overwhelming need will be to promote a greater NZ itself. Conclusions involving “plate tectonic- acceptance of the reality of NZ Plate Tectonics, in like” movements by many authors have been both thinking and writing. Should that be achieved, commonly ignored in appropriate diagrams and the next 50 years will be as exciting and rewarding papers – by various means ranging from denying all scientifically for the next generation as the last 50 discussion, to preferring a belief in zero-movement. years have been for us, and NZ will once again stimulate world thinking about the revolutionary Plate tectonic conclusions, many dating back over science of plate tectonics. decades rather than years, that seem not to be fully accepted in general papers (or need more ORAL convincing reporting?), include: Northland Allochthon it took half those 50 years, for even discussion to be acceptable. Central Volcanic Region (CVR) was created from nothing since 2.5 Ma, along with the Havre Trough. Stern’s diagram illustrating that situation is nearly 20 years old.

50thKaikoura05 -41- Kaikoura 2005 IS THE LATE CRETACEOUS WARD to the west of the London Hill Fault, a major COASTAL SUCCESSION Neogene structure forming the western boundary of ALLOCHTHONOUS? the Ward coastal area. A limited amount of dextral strike-slip movement (~4 km), as well as M.G. Laird1 & P. Schiøler2 overthrusting, was inferred to have occurred across 1Dept. of Geological Sciences, University of the fault during the Neogene (Audru, 1996), but Canterbury, PB 4800, Christchurch. this is unlikely to account for the marked difference 2Geol. Surv. of Denmark and Greenland, Ø. in sedimentary facies across it. There are, however, Voldgade 10, 1350 Copenhagen, Denmark. similarities between the Haumurian Ward coastal (malcolm.laird*canterbury.ac.nz) succession and the equivalent succession at Tora in SE Wairarapa, where similar channels, slumps and Over most of NE Marlborough, the Haumurian coarse clastic deposits also occur in the upper part sedimentary rocks consist of a lower portion, of the sequence. The Late Cretaceous succession at comprising the fine-grained clastic Whangai Tora represents the southernmost segment in the Formation (locally Herring Formation) typically eastern North Island of the partly allochthonous comprising a monotonous succession of massive or Eastern Sub-belt, and it is possible that the Sub-belt finely-laminated dark silty or very fine sandy extended further south to include the Ward coastal mudstone, which passes upwards abruptly or with area, with the London Hill Fault marking the rapid transition into the siliceous limestone of the tectonic boundary of a well-travelled block. Mead Hill Formation, occupying the upper portion. Reference. In the coastal area east of Ward, however, the Whangai Formation includes massive sandstone Audru, J-C. 1996: De la subduction d’Hikurangi à la bodies, a thick turbidite unit, and debris flow Faille Alpine, region de Marlborough, Nouvelle Zélande. deposits. Ph.D. thesis, University of Nice, France. A large proportion of the lower half of the exposed ORAL Haumurian succession, which contains dinoflagellates of late early Haumurian (I. FAULT CHARACTERISATION AND korojonense Zone) age, is occupied by a body of EARTHQUAKE SOURCE IDENTIFICATION massive well-sorted fine sandstone, up to 120 m IN THE OFFSHORE BAY OF PLENTY thick. The lower and upper contacts of the sandstone body with the enclosing Whangai Geoffroy Lamarche &PhilipM.Barnes Formation are sharp, with large, rounded blocks National Institute of Water and Atmospheric and rafts up to 2 m thick of laminated dark Research (NIWA) Ltd, mudstone of the underlying Whangai Formation P.O. Box 14-901, Wellington present in the basal 15 m, suggesting erosion and (g.lamarche*niwa.co.nz) incorporation in a sandy debris flow. The younger part of the succession is largely fine-grained, with We identify and map active faults within 100 km of scattered intervals of matrix-supported the Bay of Plenty coast, from interpretation of conglomerate or graded sandstone up to 5 m thick, >8,000 km of high-resolution seismic reflection interpreted to represent debris flows, slumps and profiles, >11,000 km2 of multibeam bathymetric turbidites, and occupying shallow channels. Soft- data, and archived side-scan sonar imagery. Active sediment slumping occurs at several horizons. The normal faulting in the central Bay of Plenty is fine-grained succession passes upwards either associated with continental back-arc extension in directly into the Flaxbourne Limestone, a ~20 m the offshore NNE-trending Taupo Volcanic Zone thick siliceous/calcareous unit of late Haumurian and southern Havre Trough. In the eastern Bay of (P. granulatum Subzone) age, or into channelled, Plenty, the faults include N-S-trending components massive, well-sorted fine sandstone bodies up to 20 of the North Island Dextral Fault Belt (NIDFB), m thick, which in turn pass upwards into the and NW-SE striking reverse faults related to the Flaxbourne Limestone. A 220+ m thick unit of deformation of north-western Raukumara turbidite sandstones occupies the stratigraphic Peninsula. The data set enables the recognition of position between the Flaxbourne Limestone and the fault displacements <0.5 m in the near-surface latest Cretaceous and Paleocene Mead Hill sediments. From the spatial relationships between Formation. The thick sandstone bodies are inferred the highly distributed surface fault traces, both at to occupy channel systems, and the turbidite unit depth and in map view, we identified specific fault represents either the infill of a depression or a zones that are interpreted to represent discrete laterally-migrating submarine fan. earthquake sources. The sources are characterised With the exception of scattered sandstone beds in by their tectonic styles (normal, reverse, strike- the otherwise fine-grained Woodside Creek slip), rupture lengths expressed at the seafloor, fault succession, none of the coarser units are traceable width, and thickness of the seismogenic zone (8 km

50thKaikoura05 -42- Kaikoura 2005 in the TVZ and southern Havre Trough; 12 and 15 km in the western and eastern Bay of Plenty The Hope Fault is the highest slip rate fault in shelves, respectively). For each earthquake source, northern South Island and constitutes the major we derive earthquake moment magnitudes (Mw) neotectonic link between the Alpine Fault and using an empirical regression relating rupture Hikurangi Subduction Zone - the main plate dimensions to Mw. We assumed Mw 5.8 as a lower boundary structures through NZ. The slip rate in the threshold for ground rupturing earthquakes in the western part of the Hope Fault (Hurunui section) is TVZ, corresponding to a rupture length of 6-7 km, c. 12 mm/yr and the recurrence time for surface according to published length-magnitude empirical faulting events is c. 310-490 yr. Though the Alpine correlations from a global compilation of faults. To Fault has an established pre-European fault rupture estimate slip rates, we mainly use (1) the event (c. 1717 AD) and the Hope River segment of displacement of the 7 to 20 kyr old post-last glacial the Hope Fault ruptured in 1888 AD, there is no transgressive surface (PGS) in water depths known rupture record for the Hurunui section. shallower than 150 m; and (2) the estimated We have cored 265 beech trees at 15 sites on or contribution of individual faults to the total tectonic adjacent to the active trace of the Hope Fault in extension (12-20 mm/yr) across the Bay of Plenty order to test whether massive landscape changes continental slope and deep water basins, on the during the last 300 yr have been recorded in the basis of fault scarp geomorphology. growth history of Beech forests there. About 65% We interpreted 166 individual potential earthquake of the trees sampled were Red (Nothofagus fusca); sources in the offshore Bay of Plenty, and 36 28% Silver (N. menziesii); and 7% Mountain (N. composite scenarios by considering the combined solandri var cliffortiodes) Beech. We compare our rupture of adjacent offshore sources during an preliminary results with 14-C dates from sites of earthquake, or the extension of an offshore rupture landscape change, tree disturbance and one hand- onto land. Most of the faults are previously dug trench along the Hurunui section to determine a unrecognised in seismic hazard models, in “most-recent” fault rupture date for the western end particular the reverse faults in the eastern Bay of of the Hope Fault. Our geomorphic model for large Plenty, and normal faults close to Tauranga. seismic events is for: i) c. 3.4 m average dextral Assigned rupture lengths range from 6 to 51 km, displacement on the fault; ii) high levels of ground and are associated with magnitudes ranging from shaking capable of affecting patches of trees along the fault trace; (iii) landsliding and sediment Mw 5.7 to 7.1. More than 75% of the earthquake generation from smaller catchments surrounding sources could generate Mw 6.0 to 6.6. From the Hurunui valley; and (iv) deposition of fluvial estimates of the seismic moment (Mo) and slip rate, we determine single event displacements and and fan deposits after the earthquake. earthquake recurrence intervals. Estimates of A preliminary analysis of the data suggest there are coseismic displacements averaged across the fault three major forest re-generation events that can be surfaces range from as little as 0.1 m to 2.4 m, and picked out from multiple sites. They correspond in are likely to be exceeded locally at the ground time to the AD 1888 event; an event in the early- surface. Recurrence intervals range from 20 to mid 19th century, and an event in the early-mid 18th 58,000 years, with an average of ~3000 yrs. There century. are 25 earthquake sources that have minimum ORAL recurrence intervals of less than 100 years, whereas intervals for the sources that probably extend onshore are more than 1000 yrs. TEREBRATULIDE AND RHYNCHONELLIDE BRACHIOPODS IN ORAL NEW ZEALAND – WINNERS AND LOSERS OF THE MESOZOIC MARINE USING TREE COLONISATION TO REVOLUTION INVESTIGATE THE AGE OF THE MOST 1 2 RECENT EARTHQUAKE ALONG THE D. E. Lee &D.A.B.MacFarlan 1 WESTERN HOPE FAULT Department of Geology, University of Otago, PO Box 56, Dunedin 2 R. M. Langridge1,R.Duncan2,V.Perez3,M. MacFarlan Geological Services Ltd, 13 Fairfax Smith2 &P.Almond2 Terrace, New Plymouth 1Institute of Geological & Nuclear Sciences, P.O (daphne.lee*stonebow.otago.ac.nz) Box 30-368, Lower Hutt, NZ 2Division of Bioprotection and Ecology, Lincoln The end-Permian extinction event removed many University, Christchurch, NZ of the brachiopod clades that had dominated 3Department of Geology, Granada, Spain Paleozoic sea floors, and decimated the remainder. (r.langridge*gns.cri.nz) By the end of the Early Jurassic, spiriferides and athyrides, members of two of the five articulated

50thKaikoura05 -43- Kaikoura 2005 brachiopod orders that had survived into the Zealand stages Whaingaroan, Duntroonian and Triassic, had finally disappeared, and brachiopod Waitakian. faunas in New Zealand, as elsewhere, became It was not until the biostratigraphy of the Oligocene dominated by a variety of ribbed rhynchonellides was much better defined that a definite age break with a few species of generally smooth between the Amuri and Weka Pass Limestones was terebratulides making up the balance. Little is proved, and by this time the correlation of these known of New Zealand Cretaceous brachiopods, limestone units was so well established that it was but from the early Cenozoic to the present day, in an easy logical step to assume that the age of the New Zealand seas as globally, terebratulides have unconformity must therefore be the same wherever become by far the most abundant and diverse group the two limestones occur. of brachiopods, greatly outnumbering At this time the Tertiary succession in the South rhynchonellides in terms of both generic and Island was being interpreted as a transgressive- species richness, and in total biomass. What caused regressive sequence, with the boundary between the this major shift or changeover in brachiopod faunas two limestones representing starvation due to since the Mesozoic? Was competition between maximum sea-level. Alternatively, global studies brachiopods and bivalves a factor? Did the were connecting the change from Greenhouse to endopunctate terebratulides come through the Icehouse climates with the development of a strong Mesozoic Marine Revolution more successfully current circling Antarctica, at around the beginning than impunctate rhynchonellides because of of the Oligocene. Both these theories were superior morphological, physiological and advanced to explain synchronous development of ecological characteristics? We will examine the unconformities across the South Island and into the morphological differences between the two groups, offshore regions. and indicate how these may have enabled the two brachiopod clades to cope with various However, the unconformity itself is quite different environmental changes (ocean chemistry, across the South Island, and may not be present in temperature and sea level fluctuations, varied some successions. Biostratigraphic studies have substrates) and biotic filters (competition, feeding confirmed the presence of multiple unconformities efficiency, predation) over the past 200 million within many successions, although only one at years. Our analysis uses examples from New others. Other dating methods are more difficult to Zealand Mesozoic and Cenozoic strata, and the apply, and only strontium isotope dating has been modern New Zealand brachiopod fauna. attempted at what has been described as the type section of the regional unconformity, at Squires ORAL Farm in South Canterbury. This date proved to be slightly inconsistent with earlier interpretations and SOUTH ISLAND OLIGOCENE some biostratigraphic results for other successions, UNCONFORMITIES – EVOLUTION OF AN but correlates well with some offshore dating from IDEA ODP Leg 181. The current status is impasse, with interpretation of Helen Lever the unconformities as being caused by a single Department of Geological Sciences, University of event still the dominant explanation, but Canterbury, Christchurch. insufficient data available to either prove or (helen.lever*canterbury.ac.nz) disprove this hypothesis. POSTER Early mapping in the Canterbury and Otago regions quickly generated controversy about the interpretation of the contact between the Amuri and DEPOSITIONAL PROCESSES AND Weka Pass Limestones and their stratigraphic SEDIMENTARY FRACTIONATION IN THE equivalent. Mappers were divided on whether the FORMATION OF TEPHRA BEDS FROM contact was conformable or unconformable. PYROCLASTIC ERUPTIONS: A STUDY OF In publications (up to the 1960s) the contact is well POTAKA AND CORRELATIVE KAIMATIRA described, but is never referred to as an PUMICE SAND DEPOSITS unconformity. In the Oamaru region the two 1 1 2 limestones are often separated by a unit of Lewis B., White J.D.L., Manville V., 1 calcareous glauconitic sandstone, and the faunal & Palin J.M. 1 differences between the underlying limestone Dept. of Geology, University of Otago, P.O Box (correlated with the Amuri in Canterbury), the 56, Dunedin 2 glauconitic sandstone and the overlying limestone Institute of Geological & Nuclear Sciences, (correlated with the Weka Pass Limestone) led to Wairakei Research Centre, Private Bag 2000, the subdivision of the Oligocene into the New Taupo (grumpsnz*yahoo.co.nz)

50thKaikoura05 -44- Kaikoura 2005 facies comprises c.60 % of the 11m lacustrine Tephra beds are commonly used to aid in succession exposed in two mining test pits. This chronostratigraphic reconstruction of sedimentary facies consists of diatom-rich light and dark deposits within which they occur. High-resolution couplets of average thickness <0.5 mm (Fig.1). stratigraphic studies of Wanganui Basin sediments Dark brown laminae also contain abundant fine have benefited from the abundance of interlayered plant matter, including leiospheres. Diagenetic tephras, many of which have been dated by fission- pyrite nodules and films are locally present. By track methods and/or are correlated with known analogy with modern lakes, the light-coloured eruptions in the Taupo Volcanic Zone. The present laminae reflect enhanced diatom production when study has a different aim; which is to investigate the conditions (light, temperature, nutrients) were physical processes involved in sedimentary optimal, probably during spring and summer; dark deposition of ash in the marine environment. To do laminae accumulated during each autumn-winter so we are examining the Potaka Tephra at two sites, period. Pinstripe lamination and absence of and the correlative Kaimatira Pumice Sand at bioturbation, coupled with exceptionally well- another two sites. preserved entire galaxiid fish skeletons, numerous The Potaka Tephra locally contains apparently leaves and rare flowers, indicate that the profundal unreworked primary tephra deposits, but through lake and its floor were anoxic, supporting no most of its thickness reflects deposition under the macrofauna. Periodic 3~10 year changes in couplet influence of waves and currents. Kaimatira Pumice thickness compare with Quaternary records of Sand consists of crystals and uncommon pumice ENSO (El-Niño Southern Oscillation) variability fragments derived from pyroclastic deposits, but and indicate that the southern New Zealand climate deposition was entirely by waves and currents, and was strongly seasonal and ocean-influenced during the original pyroclastic grain population has been the early Miocene. The second diatomite facies, reduced to a "lag" of crystals representing an as-yet dark brown ‘speckled’ beds, are up to 120 mm undetermined fraction of the mixture of crystal- thick and distributed throughout the mine bearing pumice, glass shards, and free crystals that exposures. Bases of speckled beds show minor would have characterised the primary particle scour relief, with infrequent development of rip-up population. clast breccias. Speckled beds incorporate abundant diatom aggregates, coarse plant detritus, very minor Our analysis will focus on (1) using bedding terrigenous silt, and are often texturally and colour structures to determine as precisely as possible the graded. They are invariably capped by 1~6 mm of depositional processes that formed different parts of white diatomite. Speckled beds are interpreted as the tephras, (2), geochemical investigation of glass, mass flow deposits resulting from failure of lake crystals, and whole pumice to characterise the margin slope sediment and transport by slurry flows tephras, for comparison with known primary or turbidity currents into the deep basin. eruptive products of the TVZ, and (3), for primary parts of the Potaka tephra, determine fine-scale details of the bedding structure and variations in particle population, and interpret these in terms of the processes active in deposition of particles that have been deposited via sedimentation through both air (from the eruptive plume), and water. POSTER

HIGH-RESOLUTION PALEOCLIMATE ORAL SIGNAL FROM EARLY MIOCENE LACUSTRINE DIATOMITE NEAR MIDDLEMARCH, CENTRAL OTAGO, NEW HOLOCENE TECTONIC FLUVIAL ZEALAND TERRACES AT PAKARAE RIVER MOUTH, GISBORNE REGION J.K. Lindqvist &D.E.Lee Department of Geology, University of Otago, P.O. N. Litchfield1 &K.Wilson2 Box 56 Dunedin, New Zealand 1Institute of Geological & Nuclear Sciences, PO (jonlind*es.co.nz) Box 30 368, Lower Hutt 2School of Earth Sciences, Victoria University of A 75-100+ m thick lacustrine diatomite succession Wellington, PO Box 600, Wellington near Middlemarch, 45 km northwest of Dunedin, (n.litchfield*gns.cri.nz) accumulated in a ~1 km diameter maar depression in schist basement. Two diatomite facies are Pakarae River mouth, c. 25 km NE of Gisborne, is recognised. A thinly laminated biogenic varve the region of fastest coastal uplift along the

50thKaikoura05 -45- Kaikoura 2005 Hikurangi Margin, as recorded by a flight of seven (timothy.little*vuw.ac.nz Holocene marine terraces. Each marine terrace is The D’Entrecasteaux Islands in the Woodlark Rift interpreted to be coseismic in origin. A flight of is one of the few places on earth where a mid-ocean fluvial terraces exists immediately upstream of the ridge (MOR) terminates into a zone of continental river mouth. We have investigated these to see: (a) rifting, where low-angle normal faults are if they grade to the marine terraces, and thus are seismically active, and where eclogite-facies rocks also coseismic or tectonic terraces, and (b) whether of Pliocene age are at the surface. Located <30 km they provide information about the response of the from an actively spreading MOR, eastern river to coseismic uplift. Normanby Island is a Plio-Pliestocene metamorphic The highest (mid Holocene) marine terrace T1 is an core complex (MCC) in a continental rift zone aggradational terrace formed by infilling of an between the Australia and Woodlark plates. The estuary during post-glacial sea level rise. Thus the normal fault bounding this MCC provides some primary terrace gradient would have been interesting comparisons to the Alpine Fault: both horizontal in the downstream, estuary area, or are long-lived, high displacement faults that have parallel to the low gradient river in the fluvial area exhumed lower crustal mylonitic rocks on one side. upstream. Currently T1 is 24 m above sea level In both, the uplifted mylonite zones are >1 km (a.s.l.) at the coast and can be traced as a thick, and were overprinted by a (much narrower) discontinuous surface for 3.5 km upstream, where it zone of brittle slip in the plate motion direction gradually decreases in altitude to 16 m a.s.l. This during their unroofing. Erosion has probably implies the terrace has been back-tilted. played a key role in focusing slip on the long-lived Alpine Fault, and quickly removes its scarp during Stepping down from T1 to the present river are exhumation. By contrast, in PNG, the lower plate discontinuous flights of up to 6 fluvial terraces, has been pulled out a distance of ~50 km from including the prominent modern flood level terrace. beneath the upper plate where it is preserved as The number of terraces increases downstream; the denuded surface that has been only slightly incised modern flood level terrace is the main terrace 4 km by rivers. The surface on Normanby Island is upstream. A smoothed longitudinal terrace profile striated by fault-surface megamullions and has been constructed to aid correlation of these underlain by mylonitic lineations parallel to Plio- largely degradational terraces with the marine Pliestocene plate motion. Offshore, active half- terraces at the coast. Some fluvial terraces can be grabens imply that deeper parts of the PNG projected to the marine terraces, corroborated by detachment fault are still active. Onshore, older, limited tephra age control. Therefore it is likely that abandoned parts of the detachment have been back- some of the fluvial terraces have a coseismic origin. tilted through the horizontal as a result of footwall The terrace profile also shows fanning out of the unloading and buoyant uplift of a flowing lower terraces downstream (i.e., successively younger crust beneath that denuded footwall. The terraces have steeper downstream gradients), with detachment has extensionally reactivated the base the modern flood level terrace having the steepest of a collisional suture (Papuan ultramafic sheet) to downstream gradient of all. This geomorphology return blueschists back to the surface in the lower likely reflects progressive upstream tilting with the plate of this MCC. Elsewhere in the current floodplain yet to be affected by coseismic D’Entrecasteaux Islands, the same extensionally uplift. everted ultramafic contact has been the locus of Dislocation modelling will be used to model the shear zones that exhume the world’s youngest upstream tilting with respect to inferred offshore known eclogites (as young as ~2.8 Ma). fault sources for the locally high uplift rates. Paleopiezometery based on recrystallised quartz ORAL grain-size indicates final flow stresses of ~35-55 MPa. As seismogenic normal faults throughout the Woodlark rift are active with dips of 25-30°, these A YOUNG METAMORPHIC CORE results imply extreme frictional weakness. This COMPLEX ON NORMANBY ISLAND, may refect either high pore-fluid pressures or low D’ENTRECASTEAUX ISLANDS, PNG: friction coefficient (µ), perhaps in part the result of COMPARISON WITH THE ALPINE FAULT serpentinitic protolith of the fault gouge (µ <0.45). AND IMPLICATIONS FOR CRUSTAL This frictional weakening mechanism is probably RHEOLOGY DURING RIFTING different than the cause of prolonged, focused slip

1 on the Alpine Fault, where erosion and thermal Timothy A. Little , Suzanne Baldwin, structure are more important. Focused thinning Brian Monteleone & Paul Fitzgerald2 1 near the MCC took place several m.y. prior to School of Earth Sciences, Victoria University of arrival of the (now adjacent) MOR, and 100’s km Wellington, Wellington, New Zealand 2 away from it, thus we infer that MCC-related Department of Earth Sciences, Syracuse crustal thinning pre-conditions the crust for later University, Syracuse, New York, U.S.A. break-up and lithospheric rupturing (not vise versa).

50thKaikoura05 -46- Kaikoura 2005 The MCC is bounded by deep-seated transform habitat which may be used later in analyses such as faults separating domains in which extension has defining a unique benthic community structure. been strongly localized on weak, individual faults POSTER (MCC’s) vs. where it is distributed. ORAL THE WILD WEST: IMAGING WEST COAST SEDIMENT CONDUITS MAPPING THE DEEP SEA: APPLICATION OF MULTIBEAM DATA TO DEEP SEA K. Mackay,H.L.Neil&J.Mitchell GEOLOGICAL SAMPLING NIWA, Private Bag 14 901, Kilbirnie, Wellington, New Zealand. K. Mackay, Malcolm Clark, Ian Wright, (k.mackay*niwa.co.nz) & Miles Dunkin NIWA, Private Bag 14 901, Kilbirnie, Wellington, New Zealand is in a critical location for New Zealand. reconstructing changes in westerly circulation and (k.mackay*niwa.co.nz) evaluating its role in controlling global climate change. Surrounded by vast areas of ocean, the Multibeam echosounders are becoming main axial ranges intersect the prevailing increasingly and routinely used for detailed seafloor westerlies. The Southern Alps of New Zealand are mapping up to several kilometres either side of the an ideal location to understand the history of the survey vessel. Such multibeam data have been used westerly wind system through time as the to determine seafloor bathymetry and substrate interaction between orographic effects and the composition for geological research by accurately westerlies produce significant precipitation on the map submarine topography, such as seamounts or West Coast of the South Island. canyons. In addition, the multibeam seafloor The first in a probable series of research voyages acoustic backscatter data can differentiate between projected for the West Coast Canyon region off different substrate types, including sediment and South Island, New Zealand was completed in exposed bedrock, and hence guide successful October 2005. The aim of this research programme geological sampling operations. Multibeam is to define a history of glaciation during the late mapping of the ocean bottom is markedly more Quaternary in New Zealand, in particular the efficient than conventional single-beam relationship with the Westerly Wind system and echosounders, and provides greater resolution and correlation with abrupt climate change globally and accuracy of both seafloor morphology and to determine the sources and fluxes of sediment composition. influencing the southern New Zealand region. Since 2001, the Simrad EM300 multibeam system The West Coast is supplied by 3 of the 5 largest on NIWA’s research vessel Tangaroa has been used rivers in New Zealand with respect to sediment extensively in support of ocean geology sampling load. Presently fifty times more sediment is operations, especially around the east coast of the injected into this system than that into the Bounty North Island, Cook Strait, Kermadec Ridge, Trough as a consequence of the closer proximity of Norfolk Ridge, and Lord Howe Rise. the Southern Alps source area and the lack of large The existing charts of these regions have generally natural lakes that trap up to 15% of the sediment proved to be adequate on a large scale, indicating yield to the east of the Alps. Glacial-Interglacial the approximate position of ridges or seamounts. changes recorded in sediment sequences in However, on the scale of an individual feature, the downslope basins should reflect a switch on with depth, size, and shape of a seamount are often large sediment flux in peak glacial times and a poorly charted. The width of seafloor that can be switch off during interglacials. At the last glacial mappedisupto4timesthewaterdepth,andsoat maximum, major valley glaciers reached the open 1000 m depth the bathymetry was determined 2 km coast, probably as grounded tidewater glacial fronts either side of the vessel. This enables rapid providing voluminous mud, sand and gravel via a evaluation of the shape of the seabed, which was range of processes directly to the continental slope often very different from the chart. (Barnes et al., 2001). The seafloor bathymetry is often rugged and Seafloor topography was surveyed using the complex, with the multibeam proving essential to Simrad EM300 multibeam sonar, which uses a fan the success of sampling several sites. The acoustic of 135 sonar beams to simultaneously ensonify and backscatter intensity gives an indication of map a swath of the seafloor up to a width of up to substrate composition, which was used to plan rock 5-times the water depth. These bathymetric data are dredging and/or sediment sampling operations. It processed within a GIS to form a digital terrain also gives us data on the type of sediment and model (DTM). Using spatial analysis functions of GIS, the DTM is interrogated to identify, and

50thKaikoura05 -47- Kaikoura 2005 define relationships between, products of the fauna will help fill a gap in the poorly known shark bathymetric data, such as slope, coarse- and fine- faunas of the Paleocene world wide. scaled bathymetric position and rugosity. Sediment This conclusion that the assemblage represents patterns, catchment areas and channels can be deep water is apparently at odds with the quantitatively identified and traced. In addition, interpretation of the Waipara Greensand as having acoustic backscatter intensities returned with the been deposited in a shallow marine setting under multibeam were processed to identify the conditions of very slow sedimentation (Browne and broadscale seafloor composition and possible facies Field 1985) and requires further investigation. distribution. Reference POSTER Browne, G.H. and Field, B.D. 1985 The lithostratigraphy of Late Cretaceous to Early Pleistocene rocks of northern Canterbury, New Zealand. New Zealand A DEEP-WATER SHARK FAUNA FROM geological Survey Record 6. 63 pp. THE PALEOCENE OF NORTH CANTERBURY POSTER

Al A. Mannering & Norton Hiller INTRACALDERA LAKE BREAK-OUTS Canterbury Museum, Rolleston Avenue, FLOODS: GEOMORPHIC SIGNALS, Christchurch, New Zealand MECHANISMS, AND HAZARDS (alman*i4free.co.nz) V. Manville1 & K. Kataoka2 Apart from the enigmatic Waiparaconus 1Institute of Geology & Nuclear Sciences, Private Buckeridge 1983 and the remains of a proto- Bag 2000, Taupo, New Zealand. penguin, the Waipara Greensand of North 2Research Institute for Hazards in Snowy Areas, Canterbury is not noted for its macro fossils, but Niigata University, Niigata, Japan. careful searching of exposures along the banks of (v.manville*gns.cri.nz) the Waipara River, at the K/T boundary section and downstream from the Laidmore Road ford, has Volcano-hydrologic hazards display a wide variety produced several hundred isolated shark teeth. of causative mechanisms, including those directly Preliminary identifications of these remains were related to volcanic activity such as explosive provided by the late Ian Keyes, formerly of the ejection of a crater lake, and indirectly-related Institute of Geological and Nuclear Sciences, who phenomena such as rain-triggered lahars and break- determined that at least seven species were present. out floods from temporary lake impoundments. The same stratigraphic unit was also investigated in Amongst the latter, events range in scale from exposures along the North Branch of the Waipara relatively minor outflows triggered by failure of River, close to the confluence with the South crater walls or the breaching of riverine dams Branch. composed of pyroclastic, volcaniclastic, or lava The shark fauna has now been expanded to include flow material to catastrophic floods generated by eleven genera, several of which are new records for the breaching of caldera rims. Multiple intracaldera the New Zealand biota. The orthacodontid, lake breakouts have been identified in several Sphenodus Agassiz 1837 has previously been volcanic arcs, including New Zealand, where they recorded only from the Jurassic of the northern exert a major control on drainage patterns, and hemisphere and the hexanchid, Chlamydoselachus Alaska, where three out of twelve Holocene Garman 1884 from Cretaceous to Recent of calderas have been identified as flood sources. Europe, North America, Antarctica and Western Palaeohydraulic reconstructions indicate such Australia. The squalid Megasqualus Herman 1982 events rank amongst the largest post-glacial floods is also only known from the Paleocene to Eocene of on Earth, being exceeded only by late Pleistocene Europe and Miocene of Japan and California. The deluges associated with breaching of ice-dammed odontaspidids Palaeohypotodus rutoti Winkler lakes and pluvial basins. Geomorphic and limited 1874 and Odontaspis cf winkleri Leriche 1905 have published geologic evidence suggests that not appeared in any literature associated with New numerous candidates for similar phenomena lie in Zealand Japan and Kamchatka, where the primary focus has Comparison with extant species belonging to hitherto been on physical volcanology and several of the genera present suggests that the fauna petrology rather than geomorphology and is a deep water one, probably typical of the outer sedimentology. Intracaldera and crater lake break- shelf to upper slope. Deep water shark assemblages outs constitute a significant hazard in volcanic are quite rare, especially from pre-Miocene environments worldwide, as they may occur deposits, but similar faunas are known from deep without warning, often long after the initial water clays of Denmark. This Waipara Greensand volcanic crisis has subsided, and can devastate

50thKaikoura05 -48- Kaikoura 2005 distal alluvial plains where large population centres 350 m marked by a third alloformation comprising and infrastructure are typically concentrated. cryptic fluvial strath terraces and shoreline deposits in the Rotorua basin. Resumption of down-cutting ORAL triggered an apparently catastrophic break-out through the Haroharo route prior to the 26.5 ka PAST HIGHSTANDS OF LAKE ROTORUA: Oruanui eruption and a fall in lake level to below IMPLICATIONS FOR TECTONISM AND 260 m. Episodic growth of resurgent dome PALAEOGEOGRAPHY IN THE TAUPO complexes between 21 and 9 ka progressively VOLCANIC ZONE blocked this drainage path, forcing Lake Rotorua to rise to a level where it could overtop a drainage V. Manville1,R.Marx2,J.D.L.White2 divide on the northern rim of Lake Rotoiti to re- 1Institute of Geological & Nuclear Sciences, Private occupy the former Kaituna River course, Bag 2000, Taupo, New Zealand establishing the current outlet channel. 2 Geology Department, University of Otago, POSTER PO Box 56, Dunedin, New Zealand. (v.manville*gns.cri.nz) PALEOENVIRONMENTAL Lake Rotorua currently partially occupies a near- RECONSTRUCTION OF A WELL- circular 20 km diameter volcano-tectonic PRESERVED STAGE 7 FOREST SEQUENCE depression formed at 220 ka by eruption of the CATASTROPHICALLY BURIED BY voluminous Mamaku Ignimbrite. Two distinct BASALTIC ERUPTIVE DEPOSITS, lacustrine littoral terraces that fringe much of the NORTHERN NEW ZEALAND lake basin, defined on the basis of contrasting geomorphology and field relationships and M. J. Marra1,B.V.Alloway2 separated by tephrostratigraphically dateable &R.M.Newnham3 unconformities, are here correlated with former 1 Department of Geological Sciences, University of highstands of the lake. The first and highest Canterbury, NZ elevation terrace (up to 415 m), corresponds to 2 GNS-Science, Gracefield Research Centre, PO accumulation of a lake in the newly created basin in Box 30368, Lower Hutt, NZ the immediate aftermath of the Mamaku Ignimbrite 3 School of Geography, University of Plymouth, eruption. Considerable uncertainty surrounds the Plymouth PL4 8AA, UK direction of overflow of this level, but the lake may (Maureen.marra*canterbury.ac.nz) have extended southwards through the Hemo Gorge, a v-shaped notch in the topographic rim of The well-preserved remnants of a forest sequence, the caldera, through the Ngakuru Graben and into catastrophically inundated by proximal to medial the Waikato River drainage. A highstand at this phreatomagmatic deposits, are identified on the level would be contiguous with Lake Huka in the shores of the Manukau Harbour. In this study the Taupo-Reporoa area and require a blockage in the stratigraphy and age of this forest succession was Ongaroto Gorge, possibly related to volcanism at examined in detail along with palaeoecological the Ohakuri or Maroa volcanic centres. At some proxies (palynology and beetle assemblages) from later time a northeasterly outlet became established carbonaceous muds associated with the forest at a lower level through the tectonically subsiding sequence. Optically Stimulated Luminescence Tikitere Graben into the Haroharo caldera from dating of the phreatomagmatic deposit together whereitflowedintotheBayofPlentyviathe with palaeoecological evidence for interglacial Kawerau Canyon. The second and most extensive climate suggests deposition in late Marine Isotope littoral terrace (370-380 m), the post-55 ka Rotoiti Stage (MIS) 7. This extends the known age of alloformation, is the product of a durable highstand Auckland volcanism by up to 40 ka. produced by blockage of this drainage path by Ninety-eight fossil beetle taxa were identified. All eruption of a voluminous unwelded ignimbrite from but two of the fossil taxa occur in the local modern the adjacent Okataina Volcanic Centre. Lake level fauna. Based on an extensive survey of the local was maintained by stable overspill across a welded modern fauna, the fossil beetle fauna represents ignimbrite sill west of the Tikitere Graben into the 48% of families, 20% of genera, and 13% of north-flowing Kaituna River until accumulation of species in the local modern fauna. The fossil Mangaone Subgroup tephras in the graben could no assemblage comprises taxa from forest, wetland longer keep pace with active subsidence. Lake level and beach habitats. initially dropped rapidly by c. 20 m as the unconsolidated Mangaone tephras were flushed Both beetle and pollen assemblages indicate a away, before impingement of the falling lake level kauri/podocarp forest growing adjacent to a on the underlying more consolidated Rotoiti wetland on or near a coastal plain. The pollen pyroclastics produced a short-lived stillstand at c. record shows Agathis australis- dominance between two phases of Dacrydium cupressinum

50thKaikoura05 -49- Kaikoura 2005 dominance. Despite overall similarity to the modern beach samples; 2) Cenozoic to Mesozoic outcrops flora and fauna, both the beetle and pollen within stream drainage basins; 3) piston and box assemblages include elements that are found today core samples; and 4) sandy core samples from at higher elevations in the region, indicating that Ocean Drilling Program Site 1122. The slightly cooler climate conditions existed during combination of the BFS and WSS samples sets late MIS 7 compared to present. We estimate this includes first cycle and multi-cycle sediments temperature depression at less than 1oC relative to derived from similar clastic the present, broadly consistent with other terrestrial sedimentary/metasedimentary source rocks (e.g., reports and marine (ODP-1123) record for Late Torlesse), as well as sediments derived from MIS 7. progressively metamorphosed versions of these rocks (e.g., Otago Schist), all with variable volcanic ORAL input. To date, sand detrital modes have been determined CHASING BITS AND PIECES OF NEW for parts of each system. Miocene to Quaternary ZEALAND FROM SOURCE TO SINK: sand from the Bounty Fan is micaceous and PRELIMINARY RESULTS OF SAND quartzofeldspathic with minor metamorphic lithic PROVENANCE STUDIES IN THE BOUNTY components. Its composition is similar to that of FAN AND WAIPAOA RIVER quartzofeldspathic sand from the Modern Clutha SEDIMENTARY SYSTEMS River, but contributions from the Waitaki River (feldspatholithic sand) cannot be ruled out. In 1 1 Kathleen M. Marsaglia , Dawn E. James , contrast, Waipaoa River sand is feldspar poor with 1 1 Shawn A. Shapiro , Alissa M. DeVaughn , the proportion of quartz versus lithic fragments a 1 1 2 Shelby Dawson , Kevin Rivera ,LionelCarter function of grain size: lithic fragments are 3 & Michael Marden concentrated in the coarser sand fraction and quartz 1 Dept. of Geological Sciences, California State and feldspar within the finer sand fraction. University Northridge Furthermore, there are subtle compositional 18111 Nordhoff St., Northridge, CA 91330-8266 differences among sand derived from the pre- 2 NIWA P.O. Box 14901, Wellington, NZ Pliocene units of the East Coast Allochthon versus 3 Landcare Research, P.O. Box 445, Gisborne, NZ uplifted Pliocene sedimentary successions: for (kathie.marsaglia*csun.edu) example, the latter contribute more calcareous mudstone fragments and vitric volcanic debris than Modern sand provenance studies often involve one the former. depositional setting (e.g., fluvial, shelf, deep- marine fan) with few holistic studies tracing source ORAL river sediment across shelves to deep-sea fan sinks. Deep-sea sandy turbidite successions can record the CHINKS IN THE CURTAIN – ADVANCES IN evolution of the fluvial and shelf systems that OUR KNOWLEDGE OF NEW ZEALAND supplied sand, as well as distinct eustatic, climatic, CENOZOIC NON-MARINE MOLLUSCS and tectonic signals. The records of such processes also vary according to bedrock lithology, which is Bruce A. Marshall & Phillip A. Maxwell fundamentally related to the plate tectonic setting of Museum of New Zealand, Te Papa Tongarewa, the sedimentary system. Deciphering these signals 169 Tory Street, Wellington. in modern and late Cenozoic systems increases our 257 Otipua Road, Timaru. ability to interpret continental margin history (psmaxwell*xtra.co.nz) preserved in ancient turbidite successions. The practical applications of such studies involve The New Zealand molluscan fossil record is predictions of sand composition in buried deep-sea- overwhelmingly one of marine species. A total of fan petroleum reservoirs, which in turn can be 5482 Cenozoic species were recorded in a recent directly linked to their likely diagenetic pathway(s) census; of these 5451 (99.43%) are marine, 20 and ultimate reservoir quality. (0.36%) terrestrial and 11 (0.20%) freshwater. The sedimentary systems of New Zealand are ideal Comparable figures for Recent molluscs (shelled places for holistic sand provenance studies, and we species only) are 4277, 3398 (79.45%), 838 have embarked on a series of these in conjunction (19.59%) and 41 (0.96%). We report here on recent with the MARGINS Source-to-Sink initiative of the discoveries that help redress the balance; in US National Science Foundation (NSF), funded particular, we focus on an exceptionally diverse through the NSF Opportunities to Enhance Pliocene fauna from North Canterbury. Diversity in the Geosciences program. Our study Except for the Hyriidae, which are recorded back to areas are the Bounty Fan (BFS) and Waipaoa the late Cretaceous, the oldest known possibly non- Sedimentary (WSS) Systems and our data sets are marine Cenozoic molluscs from New Zealand are derived from a combination of: 1) modern river and from the Pomahaka Formation in western Otago.

50thKaikoura05 -50- Kaikoura 2005 Many of the molluscs in the highly distinctive fauna (probably Duntroonian, Late Oligocene) are A numerical code for simulating dry flows of inferred to have been brackish-water or estuarine granular material, TITAN2D, is used to model dwellers, but they also include three species of scoria-and-ash flows from the 1975 eruption of Hydrobiidae or a related family. Most modern Mount Ngauruhoe, New Zealand. Most flows from hydrobiids are fresh water inhabitants, but some this eruption were formed by the simple collapse of live in brackish waters, so their occurrence at agglutinate, spatter and scoria piled up around the Pomahaka is ambiguous. upper vent during eruption. The deposits have Fortunately, land snails are more readily well-developed levees, channels and steep flow identifiable as such – the oldest are from three sites fronts 1.5 – 2 m in height. The lithology comprises in Northland of Otaian (Early Miocene) age, where green-black, moderately vesicular scoria; elongate, they are vastly outnumbered by marine molluscs. red-black agglutinate; dense andesitic lava blocks The material is very limited and some specimens and bombs; and xenolith bearing scoriaceous clasts. are poorly preserved, but 6 or 7 species are present, Many of the scoria clasts have bread-crusted outer representing the pulmonate families Charopidae layers and jigsaw jointing, indicators of hot and Punctidae. Very rare charopids have also been emplacement. To calibrate the method, volumes of collected from the vertebrate bed in lacustrine three deposits were calculated in ArcMap using siltstone near St Bathans (Manuherikia Group, cut/fill from pre- and post-1975 Digital Elevation 3 3 probably Middle Miocene.) Models (DEMs). Estimates of 1650 m , 2900 m and 5400 m3 were derived for these scoria-and-ash By far the most prolific sites for non-marine flow deposits, each from single flow events. The molluscs are in the upper Waipara River in North volumes were then used as initial inputs in Canterbury. The original locality – collected by TITAN2D and the flows were modelled on a pre- Don Gregg and Pat Suggate in 1961 – is no longer eruption DEM of the region. Scaled-up flow exposed, but other sites in the Kowai Formation volumes were modelled in order to evaluate the have been discovered nearby. Freshwater taxa inundation from larger events at Ngauruhoe. The (Hyriidae, Pisidium, Potamopyrgus, Glyptophysa) modelled flows were mostly confined to pre- are present in the lower part of the section (Middle existing valleys, stopping on gentler slopes. In Pliocene?), and diverse assemblages dominated by some cases flows crossed the Mangatepopo Track. land snails have been collected from two sites near During the summer months, there can be on the top of the unit. One – from opposite average more than 420 people walking this track “Bellefield” – includes Georissa (Hydrocenidae), daily; thus a pyroclastic flow-forming eruption will Cyclophoroidea, Rhytida (including eggs), present a serious hazard to tourists tramping in the Punctidae and Charopidae (Allodiscus, area. The modelling has indicated that the proposed Pseudallodiscus, Discocharopa, Fectola, Mitodon, deviation of the Mangatepopo track by the Cavellia, etc). The associated palynoflora is too Department of Conservation will increase the risk poor for dating, but one from Tommy Stream, c 20- to people using the track. The TITAN2D model 30 m lower in the section, is Nukumaruan, Late was very successful in modelling the scoria-and-ash Pliocene and indicates considerably warmer flows from the 1975 Ngauruhoe eruptions, and may conditions than those prevailing at the present day be a promising technique for predicting the (Dallas Mildenhall, pers comm). The Tommy distribution of pyroclastic flow hazards on similar Stream faunule lacks hydrocenids and types of volcanoes. cyclophoroideans but has a rich punctid and charopid assemblage. Preliminary analysis indicates POSTER only limited similarity with the “Bellefield” faunule. The Waipara land snails have considerable potential for addressing paleoclimatic and MAGMAS OF THE 17,700 YR biogeographic issues and for throwing some light REREWHAKAAITU ERUPTIVE EPISODE OF TARAWERA VOLCANIC COMPLEX on species-turnover rates. ORAL S.B. Martin1, P. Shane1,&I.A.Nairn2 1Department of Geology, University of Auckland, Private Bag 92019, Auckland COMPUTER MODELLING OF THE 245 Summit Road, Rotorua, RD5 PYROCLASTIC FLOW HAZARDS OF (sb.martin*auckland.ac.nz) MOUNT NGAURUHOE, TONGARIRO VOLCANIC CENTRE, NZ The 17.7 ka Rerewhakaaitu eruption from the Tarawera Volcanic Complex, within the Okataina K. Martelli Volcanic Centre, involved ~5 km3 of magma INR, Massey University, Private Bag 11-222, (DRE). Eruptive products include: a tuff cone Palmerston North (constructed by pyroclastic surge and flow (k.martelli*massey.ac.nz)

50thKaikoura05 -51- Kaikoura 2005 deposits), three domes, a lava flow, and plinian The aridity of the Australian continent means dust tephra fallout which covered an area of >9000 km2. storms are a common occurrence (McTainsh et al., Three separate rhyolite magmas were involved in 1989), with dust transport to New Zealand reported theeruption(T1,T2andT3).T1andT2magmas on numerous occasions resulting in red coloured are high SiO2 rhyolites, and T3 magma is a low- snow and haze (Marx and McGowan, 2005). SiO2 rhyolite. T1 magma has matrix glass K2Oof Contemporary dust events in Australia are strongly influenced by environmental conditions within dust 3.43 ± 0.11 (wt.%), whole rock SiO2 of 77.15 ± 0.24 (wt.%), whole rock Sr values of 91 ± 6 (ppm), source areas, in particular periods of drought, or orthopyroxene>hornblende mineralogy, Fe-Ti increased windiness, to which dust transport rates oxide temperature of 763 ± 12 °C, and oxygen rapidly respond (McTainsh et al., 2005). Therefore, dust deposition chronologies can be used as an fugacity (ƒO2) of +0.35 ± 0.12 (NNO). T2 magma excellent proxy for palaeoenvironmental has matrix glass K2O of 4.20 ± 0.09 (wt.%), whole rock SiO of 75.46 ± 0.26 (wt.%), whole rock Sr conditions, such as the degree of aridity in dust 2 source areas and changes in wind strength and dust values of 122 ± 4 (ppm), biotite>hornblende transport pathways in response to changing mineralogy, temperature of 704 ± 17 °C, and ƒO of 2 synoptic circulation patterns. -0.45 ± 0.14 (NNO). T1 and T2 magmas are represented throughout the pyroclastic sequence We present an
8000 year record of Australian dust and in several domes, and were erupted from the deposition extracted from an omobrotrophic peat same vent(s). T3 magma, comprising Western bog in Central Otago, New Zealand. Using novel

Dome only, has matrix glass K2O of 3.14 ± 0.06 tertiary and binary trace element mixing models dust extracted from the bog is provenanced to (wt.%), whole rock SiO2 of 74.12 (wt.%), whole rock Sr values of 174 (ppm), and hornblende- specific dust source areas within Australia on a orthopyroxene mineralogy. T1 and T2 magmas are catchment-geologic scale. Changing rates of dust found mingled in some clasts, and a few clasts deposition, along with the switching on or off of contain glass intermediate between the two particular dust source areas within Australian are compositions. This demonstrates short-lived contact thus used to interpret paleoenvironmental between the magmas, that were disrupted and conditions within the region. mixing in the conduit during eruption. T3 magma did not undergo any mixing and was erupted from a Marx, S.K., McGowan, H.A., 2005. A re-examination of separate vent. The Rerewhakaaitu eruptive event the 1928 trans-Tasman dust transport event. Weather was triggered by a mafic intrusion, which mixed and Climate, Accepted, 24, 35-55. with T1 and T2 magmas. Evidence for this includes McTainsh, G.H., Burgess, R., Pitblado, J.R., 1989. mafic micro-blebs (andesitic-dacitic glass Aridity, Drought and Dust Storms in Australia (1960- composition) in some rhyolite clasts. These clasts 84). Journal of Arid Environments, 16, 11-22. also contain a disequilibrium crystal assemblage McTainsh, G.H., Chan, Y., McGowan, H.A., Leys, J.F., that includes clinopyroxene and olivine. The Tews, K., 2005. The 23rd October, 2002 dust storm in magma dynamics of the Rerewhakaaitu eruption eastern Australia: characteristics and meteorological appears to be broadly similar to that of the 0.7 ka conditions. Atmospheric Environment, 39, 1227-1236. Kaharoa eruption. Thus, it may be common for ORAL discrete bodies of rhyolite magma to accumulate beneath Tarawera prior to priming by mafic intrusion. A 15,000 YEAR RECORD OF SURFACE- RUPTURING EARTHQUAKES AND FAULT POSTER SLIP AT SAXTON RIVER, AWATERE FAULT, NEW ZEALAND DUST AS A PROXY FOR CLIMATE D.P.M. Mason1,2, T.A. Little1 &R.J.VanDissen3 CHANGE: A RECORD OF AUSTRALIAN 1 DUST DEPOSITION IN NEW ZEALAND School of Earth Sciences, Victoria University of DURING THE HOLOCENE Wellington, PO Box 600, Wellington 2 Opus International Consultants, PO Box 12003, 1 1 Wellington Samuel K. Marx , Hamish A. McGowan 3 & Balz S. Kamber2 Institute of Geological and Nuclear Sciences, PO 1School of Geography, Planning and Architecture, Box 30368, Lower Hutt The University of Queensland, St Lucia, Brisbane, (Dougal.Mason*opus.co.nz) Qld, 4072, Australia. 2Department of Earth Sciences, Laurentian Fault offsets of a well-preserved flight of fluvial University, Sudbury, Ontario, P3E2C6, Canada. terraces on the Awatere Fault, in northeast South (s.marx*uq.edu.au) Island, New Zealand, together with trenching studies and dating results for late Quaternary sediments deposited on them, allows the

50thKaikoura05 -52- Kaikoura 2005 incremental slip history and paleoearthquake chronology to be reconstructed in some detail for Landslides are a significant hazard in Tasmania that this major strike-slip fault. At Saxton River, six have resulted in the destruction of many homes fluvial terraces have been progressively displaced over many years. Landslide damage to properties across the Molesworth section of the Awatere and infrastructure throughout the State is a Fault. Horizontal displacements were measured significant ongoing cost to the community to repair. from microtopographical maps constructed from Fortunately, there has been minimal loss of life but detailed GPS surveys, and range from ~6 m for an the potential for catastrophic events in populated ephemeral channel on the youngest terrace surface areas is well established. Unfortunately in many to 81 m for a riser above the oldest terrace. instances, the currently level of preparedness to this Eight surface-rupturing paleoearthquakes in the last hazard is insufficient despite the lessons of the 6.3 ka can be recognised from relationships Thredbo disaster and other events. A significant exposed in a paleoseismic trench excavated across a part of the process of informing communities about sagpond on the oldest terrace. The ages of these natural hazards is the production of hazard maps events are constrained by 12 14C samples. At least and the dissemination of this information source. two additional events are recognised between 6.3 While landslide maps have existed over parts of the and ~15 ka, but these have yet to be precisely state for many years, the methodology has been dated. These data indicate a mean recurrence inconsistent between areas and the concepts of interval of 1435 ±165 years on this part of the hazard and risk are not in accord with current Awatere Fault. Intervals between individual practice. paleoearthquakes range from <130 to 1750 ±320 Mineral Resources has developed a new cal. years. methodology to produce regional landslide hazard New optically stimulated luminescence ages maps of principal urban areas in the state. This indicate that abandonment of the two oldest terrace information is designed to assist land managers to treads took place at 14.5 ±1.5 and 6.69 ±0.74 ka improve their land-use planning and risk B.P. When these OSL ages are combined with management strategies. The methodology involves: previous pebble weathering rind ages of the collation of landslide data into a spatial database; younger terraces, and with GPS-based production of geology and geomorphology and measurements of the progressive terrace riser landslide inventory ‘fact’ maps; modelling of displacements, strike-slip rates on this part of the rockfall, debris flow and deep seated landslide Awatere Fault can be reconstructed through time. processes to produce three thematic potential The data indicate that the dextral-slip rate has hazard maps. The modelling components employ remained nearly constant at 5.6 ±0.8 mm/a since GIS-based deterministic techniques supported by ~15 ka B.P. Comparing the magnitudes and ages of empirically determined parameters to identify the terrace riser displacements to the source, runout and setback areas for the three paleoearthquake record allows estimation of a mean processes described. The frequency of debris-flow per-event horizontal displacement of 4.4 ±0.8 m events has been attempted through modelling over the eight most recent surface rupture events. rainfall patterns. A subsequent risk assessment of a Between ~5 ka and ~2 ka B.P. surface rupturing repetition of the 1872 Glenorchy landslide indicates earthquakes increased in frequency, and decreased that it is in the unacceptable part of the ANCOLD in their mean coseismic displacements to <2.6 m. societal risk criteria. During this time, the sense of local dip-slip also Examples of maps from the Greater Hobart and shifted from north side-up to south side-up. Rapid Launceston study areas and an explanation of the incision of the Saxton River in the mid Holocene published methodology will be provided. may have caused a perturbation in the near-surface POSTER stress directions acting on the fault plane beneath the Saxton River valley, forcing a change in the near-surface fault geometry that resulted in the shift VOLCANOLOGY OF A COMPOSITE in sense of dip-slip. CRATER-COMPLEX MARKING THE ONSET OF KAROO FLOOD BASALT POSTER VOLCANISM, SOUTH AFRICA

REGIONAL LANDSLIDE HAZARD Murray McClintock ASSESSMENTS IN TASMANIA Department of Geology, University of Otago, Dunedin C. Mazengarb1 (murray.mcclintock*stonebow.otago.ac.nz) 1Mineral Resources Tasmania, Department of Infrastructure, Energy & Resources, Volcanic activity during the initial stages of flood PO Box 56, Rosny, Tasmania 7018 Australia basalt volcanism is of interest because it includes (colin.mazengarb*dier.tas.gov.au) explosive to non-explosive magmatic and

50thKaikoura05 -53- Kaikoura 2005 phreatomagmatic activity that contrasts with Tim McConnico, Kari Bassett, & Jarg Pettinga effusion-dominated later stages. At one volcanic University of Canterbury, Christchurch, New centre formed during the first stages of flood basalt Zealand eruption in South Africa, the Sterkspruit Complex, (tsm18*student.canterbury.ac.nz) volcaniclastic rocks more than 140 m thick fill a >40 km2 crater made up of the coalesced deposits of Multiple terraces on the east side of the many small overlapping phreatomagmatic and Hawkeswood Range formed as the result of rapid strombolian debris-filled vents spaced a few uplift and erosion of the Hawkeswood Range. hundred metres apart. This crater complex is cut Terrace surfaces are composite features, with their into country rock and is surrounded by a blanket of upper parts representing sub-aerial alluvial fans, distal bedded volcaniclastic rocks. which in turn transition to their equivalent shallow Inside the complex, volcaniclastic rocks filling marine foreset beds of Quaternary Gilbert-style fan these small vents show steep, abrupt contacts with deltas. The terraces/fan surfaces are ~9 km long host rocks at deep levels but show mainly low- and ~3 km wide. Incisions have created excellent 3- angle, diffuse contacts with the deposits of adjacent dimensional views of the underlying Gilbert-style centers at shallow levels. Craters housing these fan delta complex from topsets to prodelta deposits. vents grew mainly via collapse of their margins The flat-lying geomorphic expressions of the rather than by downward quarrying. The 50-100 m terraces have their origin from the tripartite thick distal blanket of mainly bedded, fine-grained geometry of Gilbert-style fan deltas. These deposits beyond the Sterkspruit Complex records a preserved geomorphic features combined with variety of fall, flow and reworking processes. stratigraphy help uncover the complex nesting of Widespread pillow lavas associated with reworked terraces and thus a connection to the active and lacustrine sediments point to an abrupt end to tectonics of the region. It was only with the explosive volcanism at Sterkspruit followed by combination of the two techniques that a clear flooding of the lowest part of the crater and rapid picture of the development of the terraces along burial of the landscape by lava. Subtle differences Conway Coast was deciphered. in the geochemistry of intrusions, volcaniclastic The Conway Fan Delta Complex can be divided rocks and lava at Sterkspruit indicate that there into four stages of evolution based on variations in were at least five discrete magma types involved in sedimentary facies and geomorphic mapping of the eruptions. Field mapping shows that although the terraces. The first stage involves the uplift of the magma types can be used as time-markers in the Hawkeswood Range and subsequent increased volcanic sequence, implying that each constituted a sedimentation rate such that alluvial fans prograded discrete magma ‘batch’, two discrete magma types to the sea forming the Medina fan delta. Evidence were erupting at the same time, suggesting that of large slumping events are seen as the oldest fan each batch was small and fed by local dikes. delta onlaps onto pre-existing marine silts and mud. The Sterkspruit Complex records This is followed by incision, possibly from lowering sea level or from changes in the uplift and 1. shallow-level explosive phreatomagmatic and sedimentation rate. During the second stage the strombolian eruptions, Dawn Creek fan infills the incised paleovalleys and 2. shallow intrusion and effusion of basalt, progrades further basinward; it is the largest of the 3. lateral growth of large craters via coalescence fan deltas recorded along the Conway Coast. This is of many small vents by crater-margin collapse, again followed by incision. Stage 3 involves and deposition of estuarine facies, possibly lateral to a 4. transport of debris beyond the complex to fan delta similar to the modern Conway fan blanket pre-eruption topography. delta/estuary, with in situ Podocarp forest at ~ 8000 BP. This is again followed by incision which is Crater-complexes like Sterkspruit are present at the th followed by the 4 stage, the infill of the incised base of many flood basalt successions and are valley by the modern fan delta of the Conway River relevant to models of climate change associated and its progradation. with flood basalt eruptions and add to our understanding of the volcanology, structure and ORAL magmatic evolution of large igneous provinces. ORAL NEW ZEALAND’S FRESHWATER FISH: FOSSILS IN THE CONTEXT OF THE EXTANT FAUNA FACIES ARCHITECTURE OF THE CONWAY FAN DELTA COMPLEX AS IT R M McDowall FORMED TERRACES ALONG THE National Institute of Water and Atmospheric UPLIFTING HAWKSWOOD RANGE Research, PO Box 8602, Christchurch (r.mcdowall*niwa.co.nz)

50thKaikoura05 -54- Kaikoura 2005 Island in Windless Bight. These sediments record This paper explores what we know of New the history of ocean currents and the ice shelf itself Zealand’s fossil freshwater fishes, and seeks to to be investigated as part of the ANDRILL project place them in the context of the extant fauna (based (http://www.andrill.org/). largely on material collected in the last few years Here we present results of two 60-cm-long gravity by a student from the Geology Department, cores taken from the sea floor beneath the ice shelf University of Auckland; Liz Kennedy of GNS, in January 2003, and which record recent Lower Hutt; and Daphne Lee and Jon Lindqvist, sedimentation there. Core 1 was taken 5km east of Geology Department, Otago University.) the ice shelf front, and contains a record of the past In the more distant past WRB Oliver mentioned ~20,000 years. The basal unit is a diamict that eleotrids from the Pliocene (now known to be mid- contains clasts, some subrounded and striated, and Pleistocene) of the Ormond Valley, inland from derived from Transantarctic Mountains. This is Gisborne, and also some galaxiids from near interpreted as representing basal debris from an Dunedin; Gerald Stokell added galaxiids from near expanded Ross Ice Shelf/Sheet at the LGM. This Middlemarch, and I reported on all of these and passes upwards into a well-sorted sand layer, which provided a summary some 30 years ago. represents locally derived sediment either deposited Things have moved rapidly in the past year or so, through a retreating ice shelf or beneath the ice and we can now report on: shelf as a result of slope instability. Overlying the sand is a series of fine muds and muddy sands, 1. A couple of scales from an undetermined lower which are indicative of sub-ice shelf conditions, perciform family from an Early Miocene with only minor fluctuations of the ice shelf front. deposit near Bannockburn; The biogenic content also suggests that the Ross Ice 2. The first fossil record of grayling Shelf front has not retreated significantly from its (Prototroctes) from the mid-Pleistocene of the present position during the Holocene and that Ormond Valley, as well as: seasonally open water has been present in 3. Additional eleotrids of the genus McMurdo Sound for much of this period. Gobiomorphus from the Ormond Valley; Core 2, taken 12 km east of the ice shelf front, 4. An additional eleotrid from Early Miocene contains a record of the past ~10,000 years. It deposits near St Bathans; and consists mainly of locally derived sandy mud, and 5. A series of Early Miocene galaxiid fossils from contains a higher biogenic component of diatoms diatomite deposits near Middlemarch. and sponge spicules, typically more than 20%. The uniform nature of this core suggests that current There are also numerous fish otoliths in Geology flow has varied little from the present regime (5-20 Department, University of Otago collections that cm/sec; Robinson, 2005), and also supports the have not yet been looked at seriously, and which view that the ice shelf front has varied little during have potential to provide new revelations. the Holocene. I will seek to clarify the significance of these fossils Additional cores are planned for 2005/06 field in the evolutionary history of the fauna. season and will be used to develop a high resolution ORAL sedimentation model in preparation for deep drilling planned by ANDRILL for the 2006/07 season. A PRELIMINARY SEDIMENTATION MODEL FOR BENEATH THE MCMURDO ORAL ICE SHELF

1 1 1 1 LATE QUATERNARY R. McKay ,P.Barrett, G. Dunbar ,T.Naish, PALEOEARTHQUAKES ON THE M. Harper2 &L.Carter1 1 NORTHERN NORTH ISLAND FAULT Antarctic Research Centre, Victoria University of SYSTEM, NEW ZEALAND Wellington, PO Box 500 Wellington 2 School of Earth Sciences, Victoria University of 1,2 2 1 V. Mouslopoulou ,A.Nicol, T. Little , Wellington, PO Box 500, Wellington 2 2 2 D. Beetham , K. Berryman ,R. Langridge , (robert.mckay*vuw.ac.nz) 2 1,2† P. Villamor &S.Beanland 1 Victoria University of Wellington, School of Ross Island has been depressing the crust under its Earth Sciences, PO Box 600, Wellington. own weight for at least the last million years, and at 2 Institute of Geological and Nuclear Sciences, PO the same time has been acting as the western Box 30 368, Lower Hutt. pinning point for the Ross Ice Shelf. As a result, a (V.Mouslopoulou*gns.cri.nz) thick sedimentary sequence has accumulated in a sea floor depression now 900 m deep beneath the McMurdo-Ross Ice Shelf on the south side of Ross † Deceased

50thKaikoura05 -55- Kaikoura 2005 Hansen J., 1998. PhD Thesis. Massey University, New The North Island Fault System (NIFS) is the Zealand. principal strike-slip fault system of the Hikurangi Mouslopoulou et al., 2004. Geol. Soc. NZ Miscell. Pub. margin, along which the Pacific Plate is being 117A subducted beneath the overriding Australian Plate. ORAL The NIFS accommodates up to 50% of the margin- parallel relative plate motion and extends for approximately 450 km, from the Wellington region GSNZ VOICES FROM THE PAST in the south, to the Bay of Plenty coastline in the north. For its northern c.120 km, the NIFS Simon Nathan comprises three main sub-parallel strands Te Ara: Encyclopedia of New Zealand (Waiohau, Whakatane & Waimana faults). Ministry for Culture & Heritage, P.O. Box 5364, Northwards along these faults, late Quaternary rates Wellington of strike-slip decrease as rates of normal-slip (simon.nathan*mch.govt.nz) increase, a transition across which horizontal to vertical slip-ratios decrease from 5-10:1 to 0.6:1 In 1955 the geological community in New Zealand (Mouslopoulou et al., 2004). In this talk we will was rather different from today. The four university identify the position of this kinematic transition on departments were small, and the majority of each of the main faults, and assess whether it may geologists (almost entirely male) worked for the have functioned as a mechanical barrier to rupture Geological Survey. The lack of a mining industry propagation during the history of paleoearthquakes meant that there were few job openings for known for this region. We use fault-trench log data graduates. Geology was almost entirely based on from 15 trenches and >50 measurements of offset surface outcrops, and there was little knowledge of landforms. The ages of key stratigraphic markers offshore geology or the extent of major are constrained by tephra glass chemistry and 14C hydrocarbon-bearing sedimentary basins. dating. Preliminary results suggest that the This talk focuses on some of the individuals who Whakatane Fault last ruptured since 0.8 kyr BP, founded the Geological Society of New Zealand in while the Waimana and Waiohau faults last 1955, and will be illustrated by a selection of voices ruptured 1.8-2.8 and 1.8-5.6 kyr ago, respectively. from the past. Within c. 40 km of the Bay of Plenty coastline, earthquake recurrence intervals average about 2- ORAL 2.5, 3 and 4.5 kyr on the Whakatane, Waimana, and Waiohau faults, respectively. On individual faults, TWIN PEAKS: THE PRE-MANGERE the timing and number of earthquakes during the FORMATION SEQUENCE ON MANGERE Holocene appears to have varied along strike across ISLAND, CHATHAM ISLANDS the kinematic transition zone. On the Ruahine/Waiohau Fault, for example, the strike-slip V.E. Neall,G.Davies&R.C.Wallace Ruahine Fault generated 6 Holocene earthquakes, Institute of Natural Resources, Massey University, while to the north in the Galatea Basin, where the Palmerston North fault is predominantly normal-slip, only 1-2 (V.E.Neall*massey.ac.nz) Holocene earthquakes have been recorded (Beanland, 1995; Hansen, 1997). A decrease in the During early 2005, whilst studies of the Mangere number of Holocene earthquakes also appears to Formation on Mangere Island were in progress as occur northwards along the Whakatane Fault, part of the CHEARS Marsden project, an across the kinematic transition zone (between opportunity arose to investigate the pre-Mangere Ruatahuna to Ruatoki North). Although not Formation sequence. This paper re-examines the conclusive, the data suggest that some pre-Mangere Formation sequence on Mangere paleoearthquakes on the Whakatane and Waiohau Island and proposes a new Twin Peaks model. faults terminated within the kinematic transition zone, which functioned as a mechanical barrier to Rangiauria Breccia is mapped as the major volcanic propagation of large ruptures. The along-strike unit forming the edifice of Mangere and Little change in fault kinematics, defined by a 60-70° Mangere Islands. Two distinct lithofacies were northward steepening in the pitch of the slip vector originally recognised by Hay et al. (1970), but on the faults, may therefore separate fault segments subsequently amalgamated by Campbell et al. which ruptured during strike slip and normal slip (1988). The highly lithified limburgitic breccia dominated earthquakes. lithofacies forms the high bluffs of northern Mangere Island and Little Mangere Island. In contrast, a weakly consolidated limburgitic breccia Beanland, S. 1995. PhD Thesis, Victoria University of lithofacies forms the linear southern flank of Wellington, New Zealand. Mangere Island. Orientation of bedding within these lithofacies points to more than 6 centres of

50thKaikoura05 -56- Kaikoura 2005 volcanism and a linear vent oriented NE/SW the site is south of the Subtropical Front (STF), and through Douglas Basin. The Breccia and the source is overlain by cool subantarctic surface water and vents form two topographically high centres, here southern sourced deep intermediate waters. The referred to as North and South Peaks. Stepping site is in a location likely to be influenced by cross- normal faults, and clastic “dykes” infilling tensional frontal exchange of surface waters arising from the cracks from above, indicate significant post- generation of cold and warm core eddies and depositional collapse towards the linear vent. subsequent transport north or south respectively. After volcanism ceased a marine strait or To examine the ocean's response stable isotopes in embayment existed between the North and South foraminifera were analysed from slices averaging Peaks. In this setting coarse grey sandstones 120-250 yr resolution. Surface (up to 400 m deep) (Landing Point sandstone member) accumulated waters were investigated using two planktic immediately above the Rangiauria Breccia on the species. Globigerina bulloides is a surface or near- rapidly aggrading outer southern slopes of North surface dweller, but is also associated with periods Peak. Subsequently these beds were overlain by of enhanced nutrient supply. These conditions are finer yellow-brown siltstones (Black Robin often related to upwelling, which can occur in siltstone member). These beds are highly laminated different seasons in different regions. Globorotalia and cross-stratified having accumulated in the inflata’s depth range extending to 400 m, and are ocean at the foot of ridges radiating from North persistent and numerous in the core. Their oxygen Peak. isotopic compositions generally record Next, gravitational collapses began from high on temperatures colder than co-existing G. bulloides. 13 the south flank of North Peak, deforming the The tendency is for
CofG. bulloides to increase previous beds over which they flowed and under high productivity conditions, while that of accumulating in the marine strait/embayment. other species, including G. inflata, become more Subsequently, further gravitational collapses negative during increased upwelling of subsurface 12 occured northwards from South Peak, (mapped as waters enriched in C. For bottom waters, we Bag End breccia), carrying up to 6.6 m-sized examined Uvigerina peregrina, it records the megaclasts of Rangiauria Breccia into what by this isotopic signal of pore waters in the upper layers of time was a marine embayment. This blocked the sediment, which, for oxygen, is close to that of northwest entrance of the embayment to the sea, bottom water. immediately leading to lacustrine conditions under POSTER which the wood-bearing siltstones of the basal Mangere Formation began to accumulate. RHODOLITH-BEARING LIMESTONES AS ORAL TRANSGRESSIVE MARKER BEDS, SOME NORTH ISLAND EXAMPLES PRELIMINARY EVIDENCE OF DEGLACIAL 1 2 OCEAN CHANGE IN NEW ZEALANDS C.S. Nelson &R.Nalin 1 SUBANTARCTIC Dept. of Earth Sciences, University of Waikato, Private Bag 3105, Hamilton 2 Helen L. Neil1 & Penelope J. Cooke2 Dipt. di Geologia, Università di Padova, Via 1NIWA, Private Bag 14-901, Kilbirnie, Wellington, Giotto 1, 35137 Padova, Italy New Zealand (c.nelson*waikato.ac.nz) 2Department of Earth Sciences, University of Waikato, Private Bag 3105, Hamilton Rhodoliths are nodular structures mainly composed (h.neil*niwa.co.nz) of superimposed thalli of red coralline algae. Since their development is controlled by an array of We present preliminary stable isotope records from ecological parameters, rhodoliths are a valuable the subantarctic region off New Zealand which are source of paleoenvironmental information. used to demonstrate surface and deep-water However, despite their common use in responses to the last deglaciation. Data was paleoecological reconstructions, the stratigraphic obtained from a kasten core collected by the R. V. significance of rhodolith accumulations has seldom Tangaroa in 1997. Fine sampling of this moderate been addressed in detail. sedimentation rate core yields a record of SW In a study of mid-Tertiary rhodolith-bearing Pacific Ocean conditions over the last glacial cycle, deposits from the North Island of New Zealand, potentially allowing an evaluation of the timing of rhodolithic units, usually of limited lateral extent, deglacial events relative to those in Antarctica and are systematically found above major the Northern Hemisphere. The 3.5 m-long core, Y8, unconformities at the base of deepening upwards extends back to at least Marine Isotope Stage (MIS) successions. Two types of transgressive rhodolith- 6, and was recovered from 1335 m water depth, off bearing deposits may be distinguished on the basis the northeastern flank of Bounty Plateau. Presently, of texture and rhodolith internal structure. Type A

50thKaikoura05 -57- Kaikoura 2005 deposits are clast supported rhodolithic rudstones volcanic event that caused a major catastrophe containing abundant pebbles and cobbles reworked about 700 years ago, removing over half of the the from the substrate, and are characterized by Kuwae island. International publications in the rhodoliths with dense concentric to columnar mid-90’s describes these events as dacitic caldera- internal structure and a high nucleus to algal cover forming eruptions, covering Tongoa and nearby ratio. Type B deposits are rhodolithic floatstones islands with large ignimbrites. Volcanic signatures with a matrix usually consisting of bryozoan from ice cores in the Antarctic were related to these fragments, benthic foraminifera, and echinoid purportedly huge volcanic events based on timing fragments or terrigenous silty fine sand. The algal from legends and radiocarbon dating, and global nodules of type B units have usually a loose climatic impacts have been inferred. The source for internal framework with irregular to branched these events was considered by French research crusts. groups to be within a double depression mapped in The two contrasting rhodolith-bearing units are the sea floor, NW of Tongoa. However, “kastom” interpreted as characteristic facies of transgressive stories definitively state that the eruption source systems tract (TST) deposits, analogous to shell was SE of Tongoa, in a location where the concentrations formed under conditions of low net Geological Survey of the New Hebrides mapped a sedimentation. We associate our Type A deposits caldera in the 70’s. The NW caldera has been the with high energy shoreface settings or narrow source of smaller eruptions in the 1970’s and is submerged paleotopographic lows, and equate them named “Karua” (new one or second one). New to onlap shellbeds. Type B deposits are likened to fieldwork has shown that the record of young backlap or compound (mixed onlap-backlap) dacitic to rhyodacitic pumiceous deposits is shellbeds, formed at the basinward termination of a stratigraphically complex, and much more backstepping sediment body in lower energy restricted in distribution than previously settings. considered. On Tongoa, pumiceous ignimbrite and lahar deposits form successions of a few tens of The association between transgression and metres thick as coastal fans or wedges, development of rhodolithic facies is confirmed by a unconformably abutting Holocene basaltic scoria review of published fossil examples, many of cones and lavas. Pyroclastic flow deposits along which show stratigraphic and compositional the SE coast, at the type section of the Kuwae attributes analogous to those of the New Zealand ignimbrites (and where radiocarbon ages are occurrences, and also by our observations of a derived) suggest that flows travelled onshore from a modern rhodolith production site at Whangaparaoa nearby caldera to the SE. A near-vent position is Peninsula north of Auckland, where algal nodules supported by the presence of an up to 2 m thick grow above a ravinement surface cut into welded ignimbrite succession, the only one on Waitemata Group deposits during the Holocene sea Tongoa. Texture of the pumiceous deposits level rise. It is suggested that a combination of suggests deposition from low energy granular factors, such as low net sedimentary input, nature flows. Cauliflower bombs, angular juvenile clasts, of the substrate, sea level rise, inherited elutriation pipes, mud coating on large clasts and physiography, and the Heterozoan composition of massive to weak stratification of the units indicate the association all contribute to determine the magma-water interaction during the formation of relationship between rhodolith-bearing deposits and the majority of the successions. Inland, these transgressive settings. deposits rapidly thin up valleys to form a minor ORAL <0.5 m veneer toward the centre of the island at around 400 m elevation. Similarly, on the NW coast of Tongoa and on a small island to the north WAS THE AD1435 KUWAE EVENT (Laika), pyroclastic deposits of apparently similar (VANUATU) REALLY THE LARGEST (but undefined) age form coastal wedges mantling EXPLOSIVE ERUPTION IN THE SW the scoria cones and lava fields (i.e. deposited from PACIFIC IN THE LAST 1000 offshore to the N and NW). The areal distribution YEARS?IMPLICATIONS FOR REGIONAL of the deposits is small but complex, with abundant HAZARD AND GLOBAL CLIMATE clast morhopology evidence indicating magma- water interaction. These deposits imply small- Károly Németh & Shane J. Cronin volume, and low-energy explosive events similar to Massey University, Institute of Natural Resources, the 1970’s activity (i.e. Surtseyan type eruptions), PO Box 11 222, Palmerston North, NZ with some slightly larger pyroclasitic flow forming (k.nemeth*massey.ac.nz) events from within the Karua caldera area. Other low-lying coastal fans around Tongoa, are formed Kuwae is a legendary landmass inferred to form a by rapidly deposited stacks of pumice-bearing lahar large island in the Vanuatu volcanic arc between and fluvial deposits, suggesting immediate the islands of Epi, Tongoa and Tongariki. remobilisation of ignimbrite and other pyroclastics. “Kastom” stories among islanders describe a

50thKaikoura05 -58- Kaikoura 2005 These areas are also described in “kastom”stories towards Waipori Gorge earned hesitant support of vast swamp lands covering the shoreline after the from Noel Benson of Otago. However, Marshall’s Kuwae event. From our evidence it is clear that views were regarded with scepticism by Survey multiple explosive events took place in this region geologists. When Permian fossils were found from at least two submarine caldera systems. between Nugget Point and the schists, Marshall’s However, our evidence does not support that these scheme was angrily denounced and the events were as extremely explosive and as conventional view that a stratigraphic unconformity regionally hazardous as described. Instead these existed (somewhere) between the schists and the explosive events produced small- to medium greywackes was reinforced. volume pyroclastic deposits. It is very unlikely that During the 1930s, intensive petrological they could have caused significant climatic effect, investigations by F.J.Turner of progressive regional or a significant extra-regional hazard. We suggest metamorphism in Otago and Westland led to his that the mid-Fifteenth Century volcanic signatures identification of metamorphic zones based on index described from ice cores, may fit better to other minerals. Turner then abandoned any stratigraphic volcanic events in the SW-Pacific such as Kaharoa subdivision of metamorphic rocks in favour of eruption that clearly was much larger and more metamorphic zones and focussed on metamorphic explosive. processes rather than geological history. He ORAL subdivided Otago’s very large area of Chlorite zone greywackes and schists into three sub-zones and with his colleague C.O. Hutton identified a fourth STACKING THE SCHISTS: PROBLEMS IN sub-zone. Nevertheless, the New Zealand METAMORPHIC STRATIGRAPHY 1865-1955 Geological Survey map of 1947 maintained that the Otago schists were older than the greywackes. Heather Nicholson Later, the discovery of Triassic fossils in 15A Colonial Rd, Birkenhead, Auckland, New greywackes that clearly graded into schists Zealand (Wellman, Grindley and Munden 1955) showed (hnich*xtra.co.nz) that indeed, the greywackes and schists were both of the same age as the fossiliferous Hokonui rocks The theoretical problems facing nineteenth and of Southland. Soon, Wellman’s invention of the twentieth century geologists in mapping the schists New Zealand Geosyncline (1956) and petrological of New Zealand and placing them in stratigraphic studies by J.J.Reed (1958, 1959) and D.S.Coombs order are examined. The settler geologists (1960) began answering many questions about our considered that the schists and greywackes of metamorphic rocks and, happily, also uncovered north-west Nelson and Westland were continuous lots of new, enticing geological puzzles. with those of Otago and Fiordland. The gerologists were always puzzled by the way in which unaltered ORAL rocks (usually greywackes) passed ‘insensibly’ into metamorphic rocks, and their inability to find an TEMPORAL STABILITY OF REGIONAL unconformity between schists and unaltered rocks. DEFORMATION RATES WITHIN THE Nevertheless, they drew stratigraphic boundaries HIKURANGI SUBDUCTION MARGIN between the schists and unaltered rocks that were all arbitrary and all different. The beliefs that the A. Nicol & L.M.Wallace greater the metamorphism the older the formation, Institute of Geological and Nuclear Sciences, PO and that metamorphic rocks were always older than Box 30 368, Lower Hutt. neighbouring unaltered rocks were used to place the (a.nicol*gns.cri.nz) rocks in a single vertical stratigraphic order and led to assumptions of ages ranging from Carboniferous Global Positioning System (GPS) geodetic to pre-Cambrian. measurements have provided a wealth of new Controversy began early in the twentieth century information on the horizontal velocity fields of when a few geologists took up the idea that the plates and plate boundary zones over the last 10-15 ‘insensible’ gradation from unaltered greywackes to years. GPS present a snapshot of the finite schists was real. Patrick Marshall believed there deformation and, at different locations, is likely to were no unconformities between the rocks of include varying components of elastic, aseismic and Southland, the greywackes, and the Otago schist, seismic strains. Given the short duration of GPS that all were of the same age and all should be measurements, which often sample part of the included in his grand Trias-Jura Maitai System - interseismic periods of the largest active faults except for the metamorphic rocks of northwest (e.g., <10-100 years) and account for <0.01-0.001% Nelson and Fiordland. Marshall’s prepared of the total duration of deformation, uncertainties microscope slides showing increasing grades of remain as to whether contemporary velocity fields metamorphism from Nugget Point northwards and associated strain rates are comparable to those

50thKaikoura05 -59- Kaikoura 2005 measured by geological studies over many seismic David C. Nobes1, Leah Bateman, cycles (e.g., 10 kyr to millions of years). To address Caroline Butland, Mark Flintoft, this question we compare geological rates of Francie Gaiger, Joanna Lea, Scott Wilkinson extension, shortening, fault slip and vertical axis & Harry M. Jol2 rotations, derived from cross sections, seismic- 1 Department of Geological Sciences, University of reflection lines, displaced landforms and Canterbury, P.B. 4800, Christchurch paleomagnetic data and measured over the last 5 2 Department of Geography & Anthropology, Ma, with results from modelling of GPS velocities University of Wisconsin-Eau Claire, USA from the Hikurangi Subduction margin in the North (david.nobes*canterbury.ac.nz) Island. GPS velocities in the North Island are found to be influenced by two fundamental processes (1) Sacred (tapu) sites need to be treated with care and elastic strain due to interseismic coupling on faults sensitivity. Non-invasive, non-destructive in the region, and (2) long-term tectonic block geophysical surveying is an appropriate, optimal rotations (Wallace et al., 2004). It is the latter way to map the nature and extent of such sites, component of the GPS velocity field that can be particularly burial sites – urupa. Since 1997, directly compared to geological estimates of block geophysical methods have been successfully used rotation and fault slip rates. on urupa (Nobes, 1999). The response varies from Regional analysis of the Hikurangi margin suggests site to site, depending primarily on the nature of the that within the uncertainties of the data the rates of soil and the underlying bedrock. deformation for both data sets are, in most cases, The results from four sites representing three approximately equal and independent of the sample physical settings are presented here: period. Geological and geodetic datasets both 1. The Oaro urupa is on top of a hill overlooking indicate rapid clockwise rotation (2-4 °/Ma) of the the South Pacific, and was the first urupa to be eastern North Island. Extension and contractional surveyed using geophysical methods (Nobes, strains result from the rotation. Margin-parallel 1999). The site’s clay soils overlie limestone velocity gradients arising from the rotation of the bedrock. Magnetic, electromagnetic (EM) and eastern North Island account for up to 70% of the ground penetrating radar (GPR) surveys were margin-parallel component of Pacific/Australia completed. The responses are clear and relative plate motion. Stable deformation rates over unequivocal, once the influences due to fences time periods ranging from 5-10 years to millions of and the clay are removed. years are consistent with the constant rates of plate motion observed over similar temporal scales and 2. The Koukourarata (Port Levy) and Wairewa demonstrate the utility of GPS velocity fields for (Little River) sites are in loess overlying the constraining longer-term tectonic deformation (i.e. volcanic bedrock of Banks Peninsula. The EM > 1 earthquake cycle duration). The apparent responses are apparent but are not as obvious absence of faults at the ground surface as for the magnetic surveys. The GPR surveys accommodating aseismic creep and of large have clear anomalous responses that in most magnitude earthquakes over the last 10-15 years, cases can be interpreted as graves (Bateman, suggests that in the upper crust contemporary 2003). geodetic strains are predominantly elastic. These 3. The Mangamaunu urupa is situated in coastal contemporary strains are spatially distributed across beach sands, next to State Highway 1, just much of the North Island, however, the north of Kaikoura and near the hamlet of compatibility of block-rotation rates and fault-slip Hapuku. Anomalous geophysical responses are rates from geological studies and those from all present but less obvious than for the Oaro, modelling of GPS data indicates that elastic strains Koukourarata and Wairewa sites. Nonetheless, will, in the future, mainly be converted to narrow we can identify areas where the variable zones of permanent deformation on, or close to, the geophysical response is indicative of largest faults (i.e. those faults large enough to be disturbance that is likely due to graves. resolved in the regional geology data). Elastic strain release is most likely to take place during large Bateman, L., 2003. Applications of near-surface magnitude earthquakes. geophysics in the search for graves in Maori urupa. B.Sc. (Honours) project in Engineering Geology, Wallace et al. 2004. JGR 109, B12406, Department of Geological Sciences, University of doi:10.1029/2004JB003241. Canterbury, 69 pp. Nobes, David C., 1999. Geophysical surveys of burial ORAL sites: a case study of the Oaro urupa, Geophysics, 64(2): 357-367. FROM KAIKOURA TO KAITORETE: NON- POSTER INVASIVE GEOPHYSICAL MAPPING OF MAORI BURIAL SITES

50thKaikoura05 -60- Kaikoura 2005 3D IMAGING OF THE FORE- AND growth and segment linkage in the active Ostler fault BACKTHRUSTS OF THE GLEN LYON zone, New Zealand. Journal of Structural Geology, SEGMENT OF THE OSTLER FAULT 27: 1528-1546. Wallace, Shamus C., Nobes, David C., Davis, Kenneth J., David C. Nobes1, Douglas W. Burbank2, Burbank, Douglas W. & White, Antony. Three- Colin Amos2 & Kenneth Davis2 dimensional imaging of the Benmore segment of the 1 Department of Geological Sciences, University of Ostler Fault, South Island, New Zealand. Geophysical Journal International: in submission. Canterbury, P.B. 4800, Christchurch 2 Department of Geological Sciences, University of ORAL California-Santa Barbara, USA (david.nobes*canterbury.ac.nz) ACTIVE FAULTING AND PALEOSEISMICITY OF THE OFFSHORE A set of closely spaced ground penetrating radar KAPITI-MANAWATU FAULT SYSTEM, (GPR) and GPS survey lines were acquired across SOUTHERN NORTH ISLAND, NEW the fore- and backthrusts of the Glen Lyon segment ZEALAND of the Ostler Fault. The project is part of a larger ongoing study of thrust fault processes. S.D. Nodder1,G.Lamarche1 &J.-N.Proust2 We collected 21 survey lines, 50-m long and 1 m 1National Institute of Water and Atmospheric apart, and approximately centred on the fore- and Research, Private Bag 14-901, Wellington. backthrust scarps. In addition, common midpoint 2Géosciences Rennes, UMR CNRS, Univ. de (CMP) velocity surveys were completed at each site Rennes 1, 35042 Rennes cedex, France. so that the profiles could be migrated, and the travel (s.nodder*niwa.co.nz) time converted to depth. The velocity structure at the two sites was similar, yet subtly different, and Seismic hazards associated with active faulting in consistent with mostly unsaturated sandy and silty coastal regions may be under-estimated if recent gravels. At the forethrust site, the velocity was 110 offshore deformation is not accounted for in hazard m/µs (± 10 – 15 m/µs) down to about 4 m depth, analyses. At subduction margins, deformation rising to 120 ± 10 m/µs before returning to 110 ± occurs predominantly in the high-strain forearc 10 m/µs from 5 to 8 m depth. In contrast, the basin, but can also extend considerable distance backthrust velocities below the scarp were 110 ± 15 away into the back-arc environment. An example is m/µs at shallow depths (< 2m), and 120 – 130 ± 15 described here in the offshore, low contractional m/µs at depths down to 6 m. Above the backthrust strain Kapiti-Manawatu Fault System (KFMS), scarp, the velocities were more consistent with dry which is located along the eastern margin of the sands and gravels, of the order of 150 m/µs, but proto back-arc Wanganui Basin, 200 km behind the were not well constrained. Deeper velocities were Hikurangi margin subduction front. High-resolution not resolved at either site. seismicreflectiondatashowthepresenceof The 3D GPR profiles reveal a backthrust with a numerous sea-floor fault scarps and near-surface relatively simple geometry, and dipping 65° ± 8° to deformation of late Quaternary and possibly the east. For the forethrust, on the other hand, there Holocene reflectors on high-angle (>60°), are from 2 to 4 individual fault displacements reactivated reverse and normal faults within the visible in the 21 GPR lines, with dips of the order KMFS. Continuous sea-floor scarps, which are of 56° ± 9° to the west-northwest. These results are inferred to correspond to earthquake rupture consistent with measurements on outcrop (Davis et segments, range from <10 to up to ~50 km in al., 2005) and GPR profiles from the Benmore length. segment of the Ostler Fault (Wallace et al., in We derive potential maximum credible earthquake submission), which yielded dips of 50° and 51°, moment magnitudes (Mw) using empirical respectively, ± 9°. regression equations, developed from global data- The most recent main fault displacement almost sets of predominantly onshore faults that relate fault reaches the surface near the top of the current rupture dimensions to Mw. Slip rates are estimated forethrust scarp, with a thin wedge of sediment in from vertical displacements of the sea-floor (6.5 ka) front of the fault. The other fault displacements, and post-last glacial stratigraphic markers (8-9 and each with its own sediment wedge, are located at 10-11 ka), with ages constrained by the dating of successively greater depths and in front (to the east) sediment core material collected at strategic of the current scarp. The forethrust position appears locations. Maximum displacements at the sea-floor to be migrating westward toward the hinterland range from 2 to 30 m, which result in maximum with each new rupture sequence. vertical slip rates as high as 3 mm yr-1 for the largest structure in the KMFS, the Mascarin Fault, -1 Davis, Kenneth, Burbank, Douglas W., Fisher, Donald, but are typically <1 mm yr . The short-term slip Wallace, Shamus & Nobes, David, 2005. Thrust fault rates (<11 ka) are comparable to long-term

50thKaikoura05 -61- Kaikoura 2005 geological rates (<1.3 Ma). Faults of the KMFS lateral propagation and/or early coalescence of maybeabletogenerateMw of 6.0-7.5, with shorter segments, before continuing to increase in recurrence intervals ranging from 2000 to >10 000 height with slower tip extension. Two ridges have years suggesting that previous assertions regarding developed frontal imbricates within 1 Ma of the low seismic hazard of the Kapiti-Manawatu initiation. Initial growth of all the central/east region may not be substantiated, and needs to be re- Otago ranges occurred over a short time period appraised. The method used here for determining with no systematic progression towards the the paleoseismicity of offshore faults has foreland. Continuing activity across the region potentially wider applications elsewhere, and in indicates the whole thrust belt is ‘out-of-sequence’ New Zealand has already been applied to normal in terms of classical thrust kinematics. (e.g., Cape Egmont Fault, Taranaki; offshore Taupo Erosion of the ridges is very slow and they closely Volcanic Zone, Bay of Plenty), reverse (e.g., North reflect tectonic deformation above the underlying Canterbury shelf; Lachlan Ridge, Hawkes Bay) and fault. Elastic dislocation modelling of the strike-slip faults (e.g., Alpine Fault, Fiordland) in topography of North Rough Ridge indicates an the offshore environment. underlying fault dipping north-westwards at 45° or ORAL less. The slipping fault modeled extends from a depth of 1-2 km down to at least 10 km. The average spacing of the ranges of 18 km, together THE GROWTH OF ANTICLINAL RANGES with their average length of 45 km, suggests that IN AN ACTIVE FOLD-THRUST BELT, they most likely extend to the base of the CENTRAL OTAGO, NEW ZEALAND seismogenic zone.

1 2 1 The Rough Ridge system of ridges currently forms R. Norris ,E.Bennett, J. Youngson , the drainage divide between streams draining into J. Jackson2,G.Raisbeck3,&F.Yiou3 1 the Clutha system via the Manuherikia River and Dept. of Geology, University of Otago, PO Box streams draining eastwards into the Taieri system. 56, Dunedin 2 Prior to the growth of these ridges over the last 1.5 Bullard Laboratories, Dept. of Earth Sciences, Ma, it is likely that the drainage systems were quite Madingley Road, Cambridge, U. K. 3 different. The resulting major drainage changes Centre de Spectrométrie Nucléaire et may have important ecological effects, for example Spectrométrie de Masse, CNRS, Orsay, France on the evolution of indigenous fauna. (richard.norris*stonebow.otago.ac.nz) ORAL The Otago fold-thrust belt is situated east of the Alpine Fault within the zone of distributed TUBULAR CARBONATE CONCRETIONS AS deformation along the Australian–Pacific plate CONDUITS FOR METHANE ESCAPE boundary in South Island, New Zealand. Average FEEDING SEAFLOOR COLD SEEPS: SOME shortening rates across the belt, based on both long- NORTH ISLAND EXAMPLES term geological estimates and on preliminary GPS data, are only 2-3 mm/yr. We have employed a S. Nyman1,C.Nelson1,K.Campbell2, combination of geomorphology, structural geology F. Schellenberg1,3,P.Kamp1,G.Browne4, and cosmogenic isotope dating to determine the P. King4 style and rate of fault-fold propagation, and the 1 Dept. of Earth Sciences, University of Waikato, evolution of the topography in the central part of Private Bag 3105, Hamilton the belt. Cosmogenic 10Be measurements were 2 Dept. of Geology, University of Auckland, Private made on “sarsen stones”, remnants of silcrete Bag 92019, Auckland deposits in the Tertiary sediments overlying the 3 Institut für Geologie und Paläontologie, basement schist erosion surface. During uplift of Universität Tübingen, Tübingen, Germany the ranges, the surrounding sediments were rapidly 4 Institute of Geological and Nuclear Sciences, PO stripped, leaving the silcretes behind. Previous Box 30368, Lower Hutt work (E. Bennett et al., J. Geophys. Research, v. (s.nyman*waikato.ac.nz) 110, B02404, doi: 10.1029/2004JB003184, 2005) has shown that 10Be ages up to 1.3 Ma are not Several Cenozoic sedimentary formations in the saturated and provide valuable data on the timing of North Island of New Zealand include locally uplift of the underlying ranges. prominent development of carbonate concretions The data strongly support a model of rapid which exhibit a variety of broadly tubular shapes, establishment of fault length followed by increase and commonly a central conduit that may be empty in amplitude and slow tip propagation. The two or filled with sediment or multiple generations of ridge systems investigated (Raggedy Range– later carbonate cements. Stable oxygen and carbon Blackstone Hill and Rough Ridge–North Rough isotope data suggest that many of the concreting Ridge) have grown since 1.5 Ma, by either rapid and later cements were sourced primarily from

50thKaikoura05 -62- Kaikoura 2005 ascending methane fluids/gases of possible Irish Assoc. Econ. Geol.), and faults and fractures thermogenic origin. appear instrumental in localization or Reconnaissance field studies at localities in onland compartmentalization of active geothermal systems East Coast and Taranaki basins show several in the Rhinegraben, and in the Taupo Volcanic similarities in broad geological setting and Zone (TVZ, Rowland & Sibson, 2004, Geofluids). associated facies (e.g., within upper slope Faults in these systems appear to act either as mudstone), but also local differences likely conduits or barriers, and as pathways for near reflecting their tectonic environment, stratigraphic surface fluids to access ‘impermeable’ basement position, and available fluid migration pathways. rocks. However, the specific interplay of long-lived In some cases there is a clear association of the fluid convection through permeable rocks, and tubular concretions with overlying paleo-sea floor short-lived fluid pumping along seismically active seep-carbonate deposits, and we suggest they may faults, remains uncertain. We explore here the mark the subsurface plumbing network of cold seep interactions of thermally and mechanically-induced systems. Tubular concretions clearly aligned along fluid flow during extension using a fully coupled joints and fractures in the East Coast Basin finite difference code (FLAC). We used generic rift demonstrate an intimate relationship between architecture with a blanket of permeable sediments tectonics and seep development. In eastern and volcanics on a less permeable rifted basement. Taranaki, the presence of dislodged and mass- Firstly, we applied a basal heat flow and generated emplaced tubular concretions in the axial stable convection in the cover sequences, and fluid conglomerates of certain channel facies in slope penetrates down into basement with downwelling mudstone suggests a connection between the loci of zones along rift edge faults. However, when we -14 seep field development and slope failure and applied extension at strain rates around 5 x 10 /s canyon cutting on the late Miocene Taranaki (similar to those in the TVZ), stable convection margin, possibly influenced by the build up of gas cells were rapidly destroyed by fluid flowing pressures during seep development. towards dilatant sites on faults. When we turned the extension off again, stable convection reappeared, Tubular concretions afford an opportunity to but the localisation of upflow zones in the investigate the evolution of cold seeps based on convection cells was controlled by the former ancient examples, and also the linkage between position of structurally-driven upflow. Our results subsurface and surface portions of such a system. may explain why the main NE-trending part of the Seep field development has implications for the TVZ is not associated with thermal upwelling, characterization of fluid flow in sedimentary basins, because in our models the zones of active extension for the global carbon cycle, for exerting correspond with structurally-driven downflow and biogeochemical influences on marine communities, perturbation of the convection. We speculate that and for the evaluation of future hydrocarbon convective- and mechanically driven fluid flow in resources, recovery, and drilling and production extension zones is competitive, rather than coupled. hazards. Apparent coupling may be a consequence of ORAL perturbation of thermal structure by fault-driven flow, which then controls convection cell patterns once deformation subsides. NUMERICAL MODELLING OF THE COMPETITION BETWEEN EXTENSION ORAL AND CONVECTION IN HYDROTHERMAL SYSTEMS GEOLOGY & STRUCTURE OF THE HAUHUNGAROA RANGE, WESTERN N.H.S. Oliver1,B.E.Hobbs2,J.G.McLellan1, TAUPO VOLCANIC ZONE &J.S.Cleverley1 1School of Earth Sciences, James Cook University, A.G. O’Loan, J.V. Rowland & C.J.N. Wilson Townsville, Qld, 4811, Australia Department of Geology, University of Auckland, 2CSIRO Exploration & Mining, 26 Dick Perry Private Bag 92019, Auckland Avenue, Kensington, WA 6151, Australia (a.oloan*auckland.ac.nz) (nick.oliver*jcu.edu.au) The Hauhungaroa Range lies on the western In many upper crustal hydrothermal and geothermal boundary of the Taupo Volcanic Zone (TVZ), and systems, inferences have been made about the comprises a Mesozoic metasedimentary combined effects of extensional deformation and (greywacke) basement block bounded by a SE- thermally-induced circulation. Deepening facing normal fault scarp, with andesite volcanoes convection cells during progressive extension in the at its northern (Pureora and Titiraupenga) and Irish base metals province were proposed to explain southern (Hauhungaroa) extremities. The range- a temporal change in the Pb isotope composition of forming Hauhungaroa Fault scarp appears steep and ores formed near or at the surface (Russell, 1986,

50thKaikoura05 -63- Kaikoura 2005 sharpwhenviewedremotely,whichhasledto 2Skidaway Institute of Oceanography, Savannah, speculation over its role as an active structure. On GA 31411, USA the other hand, it may be a relic of past tectonism, 3Department of Geology and Coastal Resources perhaps reactivated as a border fault early in the Management Program, East Carolina University, history of rifting within the TVZ, but no longer the Greenville, North Carolina 27858, USA focus of extensional strain. Recent fieldwork has 4Virginia Institute of Marine Science, College of better delimited the outcrop areas of some TVZ William and Mary, Gloucester Pt., VA 23062, USA ignimbrites so that they can be used as (a.orpin*niwa.co.nz) chronostratigraphic marker horizons to determine the extent of Quaternary movement on the On the eastern Raukumara Ranges active tectonics, Hauhungaroa block. vigorous weather systems, and human colonisation Offset of the Ongatiti ignimbrite (1.2 Ma) together have caused widespread erosion of the mudstone- with a lack of offset on the younger Whakamaru and sandstone-dominated hinterland. The Waipaoa group ignimbrites (0.32 Ma) constrain the last River sedimentary dispersal system has responded Hauhungaroa Fault movement to 0.32-1.2 Ma. In to such changes, and is now New Zealand’s second the southern sector of the range, NW-trending largest river in terms of suspended sediment minor faults offset the Ongatiti ignimbrite to expose discharge. New sediment accumulation rate data for the peneplaned greywacke surface of the range top. the Poverty Bay continental shelf and slope derived These structures align with steps in the gravity from radiochemical tracers (234Th, 7Be, 210Pb, 137C), profile of the western boundary of the TVZ and palynological, tephrostratigraphic, and seismic their origin may be related to reactivation of pre- methods suggest rapid, margin-wide dispersal of existing basement faults. Faults further to the east Waipaoa sediment. A post-glacial mud lobe on the have been covered by the voluminous Whakamaru outermost shelf and uppermost slope has been a Group ignimbrites obscuring any direct observation locus of high sedimentation rates, attaining 40 m of pre-0.32 Ma faults. NE trending lineaments are thickness in a structurally controlled sub-basin. observed east of the Hauhungaroa Fault, suggesting Here, an offset in the last-glacial erosion surface that faulting youngs to the east. We infer that the indicates that deposition was sympathetic with fault Hauhungaroa Fault block is an early structural activity and the creation of accommodation space, feature within the TVZ and the locus of extensional implying that sediment accumulation was not strain has migrated to the east during the last 300 supply limited. Contrary to classical shelf k.y. sedimentation models, the highest modern In addition to addressing the question of tectonic accumulation rates of 1 cm/y occur in three activity on the Hauhungaroa block, detailed field depocenters: one on the outermost shelf, and two on mapping in the south east of the range has revealed the mid-shelf landward of shelf-edge anticlinal the presence of a new heavily eroded andesite cone ridges. Shelf rates are about 10 times more than the in the area previously mapped as the Hauhungaroa mid-slope plateau. Moreover, short-lived 7Be Lahars. The eastern portion of this cone appears to activities indicate fluvial sediment is rapidly by cut by a NE-trending fault that defines in part reaching the outer shelf and upper slope. Similarly, the western shore of Lake Taupo. Re-examination at sub-millennial time scales, pollen records from of the Hauhungaroa Lahar type locality slope cores fingerprint Polynesian followed by (T18/435634) leads us to suggest that this locality European settlement, and broaden the spatial extent is a lava flow with pronounced spheroidal of post-settlement sedimentation initially weathering. However, detailed mapping shows that documented from the Poverty shelf. Changes in both lava flows and laharic material are present, sedimentation infer a 2-3 times increase in along with colluvial material. The latter has locally accumulation on the shelf after European mantled the underlying Tertiary sediments (Otunui settlement, but a smaller 1-2 times increase on the Formation), acting as an armour and locally slope. Over longer time scales, seismic evidence preserving the pre-Pleistocene peneplaned surfaces. infers slower but steady sedimentation since the last transgression, and that significant cross-shelf POSTER sediment pathways pre-date the increase in sedimentation resulting from colonisation and SPATIAL AND TEMPORAL deforestation. SEDIMENTATION PATTERNS SUGGEST ORAL RAPID, MARGIN-WIDE MUD DISPERSAL AT POVERTY BAY, NEW ZEALAND

Alan R. Orpin1, Clark Alexander2,J.P.Walsh3, Steve Kuehl4 &LionelCarter1 1NIWA, Private Bag 14-901, Kilbirnie, Wellington, New Zealand

50thKaikoura05 -64- Kaikoura 2005 THE GRIFFENS ROAD TEPHRAS: the wave-cut surface of the MOI 9a (Brunswick) VALUABLE MARKER BEDS IN MAPPING marine terrace, suggesting that they all were THE QUATERNARY OF THE MANAWATU- deposited between 340 and 300ka. Tentative WANGANUI REGION correlations are made to ignimbrites in the Central North Island. A. Palmer1,J.Begg2,D.Townsend2 & K. Wilson3 1 Bussell, M., Pillans, B., 1992. Vegetational and climatic Soil and Earth Sciences, INR, Massey University, history during oxygen isotope stage 9, Wanganui PB 11-222, Palmerston North. district, New Zealand, and correlation of the Fordell 2 Institute of Geological and Nuclear Sciences, PO Ash. Journal of the Royal Society of New Zealand, 22: Box 30-368, Lower Hutt. 41-60. 3 Research School of Earth Sciences, Victoria Pillans, B., 1988. Loess chronology in Wanganui basin, University, PO Box 600, Wellington. New Zealand. In: Eden,D.N.andFurkert,R.J.(eds), (a.s.palmer*massey.ac.nz) Loess, its Distribution, Geology and Soils, pp175-191. Balkema, Rotterdam. The age of many of the terraces, their cover beds, Pillans, B., 1990. Late Quaternary marine terraces, south and underlying units in the lower Manawatu- Taranaki-Wanganui (sheet Q22 and part sheets Q20, Wanganui region, has until recently been poorly Q21, R21 and R22), 1:100,000. New Zealand known. West of Wanganui, the map of Pillans Geological Survey Miscellaneous Series Map 18. (1990) provides a detailed temporal and spatial Woolfe, K.J., 1987. The geology of the Turakina- record of marine terraces and their cover beds. In Whangaehu interfluve. Unpublished B.Sc. (Hons) Rangitikei, the aggradation terraces on the western thesis, Victoria University. side of the river have been mapped by Milne POSTER (1973), with minor revisions made by later authors. There remained large tracts of poorly known uplifted terrace land, some folded into growing AUTOSUSPENSION: THEORY AND anticlines. Theses by Massey University and EXPERIMENT Victoria University students provided some insight into the age and distribution of some of the mid-late H.M. Pantin Pleistocene deposits. However, recent examination School of Earth & Environment, University of of the landscape during Q-mapping have provided a Leeds, Leeds LS2 9JT, UK timely rationale for re-evaluation and integration of (pantin*earth.leeds.ac.uk) the stratigraphic record. Critical to determining the age of the landscape, has been the recognition and An autosuspension current may be defined as a identification of the Griffens Road tephras, the particle-driven gravity flow (turbidity current), Fordell Ash, and the Rangitawa Pumice. The ca. which can persist indefinitely without any external 350ka Rangitawa Pumice (aka Mt Curl Tephra) was supply of energy. Such a current is capable of already well known on the Aldworth river terrace entraining additional sediment, leading to that formed in Marine Oxygen Isotope Stage (MOI) acceleration. The critical combination of velocity, 10, the Ararata marine terraces (MOI 11) and older sediment content, and turbulent energy needed for terraces. The Griffens Road Tephras, a group of the current to persist is known as the ignition point three rhyolitic beds (informally “upper”, “middle” (Parker et al., 1986). In their analysis, Parker et al. and “lower”), were previously known from sites (loc. cit.) restricted their investigation to spatially- north of Marton (Pillans 1988), and a few sites developing currents, and to those in the between the Whanganui and Turakina Rivers supercritical field (densiometric Richardson (Woolfe 1987, Bussell and Pillans 1992). The number Ri < 1). slightly younger Fordell Ash, was also found near The Parker et al. model can appropriately be used Wanganui. on those submarine channels where topography, The Griffens Road tephras are found in the marine sediments, or bedforms provide evidence of active sands, dune sands, gravels and loess that form the autosuspension. A good example is the Kaikoura Galpin, Marton, Halcombe-Mt Stewart and Feilding Canyon
Hikurangi Channel system, east of New anticlines and southern and western flanks of the Zealand (Lewis & Pantin, 2002). When the model Pohangina anticline, allowing surfaces in the area was applied to this channel system, with plausible to be mapped with confidence. All three may be values of bottom slope, flow thickness, and found in loess on river terraces that can now be sediment grade, it was found that autosuspension correlated to the MOI 10 Aldworth terrace. The was indeed possible, under suitable conditions. middle and upper tephras occur in the marine and However, it was also found that whenever an terrestrial deposits of the MOI 9c (Braemore) ignition point was obtainable, the Ri number marine terrace. Neither the Griffens Road tephras, always fell within the supercritical field. The nor the slightly younger Fordell ash are found on suspicion grew that perhaps, in the subcritical field

50thKaikoura05 -65- Kaikoura 2005 (Ri > 1), there might be no ignition points, and thus SEPTARIAN CONCRETIONS, FRACTURE no autosuspension. Such a current would deposit FILL ORGANICS AND THE ROLE OF sediment, and hence decelerate. BACTERIA IN CONCRETION FRACTURING This possibility was tested, using a theoretical model derived from Parker et al., in which Michael J Pearson &CampbellSNelson subcritical Ri numbers were imposed, together with Department of Earth Sciences, University of different values of bottom slope, flow thickness, Waikato, Private Bag 3105, Hamilton and sediment grain size. The resulting values of (michaelp*waikato.ac.nz) flow velocity, sediment content, and turbulent energy were then entered into the turbulent-energy Stratabound concretion bodies of marine origin in equation. The energy balance was found to be New Zealand and elsewhere commonly consist of consistently negative, i.e. energy was being anhedral calcite microspar surrounding randomly consumed, and thus there would indeed be no oriented clay and have high minus-cement ignition, and no autosuspension. The important porosities. Calcite 13C and 18O values typically consequence is, that if a change from super- to range from -15 to -20‰ PDB and +1 to -2‰ PDB subcritical flow (hydraulic jump) can be identified, respectively. These data indicate geologically rapid, all of the channel downstream of this point must be pervasive cementation in marine pore fluids shortly essentially depositional. after deposition, with bicarbonate sourced dominantly from bacterial organic matter oxidation. Natural, submarine autosuspension currents are Septarian fracturing in examples from Moeraki obviously very difficult to observe, and the reality (Palaeocene, New Zealand) and Staffin (Jurassic, of autosuspension would therefore be much more Scotland) was probably synchronous with incipient convincing if it could be demonstrated in the cementation of concretions and resulted in up to laboratory. A series of experiments with this 40% volume reduction of the host material. Crack- objective has been carried out by the lining brown, fibrous calcite began to precipitate in Sedimentological Fluid Dynamics Group at Leeds. oxic to suboxic conditions utilising the same Gravity currents were generated by allowing a bicarbonate pool and marine pore fluid as the gravity current (saline solution or silica suspension) concretion bodies but recording a relative lowering to flow from a header tank down an elongated tube of the redox boundary during a depositional hiatus. (5 cm diameter), the whole rig being immersed in The colour of the brown calcite results from an plain water. Roughness elements, to improve included gel-like polar organic fraction that sediment entrainment, were positioned inside the probably represents bacterially degraded biomass. tube, and a test bed of silica emplaced (the same Putative bacterial remains are also present in the grade as in the suspensions). The current velocity Staffin fracture fill. was monitored throughout the run, together with the shape of the descending plume as it emerged at A postulated origin for the fracturing suggests it the lower end of the tube. Allowance was made for predates or is synchronous with carbonate any change in hydraulic resistance, due to scouring cementation. Sufficient rigidity for sediment of the test bed. The time-velocity curves, together rupturing is provided through the binding of with measurements of plume shape, showed good flocculated clay by bacterial secretions. evidence of acceleration due to entrainment of test- Development of septarian (shrinkage) cracks in bed sediment. Significantly, this confirmed that muds is envisaged to require pervasive in situ autosuspension had occurred. bacterial colonisation of sediment volumes, and to depend on the rate of carbonate precipitation versus breakdown of the bacterial clay-complex. Bacterial Lewis, K.B. & Pantin, H.M. 2002. Channel-axis, degradation products are incorporated into early overbank, and drift sediment waves in the southern Hikurangi Trough, New Zealand. Mar. Geol., 192, crack-lining brown calcite crystals. 123-151. Modification of the early-formed septarian Parker, G., Fukushima, Y., & Pantin, H.M. 1986. Self- concretions includes brittle (non-septarian) accelerating turbidity currents. J. Fluid Mech., 171, fracturing, and precipitation of strongly ferroan 145-181. sparry white or yellow calcite cements. Fracture morphologies and internal brecciation of earlier ORAL cements suggests a hydraulic fracture mechanism. Carbonate-bound lipid distributions from the yellow calcite cement probably reflect organic matter breakdown and aqueous solubility of resultant fatty acids or their salts. 13C and 18O data for such late cements are variable suggesting no single bicarbonate source can be invoked. Similar late fracture fills occur in non-marine

50thKaikoura05 -66- Kaikoura 2005 sideritic concretions that occur in Eocene Waikato K. J. Peters1,T.A.Little1,S.L.Baldwin2 Coal Measures in New Zealand. &P.G.Fitzgerald2 1School of Earth Sciences, Victoria University of ORAL Wellington, PO Box 600, Wellington. 2Dept. of Earth Sciences, Syracuse University, ANTISCARP INITIATION AND EVOLUTION Syracuse, N.Y., U.S.A (peterskati*student.vuw.ac.nz) Verne H. Pere, Tim Davies & Jarg R. Pettinga Dept. Geological Sciences, University of The oblique collision of the Australian and Pacific Canterbury, Private Bag 4800, Christchurch. plates has resulted in a complicated zone of micro- (v.pere*geol.canterbury.ac.nz) plates in SE Papua New Guinea. The actively spreading Woodlark rift forms the boundary Antiscarps are defined here as any uphill facing between the Australian and Woodlark plates to the scarp that may be observed on slopes, regardless of southeast of the Papuan Peninsula. Seafloor size or scale, and are variously referred to in spreading rates vary between 30-40 mm/yr at literature as sackungen, ridge rents, obsequent 152°E and ~70 mm/yr at 156°E (Abers et al, 1997) scarps and reverse scarps. Antiscarps are not a and are among the fastest in the world. Continental feature of all slopes, but where they are observed in rifting gives way to sea-floor spreading to the east New Zealand, they typically occur sub-parallel to of 151.4° E providing a unique opportunity to study the valley axes near the ridge crests in mountainous this transition. The rift is a known area of active regions. In Scotland they have been observed over low-angle normal faulting and metamorphic core the entire slope that is from the ridge crest to the complex (MCC) formation including Misima valley floor. Island, a MCC situated on the Pocklington Rise, This research project aims to identify how seismic ~75 km to the south of the Woodlark spreading activity, slope rock mass properties, and mountain centre and 100 km east of its western tip. stress field changes by slope loading and unloading A normal fault, which dips ~25° to the NE, is the from glacial and rock avalanche events, contribute dominant structural feature on Misima Island, to the initiation and evolution of antiscarps. splitting it into two distinct geological domains. Research for this project has so far identified case Amphibolite-facies felsic and mafic gneisses occur study areas in New Zealand and in Scotland in the lower plate and are placed against suitable for analysis of antiscarp formation. In all of greenschist-facies schists and overlying the field areas investigated the antiscarps are unmetamorphosed conglomerates, volcanics, and evident as linear features across the slope with other sedimentary rocks in the upper plate. observed lengths ranging from 200–1000+m. Separating these two domains is a fault zone with a Vertical separation from the crest of the antiscarp to layer of gouge >3m thick. The measured NNE slip the scarp intersection with the slope ranges direction on the fault (slickenlines) is parallel to the between 1-5m on the antiscarps observed in New Australia-Woodlark plate vector between 500 ka Zealand, and 1-10m for those in Scotland. and 3.5 Ma, calculated from seafloor spreading data (Taylor et al., 1999), showing that the development None of the chosen case study areas show any of this structure was directly related to the evidence to suggest that antiscarp formation is extensional tectonics of the Woodlark rift. Beneath driven by translational movement. The case study the fault there is a 2-3 km thick zone of gneisses antiscarps are typically aligned with defects that were ductilely deformed in the lower crust observed within the respective slopes suggesting during the extension. These gneisses have that these antiscarps are in situ deformations of the stretching lineations, commonly defined by slope rather than secondary features within a larger elongate hornblende crystals, that trend towards slope failure. Primary mechanisms considered to NNE, in the plate motion direction and a shallow drive in situ slope deformation are post-glacial dipping foliation that is sup-parallel to the rebound, seismic activity, gravity faulting, and overlying fault plane. Structurally deeper rocks unloading of the slope for mountain by large further to the west retain E-W trending lineations rockfalls. on a sub-horizontal foliation, which we interpret as POSTER an older, collisional fabric. Directly beneath the fault the basement gneisses are strongly lineated and flaggy, appearing mylonitic at outcrop scale, HIGH-TEMPERATURE DUCTILE but lack typical microstructural evidence for non- EXTENSION PRESERVED IN THE coaxial deformation as is commonly seen in the FOOTWALL OF A LOW-ANGLE NORMAL lower plate of other MCCs, including those in the FAULT, MISIMA ISLAND, PAPUA NEW nearby D’Entrecasteux Islands. Quartz CPO GUINEA analyses by U-stage and electron backscattered diffraction techniques show that deformation

50thKaikoura05 -67- Kaikoura 2005 beneath the detachment involved a component of Orthogonal rock defects also partly control the simple shear parallel to the lineation with a top-to- lateral slide boundaries. The slides are triggered by the NE sense-of-shear. High-temperature quartz both short- and long-term tectonic (earthquakes; and feldspar deformation mechanisms, and minimal regional uplift) and climatic (seasonal and glacio- retrogression suggest that the lower plate tectonites eustatic cycles) forcing. preserve an early snapshot of extensional fabrics in Large bedrock landslide dams are recognized in a the lower crust. These fabrics are preserved number of catchments (e.g. Ngatapa, Waipaoa, because they were exhumed by dominantly brittle Tutira, Waikaremoana, Ponui) and these transient processes, involving localised slip on a deeply features block drainages and dramatically alter penetrating detachment fault that transects the catchment sediment fluxes for periods ranging up to middle crust. Localisation of slip on the fault could 104 years. Reservoir deposits allow quantification be due to a weakening effect of high strain-rates on of the degree and timing of perturbations to fault gouge material or deep embrittlement caused sediment flux, and provide constraints on variations by prolonged maintenance of high pore-fluid in catchment sediment yield attributable to long- pressures or high strain rates. term glacio-eustatic climatic forcing cycles. The ORAL influence of these large slope failures is likely to affect the geomorphic development of catchments over a time scale of 104 –105 years. LATE QUATERNARY LARGE-SCALE We have quantified key material strength and ROCK-MASS DEFECT CONTROLLED landslide geometry parameters that allow numerical LANDSLIDES OF EASTERN NORTH landscape evolution models to include large ISLAND, NEW ZEALAND: TECTONIC AND bedrock failures. Such models are needed to CLIMATIC FORCING IN LANDSCAPE investigate the range of conditions leading to EVOLUTION sliding (e.g. uplift rates, incision rates, earthquake

1 2 1 recurrence and shaking intensity) and the Jarg Pettinga ,JimMcKean, Joshu Mountjoy , geomorphic consequences of the failures. Verne Pere1, Kerry Leith1 & Ben Mackey1 1Geological Sciences, University of Canterbury, POSTER P.B. 4800, Christchurch, New Zealand 2USDA Forest Service, Rocky Mountain Research WHAT DOES THE COLOUR OF PUMICE Station, 316 E. Myrtle Street, Boise, ID 83702 USA TELL US? (jarg.pettinga*canterbury.ac.nz) T. Platz1,S.J.Cronin1,K.V.Cashman2 Rock mass defect controlled landslides are &R.B.Stewart1 widespread in the Tertiary bedded marine soft rock 1 Institute of Natural Resources, Massey University, terrain of eastern North Island. The location and Palmerston North, New Zealand frequency of these deep-seated bedrock landslides 2 Department of Geological Sciences, University of is somewhat predictable and the slides are a Oregon, Eugene, USA dominant process affecting both sediment fluxes (t.platz*massey.ac.nz) and landscape evolution. Most slides appear to be base level controlled and occur after stream incision The most recent andesitic sub-Plinian eruption of has exposed a critical stratigraphic horizon, Mt. Taranaki (Burrell Lapilli, AD 1655) produced defined by thin (typically <20mm), comparatively differing coloured and textured pumices. Porosity, weak and laterally continuous bedding parallel permeability, and textural studies were carried out layers. These horizons are of sedimentary origin to understand the mechanisms of pumice formation (e.g. bedding partings; thin sand, clay and volcanic during this one eruptive episode. ash horizons) and may have experienced some prior tectonically induced shear displacement (e.g. Pumice samples were categorized into four groups flexural slip and/or fault shear). The residual based on their colour; [1] uniform pale grey, [2] strength of these sedimentary horizons (Cr’=2.6– brown, and [3] black pumice, and [4] banded to o 20 kPa, and r =2 – ~20°) is very low relative to transitional clasts ranging from pale grey to dark the peak strength of the dominant lithology (Cr’= brown. o <300 kPa, and r =30 - 37°). New failures are Porosity (n=221) and permeability (n=83) triggered episodically as deeper critical measurements were performed on drilled cores stratigraphic horizons daylight following stream (2.54cm x 2.54cm), often collected in two or three incision. Failure on multiple near-horizontal critical mutually perpendicular orientations. Vesicle stratigraphic horizons leads to the development of a textures were characterised by optical microscope “stepped” landscape morphology with extensive and using SEM. block slides, while wedge failures dominate Bulk vesicularities ( ) are highest for [2] with a catchments with moderately dipping successions. median of 70.7%, followed by [1] with 68.5%, [4]

50thKaikoura05 -68- Kaikoura 2005 with 63.8%, and then [3] with 49.9%. The 2 Department of Geological Sciences, University of permeability of the Burrell Lapilli samples is Auckland, Auckland, New Zealand generally up to 10 times higher at given porosities 3 Institut für Geowissenschaften, Universität Mainz, (e.g. 5.3x10-11m2 at =75.1%) compared to Mainz, Germany literature data for dacitic and rhyolitic pumice (t.platz*massey.ac.nz) compositions. In cores drilled on three mutually perpendicular directions, there was no correlation The volcanic activity at Mt. Taranaki, New Zealand between porosity and permeability. However, in is principally characterised by three end member four specimens with >60%, the highest type eruptions: [1] lava flow eruptions (effusive), permeability occurred with the oriented core of [2] lava dome forming eruptions intermediate porosity value. This result suggests (effusive/explosive), and [3] sub-Plinian eruptions that vesicle structure is anisotropic in respect to (explosive). The geological record of volcanic flow path. events at Mt. Taranaki is predominantly marked by Long cores cut into two were analysed for type [1] and [2]; in the past 800 years reproducibility and homogeneity. The data clearly predominantly by [2]. The transition from effusive show that the four pumice types are internally to explosive eruption style within one eruptive homogenous with minor within-category event and within long term eruptive periods is still differences in of 0.1 – 4.0%. However, single poorly known. To understand the different eruptive larger pumice clasts are heterogeneous and their behaviour, petrographical and geochemical studies bulk vesicularity can vary up to 19.9% (n=6). have been undertaken to approach this problem. The bulk rock compositions of all pumice types is The Taranaki andesite rocks can broadly be nearly identical, implying the difference among subdivided into three categories: virtually pumice types is solely based on physical properties. hornblende (hbl) free rocks [1], hbl containing Vesicle textures reveal that type [1] pumices have rocks with different degrees of hbl alteration [2], thinner bubble walls and less microlites as well as and unaltered hbl containing rocks [3]. The heterogeneous bubble size distributions compared presence or absence of hbl in volcanic rocks is to type [2]. Vesicles in [2] are often deformed, crucial in terms of water contents of the magma, presumably causing higher porosities and which strongly influences the eruptive style. permeabilities due to the creation of additional Petrographical data, e.g. degree of alteration of hbl apertures between neighbouring vesicles. and groundmass glass textures, as well as The development of different coloured pumice geochemical data based on e.g. melt inclusions in types is the result of slightly differing physical clinopyroxene and hornblende, give rise to the magma properties, such as temperature and conclusion that there are two end member magma viscosity, resulting in changes in vesicle texture and compositions. We propose the existence of a dry glass composition. This is directly controlled by and a wet andesitic magma. The terms dry and wet syn-eruptive decompression and fragmentation are used to illustrate whether the magma contains processes rather than the pre-eruptive magma hbl (wet) or not (dry). evolution. We conclude that both magmas are derived from Type [1] pumice represents the initial the same initial parental melt at the base of the heterogeneous magma foam just prior to eruption continental crust which then evolves differently followed by type [2] which was able to crystallise during ascent within the crust. The two magma microlites due to sudden decompression and/or compositions erupt either as lava flow (dry) or slower ascent rate. During magma ascent these two pumice fall (wet), representing the effusive and magma foams mingle in the conduit imperfectly explosive end members as observed on the earth’s due to viscosity variations, as observed in [4]. surface. Lava dome forming eruptions producing Deformation in type [2] pumices is related to higher predominantly block-and-ash flow deposits eruption temperature, and hence lower viscosity, represent hybrid magmas caused by than type [1] pumice. mixing/mingling of dry and wet magma. POSTER ORAL

EXPLOSIVE VS. EFFUSIVE – THE JEKYLL AND HYDE NATURE OF TARANAKI ANDESITES

T.Platz1,S.JCronin1,R.B.Stewart1, I. E. M. Smith2 &S.F.Foley3 1 Institute of Natural Resources, Massey University, Palmerston North, New Zealand

50thKaikoura05 -69- Kaikoura 2005 REFLECTIONS ON DIP SLOPES AND crests of ridges. The original gravity faulting LANDSLIDES IN NORTH-EAST mechanism of topographic adjustment proposed by MARLBOROUGH AND THE SOUTHERN Alan Beck in 1968 remains a current model in ALPS internationally accepted slope failure classification. Toppling may now be considered as an alternative Warwick M. Prebble mechanism and is arguably a better fit of the Dept. of Geology, The University of Auckland, topographic features and structural details seen in Private Bag 92019, Auckland. these slopes. Toppling can also be seen as a (w.prebble*auckland.ac.nz) mechanism for developing bending surfaces, which release rock slides, rock avalanches and debris Structure, tectonics and geomorphic expression are flows. These slope failures feed copious quantities themes which run through the last 120 years of of sediment into streams and rivers. They start a geologic exploration of the limestone dip slopes of chain of events, which transfers material from the north-east Marlborough. A complementary mountains to the abyss. development is the gravity faulting model of ORAL topographic adjustment, which is based upon greywacke Mountains in Marlborough and the Southern Alps. This model has been perpetuated in DECONVOLUTING MIXING, landslide classifications and the geotechnical FRACTIONATION AND ASSIMILATION literature. PROCESSES IN ANDESITES FROM The magnificent dip slopes and limestone gorges of RUAPEHU VOLCANO, NEW ZEALAND the Chalk Range and Ben More anticline evoked 1 2 eloquent and passionate comments from Alexander Richard Price , John Gamble , 3 4 5 McKay in 1885 and Charles Cotton 70 years later. Rhiannon George ,IanSmith & Craig Cook 1 In the same year (1955) Harold Wellman School of Science and Engineering, University of recognised the Nidd Landslide in limestone and Waikato, Private Bag 3105, Hamilton. 2 flint near Whernside ridge, parallel to the Chalk Department of Geology, National University Range. Since then, closer examination of the dip Ireland, University College Cork, Ireland. 3 slopes has revealed signs of widespread instability GEMOC Key Centre, Macquarie University, North such as fracture dilation, ravines, debris flows and Ryde, Sydney, Australia. 4 screes. Department of Geology, University of Auckland, Auckland. Geotechnical mapping indicates that flexural 5Department of Earth Sciences, University of toppling affects 30 of 34 discrete slope segments, Waikato, Hamilton. the remainder being rock slides. Each failure is 2 (r.price*waikato.ac.nz) approximately 1 km . Toppling is found down to 70m deep in the cataclinal under-dip slopes in which the bedding and dominant fractures dip in Andesites are now widely recognised as mixtures of crystals and melts that have experienced complex the same direction as the slope but more steeply and 0 polybaric, polythermal events en route to their sites in excess of 25 , the apparent friction angle. Where 0 of eruption. Typical Ruapehu andesites are charged the bedding and fractures dip less than 25 there is with a cargo of crystals, xenocrysts and xenoliths an abrupt transition to parallel dip slopes, which ranging in size from cm-scale to sub-microscopic, develop rock slides on bedding parallel crush indicating that to varying extents the melts have zones. Slope failure is absent where the limestone is interacted with and scavenged their surroundings not closely fractured and does not contain crush and sources prior to eruption. Complex zoning zones. Recent investigations show that the original patterns and melt and crystalline inclusions in the model of uniform toppling proposed for the cataclinal slopes is a simplification. Zones of phenocryst/xenocryst populations attest to this chaotic slope debris intercalated with coherent but complexity. disrupted rock mass suggest partial slope collapse Magma batches from relatively short-lived events in tandem with toppling. Non-uniform toppling (months /years) can show variation that can across a slope, sideways twisting of toppled masses replicate almost the complete range of and sector collapse of topple complexes are features compositions erupted from Ruapehu over much of current slope failure models. longer (1-10 ka) time spans. High precision trace Further south in greywacke and schist some topple element and Pb-Sr-Nd isotopic information and 2 3 new U-Th-Ra disequilibrium data show that it is complexes are up to 20 km in area and 2 km in possible to distinguish between Fractional volume. Reverse scarps, ridge top depressions and Crystallisation (FC) and Assimilation with ridge rents are linked to massive toppling of slopes, Fractional Crystallisation (AFC) processes in small in some cases back to back. Multiple cracks, a few melt batches. This has important and somewhat m wide, several tens of m long and at least a few unexpected consequences for the interpretation of tens of m deep testify to active spreading along the

50thKaikoura05 -70- Kaikoura 2005 U-Th-Ra disequilibria data. In particular, it raises modelling approach is being used to answer these questions about the usefulness of geochronological questions and to try constructing more-dynamic interpretations of these data for andesitic volcanoes. hazard maps that can take current topography into The 1995 – 1996 eruptions of Ruapehu were the account. The Titan2D program (developed by the largest and best sampled events since the dome – GMFG at SUNY Buffalo) is a “shallow water”, forming eruptions of 1945. Nonetheless, the continuum solution-based, granular-flow model. eruptions were small in global terms (< 0.02 km3) The program is adapted by the user for various flow and entirely pyroclastic. Collectively, samples from mechanical properties by changing values for the eruptions over the past 60 years display a internal and basal friction as well as the dimensions spectrum of chemical compositions extending from of the initial pile. Before this model can be applied andesite to dacite and covering much of the range to Taranaki BAFs, we must evaluate the input shown by the prehistoric record, extending back parameters. For this we use the AD 1755 case- 150 ka. The temporal variations in isotopic and scenario, since initial collapse volume can be well trace element variation for andesites and dacites constrained to the partially preserved summit dome. erupted between 1945 and 1996 are systematic and, Internal and basal friction angles were evaluated in comparison with prehistoric eruptives, they through an iterative approach by broadly comparing provide the basis of a model for predicting future modelled flow inundations with mapped AD 1755 eruption patterns. The model we have developed BAF deposit boundaries (especially run-out). A for the Ruapehu magmatic plumbing system could range of possible input parameters were determined also be used to design seismic experiments that to produce a suite of potentially inundated areas might be able to image magma storages beneath the under present-day terrain. This suite of around 10 volcano, thereby providing a more precise basis for forecasts from a uniformly distributed range was predicting future eruptions. then analysed statistically to determine an overall map displaying relative probabilities of inundation ORAL by a future event of the same magnitude as AD 1755. Using this constrained the range of input FORECASTING HAZARDS FROM MOUNT parameters, future hazard forecasts for this scale TARANAKI USING TITAN2D and type of event can be undertaken using the present summit configuration, and altered to Jon Procter1, Shane Cronin1,Abani Patra2, include any changes to topography in the future. Keith Dalbey2, Mike Sheridan2 This type of approach may also be adapted to &ThomasPlatz1, developing appropriate models for other types and 1Institute of Natural Resources, Massey University, scales of mass flows possible on Mt Taranaki. Palmerston Nth, New Zealand Using this approach with outputs representing 2GMFG, State University of New York at Buffalo, differing probabilities for each event modelled what New York, USA methods can be applied to effectively and (j.n.procter*massey.ac.nz) efficiently display the hazard and associated risk. ORAL Over the last c. 800 years at Mt Taranaki at least nine distinct eruption episodes occurred, all of which involved lava dome production and collapse. PROGRESS REPORT: PALEOMAGNETIC Each episode produced several Block-and-Ash ANALYSES OF KASTEN CORES FROM THE Flows (BAFs) that were directed north-westward WAIPAOA BASIN, NEW ZEALAND out of a breached crater wall. The latest dome- collapse in AD 1755 produced a deposit that A. Quinn,J.Robbins&G.Wilson covered an area of approximately 2.06x106 m2 and Geology Department, University of Otago, PO Box reached up to 9.6 km from source. Future activity 56, Dunedin. of this type could have a devastating effect on the (quial125*student.otago.ac.nz) Taranaki Region’s communities, infrastructure and economy. For hazard planning purposes, a U-channel samples were collected from several Volcanic Hazard map of Taranaki was created in kasten cores in January 2005 from a research cruise 1996, with relative hazard zones relating to the (KM0502) as part of the Margins Source to Sink frequency with which areas were inundated by research programme in the Waipaoa Basin, New volcanic flows in the past, with little consideration Zealand of present-day topography. If a similar sequence of (http://www.margins.wustl.edu/S2S/S2S.html). events occurred today, what effect would current Magnetic measurements of NRM intensity and topography have on flow distribution? direction, magnetic susceptibility (
)and Additionally, would modelled flow inundation treatments of AF demagnetisation, ARM and IRM areas be similar to the mapped inundation zones have been performed. The results from these based on past activity? A numerical geo mass-flow measurements are being used in studies to

50thKaikoura05 -71- Kaikoura 2005 determine a record of secular variation and coseismic faulting is responsible for the diffused paleointensity for New Zealand, and for an pattern of observed seismicity. environmental magnetic study of the Waipaoa The submarine canyons are relict features from the Catchment. Records of inclination of the Late Miocene/Early Pliocene that have developed geomagnetic field, NRM intensity and magnetic primarily by downslope erosional processes. They susceptibility are presented. Samples have low have experienced several episodes of re-incision -6 -5 NRM intensities (10 –10 A/m) and similar mean and infilling events, the latest occurring during the destructive fields (MDF ~40mT), which indicate late Pleistocene period of lowered sea level and that the magnetic minerals have a fine grain size, subsequent marine transgression. Presently, are magnetically soft and easily demagnetised. headward erosion of the canyons into the marginal IRM measurements indicate magnetite is the major shelf is occurring by seismically triggered magnetic mineral present in the cores. The basinward sliding of masses at the canyon heads. prognosis for paleomagnetic applications to The head of these canyons indent the marginal shelf environmental and magnetic field studies is good as and they coincide with deep water passages that is the potential for the development of a high- segment the barrier coral reefs protecting the inner resolution paleomagnetic age model for the cores. lagoon and coastline. The canyon heads are Samples are generally well behaved, with sufficient positioned to act as sinks for the coastal sediment magnetic intensity and variations in inclination and transport system. Steep slopes of the canyon heads magnetic susceptibility. NRM intensities appear to are only marginally stable due to rapid deposition provide reliable estimates of relative paleointensity of carbonate sediments from the barrier reef fronts and variations in magnetic grain size, and outflowing lagoonal sediments through the reef concentrations of magnetic grains and magnetic passages. Slope instability is exacerbated here by minerals are jointly indicated by
,MDF,ARM slope oversteepening and undercutting by canyon and IRM. currents. Submarine landslides at the canyon heads POSTER are initiated primarily by periodic short term stresses generated by earthquakes, which have induced destructive local tsunami in the past. The THE OFFSHORE MORPHO-STRUCTURE canyon heads, all of which are within 5 km of the OF THE SOUTHEASTERN VITI LEVU coast, are potential local tsunami source areas that SEISMIC SOURCE REGION, FIJI pose a substantial threat to the coast.

Tariq Rahiman & Jarg Pettinga POSTER Dept. of Geological Sciences, University of Canterbury, P.B. 4800, Christchurch NUMERICAL MODELLING OF (t.rahiman*geol.canterbury.ac.nz) SUBMARINE LANDSLIDE TSUNAMI AND THE LOCAL TSUNAMI HAZARD OF SUVA SE Viti Levu is a seismically active intra-plate CITY, FIJI region of Fiji. The city of Suva (pop. ~150 000), in the SE coast of Viti Levu is vulnerable to the Tariq Rahiman1, Jarg Pettinga1 & Phil Watts2 effects of potential offshore earthquakes and 1Dept. of Geological Sciences, University of associated seismic hazards. Recently acquired Canterbury, P.B. 4800, Christchurch SeaBat multibeam bathymetry and high resolution 2Applied Fluids Engineering, Inc., Long Beach, seismic reflection data reveals for the first time the California physiography of the marginal slope of SE Viti Levu (t.rahiman*geol.canterbury.ac.nz) in unprecedented detail. The marginal slope is divided into five morphological domains, which are An important aspect of tsunami hazard assessment primarily influenced by the underlying geology and and mitigation is to produce predictive simulations structure, and sedimentation from terrestrial of tsunami generation, propagation and run-up. sources. The eastern slope, an area between 178.2 Such simulations require accurate geological data and 178.4 E longitude and 18.2 and 18.4 S latitude, on tsunami sources and a high quality has had added influence from active tectonic computational grid, which is preferably based on processes and seismicity. The surface of this slope high resolution bathymetry data. Predictive models is scarred by linear submarine canyons, which are used for simulations need to be tested and proven the surface expressions of faulted grabens. These by running successful historical case studies. With submarine canyon faults extend onshore as fault a complete range of critical input datasets required valleys and structural lineaments and they for running predictive simulations, the coastal city collectively define continuous onshore/offshore of Suva in Fiji, provides a rare opportunity for fault zones. These fault zones form a complex assessing the tsunami hazard potential of submarine network of faults, through which mesh style landslides. Suva City has experienced damaging historical earthquakes and associated submarine

50thKaikoura05 -72- Kaikoura 2005 landslide tsunami in the past. Recently acquired including the NZ Fossil Record File database high resolution Reson SeaBat 8160 multi-beam (FRED) and the National Paleontological bathymetry shows in unprecedented detail the Collection (NPC). This has enabled GNS to set up, locations and geometries of large slope failure scars for the first time in the current funding regime, an off the coast of Suva. The destructive tsunami explicit paleontological databases programme - which followed the 1953 Suva earthquake provides formerly these activities were supported either a well documented account of a previous submarine through GNS's own resources or as small landslide tsunami in the Suva area. Run-up data and components of other FRST programmes. Aims of arrival times from this event provide a benchmark the new programme are to 1) develop and maintain for predictive models when creating tsunami hazard comprehensive computer databases of fossil scenarios for Suva. localities, collections, identifications, and Using high resolution bathymetry data and paleontological interpretations; 2) provide easily historical records we define the source of the 1953 accessible and useable database interfaces with Suva tsunami as a ~3 x 106 m3 submarine landslide extensive search and retrieval capabilities; and 3) at the head of the Suva Canyon, located 5 km SW attract routine participation (data provision and of Suva. Geometrical parameters from this retrieval) by New Zealand and overseas submarine landslide are used in the researchers. TOPICS/GEOWAVE tsunami initialisation and The NPC was initiated in 1865 by the Colonial propagation model to successfully simulate Museum, and subsequently passed to the NZ observed run-ups and arrival times of the 1953 Geological Survey and its successor, GNS. Suva tsunami at eight different locations along the Collections represent over 55,000 localities, coast of Suva and nearshore islands. The primarily from the NZ mainland, offshore islands, computational grid used in this simulation was and submarine cores and dredgings from the NZ adjusted to low tide to simulate sea level during the region. There are also important holdings from 1953 event. Antarctica and the SW Pacific, and global-scope The bathymetry data shows that the submarine reference collections of fossil and modern species. landslide of 1953 is one of several failures that has Collections include the gamut of animal, plant and occurred in this part of the Suva Canyon head in the trace fossils from Ordovician to Recent, but the past. These slope failures form a large retrogressive main strengths are in macrofossil invertebrates, failure system that has been indenting the outer protist microfossils, and plant macrofossils and edge of the coral barrier reef. Two coral limestone palynomorphs. Most NPC identifications are boulder zones mapped on the reef crest represent databased in FRED, but we plan to computerise tsunami deposits from the last two tsunami physical collection records, type catalogues, etc. to generating submarine landslides from this slope streamline maintenance and extend the use of the failure system. A set of curved fractures mapped on collections. Much of the data will be publicly the barrier reef behind the headscarp of the 1953 available online, and we also plan to make the failure is an indication of the likelihood of the next facility and software available for use by other NZ failure event and ensuing tsunami that will occur at institutions or individuals. this site. A predictive simulation of this future slope Over the last few years FRED has been transferred failure event was done using the source parameters to a new database platform, with public Internet similar to the 1953 landslide and with the access for basic search and retrieval computational grid adjusted to represent high tide, a [http://data.gns.cri.nz/fred/]. This has been a potentially worse case scenario. The results of this challenging process, and further development of simulationshowmaximumverticalrun-upupto4 data entry and retrieval interfaces is planned within m and maximum horizontal inundation up to 400 m the new programme. New capabilities will include at the Suva coast. locality and fossil images, and sophisticated data manipulations (e.g., for research into biodiversity ORAL and statistical biostratigraphy). Following GNS- GSNZ consultation in May 2005, online GNS PALEONTOLOGICAL DATABASES registration of new localities, with continued PROGRAMME participation of regional masterfile centres, is about to begin and this should ensure that new data is fed J.I. Raine, J.S. Crampton, E.M. Crouch, directly into the database. The backlog of existing I. Matcham & B. Morrison locality records not yet in FRED will also be GNS Science, PO Box 30368, Lower Hutt. systematically entered through the new programme. (i.raine*gns.cri.nz) Within the programme we will also maintain and develop associated databases, such as the existing The New Zealand government, via FRST, recently NZ Stratigraphic Lexicon increased available funding for designated [http://data.gns.cri.nz/stratlex/], and taxonomy- Nationally Significant Databases and Collections, oriented databases such as the recently released NZ

50thKaikoura05 -73- Kaikoura 2005 spore-pollen catalogue names. Where space on the map permits, local [http://data.gns.cri.nz/sporepollen]. Our aim is to stratigraphic detail has been preserved to reflect the integrate these with the NPC and FRED databases diversity of multiple depositional basins, to provide a single "seamless" system. particularly for the Late Cretaceous and Miocene rocks. These rocks are predominantly of marine ORAL origin but locally significant terrestrial and volcanic rocks occur. Igneous rocks are relatively abundant QMAP KAIKOURA: THE NEW 1:250 000 in the east of the map area. The most conspicuous GEOLOGICAL MAP OF NORTHEASTERN of these is the Tapuaenuku Igneous Complex, a SOUTH ISLAND discrete mafic igneous pluton which intrudes Pahau terrane and is accompanied by an extensive, largely M.S. Rattenbury1,D.B.Townsend1 radial dike swarm. Time transgressive units such as & M.R. Johnston2 the Amuri Limestone are another feature of the 1 GNS Science, PO Box 30368, Lower Hutt sheet. 2 395 Trafalgar St, Nelson, New Zealand 7001 Glacial till and associated outwash gravel in (m.rattenbury*gns.cri.nz) alluvial terraces dominate the widespread Quaternary deposits of the region. Scree, rock A pre-publication version of the new 1:250 000 glacier and alluvial fan deposits are common in the geological map of the Kaikoura region is presented. mountains and raised interglacial beach deposits 2 The map covers 18 100 km of northeastern South adjacent to the coast reflect Late Quaternary uplift. Island, from northern Canterbury to southern Many lakes in the region are dammed by landslide Marlborough, including Kaikoura and parts of deposits, most of which are attributed to strong Buller and Nelson. The region straddles the earthquake shaking. Australia-Pacific plate boundary and the prominent Marlborough Fault System, incorporating the POSTER Alpine, Awatere, Clarence, and Hope faults amongst others, is a feature of the area. The map SOME LIKE IT HOT! CORE COMPLEX significantly refines the location of many of the FORMATION IN THE CENTRAL AEGEAN known active faults and many new traces have been SEA, GREECE, AND POSSIBLE identified. IMPLICATIONS FOR THE PAPAROA CORE The basement rocks include parts of most New COMPLEX IN BULLER, SOUTH ISLAND, Zealand tectonostratigraphic terranes. North of the NEW ZEALAND Alpine Fault the Buller and Takaka terranes occur in the far northwest of the map and are intruded by Uwe Ring1, Klaus Gessner2, Stephanie Brichau3 the granitic Karamea and Rahu suites. The Median & Johannes Glodny4 Batholith to the east includes the mafic Rotoroa 1Department Geological Sciences, Canterbury Complex and the dominantly felsic Tasman University, Christchurch, New Zealand. Intrusives and Separation Point Suite granite. 2School of Earth Sciences, University of Western Closer to the Alpine Fault are relatively restricted Australia, Perth, Australia. outcrops of the Brook Street and Murihiku terranes, 3Department of Geology, University of Kansas, and a wider exposure of the Dun Mountain-Maitai Lawrence, KS 66045, USA. and Caples terranes. Southeast of the Alpine Fault, 4GeoForschungsZentrum Potsdam, 14473 Potsdam, the Torlesse composite terrane dominates the map Germany. sheet area comprising greywacke of Rakaia and (uwe.ring*canterbury.ac.nz) Pahau terranes in the west and east respectively. The Rakaia rocks of Triassic age are increasingly Continental extension is very differently expressed metamorphosed towards the west, up to greenschist and varies from rifting with little extension resolved facies, textural zone III schist near the fault. The on slowly displacing high-angle faults through weakly metamorphosed Late Jurassic-Early core-complex forma-tion, which in extreme cases Cretaceous Pahau terrane greywacke is generally may accommodate more than 100 km of less structurally deformed than the Rakaia terrane displacement with slip rates >10 km/Myr on the apart from several zones of melange and broken master fault. Numerical simulations suggest that the formation. One of these, the Esk Head belt, occurs viscosity of the lower crust plays a fundamental at the western edge of the Pahau terrane and is role in the mode of continental exten-sion (Wijns et structurally discordant to the Rakaia terrane. The al. 2005). A high viscosity lower crust (and thus a Esk Head belt also contains large areas of poorly small viscosity con-trast between the ductile lower bedded and structurally discontinuous sandstone. and the brittle upper crust) during extension favours The Late Cretaceous and Tertiary rocks of the rift development. A lower strength of the lower region have been unified under a simplified crust, due to a low viscosity, favours a core stratigraphic schema using existing, established complex mode of continental extension. Within the

50thKaikoura05 -74- Kaikoura 2005 core complex mode, temperature driven viscosity PALAEOMAGNETISM OF VOLCANIC variations can determine whether the lower crust ROCKS IN WAITAKERE AND flows in a distributed manner or localisation occurs. COROMANDEL, AND MIOCENE This may allow a distinction between ‘cold’ or RECONSTRUCTION OF NEW ZEALAND ‘strong’ core complexes and ‘hot’ or ‘weak’ core complexes. The latter develop when the lower crust D.J. Robertson has a markedly low viscosity. Hot core complexes Physics Department, University of Namibia, P/Bag in numerical simulations are characterized by large- 13301 Windhoek, NAMIBIA. scale normal faults with great slip and cooling rates (DJR*unam.na) and the de-velopment of an overall symmetric geometry expressed by a relatively late, secondary Samples from 8 sites in the Waitakere Group, ductile shear zone with an antithetic movement located to the west of Auckland, and 8 sites in the sense caused by symmetric, plume-like extrusion of Coromandel Group in the Coromandel Peninsula the hot and weak lower crust. In nature, hot core have been studied palaeomagnetically using complexes may be ex-pressed by extension-related complete progressive af demagnetisation. The two migmatite domes in their footwalls. Most core Groups lie on opposite limbs of a gentle anticline, complexes worldwide appear to belong to the and the respective formation mean palaeofield monovergent cold case. We report on a hot core directions become more consistent after unfolding complex exposed on the islands of Naxos and Ios in is carried out on a regional basis. After unfolding, the Aegean Sea. the palaeofield directions are 346.9°, -62.1°, 26.7° The Aegean Sea is an example of ongoing (as declination, inclination and
95) for the continental extension and core complex formation Waitakere Group and 347.5°, -57.9°, 14.1° for the caused by the retreating Hellenic subduction zone. Coromandel Group. Comparison of these results The extension-related migmatite dome on Naxos with palaeomagnetic data for other parts of New Island is characterized by cooling rates Zealand indicates that, relative to the southeast >100°C/Myr. Low-temperature thermochronology South Island and Chatham Rise, the Northern North reveals great slip rates of ~10 km/Myr associated Island has migrated northwards by an amount in the with the top-N Naxos detachment, which is the order of 1000 km and rotated by some 12° major detachment of the hot core complex. The anticlockwise and since Miocene time. This is secondary, antihtetic top-S normal fault is exposed consistent with large scale dextral displacement of on Ios Island some 40 km south of Naxos. Age data the Alpine Fault, compression in the Southern Alps suggest that the top-S shear zone on Ios formed ~2- and dilatation in the North Island. Anomalous 5 Myr after the Naxos detachment. These data are clockwise rotation in the order of 15° to 45° which consistent with the numerical simulations of hot has been reported for the eastern North Island and core complexes. Exhumation of hot footwall Marlborough is attributable to dextral shear material on Ios did not expose magmatites but deformation in a zone incorporating the Hikurangi triggered anatexis in the lower crust producing syn- Trench system and likely extensions of the Alpine extensional S-type granites in the footwall. Naxos Fault. and Ios are presently situated in a central position above the retreating Hellenic subduction zone. We ORAL argue that asthenospheric flow associated with subduc-tion-zone retreat caused increased heat GEOCHEMICAL ASPECTS OF THE input in the center of the region affected by sub- COROMANDEL VOLCANIC ZONE: TRACE duction-zone retreat causing the anomalous hot ELEMENT AND RARE EARTH ELEMENT conditions on Naxos and Ios. DATA The Paparoa core complex in Buller, South Island, is a symmetric core complex (Tulloch & K.A. Robertson1, R.M. Briggs1, Kimbrough 1989) suggesting it fits the hot core & M.I. Leybourne2 complex case. High cooling rates of the Buckland 1Department of Earth Sciences, University of granite in the footwall of the Paparoa core complex Waikato, P B 3105, Hamilton. (Spell et al. 2000) are in line with this 2Dept. of Geosciences, University of Texas at interpretation. In addition, the Paparoa core Dallas, Richardson, TX, USA complex should have detachments with slightly (kr48*waikato.ac.nz) different ages, with large displacements and high slip rates. Furthermore, high-grade rocks should Late Cenozoic volcanic activity in the North Island occur in the footwall (White et al. 1994) and their of New Zealand has been attributed to a series of peak metamorphism should be of Late Cretaceous volcanic arcs following the movement of the age. subduction zone boundary between the Pacific and Indo-Australian plates. The Coromandel Volcanic ORAL Zone (CVZ) is one such volcanic arc active from 18

50thKaikoura05 -75- Kaikoura 2005 Ma to 1.9 Ma that encompasses Coromandel Eight mappable benthic foraminiferal associations Peninsula, the Kaimai ranges, Great Barrier Island, are recognised by Q-mode cluster analysis of the and the offshore islands east of the peninsula census data (>63 m, 214 species, 68 samples). (except Mayor Island). Canonical correspondence analysis and a Volcanic rocks in the CVZ range from basalts, correlation coefficient matrix were used to relate basaltic andesites, andesites, dacites, to rhyolites. the faunal data to a set of environmental proxies. Volcanic activity was initiated about 18 Ma along These show that factors related to water depth the western Coromandel Peninsula and Great (especially decreasing food supply with increasing Barrier Island, and involved basaltic-andesite, depth) are the most significant in determining the andesite, and dacite cone volcanism which built up overall foraminiferal distribution. Other a large portion of the peninsula. This phase of contributing factors include surface water activity lasted until about 12 Ma, when eruptions productivity and its seasonality, bottom water shifted eastwards and changed to more silicic ventilation, energetic state of the benthic boundary caldera-forming volcanism that continued until 1.9 layer and resulting substrate texture, and bottom Ma as arc volcanism moved from the CVZ to the water carbonate corrosiveness. active Taupo Volcanic Zone (TVZ). Three shallow-water associations (50-700 m), Geochemical analyses of a representative suite of dominated by Cassidulina carinata, Trifarina rocks from the CVZ by XRF (at the University of angulosa, Globocassidulina canalisuturata, Waikato) and ICP-MS (at the University of Texas Gavelinopsis praegeri,andBolivina robusta, occur as Dallas) show that there is a continuous spectrum in coarse substrates on the continental shelf and on of compositions in CVZ. They have similar major the crests and upper slopes of four seamounts under and trace element compositions to TVZ, apart from well-oxygenated, high energy regimes, and high food input. Three mid-bathyal to upper abyssal the high-K rhyolites (up to 5.5 wt % K2O) which are common as sanidine-bearing rhyolites in the associations (500-3300 m), dominated by CVZ, but rare in the TVZ. REE patterns in CVZ Alabaminella weddellensis, C. carinata,and Epistominella exigua, occur in biopelagic sandy andesites and rhyolites have moderate slopes (LaN/ mud, beneath a region of strongly seasonal food YbN average 4 to 8) and moderate Eu anomalies (Eu/Eu* average 0.6 to 0.95). The general supply, with composition influenced by total food geochemical similarities between CVZ and TVZ flux, ventilation (Oxygen Minimum Zone), and suggest that they had similar petrogeneses, with the bottom current strength. An unusual lower bathyal difference that there is a greater proportion of mafic association (1200-2100 m), dominated by T. magma in CVZ. angulosa and Ehrenbergina glabra, occurs in a belt of coarser sandy substrates that runs along the crest ORAL of the submarine plateaux slopes beneath the strongly flowing Subantarctic Front. A deep abyssal FACTORS INFLUENCING THE association (3500-5000 m), dominated by DISTRIBUTION OF SUBANTARCTIC DEEP- Epistominella umbonifera and Globocassidulina SEA BENTHIC FORAMINIFERA, SOUTH- subglobosa, occurs on the abyssal plain beneath EAST OF NEW ZEALAND oligotrophic Circumpolar Water south-east of the Subantarctic Front, and is strongly influenced by Ashwaq T. Sabaa1, Bruce W. Hayward1, cold, carbonate-corrosive, lower Circum-polar Hugh R. Grenfell1,HelenL.Neil2 Deep Water. 1 Geomarine Research, 49 Swainston Rd, St Johns, ORAL Auckland 2National Institute of Water and Atmosphere, P.O. Box 14 901, Kilbirnie, Wellington PROVENANCE OF DEVONIAN BEACON (a.sabaa*geomarine.org.nz) SUPERGROUP SEDIMENTS IN SOUTHERN VICTORIA LAND, ANTARCTICA In this study we investigate the combination of environmental factors that influence the distribution Jeni Savage, Margaret Bradshaw & Kari Bassett patterns of benthic foraminiferal tests (>0.63 µm) in Dept. of Geological Sciences, University of a topographically varied region crossed by both the Canterbury, Priv. Bag 4800, Christchurch. Subtropical and Subantarctic Fronts, south-east of (margaret.bradshaw*canterbury.ac.nz) New Zealand. Seafloor sample sites extend from outer shelf (50 m) to abyssal (5000 m) depths, are Conglomerate beds in the basal part of the bathed by five different water masses, and receive Devonian Taylor Group (Beacon Supergroup) in phytodetritus from Subtropical, Subantarctic and southern Victoria Land provide valuable evidence Circumpolar surface water masses. of provenance and palaeoenvironment. The conglomerates occur within the Sperm Bluff Formation, a unit that overlies an unconformity

50thKaikoura05 -76- Kaikoura 2005 truncating three plutonic suites of the Cambrian deformation (Tabberabberan Orogeny) and Granite Harbour Intrusives (Dry Valley 1a & 1b, subsequent granite magmatism in Australia, New and DV 2) and their metamorphic country rocks. Zealand, northern Victoria Land and West Provenance analysis was carried out on both Antarctica. sandstones and conglomerates using clast counts, POSTER petrographic analysis and U–Pb detrital zircon analysis. Conglomerates are dominated by silicic igneous clasts, mainly rhyolites, and fine-grained LATE CRETACEOUS EUSTASY AND THE quartzites, both of which are unknown in outcrop in EAST COAST BASIN - THE BAD NEWS! southern Victoria Land. Previously recorded 1 2 granitoid clasts could not be found. Poul Schiøler , James S. Crampton &MalcolmG.Laird3 Rhyolite clasts have a geochemistry typical of 1 highly evolved subduction-related rocks. Previous Geol. Surv. of Denmark and Greenland, Ø. Voldgade 10, 1350 Copenhagen, Denmark. workers have dated rhyolite and tuff clasts at 2 between 497±17 Ma and 492±8 Ma, ages that are Inst. of Geol. & Nucl. Sci., PO Box 30 368, Lower Hutt within error of the Granite Harbour magmatic 3 suites. This suggests that the volcanic clasts came Dept. of Geol. Sci., Univ. of Canterbury, Private from a co-magmatic volcanic arc rather than a Bag 4800, Christchurch. northern Victoria Land source as tentatively (pos*geus.dk) proposed by earlier workers. Detrital zircon U–Pb ages for the quartzite clasts suggest derivation from A palynofacies analysis of four sections through the the East Antarctic craton and that the sandstones Paton and Herring Formations of the East Coast had been deposited before the Ross/Delamarian Basin in southern Marlborough shows that the two Orogeny. formations were deposited in a marine environment with conspicuous input of plant material from Sandstones in the Sperm Bluff Formation are adjacent land area. The Paton Formation was arkosic to quartzose in composition but deposited on the inner to mid-shelf under oxic conspicuously lack plagioclase, indicating conditions and in proximity to a river delta. The significant weathering of a continental source. deposition of the Herring Formation took place Detrital zircon analysis gives a strong 500 Ma peak farther offshore, on the mid-shelf, in a mud- characteristic of Ross/Delamarian orogen magmatic dominated environment under poorly oxygenated rocks, and consistent with a local source. conditions at the sediment/water interface, Basin analysis of the six lithofacies comprising the following a landward shift of shoreline. A Sperm Bluff Formation suggest foreshore– stratigraphic analysis of changes in palynofacies shoreface, shallow marine, estuarine and wave- and lithology through the four sections allows a dominated deltaic environments. A large delta, or breakdown of the succession into seven fan-delta, composed partially of easterly-derived depositional sequences, separated by conglomerates, as indicated by palaeocurrent unconformities or their correlative conformities. A directions and channel orientation where the regional sea-level curve for the Middle Coniacian– conglomerates are thickest, became buried by Upper Campanian in the East Coast Basin is marine sandstones during a relative rise in sea level. proposed on the basis of the inferred sequences and The presence of pre-Ross quartzite clasts suggests chronostratigraphic control from dinoflagellate that older continental rocks existed to the east. biostratigraphy. The sea-level cycles thus inferred Westward subduction during the Late Cambrian led for the East Coast Basin show a poor correlation to the emplacement of the Granite Harbour with the re-scaled Haq cycle chart, suggesting that Intrusives and their superstructure of rhyolitic regional tectonics rather than eustasy controlled the volcanoes (DV 1). Dry Valley Suite 2 intrusive East Coast Basin sequences. rocks and associated volcanic rocks were probably

emplaced slightly later in a downfaulted s Dinoflagellates (Schiøler & Wilson, 1998; Chronostratigraphy stage Roncaglia et al., 1999; Sea-level curve Ma extensional intra-arc basin. This had the effect of with modifications from Regional (time-scale after (Haq et al., 1987 NZ Hardenbol et al., 1998) Crampton et al., 2000; Sea-level curve, as re-scaled by and herein) Study sections East Coast Basin Hardenbol et al., 1998)

preserving the volcanic superstructure in the n a

) 71.3 er s uri r WE a pp Isabelidinium High Low (p U downfaulted block while the volcanic rocks were aum pellucidum IZ H

UBM ?sb 6 being eroded from the upfaulted block to expose Isabelidinium HST korojonense IZ ?mf 5 Z I

m NS Campanian the much deeper Granite Harbour Intrusives. Basin e LST-TST murian Vozzhennikovia H

diniu H riens au

o spinulosa ISZ u H inversion during the Devonian caused uplift of the tyr a

er sb 5 S w HST haum Trithyrodinium KR BMS mf 4 Lo suspectum ISZ H LST-TST preserved volcanic rocks, supplying rhyolitic and sb 4 HST P H Nelsoniella aceras IZ ?mf 3 83.5 older quartzite clasts to the lower part of the new LST-TST Isabelidinium cretaceum IZ sb 3 Santonian Piripauan Odontochitina porifera IZ HST 85.8 P mf 2 Conosphaeridium abbreviatum IZ P LST-TST

) P sb 2 an Beacon Supergroup basin. The basin inversion may s LST-HST sb 1 Cymososphaeridium

ar Coniacian rat HST benmorense IZ HST ?mf 0 e (p T Chlamydophorella ambigua IZ 89.0 have been a far-field effect of tectonic changes Turonian (part) indicated by widespread mid-Devonian

50thKaikoura05 -77- Kaikoura 2005 Inferred regional sea-level curve for the East Coast have been rotated from the horizontal since the Basin. Section abbreviations are: BMS=Ben More Cretaceous. The extent of rotation in Central Stream tributary; KR= Kekerengu River, Fiordland is unknown, but is of fundamental headwaters; NS=Nidd Stream; UBM=Ben More importance to this study because two scenarios are Stream, upper reaches. H=Herring Formation, implied. These are (1) with no block rotation the P=Paton Formation, HST=highstand systems tract, GSZ may have been an Early Cretaceous, ~vertical, LST= lowstand systems tract, TST=transgressive oblique slip fault, active along the margin of systems tract, mf=maximum flooding, sb=sequence Central Fiordland, or (2) back-rotating boundary. unconformities closest to the GSZ requires that in pre-Tertiary time the GSZ dipped (present-day) to the east, and therefore may have faulted Eastern ORAL Fiordland over Central Fiordland during the Early Cretaceous. PETROLOGY AND TECTONICS OF ORAL EASTERN FIORDLAND: SOME EARLY RESULTS MARINE TEPHROSTRATIGRAPHY, J. Scott1,A.Cooper1,M.Palin1 & A. Tulloch2 NORTHERN NEW ZEALAND: 1Geology Department, University of Otago, P.O. IMPLICATIONS FOR TAUPO VOLCANIC Box 56, Dunedin ZONE, MAYOR ISLAND AND WHITE 2Geological and Nuclear Sciences, Private Bag ISLAND VOLCANOES 1930, Dunedin 1 2 3 (james.scott*paradise.net.nz) Phil Shane ,E.L.Sikes & T. P. Guilderson 1Department of Geology, University of Auckland, Private Bag 92019, Auckland The paleo-Pacific arc margin to Gondwana records 2 a dynamic (500-100 Ma) history of regional Institute of Marine & Coastal Sciences, Rutgers University, NJ 08901-8521 plutonism, metamorphism and tectonic activity. 3 The behaviour and timing of these events, however, Lawrence Livermore National Laboratory, remains poorly understood. From Eastern Livermore, CA 94551 Fiordland, New Zealand, we present some early (pa.shane*auckland.ac.nz) findings of an investigation into the Paleozoic and Mesozoic evolution of this arc, and in particular Twenty piston cores were collected from depths of structures exposed in the Manapouri region that 600-3000 m from offshore of northern North might clarify a complex period of Early Cretaceous Island, New Zealand. They contain tephra from 11 tectonism. Okataina Volcanic Centre and 4 Taupo Volcanic Centre rhyolite eruptions during the last ~50 kyr The Grebe Shear Zone (GSZ) is a several hundred that produce a tephrostratigraphic framework across metres wide, steeply dipping, ductile, shear zone a tectonically and volcanically complex region of extending from south of Lake Hauroko at least southern Havre Trough, Alderman Trough and the 70km to Lake Manapouri, Fiordland. Mapping, Bay of Plenty continental shelf. This allows on- geochemistry and petrography indicate that it forms shore to off-shore correlations up to 200 km from a significant Cretaceous tectonic suture. source volcanoes, covering much of marine isotope Volcanogenic metasediments of the Jurassic Loch stages 3 and 2. The framework temporally Burn Formation, and Paleozoic to Mesozoic diorite, constrains poorly dated and newly recognised gabbronorite and hypersolvus granite, crop out to volcanic events. Macroscopic tephra layers from the east of the GSZ. Early Paleozoic(?) psammitic the peralkaline Mayor Island volcano are and calc-silicate metasediments intruded by weakly documented for the first time at pre-50 ka, post-50 deformed monzonites occur directly to the west. ka, 39.6 ka, 36.3 ka, 21 ka, and 14.2 ka, in addition During deformation, strain was largely partitioned to the known 7 ka event. These represent some of into ~Late Jurassic- Early Cretaceous granitic the most explosive events from this volcano, and bodies. Rotated K-feldspar porphyroclasts suggest provide new marker horizons. They are dispersed sinistral oblique slip (lineations plunge ~45° up to 90 km north-east to east of the edifice. The southwards). Massive granites, of similar tephra contain high SiO2 (73-75.5 wt %) glass and appearance and composition to the Early subordinate basaltic components, and each Cretaceous Separation Point Suite, cut the GSZ represents a distinct magma batch that can be mylonitic fabric. Dating of these post-GSZ fingerprinted. They form two temporal trends granitoids is in progress. toward less evolved magma compositions, Moderately dipping (~30°) Tertiary unconformities punctuated by a large caldera-forming event at 36 on the eastern and southern limits of Fiordland ka. Minor tephra dispersal is also recorded at 17.7 suggest that the margins of the Fiordland block ka, 25 ka, 35 ka and pre-50 ka. The historically

50thKaikoura05 -78- Kaikoura 2005 active, andesitic White Island volcano has not Margin, and in areas of active compressional widely dispersed tephra, and the oldest primary inversion (e.g. NW Nelson - Taranaki Basin). deposit found is ~20 ka. Five pre-50 ka rhyolite ORAL eruptions from an unknown Taupo Volcanic Zone source provide evidence for explosive activity in a time interval poorly documented on-land. The cores ACTIVE CRUSTAL FLUID FLOW AROUND demonstrate the patchy and uneven preservation of THE NEW ZEALAND PLATE BOUNDARY – large magnitude tephra falls caused by local A RESEARCH FOCUS FOR THE 21ST bioturbation and ponding in bathymetrically CENTURY complex regions. Reworked tephra layers are common and often lack indicative lithological R. H. Sibson features. Such units could easily be misinterpreted Dept. of Geology, University of Otago, P.O. Box as primary events without micro-beam geochemical 56, Dunedin. analyses of glass shards. (rick.sibson*stonebow.otago.ac.nz) POSTER Crustal-scale fluid flow is a frontier area in Earth Science, critically relevant to exploration for, and 3-D STRUCTURAL PERMEABILITY IN future exploitation of, energy and mineral resources CONTRACTIONAL SETTINGS (oil, gas, geothermal power, hydrothermal mineral deposits). The New Zealand plate boundary R. H. Sibson (NZPB) is a geochemical factory where the Dept. of Geology, University of Otago, P.O. Box interplay of tectonic and magmatic processes 56, Dunedin. promotes fluid redistribution between the (rick.sibson*stonebow.otago.ac.nz) atmosphere, continental and oceanic rock assemblages, the ocean water mass, and the deep Fluid flow in the Earth’s crust is influenced by Earth. The diverse character of the boundary, anisotropic permeability as well as by hydraulic comprising opposite-facing subduction zones along gradients in the crust. 2-D modelling of flow the Hikurangi and Fiordland Margins linked by an systems based on cross-sections drawn imperfect transform fault system, gives rise to an perpendicular to the strike of orogenic belts can be array of sites where aqueous and hydrocarbon misleading when considering fluid redistribution fluids are being actively redistributed within the during contractional orogenesis, because of the crust. These include: tendency to think of flow as restricted to the plane i. active hydrothermal circulation coupled to of the section. Topographically driven flow and magmatism in the Taupo Volcanic Zone (TVZ) flow in overpressured systems may both be affected (and its northeastward continuation along the by directional permeability parallel to strike. Lau-Havre Trough); Bedding anisotropy and other forms of primary rock layering combine with stress/strain-controlled ii. zones of sediment compaction and structural permeability, embracing systems of faults compressional ‘squeegee’ deformation with and fractures as well as fold closures, foliations, associated fluid loss along the Hikurangi and etc. In simple fold-thrust belts associated with Fiordland subduction interfaces; accretionary prisms, collisional, and compressional iii. areas of ongoing compressional inversion inversion orogens, structural permeability is associated with hydrocarbon migration in the dominated by fold hinges and duplex structures, Taranaki Basin and in the northwestern and plus fault-fracture intersections aligned parallel to southern South Island; and strike. In both active and ancient fold-belts, iv. topography-driven flow in the uplifted Southern evidence exists for high levels of hydraulic Alps and other mountain ranges flanking the communication extending along fold hingelines for linking transform fault system, and around major kilometres to tens of kilometres along strike. Where volcanic edifices. Fluid redistribution is convergence varies along contractional orogenic variously driven by topographic relief and belts, fluid may thus be expelled laterally along this precipitation, upwelling mantle and magmatic directional permeability from the regions of most intrusion leading to convective circulation of intense shortening. The volume of fluid passing hydrothermal fluids, compaction, deformation, through a cross-strike section is then likely to be far and metamorphic dehydration of thick greater than that inferred from considering fluid sedimentary sequences, and changes in the redistribution restricted to the plane of the section. regional stress state. While flow in near-surface Along the New Zealand plate boundary, 3-D systems typically occurs under near-hydrostatic structural permeability affecting fluid redistribution fluid pressure (the ‘normal state’), fluids at depth seems likely to be especially important within the may be structurally compartmentalised and dewatering accretionary prism of the Hikurangi overpressured well above hydrostatic values.

50thKaikoura05 -79- Kaikoura 2005 Flow systems are influenced by structural 2. During arc infancy (0.5-1.0 my) heat is permeability and modulated by stress cycling transferredbyconvectiontothelowerarc which accompanies intermittent rupturing on crust. Hydration of crust through reaction of faults, with coupled changes in fault-fracture pyroxene + olivine –bearing lithologies with permeability. hydrous fluids produces amphibole. Surficial The NZPB thus provides a world-class natural eruption continues with eruption of basalt- laboratory where dynamic flow systems are andesite magmas. accessible to investigation by geological, 3. A stage of arc adolescence (1-2 Ma) geochemical and geophysical techniques, both commences as the temperature of a significant onshore and offshore, and by numerical modelling. volume of lower crust approaches the Questions to be addressed for each of the tectonic amphibole-saturated solidus at 850-950oC. domains include the fluid sources, the rates of flow, Dehydration melting fluxes the crust and melt the degree of water–rock interaction along flow volumes of a few km3 to tens of km3 are paths, the influence of structural permeability on rapidly generated. A 20-30% melt fraction fluid redistribution, and the total fluid budget. A segregates from a granulitic residue and Discussion Meeting and Workshop is proposed for ascends to upper levels in the system. late 2006, hosted by GNS Science at Avalon in Triggering mechanisms include episodic Lower Hutt, to evaluate our present state of transfer of extensional strain into the crust or a knowledge, define areas for future research, and pulse of magma associated with a major devise research strategies to enhance understanding recharge event. Felsic magmatic eruptive in this field of ever-increasing importance. activity may be interspersed with continuing basaltic-andesitic activity. ORAL 4. Arc maturity (>3 Ma) sees a continuation of basaltic to andesitic activity. The lower crust SILICIC MAGMAS IN SUBDUCTION having undergone dehydration melting is now SYSTEMS anhydrous granulite significantly below its solidus temperature and it acts as a thermal Ian E M Smith insulator preventing convection of Department of Geology, University of Auckland, hydrothermal fluids. Further anatexis can only PB92019, Auckland, New Zealand occur if appropriate source materials remain to (ie.smith*auckland.ac.nz) participate in the hydration-dehydration cycle.

A widely accepted paradigm is that continental crust is exclusively generated in continental Work in andesitic volcanic systems shows that the subduction systems where large volume silicic composition of erupted magmas varies magmas are produced by crustal anatexis. systematically with time a feature that is interpreted However, work in oceanic arcs suggests that this as increasing involvement of a crustal component general conception is not valid. Although oceanic as the isotherm rises in response to magmatic flux. subduction systems mainly produce magma ranging By analogy with the proposed model for oceanic from basaltic to basaltic andesite, silicic magmas arcs rhyolitic magmatic systems in continental, can be locally abundant. For example, a feature of subduction linked settings represent the end the Tonga-Kermadec oceanic arc is the abundance member state of this evolutionary spectrum of of silicic compositions typically associated with petrological processes where the crustal component calderas comparable in scale to those of continental has come to dominate. settings. In the thermal evolution of an oceanic arc ORAL system the processes of underplating, together with the continuous magmatic (and thermal) flux, can generate a crustal thickness in which dehydration TRENDS IN RHYOLITE GEOCHEMISTRY, melting of under plated arc material generates felsic MINERALOGY, AND MAGMA STORAGE magmas. DURING THE LAST 50 KYR AT OKATAINA AND TAUPO VOLCANIC CENTRES Oceanic arcs evolve through the following four stages: Victoria C. Smith1,P.Shane1 &I.A.Nairn2 1. Generation of subduction-related basaltic 1 Department of Geology, The University of magmas initiates a volcanic system on oceanic Auckland, Private Bag 92019, Auckland. crust. Under-plating magmas cool and 2 45 Summit Road, Rotorua RD5. crystallize and hydrothermal convection (v.smith*auckland.ac.nz) develops through the lower crust. At the top of the system relatively fractionated magmas During the past 50 kyr, rhyolitic volcanism at OVC begin to build a volcanic edifice. and TVC caldera centres has been more frequent

50thKaikoura05 -80- Kaikoura 2005 and voluminous than at any on Earth. The high ion-microprobe analyses (at University of frequency of episodes appears to reflect the thin Edinburgh) of the volatile contents and trace crust, high heat flow, and active tectonic regime of element compositions of quartz-hosted melt the central North Island, New Zealand. The two inclusions and their associated matrix glasses. The contemporaneously active calderas, OVC and TVC, melt inclusions provide information on dissolved that have been active in the last 50 kyr display volatile concentrations, minimum pressures of contrasting volcanic and magmatic histories. crystallisation, and degassing processes in the pre- Following the last caldera-forming episode at ~50 eruption magmas. The trace-element compositions ka (Rotoiti) from OVC, intra-caldera episodes have of the inclusions and matrix melt can reveal magma tapped progressively more evolved (~71- 77 wt % variation and mixing processes. Very little was SiO2), shallower (>400- 150 MPa), and cooler (940 previously known about volatile abundances and -730°C) magmas. Directly following the caldera- trace elements in the melt phases of Okataina forming episode, eruptions were rhyodacites and rhyolites. derived from deep, hot magmas, containing More than 70 melt inclusions (>20 µm) have been clinopyroxene. The most recent OVC eruption analysed in this study. Volatile contents vary episodes (post-26.5 ka) were from shallow, cool significantly between and within the magmas; the magmas, and are dominated by hydrous mineral wide ranges indicating that inclusions were trapped phases. In general, the frequency of episodes has at different stages of degassing-induced decreased and volume of eruptions appear to have crystallisation. H2O contents range from 0.7 to 5.4 increased over time at OVC. At TVC, pre-26.5 ka wt %, and CO2 concentrations between 30-660 eruption episodes were relatively infrequent, and ppm. Most of the CO2 variation is seen between were derived from shallow (~100 MPa), cool magmas, with typical variation within a magma (~750oC) magmas, containing hydrous mineral <150 ppm. All the inclusions were trapped at phases. After the caldera-forming 26.5 ka Oruanui pressures equivalent to depths <8 km, with most at episode at TVC, initial eruption episodes were about 4 km. These pressures agree with dacitic, infrequent, and derived from small volume, crystallisation closure pressures estimated by hot (>900°C), and possibly deep (~400 MPa) projecting matrix glass compositions onto a magmas. At 12 ka TVC rhyolitic activity re- synthetic Qz-Al-Or-H2O system. Li concentration commenced, episodes since have been more correlates positively with H2O, which suggests it was being partitioned into the vapour phase and lost frequent, hotter (~790 -850°C) and it is likely that from the melt during degassing. It appears that most they progressively tapped deeper (~140 -300 MPa) of the Tarawera rhyolite magmas experienced a magmas. Following caldera-formation, erupted combination of open and closed system degassing. magmas at both OVC and TVC were the least Major element compositions of Tarawera rhyolite evolved, hottest (>900°C), and were likely from melts (determined by electron-microprobe at deep (~400 MPa) chambers. This suggests that University of Auckland) are usually similar these magmas rose rapidly after formation and between inclusions and their associated matrix exploited new conduits generated during the glasses. However, the trace element concentrations caldera collapse. (by ion-microprobe) vary between the melt POSTER inclusions and matrix glasses, the amount of variation is different in each magma. Variations in ratios of incompatible trace elements (e.g. Nb/La) VOLATILE AND TRACE ELEMENT in the melt inclusions of some Tarawera magmas CONCENTRATIONS IN MELT INCLUSIONS suggests that the trace-element variation is not just AND MATRIX GLASSES FROM POST-25 KA a function of crystallisation, and that some mixing TARAWERA RHYOLITES, OKATAINA of magmas must have occurred. VOLCANIC CENTRE ORAL V.C. Smith1,I.A.Nairn2 & P. Shane1 1 Department of Geology, The University of GEOTECHNICAL INVESTIGATIONS AND Auckland, Private Bag 92019, Auckland. 2 GROUNDWATER MONITORING FOR 45 Summit Road, Rotorua RD5. WELLINGTON INNER CITY BYPASS (v.smith*auckland.ac.nz) J. Speed Three of the four rhyolitic episodes (21.4 ka Opus international Consultants Ltd, PO Box 12- Okareka, 17.7 ka Rerewhakaaitu, 13.8 ka Waiohau, 003, Wellington. and ~AD1315 Kaharoa) from Tarawera in the last (Josephine.Speed*opus.co.nz) 25 kyr have each tapped two or more rhyolite magmas. The relationships and properties of all The Wellington Inner City Bypass project involves these Tarawera rhyolites are being examined by developing an arterial route from the existing

50thKaikoura05 -81- Kaikoura 2005 Terrace Tunnel South Portal to the Basin Reserve, undertaking in a dynamic urban environment, with in Wellington City. The bypass is predominately at traffic, vandalism, road maintenance, and urban street level, but a section of the northbound lanes development making continued monitoring from Willis Street / Abel Smith Street intersection challenging work. to Ghuznee Street involves construction of a POSTER depressed two-lane road. Opus International Consultants is Transit's consultants for this project from its inception to detailed design and currently TRANSITION FROM SOFT-SEDIMENT TO construction management, and has developed WEAK ROCK DEFORMATION IN innovative approaches to resolve the geotechnical TURBIDITES OF THE MIOCENE challenges. WAITEMATA PIGGY-BACK BASIN, The depressed section will pass under a new bridge NORTHERN NEW ZEALAND at Vivian Street and will require extensive retaining structures. The innovative trench design K. B. Spörli &J.V.Rowland incorporates a propped reinforced trough structure Department of Geology, University of Auckland, and 200 m long soil nail retaining walls between Private Bag 92019, Auckland. the Terrace Tunnel portal and Abel Smith Street. (kb.sporli*auckland.ac.nz) The up to 7 m high soil nail walls are supported by a total length of about 7000 m of soil nails. This The well known, spectacular shore platform and will be the largest soil nail wall in New Zealand. cliff exposures of the Miocene Waitemata Group on Extensive geotechnical site investigations have eastern Whangaparaoa Peninsula 50 km north of been carried out to determine ground and Auckland provide a world-class example of weak groundwater conditions in the vicinity of the bypass rock deformation, the neglected domain between route, particularly where the proposed road will be soft-sediment and hard rock deformation. As a new depressed below existing ground level, and adjacent convergent plate boundary propagated southwards to existing buildings. In the propped wall section, through northern New Zealand in the Late groundwater levels will be temporarily lowered Oligocene, the Northland Allochthon was during construction, then allowed to recharge. In emplaced. The allochthon subsequently formed a the soil nail sections, groundwater levels will be mobile base for the Waitemata piggy-back basin, permanently lowered. During construction a resulting in a complex interaction between tectonic limited amount of excavation will be opened at any and gravity-driven shallow deformation. Quartz- one time to minimise the amount of drawdown in poor clastic sequences of the Waitemata Group at groundwater levels. Artesian pressure relief wells Whangaparaoa display a protracted sequence of are being drilled into bedrock to relieve deformations: D1, syn-sedimentary slumping at the groundwater pressures are underway. Building top of the sedimentary sequence and including condition surveys, before during and after the seismites; D2, large scale deeper-seated sliding and construction are being undertaken. extensional low-angle shearing, associated with generation of boudinage and broken formation; D3, A programme was developed to monitor the contractional shearing at low angle to bedding groundwater, ground deformation, and subsidence. associated with thrust faults and inclined folds, Instrumentation comprises of piezometers, indicating transport mostly to the SE; D4, thrusting inclinometers and settlement stations which were and folding in the opposite direction; D5, further installed prior to commencement of excavation. folding including sinistral shear; D6, steep faults. Multiple piezometers were installed in many of the The deformation sequence suggests continuous or boreholes to record and monitor the groundwater intermittent southeast-ward transport of units with levels in different aquifers. Over 90 vibrating wire increasing sedimentary and structural burial. Phase and standpipe piezometer combinations were D3 boudinage and broken formation are localised installed in 41 different boreholes throughout the and, with a few exceptions, occurred by brittle Wellington Inner City Bypass area, measuring a deformation. Subsequent folds show little variation number of different aquifers. Vibrating wire in bedding thickness around their hinges. By phase piezometers were used at locations important for D3, the rocks had therefore passed from the soft- construction monitoring, as they respond more sediment state to low levels of consolidation. quickly to groundwater level changes that may However, with a compressive strength of ~5 MPa occur during construction, especially in the bedrock they are weak rocks even today. These aquifer that will be drawn down during construction deformations, although more intensive than of the walls. elsewhere, are typical for the entire Waitemata The piezometers were installed in a number of site basin. Such weak-rock deformation must be investigation stages. All 41 piezometer sets will be important in other sedimentary basins, especially in monitored regularly throughout the Wellington those associated with active convergent plate Inner City Bypass construction, a difficult

50thKaikoura05 -82- Kaikoura 2005 boundaries and with immature source areas for their 10-17 m2, we calculate that water is supplied to the sediments. root of the Alpine fault zone at a rate that is about 40 times greater than it can bleed off through crust ORAL of regular permeability. For the majority of plate motion to be carried on a GEOPHYSICAL EXPLORATION OF THE single inclined fault plane the fault itself is likely to ALPINE FAULT ZONE AND EVIDENCE FOR be weak or of low friction. Most continental HIGH FLUID PRESSURE transforms with a component of convergence partition motion into a vertical strike slip fault and 1 2 3 Tim Stern , David Okaya & Stuart Henrys distributed thrust faults. Southern California is an School of Earth Sciences, Victoria University example. We therefore argue that it is high fluid Dept. of Geol. Sci., Uni. of Southern California, pressure, due largely to fluid-release from prograde Los Angeles, USA metamorphism that reduces effective normal IGNS, Lower Hutt. stresses in the Alpine fault zone. And it is possibly (tim.stern*vuw.ac.nz) this reduction in normal stresses that allows plate motion to focus on a single inclined plane. In light A fresh look at the problem of sustaining fluid of recently published findings of periodic slip and pressures in active fault zones can be obtained by “slow” seismic tremor associated with fluid- studying a major continental transform other than saturated parts of other plate boundaries, it seems the San Andreas Fault. The Alpine Fault (AF) of important to undertake long-term seismic and GPS central South Island is one such example. From a monitoring of the central section of the Alpine global perspective the AF is unusual as it is a Fault. continental transform where both strike-slip (~ 35 mm/y) and dip slip (~10 mm/y) movement take ORAL place on the same fault plane. Moreover, geophysical evidence shows this fault plane dips at SEISMIC HAZARD ANALYSIS IN NEW o 40 to 60 from the Earth’s surface down to a depth ZEALAND DURING THE LIFETIME OF THE of at least 30 km where it soles out into what we GEOLOGICAL SOCIETY interpret to be a decollement surface. Detailed analysis of seismic travel time anomalies and M.W. Stirling, G.H. McVerry, K.R. Berryman, seismic reflection amplitudes show that above the &W.D.Smith dipping fault-plane is a banana-shaped region Institute of Geological & Nuclear Sciences, PO where seismic P-wave velocities are reduced by 6- Box 30368, Lower Hutt 10%. This low-velocity region has dimensions of (m.stirling*gns.cri.nz) roughly 20 x 40 km with the shallowest and deepest points being at ~ 8 and 35 km, respectively. A New Zealand sits astride the boundary of the magnetotelluric study shows a low electrical Australian and Pacific Plates, where relative plate resistivity zone in the crust that correlates closely motion is expressed by frequent, and often with the region of low seismic velocities. damaging earthquakes. The Geological Society of Interconnected water at, or close to, lithostatic New Zealand has been in existence throughout the pressure is the physical condition that would give evolution of earthquake hazard analysis in New rise to both the low resistivity and low P-wave Zealand, and many Society members have velocities. Corroborative geological evidence for contributed to the associated advances in the high fluid pressures can be seen in the form of science. The 1960s saw major contributions to young, undeformed, quartz veins that are within understanding the patterns of seismicity in New freshly exhumed crust east of the surface exposure Zealand, and the relationships between active faults of the Alpine fault. The question then arises: how and earthquakes. Prominent scientists such as the are high fluid pressures contained in the fault zone? late Frank Evison and late Gerald Lensen were A simple answer is that fluid is supplied to the root leaders in these efforts, along with Robin Adams, of the fault zone at a rate that is higher than it can who showed the importance of parameters like be removed via porous flow through the crust. tectonic setting, fault slip type and soil properties in Greywacke-schist rocks that are transported into the the assessment of earthquake hazard. The USA- fault zone are thickened as they travel down a based formulation of probabilistic seismic hazard decollement surface; this surface has been partially (PSH) methodology by Allin Cornell in the late imaged with seismic reflection methods. As the 1960s led to the development of PSH models for crustal rocks are thickened water will be released New Zealand in the 1970s and 80s. These PSH (zeolite amphibolite prograde metamorphism) at models were often the combined products of an estimated rate of 0.15 % wt per km of burial. On engineering seismologists, seismologists and the basis of our seismic crustal structure models, geologists, but largely limited to the historical and assuming a regular continental permeability of record of seismicity. The well-known “Smith and

50thKaikoura05 -83- Kaikoura 2005 Berryman” model was used as the basis for material into the crust. What constitutes a Moho in Loadings Codes from the mid-80s almost to the this region of high extension rates and elevated heat present day. The growth and acceptance of flow is also less clear. Beneath the back-arc the paleoseismology as a discipline eventually resulted most prominent boundary, from long-range in PSH models that included active faults explicitly refraction and reflection data, is between the as earthquake sources in the 1990s, initially in extended and intruded upper crust, and a layer of regional studies, and eventually at a national scale. new crust formed by underplating. From the top of The most recent national PSH model includes over the underplating, seismic velocities increase with 300 fault sources, and incorporates the latest depth, imply an increasingly mafic composition ground motion attenuation model for New Zealand. with depth. Mantle velocities and hence the base of Multidisciplinary and multi-institutional the crust are reached at ~ 20 km depth. Thus the collaborations are the basis for the new breed of transition from lower crust to upper mantle is models. Present efforts are focused on improving broad, and a conventional Moho does not exist the fault and seismicity source input to the national beneath the CVR. model. The latest iteration of the model now ORAL includes an additional 100 fault sources largely from offshore, courtesy of the National Institute of Water and Atmospheric Research. Equally THEN AND NOW - AND QUITE A BIT THEN important are efforts focused on validating the AND NOW - AND QUITE A BIT BEFORE national model against independent data, and AND IN BETWEEN relevant research into “time-varying” phenomena such as earthquake interactions in space and time, R. P. Suggate and elapsed time since the last earthquake. Institute of Geological & Nuclear Sciences, ORAL P.O.Box 30368, Lower Hutt (p.suggate*gns.cri.nz)

CRUSTAL EXTENSION AND THE MOHO IN I present a personal view, starting by setting the THE CENTRAL VOLCANIC REGION scene over the 25 years before 1955, during which significant advances held out the promise of far 1 1 W.R. Stratford &T.A.Stern greater understanding to be obtained by well 1. Victoria University of Wellington, PO Box 600, focussed studies. Wellington. (Wanda.Stratford*vuw.ac.nz) The next 50 years saw the New Zealand Geological Survey present a series of 1:250 000 maps for the Crustal thickness measurements in the Central whole of New Zealand, and become involved with Volcanic Region (CVR), the back-arc basin in both important industrial developments and with North Island, show that here the crust has been “Think Big” projects. It developed specialist thinned by at least 50 %. This wedge shaped sections in basin studies, engineering geology, earth segment of extended crust is the onshore deformation and computers, while retaining continuation of the oceanic Lau-Havre back-arc previous paleontology and petrology sections. It spreading centre. A region of negative residual balanced application with research. When later the gravity anomalies clearly outlines the western and Survey was joined with DSIR’s Geophysics eastern margins of the CVR. Andesite arcs also Division and then subsumed into the Institute of define the boundaries of the CVR. An east moving Geological & Nuclear Sciences, much of the and rotating subduction zone through time is Survey’s expertise remained relevant and the reflected in an apparent fan like opening and Survey’s records have stood the new institute in migration of the volcanic arc from the ~ 4 Ma good stead. remnant western arc to the present day eastern arc. University geology staff numbers increased rapidly Despite the complex opening structure of the back- when the colleges of the University of New arc basin, evidence from offshore seismic data Zealand gained university status and then Massey indicates the basement across the whole area has and Waikato universities established departments in subsided by similar amounts and hence the region which geology was taught. The staff and the has undergone similar amounts of extension. increasing numbers of research students began to Apparent extension strain rates in the back-arc are put out many new data and interpretations. New ~ twice that of most continental rifts, and the modes ideas, for example plate tectonics in the late 1960s, of extension are less clear. The accepted end were adopted and adapted to New Zealand by the member extension models of pure and simple shear universities, ahead of the Geological Survey. New are less applicable in a region of such high techniques were commonly used as early as extension rates, where a significant amount of the possible. extension is expressed by the intrusion of new

50thKaikoura05 -84- Kaikoura 2005 The new era of commercial viability, accountability project, indicating how they relate to studies and competitive funding led to the CRI model, and currently in progress on other South Canterbury to significant impacts on universities. The sections. pestilence of paper work and problems of keeping POSTER valuable projects going were balanced by increased flexibility in detailed expenditure and a valuable need to collaborate with other institutions. At TERTIARY SKELETAL LIMESTONES AND present, many fields of research are moving CARBONATE DYKES ON CHATHAM forward, and the challenge now is to identify and ISLANDS tackle key problems in our geological history. Geology must also retain its relevance to the needs J.Q. Titjen1,C.S.Nelson1,N.P.James2, of the country. B.J. Jones3 & H.J. Campbell4 1 Earth Sciences, University of Waikato, Private ORAL Bag 3105, Hamilton 2 Geological Sciences, Queen's University, THE CENOZOIC SEQUENCE FROM A Kingston, Ontario K7L 3N6, Canada 3 DRILLHOLE IN SOUTH CANTERBURY Earth & Atmospheric Sciences, University of Alberta, Edmonton T6G2E3, Canada 4 K. Tinto1,H.Morgans2,G.S.Wilson1 Institute of Geological & Nuclear Sciences, PO &T.Naish2 Box 30368, Lower Hutt 1Geology Department, University of Otago, PO (jqt1*waikato.ac.nz) Box 56, Dunedin, NZ 2Institute of Geological and Nuclear Sciences Ltd., Tertiary limestone occurrences on the Chatham PO Box 31312, Lower Hutt, NZ Islands, 800 km east of South Island, are very (kirsty.tinto*stonebow.otago.ac.nz) limited in distribution but are diverse in age (Paleocene to Pliocene), fossil content, facies type, The Cenozoic sedimentary sequence in the South and diagenetic history. Their stratigraphy and Canterbury basin has been widely studied and is general field features have previously been considered to be of global significance. reviewed by Wood et al. (1989) and Campbell et al. Unconformities, disconformities, paraconformities (1993). During February 2005 we conducted and variations in lithology within the basin have detailed sedimentological field work on most of the been variously attributed to changes in global main limestone sections cropping out on both climate, eustatic sea level and ocean circulation. Chatham and Pitt Islands. This poster reports, However, the ability to correlate directly with other mainly through photographic images, some of the global proxies has been hampered by poor characteristics of the limestones in the field, and resolution of chronology and temporally limited notes our intention to undertake detailed outcrop patterns. petrographic and geochemical studies of the limestones in the future, principally to assess their In association with the ANDRILL testing skeletal make-up and assemblages, their programme, the opportunity has arisen to recover a depositional paleoenvironments, and their drillcore from the onshore part of the basin. This diagenetic properties. Much of this work is will provide a sufficiently long and continuously presently underway, and other aspects will be exposed section of the sequence for a chronological included as part of the MSc study of the presenting and environmental study of suitable resolution. author (JQT). The drillcore record will be obtained from a site There are several unique aspects about the near Cave, on the Tengawai river and is expected to limestones on the Chatham Islands. First, they are include ~500m of sequence ranging in age from temperate latitude limestones developed upon ~40 to ~15Ma. This will include a variety of isolated oceanic islands far from mainland New lithologies and incorporates a number of Zealand, not upon extensive shelves or platforms. unconformities, including the “Marshall Second, oceanographically the islands straddle the Paraconformity”. By investigating the late Tertiary position of the Subtropical Front foraminiferal content, paleomagnetic record and bounding cool subtropical water to the north from other geochronological indicators, it will be subantarctic water to the south, which should be possible to construct an age model. By acquiring a reflected in the development of distinctive continuous core, a finer resolution of measurement limestone facies. Third, the wide spread of ages of can be made across the unconformities in the the limestones throughout the Tertiary affords an section to indicate their timing, duration and excellent opportunity to compare biotic and facies significance. changes over time. Fourth, stratigraphically these Drilling is scheduled to commence in October 2005 temperate limestones are intimately associated with and we will present the preliminary results of the coeval basaltic volcanic and volcaniclastic deposits

50thKaikoura05 -85- Kaikoura 2005 that appear to have exerted a strong influence on Kawakawa tephra (c. 26.5ka) is disseminated their distribution and geometry, as well as on their within the youngest loess at all three sites, and an facies associations and skeletal assemblages. Fifth, unidentified tephra occurs in the oldest loess at unlike many mainland New Zealand limestones, the Charwell. carbonates have never been deeply buried, so that Kaikoura Peninsula has a sequence of five marine pressure-dissolution is unlikely to be a source of terraces. The distribution of loess on terraces is calcite cement. While many of the limestones are mapped and the soil stratigraphy of loess revised. expectedly only weakly cemented, others are tightly Present age estimates indicate that three loesses cemented, implying either a marine or subaerial overlying shallow marine deposits on the bedrock rather than burial origin like many other New strath of the oldest terrace have accumulated since Zealand limestone occurrences. And sixth, the last interglacial (OIS5). The loess - terrace limestone dykes are associated with several of the relationships on the peninsula provide a local Chatham limestone sections, seemingly as forceful correlation with changes in sea level, and tectonic downward fissure injections and veins into uplift since the last interglacial. volcaniclastic substrates. Multiple episodes of Coastal ekerengu terraces are remnants of alluvial injection are sometimes evident. All these aspects fans and valley fills separated by low hills eroded will be addressed and interpreted in our ongoing from weathered conglomerates and marine rocks. A work and, where appropriate, comparisons will be sequence of fill and fill-cut terraces is recognised, made with age-equivalent limestone facies and the youngest fill terrace with thin overbank but no associated deposits in mainland New Zealand. loess cover and one, two and three loesses on the successively older terraces. Strongly weathered Campbell, H. J. et al., 1993: Cretaceous-Cenozoic sandy clays, and/or sandstone conglomerates geology and biostratigraphy of the Chatham Islands, underlie the oldest terrace remnants. The presence New Zealand. IGNS, Lower Hutt, NZ. or absence of loess, and the number of loesses on Wood, R. A. et al., 1989: Cretaceous and Cenozoic terrace remnants were used to map and correlate geology of the Chatham Rise region, South Island, surfaces. The purpose of this mapping was to assess New Zealand. NZGS, Lower Hutt, NZ. the late Pleistocene and Holocene movements on ORAL the Kekerengu Fault, which offsets the terraces. For example, a beheaded channel on a one-loess fan surface (correlated to OIS3) is offset from its likely SOIL STRATIGRAPHY OF LOESSIAL Glencoe Stream source by c. 700 m, indicating a SEQUENCES ON COASTAL MARINE AND lateral slip rate of approximately 20 mm/yr. RIVER TERRACES, NORTHEASTERN SOUTH ISLAND, PROXY RECORDS OF Inland Charwell River terraces are underlain by TECTONIC AND ENVIROMENTAL gravelly alluvium deposited during five late CHANGE Pleistocene depositional episodes. Fill and fill-cut terraces are formed in the four youngest Tonkin, P.1,VanDissen,R.2,Burke,R.3, aggradation gravels, with overbank and or thin Hughes, M.4 &AlmondP.4 loess on the youngest fill terrace and one, two and 1Department of Geological Sciences, University of three loesses on the successively older fill terraces. Canterbury, Christchurch. The landform on the oldest loess mantled terrace 2 has a low relief hilly topography with evidence of Geological and Nuclear Sciences, Lower Hutt. 3 erosion and dissection of the terrace during and Humbolt Sate University, Arcata, California. 4 between episodes of loess accretion. Late Soil and Physical Sciences Group, Lincoln Quaternary ecological and environmental changes University, Canterbury. are interpreted from phytolith analysis, soil chemistry and tephrochronology. A paired In the late Pleistocene and Holocene, river upbuilding – erosion loess record suggests that soil aggradation and degradation in NZ has formed transport rates did not change significantly flights of fill, fill-cut and strath terraces. Soils and throughout the late Pleistocene-Holocene climate the soil stratigraphy of loess and tephra cover beds transition although soil transport mechanisms did. is used in this work-in-progress study to correlate Ongoing work will develop a tephrochronological fill terraces between catchments and to coastal framework for loess accumulation and other marine terraces at three sites in northeastern South environmental changes, and further explore the Island - coastal Kaikoura Peninsula and Kekerengu, biogeomorphic effects of glacial-interglacial and inland Charwell River. ecosystem changes. At each of the three sites, the soil stratigraphy of the loess shows similar morphological features with POSTER the exception of texture, with the oldest loess at Kekerengu and Charwell, and all the loess on Kaikoura Peninsula having clay textures.

50thKaikoura05 -86- Kaikoura 2005 TECTONICS OF THE GALATEA BASIN CONSTRUCTING A BRITTLE–DUCTILE USING GEOPHYSICAL TECHNIQUES RHEOLOGICAL MODEL OF CONTINENTAL LITHOSPHERE Suzannah Toulmin & Tim Stern Institute of Geophysics, Victoria University of John Townend Wellington, P O Box 600, Wellington. School of Earth Sciences, Victoria University of (suzannah.toulmin*vuw.ac.nz) Wellington, PO Box 600, Wellington (john.townend*vuw.ac.nz) Unusually deep basins can occur in regions subjected to both active extension and strike-slip. Idealised rheological models — elastic, ductile, Such “pull-apart” basins are known to occur in viscoelastic etc. — provide physically reasonable, Southern California, where they have been explored mathematically useful descriptions of the for more than 100 years. In New Zealand, examples lithosphere’s large-scale mechanical characteristics of pull-apart basins include the Hamner Basin in different circumstances. However, these models (Hope fault, Canterbury) and the Dagg Basin do not directly represent small-scale deformation (Alpine fault, Fiordland). It is arguable that the mechanisms known to operate under particular dextral strike-slip Wellington fault also exhibits geological conditions. In particular, the parameters pull-apart character at eastward en echelon describing common rheological models are not releasing steps as it passes through the Hutt Valley straightforwardly reconciled with the brittle and into the Wairarapa. ductile modes of deformation thought to operate at The Galatea Basin, located in southern Bay of shallow and deep levels within the crust and Plenty, straddles the eastern margin of the lithospheric mantle. Moreover, it is difficult to extensional Central Volcanic Region and is account for the vertical and horizontal distributions juxtaposed against strands of Waiohau and Te of crustal seismicity using existing rheological Whaiti faults. These faults define the western limit models in which the lithosphere’s mechanical of the North Island Dextral Fault Belt. Although properties are uniform. part of a principally dextral strike-slip system of In this presentation, I will discuss progress towards faults, motion on the Waiohau fault has been constructing a rheological model for continental identified recently as being dominantly normal, lithosphere that combines geological evidence for with an average dip-slip rate of 0.6-0.9 mm/yr. brittle and ductile deformation mechanisms, and Over 170 new gravity measurements were acquired seismicity, with geophysical measurements of the the Galatea Basin with the aim of better defining lithosphere’s long-term, long-wavelength the dimensions of an associated Bouguer anomaly mechanical properties. and determining the sub-surface structure of the If the brittle–ductile transition in continental crust is basin. In addition, a single 5 km seismic refraction controlled by the crust’s thermal structure and the profile and a 2.5 km reflection profile were ambient strain rate (e.g. Sibson, 1983), then the recorded along a line perpendicular to the Waiohau large-scale vertically averaged rheology of the fault and strike of the Galatea Basin. lithosphere as a whole is temperature-dependent. The residual gravity anomaly is –27 mGal at the Based on borehole observations indicating that the centre of the basin. Results from ray-tracing have brittle crust is in a state of frictional failure identified that the Waiohau fault dips in excess of equilibrium, Zoback and Townend (2001) 45° at depth, and, combined with other methods, hypothesized that the rate at which continental we conclude that basin depth reaches at least 1000 lithosphere deforms can be expressed in terms of m. Basin fill is Quaternary volcanics, including heat flow if the total strength of the lithosphere is Matahina Ignimbrite and Rangitaiki Ignimbrite known. The corollary is that for a given crustal underlain by Pleistocene sediments including Lukes structure and heat flow, the corresponding Farm Formation and possibly older Tertiary units. lithospheric strain rate and the depth of the brittle– ductile transition (and the base of the seismogenic The distinctly deep gravity anomaly combined with zone) can be estimated. In other words, any two of the steeply faulted eastern margin suggests a pull- four key data sets listed in the schematic below can apart origin for the Galatea Basin. be used to compute the two others. All four data ORAL sets exist for California, providing a rare opportunity to test these ideas.

50thKaikoura05 -87- Kaikoura 2005 Restoration of strike-slip on the MFS and of the Sibson, R.H., 1983. Continental fault structure and the above-described rotations realigns the Early shallow earthquake source. Journal of the Geological Miocene FCFS back to its original NW-SE strike Society of London, 5, 741–767. and NE- (seaward-) vergent configuration. The Zoback, M.D., and Townend, J., 2001. Implications of proto-Clarence Fault (Flags Creek Fault) initiated hydrostatic pore pressures and high crustal strength as a NW-SE striking thrust within the Early for the deformation of intraplate lithosphere. Miocene subduction complex, and accrued >10 km Tectonophysics, 336, 19–30. of NE-vergent slip (with an additional 16 km of POSTER shortening within the FCFS) before being folded, strongly clockwise-rotated, and locally reactivated. Subsequently, oblique plate motion has allowed this THE EARLY MIOCENE PLATE BOUNDARY and other faults in the MFS to remain active while IN MARLBOROUGH, NEW ZEALAND: transitioning from dip-slip to oblique- or strike-slip THRUST FAULTING AND REGIONAL styles of deformation. CLOCKWISE VERTICAL-AXIS ROTATION

1 2 Roberts, A. 1995: Tectonic rotation about the termination D. B. Townsend &T.A.Little of a major strike-slip fault, Marlborough fault system, 1GNS, PO Box 30368 Lower Hutt 2 New Zealand. Geophysical Research Letters 22 (3), School of Earth Sciences, Victoria University, PO 187-190 Box 600 Wellington Vickery, S., Lamb, S. 1995: Large tectonic rotations (d.townsend*gns.cri.nz) since the Early Miocene in a convergent plate boundary zone, South Island, New Zealand. Earth and Plate reconstructions for the Early Miocene suggest Planetary Science Letters 136, 44-59. that the Pacific-Australia plate boundary trended Little, T., Roberts, A. 1997: Distribution of Neogene to NW-SE and consisted of an array of thrust faults present-day vertical-axis rotations, Pacific-Australia striking parallel to the paleo-Hikurangi margin. plate boundary zone, South Island, New Zealand. Parts of that subduction complex are preserved Journal of Geophysical Research 102 (B9), 20447- onshore in the Raukumara Peninsula, Wairarapa 20468 and Marlborough, where it was pinned at its eastern POSTER end by the Chatham Rise. The plate boundary zone in Marlborough has experienced a complex structural history, culminating in the late Neogene FABRIC TRANSITIONS IN THE ALPINE development of the NE-striking, dextral strike-slip FAULT MYLONITES: VARIATION IN THE Marlborough Fault System (MFS). TEMPERATURE OF THE BRITTLE- Inception of the Early Miocene plate boundary PLASTIC TRANSITION DUE TO CHANGES through New Zealand is recorded in Marlborough IN STRAIN RATE by development of the imbricate Flags Creek Fault V.G. Toy1,R.J.Norris1 &D.J.Prior2 System (FCFS) and coeval deposition of the 1 (Otaian-Altonian) Great Marlborough Geology Department, University of Otago, PO Box 56, Dunedin. Conglomerate. New structural mapping and 2 analysis of folded thrust sheets in the FCFS has Department of Earth and Ocean Sciences, yielded a predominant in-situ SE vergence, which University of Liverpool, L69 3GP, U.K. is strongly discordant to the inferred NW-SE strike (virginia*geology.co.nz) and NE (seaward) vergence of the Early Miocene subduction complex. The Alpine Fault is the major structure within the Australian–Pacific plate boundary and Five new paleomagnetic samples from around the accommodates c. 25 mm/yr displacement. Due to arcuate FCFS coupled with existing paleomagnetic the oblique convergence across it, mylonites data from coastal Marlborough suggest that the formed by ductile shear at depth are exhumed in the entire area has undergone clockwise vertical-axis hanging wall immediately east of the present fault rotation of at least 100º during the Middle and early trace. They grade from ultramylonite close to the Late Miocene [Vickery and Lamb 1995; Little & fault to protomylonite adjacent to the Alpine Schist Roberts 1997]. Late Miocene to Pliocene clockwise protolith c. 1 km to the east. vertical-axis rotation of up to 44º has affected coastal Marlborough to the north of the FCFS In order to gain further information about the [Roberts 1995; Little & Roberts 1997]. Late distribution of strain and deformation conditions Pliocene to Quaternary dextral shear strain within within the hanging-wall, Alpine Schist-derived ~5 km of the active Kekerengu Fault has locally Alpine fault mylonites, we have collected quartz produced additional clockwise vertical-axis rotation crystallographic preferred orientation (CPO) data (up to 45º) near Woodside Creek. from mylonite samples along two transects perpendicular to the Alpine fault. Analyses were

50thKaikoura05 -88- Kaikoura 2005 performed by the electron backscatter diffraction 1 GNS Science, Private Bag 1930, Dunedin, New (EBSD) technique, using a Camscan SEM and Zealand. Channel 5 indexing software. 2 Dept of Earth, Atmospheric & Planetary Sciences, MIT, Cambridge, MA 02139, USA. Most crystallographic fabrics in the mylonite zone 3 are characteristic of a high ratio of simple to pure School of Earth Sciences, James Cook University, shear. The most obvious trend in the axis Townsville, Australia. distributions is a transition from single Y-axis (a.tulloch*gns.cri.nz) maxima and single girdles with marked rhomb - slip peaks, to Type I and rare Type II crossed-girdle Mesozoic magmatism in NZ is dominated by the fabrics at a distance of approximately 400m from 800+ km-long Median Batholith. The main phase the Alpine fault. A transition from single maxima of magmatism spans 170-100 Ma with no and single girdle to crossed girdle fabrics can occur significant arc-parallel age variation, and can be due to a decrease in deformation temperature or a subdivided into two margin parallel-belts (Tulloch decrease in the rotational strain component of the & Kimbrough 2003; GSA Sp paper 374, 275-95). A deformation. 130-100 Ma inboard belt is characterised by plutons with relatively high Na, Sr, Al and low Y (HiSY, CPO patterns in high strain mylonites are likely to for Sr/Y> 40; also known as adakitic or TTG-like); record only the latest stages of deformation due to an older outboard belt has complementary LoSY destruction of previous fabrics by recrystallisation; chemistry. There is a rapid change from LoSY to hence the fabric transition observed at 400m from HISY at ~130 Ma with HiSY magma flux rates ~ the fault is unlikely to result only from a variation 5x greater than that of the preceeding LoSY belt. in the total finite strain. The transition can Several small bodies of A-type and peralkaline therefore most easily be explained by a variation in granite have ages of ~130 Ma. The HiSY magmas temperature during the last increment of ductile are likely derived from partial melting of basaltic deformation. In this scenario the CPO fabrics are continental lithosphere generated during preceeding ‘frozen in’ as the mylonites are exhumed through LoSY arc magmatism. Shallowing subduction and the brittle-plastic transition, which occurs at higher pinching out of the mantle wedge may explain temperatures close to the Alpine fault due to the cessation of (LoSY) magmatism, and the inboard higher strain rate. location of the HiSY plutons, but not the significant Subsidiary observations from the dataset include: mantle heat input heat necessary for large scale (a) foliation-parallel quartz veins in ultramylonites crustal melting. have fabrics that are not easily related to the Early Cretaceous magmatism in eastern Australia is kinematics of the mylonite zone. These veins may dominated by the ~132-95 Ma Whitsunday have formed late in the deformation history and Volcanic Province. The 900 km long province retain a growth fabric; (b) the presence of feldspar ranges from basalt to high-silica rhyolite although as a second phase mineral weakens the CPO fabric the latter dominate. The rhyolitic rocks and some more than the presence of mica; (c) the CPO fabrics granites commonly have elevated Zr, Y (and thus are asymmetrically distributed about the foliation hints of A-type geochemistry), and ages <125 Ma. plane, indicating that a previously occurring Granitic rocks with HiSY and LoSY chemistry are preferred orientation is selectively strengthened by also present but the HiSY rocks have not been the mylonitic deformation; (d) a fabric indicative of directly dated. This magmatic belt has been dominantly pure shear is attained close to the interpreted (Bryan et al. 1997; EPSL 153, 85-102) mylonite-schist transition, indicating flattening as having been formed in an extensional strain does occur during the initial stages of environment related to 84-55 Ma Tasman Sea mylonitisation; (e) there is no systematic change in spreading. However, Allen et al. 1998 (AJES 45, pattern or fabric opening angle within the 875-88) argue that the time lag of up to 50 Ma until protomylonite zone, indicating that there is no ocean crust formation is too long for a causal simple variation in temperature towards the fault in connection. this zone. This may reflect an inhomogeneous distribution of the strain rate within the Both the NZ and Queensland magmatic belts have a protomylonites. similar age span, and both contain a similar variety of distinctive rock types which are commonly ORAL regarded as atypical of subduction zones; e.g. HiSY (minor in Queensland, major in NZ) and rift- SIMILARITIES BETWEEN EARLY related/A-type igneous rocks (major in Queensland, CRETACEOUS MAGMATIC BELTS IN minor in NZ). Both exhibit a major change in QUEENSLAND AND NEW ZEALAND character at similar time (~125 Ma in Queensland, ~130 Ma in NZ). As such, the Early Cretaceous Andy Tulloch1 Jahandar Ramezani2, magmatic belts of NZ and Queensland can Andrew Allibone3 &NickMortimer1 considered to be part of the same Gondwana- margin arc, crosscut by later continental rifting. The

50thKaikoura05 -89- Kaikoura 2005 large volumes of A-type magmatism in Queensland that extends from northeast of Lake Manapouri to may shed light on the significance of its apparently the Princess Mountains. The presence of the c. 164 rare equivalent in NZ. Thus A-type magmatism at Ma Lake Mike Granite in SW Fiordland indicates ~130 Ma in NZ may explain the sudden major this Jurassic plutonism locally extended further HiSY flux as being due to heat associated with an west. Younger HiSY plutons, correlated with the otherwise largely unrecognised incursion of Separation Point Suite, form a narrow belt asthenospheric mantle-derived magmas, probably extending south from the western side of Lake by slab rifting or roll back. In Queensland, by Manapouri to Lake Poteriteri. Elsewhere in analogy, the “extension-related” magmatism may southern Fiordland, Cretaceous HiSY rocks are also have been “intra-arc”, rather than strictly restricted to isolated plutons in the eastern Hunter intracontinental. Mountains and south of Dusky Sound. Numerous LoSY tonalitic to leucogranitic plutons, some dated ORAL at c. 130-135 Ma, occur in SW Fiordland; their affinity with other documented suites is not yet PROGRESS ON QMAP FIORDLAND clear. Cretaceous and Cenozoic sedimentary rocks had 1 2 1 Turnbull , A. Allibone , R. Jongens , generally been mapped and described prior to the 1 1 H. Fraser ,A.Tulloch QMAP programme. However, newly discovered 1 Institute of Geological and Nuclear Sciences, fossiliferous Pleistocene sediments that fill a Private Bag 1930, Dunedin submarine canyon east of Puysegur Point give 2 School of Earth Science, James Cook University, valuable control on tectonic uplift rates for flights Townsville, Q4811, Australia of marine terraces in SW Fiordland. (i.turnbull*gns.cri.nz) The Grebe Shear Zone, previously interpreted as the boundary between Eastern and Southern Work on the Fiordland QMAP sheet has been under Fiordland Blocks, is cut by probably Early way for four field seasons with the southern two- Cretaceous (Separation Point Suite) granitoids, thirds of Fiordland now largely mapped. Some of implying correlation with the Gutter Shear Zone on the more significant findings of the work to date are Stewart Island. Innumerable brittle faults have been highlighted on this poster. mapped; some offset the contacts of the Western Schistose amphibolite facies metasediments, Fiordland Orthogneiss. Demonstrable Late previously interpreted as the upper plate of a Quaternary faulting is rare. Western Fiordland Block, are now known to extend as far south as Chalky Inlet rather than terminating POSTER in Dusky Sound. These metasediments, and several younger granitoid units, strike across the mouth of WORKING TOWARD A HIGH-PRECISION Dusky Sound and indicate that the Dusky Fault RECORD OF MT TARANAKI ERUPTIONS does not extend out to sea as previously postulated. AND ASH FALLS, NEW ZEALAND Movement is instead accommodated on a major SW-trending fault that crosses the coast near West M. Turner1, S. Cronin1,M.Bebbington2, Cape; consequently the Dusky Fault, previously B. Stewart1,V.Neall1and I. Smith3 thought to separate distinct Western and Southern 1Institute of Natural Resources, Massey University, Fiordland Blocks, appears to be of local rather than Palmerston North, New Zealand regional importance. Ordovician graptolitic shales 2Institute of Information Sciences and Technology, and interbedded sandstone and quartzite previously Massey University, Palmerston North, New included in a Southern Fiordland Block, as well as Zealand the schistose amphibolite facies rocks, are intruded 3Department of Geology, University of Auckland, by the Brothers and c. 350 Ma Evans Plutons, Auckland, New Zealand indicating that they have been in close proximity (M.B.Turner*massey.ac.nz) since the mid Paleozoic. The c. 30+ granitoid plutons mapped show regional A probabilistic assessment of eruption recurrence at variations in composition and age across southern any volcano requires quantification of the Fiordland. Carboniferous plutons are largely frequency and magnitude of each style of possible confined to the area between Dusky Sound and the volcanic hazard. Existing eruption age data for Princess Mountains, and include at least 3 distinct frequency analysis at Taranaki is, as for many groups, one of which correlates with the Ridge volcanoes, poorly constrained and relies on a few Orthogneiss on Stewart Island. Gabbroic, dioritic radiocarbon dates from widely distributed and related LoSY granodioritic rocks, c. 170-140 stratigraphic sections on and around the volcano. Ma old, similar to those mapped in northern We have extracted what seems to be the highest Stewart Island and northeastern Fiordland, form a resolution record yet of Taranaki volcanism from belt of heterogeneous variably deformed intrusions peaty lacustrine sediments within a small lake,

50thKaikoura05 -90- Kaikoura 2005 25km northeast of the volcano. Although not member. Nevertheless, experimental partition directly downwind of Mt Taranaki, this site holds coefficient data are consistent with the differences >90 Holocene tephras, which have been sampled between the fluid and sediment components being within the top 4 m of sediment. Ten new formed in the presence of different residual radiocarbon dates throughout the length of this core mineralogies. Sediment fluids appear to be poor in enable a very detailed sedimentation rate curve to incompatible elements, relative to those derived be established and each individual tephra layer can from altered oceanic crust and cannot easily be assigned an age based on its position within the replicate the sediment end-member. We suggest core. This key site is correlated to syn-eruptive that subducted sediments dehydrate at relatively deposits in other locations, including those on the shallow levels and that these fluids are not strongly edifice, by physical and petrological characteristics sampled by arc lavas. Altered oceanic crust may as well as titanomagnetite mineral chemistry finger- dehydrate more extensively and to greater depths printing techniques. By using these tephras as age and may be buffered against melting. Model melts horizons, other proximal eruption deposits which of dehydrated sediment residues provide a much are not in the distal record can also be assigned a better simulation of the inferred sediment end- relative age and added to the event database. The member but may require ~800 C at ~ 2GPa, new database will be used to develop the first consistent with recent temperature-dependant comprehensive probabilistic eruption forecast for viscosity models. These general inferences are ash eruptions from Mt Taranaki. strongly supported by 10Be and U-series isotope A probabilistic temporal model is then required to data which suggest that the sediment (melt) end- handle the stochastic nature of the observed record, member is added 100’s kyr to several Myr prior to as well as the imprecision and inaccuracy inherent eruption whereas addition of fluid components in the age data obtained via radiocarbon continues until a few 1000 yrs prior to eruption. dating/sedimentation rates and that of the Thus, the fluid and sediment end-member correlation uncertainties. Such models are usually contributions are separate in composition, space assembled using techniques from renewal theory, and time. These data argue strongly against the (marked) point processes, or hidden (semi-)Markov involvement of any single supercritical fluid. models. Combining the resulting model with a ORAL quantitative assessment of the styles and properties of eruptions possible at Taranaki will allow the model parameters to be estimated, and the goodness DEVELOPMENTS IN THE EAST COAST of fit to the observed record assessed. A suitably BASIN, NORTH ISLAND, NEW ZEALAND. well fitting model can then provide a probabilistic forecast of future eruptions at Taranaki. Chris Uruski, Brad Field, Rob Funnell, Chris Hollis, Andy Nicol & Guy Maslen POSTER Institute of Geological & Nuclear Sciences PO Box 30368 MASS TRANSFER IN SUBDUCTION ZONES: Lower Hutt, New Zealand AN ELEMENTAL AND ISOTOPIC (c.uruski*gns.cri.nz) PERSPECTIVE The East Coast Basin saw oil production in the late 19th century from wildcat wells near oil seeps. By Simon Turner & Rhiannon George th GEMOC, Macquarie University, Sydney, NSW, the mid-20 century, geology was being applied to 2109, Australia oil exploration, but with little success. In the late th (sturner*els.mq.edu.au) 20 century seismic techniques were added to the exploration arsenal and several gas discoveries Little doubt remains that subduction zone lavas were made. At each stage it was recognised that contain elements recycled from the subducting slab. exploration in this difficult but tantalising basin However, whether the key agents of this mass required more information than was available. transfer are fluids, supercritical fluids or melts has Continuing work by exploration companies as well major implications for the thermal structure of the as by the Institute of Geological & Nuclear mantle wedge. The evidence for contributions from Sciences (GNS) has begun to reduce the risk of both subducted sediment and altered oceanic crust exploration. Source rocks have been identified and are compelling and in most arcs their relative sophisticated thermal models show that petroleum proportions vary inversely. Thus, so-called “fluid- is being generated and expelled from them as rich” lavas with high Ba/Th and Sr.Th ratios have witnessed by the more than 300 oil and gas seeps low 87Sr/86Sr and 10Be/9Be etc and the converse is onshore. Numerous reservoir facies have been true for the so-called “sediment-rich”lavas with recognised from outcrop studies and depositional elevated La/Sm. A complicating factor is that many models are being refined. All components of individual arcs tend to be dominated by one end- petroleum systems have been demonstrated to be

50thKaikoura05 -91- Kaikoura 2005 present. The most important deficiency to date is oceanographic conditions around the island for the the general lack of high-quality seismic data. Holocene and back to oxygen isotope stage 3. Recently, Crown Minerals, the New Zealand Component analysis was undertaken to assess the government group charged with promoting and species composition and shifts in floral and faunal regulating oil and gas exploration, commissioned a composition across this oceanographic boundary. high specification regional 2D survey intended to Preliminary analysis of the planktonic foraminifer address some of the main data gaps in the East data show three distinct changes related to different Coast Basin. A broad grid was planned to be water masses coming in through the core. acquired with a 12,000 metre streamer. It was Compositional analysis of the whole core indicates expected that the long streamer would increase that 2 distinct phases of deposition have occurred at resolution of Paleogene and Cretaceous units. Infill the top (50 mm) and in the middle (1200 mm) of lines were to be acquired with a streamer 8000 the core shown by a large decrease in abundance of metres long. The resulting 2,800 km data set the major components (foraminifera, corals, consists of a series of northwest-southeast lines carbonate gastropods and ostracods) possibly approximately orthogonal to the coast at a spacing relating to glacial periods and lowered sea level. of approximately 10 km as well as several long One of the AMS dates places the top of the core at strike lines. oxygen isotope stage 3. A complicating factor for The new data set has confirmed the existence of a the study is whether material eroded off the island large, little-deformed basin to the north of North and transported to the core site alters the preserved Island and the Bay of Plenty, it has elucidated the climatic signal. Another factor to consider is complex structure of a large part of the East Coast whether the presence of intermediate water masses Basin and has enabled generation of a general has modified the sea surface temperature record sequence stratigraphic model which assists in found in the sediment around Lord Howe Island. delineating reservoir targets. ORAL ORAL BALANCING THE PLATE MOTION PALEOCEANOGRAPHIC RESULTS FROM BUDGET IN THE SOUTH ISLAND, NEW A MARINE SEDIMENT CORE NEAR LORD ZEALAND USING GPS, GEOLOGICAL AND HOWE ISLAND, TASMAN SEA. SEISMOLOGICAL DATA

1 1 C. Waikari1,D.M.Kennedy1 &H.L.Neil2 Laura M. Wallace , John Beavan , 1 Rob McCaffrey2 & Kelvin Berryman1 School of Earth Sciences, Victoria University of 1 Wellington, PO Box 600, Wgtn. Institute of Geological and Nuclear Sciences, P.O. 2 Box 30368, Lower Hutt. National Institute of Water and Atmosphere, 2 Wellington, New Zealand. Dept. of Earth and Env. Science, Rensselaer (waikarcael*student.vuw.ac.nz) Polytechnic Inst, Troy, NY, USA. (l.wallace*gns.cri.nz) Lord Howe Island (33°S, 159°E) is the eroded remnant of a basaltic shield volcano, approximately The landmass of New Zealand exists as a 500 km east of Australia and is situated in the path consequence of transpressional collision between of an ocean boundary called the Tasman Front. the Australian and Pacific plates, providing an This boundary marks the southern limit of the excellent opportunity to quantify the kinematics of warm East Australian Current which flows from the deformation at this type of tectonic boundary. We Coral Sea down the east coast of Australia and implement an elastic, rotating block approach in the across to New Zealand (between 30° and 35°S). interpretation of GPS, geologic (fault slip rate and The purpose of the study is to examine the azimuth) and seismological (earthquake slip influence of the shifting Tasman Front on the vectors) data to describe the active deformation in palaeoenvironment near an island setting. the South Island, New Zealand. This method concomitantly allows us to “balance” the A 2.8 m piston core was collected from 780 m Pacific/Australia relative plate motion budget in the water depth in a trough between Lord Howe Island South Island. Using this approach, we and Balls Pyramid (a smaller island 25 km SSE of simultaneously invert the data for angular velocity Lord Howe Island). Oxygen and carbon isotope vectors of rotating tectonic blocks and the degree of analyses were conducted using the planktonic interseismic coupling on faults bounding the foraminifera Globigerina bulloides and blocks. The data are fit to within error, indicating Globigerinoides ruber and the benthic foraminifer that the “elastic block” method is plausible for Uvigerina. In combination with standard and AMS interpretation of geodetic data within this plate radiocarbon ages these analyses provide a boundary zone. temperature and productivity proxy for

50thKaikoura05 -92- Kaikoura 2005 Most of the tectonic blocks in the South Island have thrusts. West of the suture, the bulk of rocks is vertical axis rotation rates similar to the Pacific Triassic, in three associations. The Otematata and plate (~ 1 degree/Myr, counter-clockwise). This is Balmacaan Groups (Retallack 1979, Oliver & in contrast to the North Island, where we have Keene 1990) are estuarine and subdeltaic, judged estimated high rates (2-4 deg/Myr) of clockwise from plant remains, coal, conglomerate and marine tectonic block rotation. We also present estimates fossils, and overlain by the Jurassic substantially of the degree of interseismic coupling on the major non-marine Clent Hills Group. Westwards lies SouthIslandfaults. transitional or submarginal facies, mostly the The kinematic block model predicts long-term rates Acolyte Formation of some 6-9 transgressive and of motion accommodated on some major faults recessive units of sandstone and shallow-water zones in the South Island. With a few exceptions, black shale. These are overlain by continental slope the fault slip rates agree well with those estimated deposits of the Fingers, Onslow and Baker from geological studies. We estimate that 3-6 Formations. Rarely, Acolyte equivalents include mm/yr of oblique convergence must occur to the plant fossils and detached coal blocks, as at Tank east of the Southern Alps, and within Southland and Gully, Clyde River, followed by shallow-marine Mt central Otago. Our kinematic model requires 5-8 Potts Group (Campbell & Force 1972). Still further mm/yr of oblique shortening (right lateral) within west are found deep-water trough and outer slope the Porter’s Pass fault zone, suggesting that turbidtes, extending as far as the Alpine Fault, and geologic studies may have underestimated the ranging north into Wellington. Several sequences amount of plate boundary zone deformation may be recognised, with estuarine-subdeltaic accommodated in the North Canterbury region. Up unconformities at ?Late Permian, ?Scythian, early to 5 mm/yr of deformation may occur within the Ladinian or late Anisian (Etalian-Kaihikuan), and Main Divide Fault Zone, just to the east of the Late Triassic, as well as Jurassic levels. Some Alpine Fault. unconformities persist into the marginal facies, and in the trough facies, correlative conformity levels Australia/Pacific relative motion is partitioned may be tentatively indicated. Permian rocks of this within the New Zealand plate boundary zone in a basin are readily distinguished from Triassic and variety of ways. The role of block rotations in from easterly Permian by their greenish colour, accommodating plate boundary deformation is presence of basic minerals and less quartz, and more pronounced in the North Island than in the widespread occurrence of red argillite, green South Island. The southward migration of the siltstone and pillow lava with some limestone. The Chatham Rise along the margin (relative to rocks seem likely to be related to those of the Australia) has a large influence on the evolution of Wakatipu lithologic association. No Carboniferous the Hikurangi Subduction zone (North Island), the is known, and the presence of Jurassic possible, but Marlborough Fault System, and the Alpine Fault. not yet established. ORAL Campbell, J. D., Force, E. R. 1972: Stratigraphy of the TORLESSE SEQUENCE STRATIGRAPHY Mt Potts Group at Rocky Gully, Rangitata Valley, AND FORMATIONS BETWEEN THE Canterbury. New Zealand Journal of Geology & Geophysics 15: 157-167. RAKAIA AND WAITAKI RIVERS Oliver, P. J., Keene, H. W. 1990: Clearwater area. Geological Map of New Zealand. Sheet J36BD and J. B. Waterhouse part sheet J35 1:50 000. N. Z. Geological Survey, 25 Avon Street, Oamaru, New Zealand Lower Hutt. (Loris*xtra.co.nz) Retallack, G. J. 1983 Middle Triassic estuarine deposits near Benmore Dam, southern Canterbury and northern The make-up of “Torlesse” rocks is analysed from Otago, New Zealand. New Zealand Journal of the my 1:50 000 mapping for 20 years. Most significant Royal Society of New Zealand 13 (3): 107-127. is the delineation of a narrow suture zone from the Waitaki to Rangitata Rivers, defined by schist and ORAL Cretaceous intrusions, and separating two basin complexes with different stratigraphic sequences. COASTAL DUNE RIDGE SYSTEMS AS The interbasinal divide and major source rocks CHRONOLOGICAL MARKERS OF were geochemically like those of northern PALEOSEISMIC ACTIVITY – A 600 YEAR Queensland, and possibly detached from that region RECORD FROM SOUTHWEST NEW by strike-slip and sea-floor spreading. Later ZEALAND subducted, it provided the volcanics and intrusions of the Mt Somers region. To the east, rocks of Andrew Wells1 & James R. Goff2 Carboniferous to Triassic age involve limestone, 1Institute of Geological and Nuclear Sciences Ltd, chert, clastics and scattered ocean-floor lavas, with PO Box 30368, Lower Hutt, New Zealand. rare conodonts, folded and refolded, but without

50thKaikoura05 -93- Kaikoura 2005 2National Institute of Water and Atmosphere Ltd, sedimentation at intertidal elevations throughout the PO Box 8602, Christchurch, New Zealand. early Holocene. Radiocarbon ages allow (a.wells*gns.cri.nz) comparisons between the thickness of sediment preserved and the amount of accommodation space A study of five shore-parallel dune ridge sequences expected to have been created within the estuary in southwest New Zealand shows that tectonic due to eustatic sea level rise. Accommodation space activity has been the primary controlling influence deficits indicate tectonic uplift did take place during in their formation since at least AD 1450. The deposition of the sequence, yet the continuity of timing of dune building episodes at the mouths of estuarine sedimentation implies this tectonic uplift the Haast, Okuru, Waiatoto, Arawhata and Awarua was relatively gradual and continuous as opposed to Rivers was determined using the ages of colonizing the sudden and infrequent uplift characteristic of trees. Episodic dune formation was indicated by earthquakes. clear discontinuities in tree ages, with distinct Raised beach ridges at Te Araroa, ~ 8 km southeast cohorts having colonized successive, newly- of Hicks Bay, display a seaward-sloping, stepped formed, dune ridge-swale units. At Haast and morphology. The seaward slope indicates that Okuru, four dune ridge-swale units have formed gradual tectonic uplift continued through the mid- since AD 1460, with each unit closely post-dating late Holocene. The beach ridge steps have an an Alpine fault rupture (c. AD 1490, c. AD 1615, amplitude of <1 m and may have formed due to AD 1717, AD 1826). At Waiatoto, Arawhata and sudden uplift events. Additional evidence for Awarua, three dune-swale units have formed since sudden uplift events in the region is the sequence of AD 1490 and each of these also closely post-dates raised mudstone platforms on the coast between Te an Alpine fault rupture (c. AD 1490, AD 1717, AD Araroa and East Cape. 1826). Colonizing cohorts of trees started growing Radiocarbon ages from estuarine sediments at within 17-47 years after an earthquake, and at all Hicks Bay yield early Holocene uplift rates of 1.6 ± five sites all known major regional earthquakes that 0.2 mm yr-1. Raised beach ridges at Te Araroa affected each site since AD 1460 had resulted in a indicate average mid-late Holocene uplift rates of dune building episode at that site. No other dunes 2.5 ± 0.2 mm yr-1. These rates indicate back-tilting are present at any site. approximately normal to the strike of the Progradational coastal dune systems have potential subduction zone. This is mirrored by the as a tool for paleoseismic studies. In regions with Pleistocene marine terraces. The most widespread high background levels of sediment delivery to of these decreases in elevation from 200 m at Te limit erosion/burial of dunes and with little Araroa to 130 m at Hicks Bay with a distance coseismic subsidence, dune systems may offer a between them of 12 km. The terrace was previously near-complete, spatially discrete record of estimated to be the Marine Isotope Stage 5e terrace, earthquake-induced sedimentation events over the but an OSL date collected by us yielded an age of last 6500 years or so. Earthquakes are a key driver 68.7 ± 5.6 ka. This age suggests terrace formation of paleoenvironmental change and coastal plain during Stage 5a. Uplift rates calculated from this development in this tectonically active region. terrace assuming a Stage 5a age are 1.6 ± 0.2 ORAL mm/yr at Hicks Bay and 2.5 ± 0.2 mm/yr at Te Araroa. The remarkable consistency between these short- and long-term uplift rates implies an uplift MECHANISMS OF LATE QUATERNARY mechanism operating uniformly over the past 80 ka FOREARC UPLIFT: A CASE STUDY OF THE at least. NORTHEASTERN RAUKUMARA In summary, the dominant uplift signal in the Hicks PENINSULA, NEW ZEALAND Bay – Te Araroa region is one of gradual uplift.

1 2 1 This may be driven by sediment underplating on Kate Wilson , Kelvin Berryman , Tim Little , the subduction interface which is ~20 km beneath Nicola Litchfield2 & Ursula Cochran2. 1 the coastline. Sudden uplift events comprise a Victoria University of Wellington, PO Box 600, weaker, secondary uplift signal and may have been Wellington. 2 generated by interface rupture or on an unidentified Institute of Geological and Nuclear Sciences, PO offshore thrust fault. Box 30368, Lower Hutt. (K.Wilson*gns.cri.nz) POSTER

On the northeastern Raukumara Peninsula at Hicks Bay and Te Araroa, we have investigated Holocene landforms and coastal stratigraphy with the aim of documenting coastal uplift mechanisms. Drill cores of incised-valley infill sediments at Hicks Bay show apparently continuous estuarine

50thKaikoura05 -94- Kaikoura 2005 TECTONIC AND NON-TECTONIC CAUSES important difference is the result of tectonic uplift OF EARLY HOLOCENE RELATIVE SEA during deposition. Supplemented by detailed LEVELCHANGEWITHINA microfossil studies and radiocarbon dates, we TRANSGRESSIVE ESTUARY ON A identify which facies transitions within the middle SUBDUCTION MARGIN, PAKARAE RIVER, section are tectonic and non-tectonic in origin. One NORTH ISLAND, NEW ZEALAND. uplift event of at least 2 m occurred between 8695 – 8376 cal. yrs B.P. One or two uplift events occurred Kate Wilson1, Kelvin Berryman2, Tim Little1, after deposition of the Rotoma tephra at ~ 9500 cal. Ursula Cochran2 & Nicola Litchfield2. yrs B.P and before 9255 – 8990 cal. yrs. B.P. Our 1 Victoria University of Wellington, PO Box 600, data extends the paleoseismic history of this Wellington. important location which has one of the highest 2 Institute of Geological and Nuclear Sciences, PO uplift rates along a subduction margin without an Box 30368, Lower Hutt. historical record of subduction earthquakes. (K.Wilson*gns.cri.nz) ORAL The highest Holocene marine terrace at Pakarae, North Island, New Zealand, corresponds with the IMPACTS OF TEPHRA FALL ON A DAIRY maximum Holocene marine flooding surface. This FARMING OPERATION AT terrace is underlain by a sequence of estuarine, REREWHAKAAITU, EASTERN TAUPO fluvial and marine sediments that were deposited VOLCANIC ZONE, NEW ZEALAND under rising eustatic sea level (SL) conditions. These sediments are presently exposed at elevations T.M. Wilson1 &J.W.Cole1 up to 20 m above modern mean SL as a result of 1 Natural Hazards Research Centre, Department of tectonic uplift. This sedimentary sequence provides Geological Sciences, University of Canterbury, an opportunity to study the paleoenvironmental Christchurch, New Zealand development of incised valleys under conditions of (tmw42*student.canterbury.ac.nz) rising SL and tectonic uplift. The stratigraphy is valuable for comparison with traditional facies Much of New Zealand’s dairy farming industry, models of incised valley infills, which were central to New Zealand’s economy, is based in the developed exclusively from studies on stable central North Island, in or near the Taupo Volcanic coasts. We use sedimentology, macropaleontology Zone, and is highly vulnerable to tephra fall. and micropaleontology (benthic foraminifera) to A vulnerability analysis was undertaken of, reconstruct the paleoenvironments that ‘Tulachard’ a study farm at Rerewhakaaitu, eastern accompanied infilling of Pakarae valley and to Taupo Volcanic Zone, to assess the susceptibility of estimate the frequency, magnitude and timing of dairy farm’s infrastructure and operational uplift events that occurred during the depositional processes to tephra fall. ‘Tulachard’ was period (c. 10,500 – c. 7,000 cal. yrs BP). particularly appropriate as it is close to Tarawera We divide the Pakarae valley infill sequence into Volcano. Power supply, water supply and ability to eight bio-lithofacies, each relates to a particular use the tractor were identified as the most paleoenvironment. These are grouped into four vulnerable elements to ‘Tulachard’s’ ability to paleoenvironmental facies: barrier, estuarine, respond and recover from tephra fall. One of the estuary-head delta and fluvial. The basal fluvial most vulnerable components of a milking shed is facies, the immediately overlying estuary-head the condenser used for cooling milk because of its delta facies, and the capping barrier facies correlate exposed nature and requirement for circulating well with models of incised valley infill from stable outside air. An air conditioning condenser, similar coasts and indicate that the complete sequence of to condensers used in milk cooling systems, was valley infill is probably present within the Pakarae laboratory tested where it performed moderately outcrops. However the middle section of the well when inundated with dry tephra, but rapidly Pakarae stratigraphy displays alternations of failed with wet tephra. estuarine and fluvial facies. This contrasts both A telephone survey of the Rerewhakaaitu dairy with models of incised valley infill and with farming community established their perceptions of individual estuary infill studies; which predict that the risks faced from volcanic hazards. Although all only central estuary basin sediments should be respondents were aware of volcanic hazards, over present between the transgressive estuary-head half did not believe their farm would be affected by delta and the barrier facies. a volcanic eruption in their lifetime. None had The whole Pakarae sequence is compressed relative prepared for a future volcanic eruption. This has to the amount of accommodation space estimated to important education implications for key have been created by eustatic SL rise during the organisations that would be affected if dairy farms depositional period. Only a small proportion of this were affected by eruptions. can be explained by compaction, most of this

50thKaikoura05 -95- Kaikoura 2005 Generic recommendations are presented for quartz and schistose moa gizzard stones were measures that will decrease the vulnerability of associated with the bones. Some of these are the dairy farms to tephra fall hazards. These include a largest recorded moa gizzard stones, up to 110mm modern, well maintained electrical power supply, long, and weighing up to 217g. The content of one large covered water storage capacity, reserves of gizzard included 2.25kg of stones, and clipped supplementary feeds, tractor with bucket or grader twigs of lacebark (Hoheria sp.) and tree daisy blade attachments, spare air and oil filters for (Olearia sp.), up to 16mm diameter. engines, air compressor for blowing tephra out of ORAL machinery, and appropriate knowledge of rehabilitation strategies for pastures covered with tephra. ANAGLYPHS AS A TOOL FOR VIEWING TAPHONOMY: AN EXAMPLE FROM A POSTER HOLOCENE MOA FEN DEPOSIT, STYX VALLEY, CENTRAL OTAGO TAPHONOMY OF A HOLOCENE MOA FEN DEPOSIT, STYX VALLEY, CENTRAL Jamie R. Wood & Stephen E. Read OTAGO Department of Geology, University of Otago, P.O. Box 56, Dunedin Jamie R. Wood (wooja716*student.otago.ac.nz) Department of Geology, University of Otago, P.O. Box 56, Dunedin Coloured stereograms, or anaglyphs, are examined (wooja716*student.otago.ac.nz) as a tool for gaining an overall perspective on the taphonomy of a fossil deposit. The method was trialled using the excavation of a Holocene moa fen Significant deposits of bones from large, extinct, deposit, Styx Valley, Central Otago. 3D flightless birds, predominantly moa orientations were recorded for 63 moa leg bones by (Dinornithiformes) and New Zealand goose measuring X,Y,Z coordinates for the proximal end (Cnemiornis), occur in alkaline mires (fens) of each bone, bearing and inclination to the distal throughout New Zealand. Discovery of these sites end of the bone, and bone length. Trigonometry is usually associated with the digging of drainage was used to find X,Y,Z coordinates for the distal ditches, which causes major disturbance to the end of the bone. Proximal and distal coordinates deposits. As a result, past scientific excavations were used to create points in 3D space using the have tended to be haphazard, and little taphonomic GIS program ArcGIS. Points from the same bone or orientation data is associated with historic were joined using a purpose-built script ( supplied collections. Results are presented for a newly by Susan Jones, Eagle Technology Group Ltd.). discovered, undisturbed moa fen deposit near The ground surface and edges of the excavation pit Paerau in Styx Valley, Central Otago, where 3- were symbolised and displayed along with the dimensional long bone position and orientation data bones (symbolised as simple 3D tubes) in different wasrecordedduringexcavationofa1x2mL- perspective views. Selected views were then shaped test pit. The age of the deposit is currently converted to anaglyphs using an inbuilt application being determined but it is likely to be of ArcGIS. This provided a useful way of contemporaneous with a similar mid-late Holocene representing bone orientation data, and may have deposit 5km to the east. Bones were generally in applications for other paleontological researchers. poor condition due to infiltration by fine grass POSTER roots. The collected assemblage consisted of heavy- footed moa (Pachyornis elephantopus)(Minimum Number of Individuals (M.N.I.) = 11), stout-legged SEDIMENT DISPERSAL AND DEPOSITION moa (Euryapteryx geranoides) (M.N.I. = 1), South ON A MUDDY CONTINENTAL SHELF AT Island giant moa (Dinornis robustus) (M.N.I. = 1), THE ACTIVE HIKURANGI MARGIN, eastern moa (Emeus crassus)(M.N.I.=2)and POVERTY BAY, NEW ZEALAND South Island goose (Cnemiornis calcitrans)(M.N.I. = 1). Long bones were mostly lying horizontal, as 1Matthew Wood, 2Lionel Carter, 1Peter Barrett was found in a moa fen excavation at Glencrieff, & 1Andrew Mackintosh Canterbury (Worthy & Holdaway 1996), but 1School of Earth Sciences, Victoria University of showed no apparent preferred alignment with Wellington, PO Box 600, Wellington respect to compass bearing. Bones were 2National Institute of Water and Atmospheric encountered at depths of 200-800mm, but were Research, Greta Point, Wellington most abundant from 500-600mm. No articulated (woodmatt*student.vuw.ac.nz) bones were found, although bones from individual birds were found in close association. Common

50thKaikoura05 -96- Kaikoura 2005 The continental shelf of the Poverty Bay margin is and storm conditions, and the timing of muddy characterised by very high sediment delivery by the flood deposit resuspension events. muddy Waipaoa River, which is among the largest POSTER in New Zealand in terms of suspended sediment load. This situation reflects favourable geological, tectonic and climatic conditions as well as the HOW STRONG IS THE ALPINE FAULT? effects of human settlement and land-use (Foster EVIDENCE FROM FLUID FLOW AND and Carter, 1997). The Waipaoa provides an DEFORMATION PARTITIONING IN THE opportunity to study how such high discharge PACIFIC PLATE HANGING-WALL systems interact with the marine environment. The main research objective is to determine the spatial Ruth H Wightman & Timothy A Little distribution of modern sediment on the continental School of Earth Sciences, Victoria University of shelf of the Poverty Bay margin, and to understand Wellington, PO Box 600, Wellington how the pattern of various seafloor facies have been (ruth.wightman*vuw.ac.nz) affected by the hydraulic regime (waves and currents), shelf morphology (including the Lachlan An array of near-vertical backshears in the central and Ariel anticlines), and sediment supply. This Southern Alps are interpreted to have formed study has been carried out within the research sequentially in an escalator-like fashion and to play objectives framework of the Margins Source to an important role in channelling the upward flow of Sink (S2S) Initiative and this presentation metamorphic fluids through this active orogen. The represents an early stage progress report. 1-2 km-wide array of backshears is exposed only in The study relies on the integration of geophysical the central region of the Southern Alps around Fox data collected on various research cruises, recently and Franz Josef glaciers. There, fluid inclusion, collected physical samples and existing stable isotope, and thermochronometric data environmental databases. A suite of sediment indicate shear failure of a transiently embrittled samples, representing the top 1cm of 87 box cores lower crust down to depths of >20 km. In are analysed for grain size distributions. Contour quartzofeldspathic schist, the shears initiated and mapping a number of sedimentary parameters, accumulated slip brittlely (but probably steadily including % mud and mean grain size, constrains and aseismically) but ductilely in weaker, pre- the position of various sedimentary facies across existing quartz veins that were subject to finite the shelf. Preliminary results suggest that shear strains averaging 4.8 ± 0.8. Blunting of the terrigenous organic carbon-rich fluid muds brittle crack-tips into the coherently deformed predominate in mid-shelf basin depocentres and are quartz veins suggests that ductile flow was the rate- likely to represent recent flood deposits. Samples controlling factor during backshear deformation. from the landward limb of the Lachlan Anticline The backshears are systematically spaced (53 ± 4.7 are typically sandy shell hash with associated cm), with an average slip of 14.1 ± 1.2cmina pebbles. This situation reflects the seafloor outcrop direction pitching 36°SW and are dextral-oblique. of Neogene strata and potentially the winnowing Relative to plate motion, they accommodated an action of ocean currents. Contour mapping of excess of margin-parallel dextral-slip. This carbon/nitrogen ratios of the sediment will show the situation implies some partitioning of oblique varying influences of marine and terrestrial carbon motion components between the Alpine Fault and within the shelf sediments, and highlight sediment its dextrally wrenched hanging-wall to the east. A pathways and depocentres from river plumes. corollary to this is that the Alpine Fault, despite its An acoustic facies classification scheme for the inferred thermally induced weakness, was not weak shelf is proposed, based on the type of seafloor enough to accommodate perfectly plate motion- surface seismic response parallel slip at the time when the shears were (diffuse/distinct/hyperbolic), and the degree of active. seismic subsurface penetration, as shown in 3.5kHz We infer that presence of fluid in the Pacific Plate and ‘chirp’ FM pulse (0.5-7.2kHz) seismic profiles. crust was integral to the formation and Gas-masking of the subsurface is prevalent across accumulation of shear along these structures. Near- much of the mid-shelf basin. Significant influence lithostatic fluid pressures were a chief agent that of non-tidal currents may be represented by originally triggered deep embrittlement and shear moating of sediments against the western limbs of failure at the lower crustal depths. After formation, the growing anticlines of the shelf break. Further hydrolytic weakening due to high water fugacity mapping work will include seafloor textural allowed deformation in the fluid-weakened quartz mapping from a side-scan sonar and multibeam veins to accrue at high strain-rates but without backscatter datasets. Wave and wind regime sufficiently high differential stresses to cause their datasets and existing knowledge of ocean currents brittle failure. As the strength of these veins will be integrated with satellite imagery to develop controlled that of the backshears terminating into a model to explain sedimentation in both normal them, this process may have significantly weakened

50thKaikoura05 -97- Kaikoura 2005 the bulk strength of the Pacific Plate crust above the been the source of frequent swarms of acoustic T- Alpine Fault ramp. The shears also provided a wave events every few years. On 24 May 2002 means for suprahydrostatic metamorphic fluids to there was a particularly large seismoacoustic event escape upwards, acting as a closely spaced array of with a duration of 6-8 minutes and an exceptional planar, vertical conduits cutting across the amplitude that was 4-5 times larger than any other otherwise low permeability (1 x 10-18 m2) schist. T-wave signal recorded from Monowai. We calculate that an aqueous fluid volume of 5.6 x Bathymetric surveys of Monowai that bracket this 1010 m3 was required to deposit the 1-3 mm thick event were collected with multibeam sonars in 1998 veins that currently seal the backshears throughout and 2004 by R/V Sonne (Hydrosweep) and R/V the 30 km-long by ~2 km-wide array, equivalent to Tangaroa (EM300), respectively. A new collapse an integrated fluid flux of 486000 m3/m2.Upward feature is apparent on the SE side of the volcano in draining of this metamorphic fluid into the hanging- the 2004 bathymetry. The two surveys were wall would have left the underlying source region compared using a quantitative technique that has near its base residually drier. Fluid expulsion may been used for documenting depth changes due to thus have accomplished a net devolatilisation and volcanic eruptions on mid-ocean ridges. The rheological strengthening along the Alpine results of this comparison show that the summit mylonite zone at depth at the same time that depth of Monowai changed from 69 m below hydrolytic weakening softened structurally higher sealevel in 1998 to 135 m in 2004, a difference of - rocks in the hanging-wall. These fluid-related 66 m, and the location of the shallowest point strength changes may have limited the degree to moved ~200 m to the NNW. However, the which the Alpine Fault could slip in the plate maximum depth change between the surveys is - motion direction without some partitioning of 105 m and is located near the 1998-summit, which deformation into its hanging-wall. in 2004 is south of the new headwall scarp on the SE flank of the volcano. The total area of POSTER significant depth change is 1.26 x 106 m2,andthe decrease in volume is 6.12 x 107 m3 (or 0.06 km3). COLLAPSE AND RE-GROWTH OF From the distribution of the depth changes it is also MONOWAI SUBMARINE VOLCANO, clear that four things occurred between the surveys: KERMADEC ARC, 1998-2004 removal of volume from slope failure, the subsequent addition of volume from an eruptive Ian C. Wright1, William W. Chadwick2, vent within the new slide scar, the removal of part Cornel E. J. de Ronde3, Dominique Reymond4, of that additional volume by a further slope failure, Olivier Hyvernaud4, Stephen Bannister3, and the addition of more volume within the Peter Stoffers5 & Kevin Mackay1 eruptive vent. Therefore, the volume removed by 1 slope failure was probably closer to 0.1 km3 National Institute of Water and Atmospheric whereas the volume added back by eruption is Research, 301 Evans Bay Parade, 3 approximately 0.03 km . It is not known whether Greta Point, Private Bag 14-901, Kilbirnie, the slide triggered the eruption or visa versa, but the Wellington, 6003, New Zealand 2 recent history of frequent volcanic activity at CIMRS, Oregon State University, 2115 SE OSU Monowai suggests that an eruption-triggered slide Drive, Newport, OR, 97365, USA maybemorelikely. 3 Institute of Geological & Nuclear Sciences, 30 POSTER Gracefield Road, PO Box 31-312, Lower Hutt, New Zealand 4 Laboratoire de Geophysique, CEA/DASE/LDG, FINGERPRINTING SLAB–DERIVED Tahiti, P.O. Box 640, Papeete, French Polynesia AQUEOUS FLUIDS IN THE MANTLE 5 Institute of Geosciences, University of Kiel, Kiel, SOURCES OF ARC LAVAS: AN EXAMPLE Germany FROM THE SOUTHERN KERMADEC ARC (k.mackay*niwa.co.nz) R.J. Wysoczanski1,I.C.Wright2,J.A.Gamble3, 4 5 6 Monowai submarine volcano is located at E.H. Hauri , J.F. Luhr ,S.M.Eggins, &M.R.Handler1 25°53.5’S/177°11.1’W, about 1400 km NNE of 1 New Zealand along the Kermadec arc, and consists IFREE, Japan Agency for Marine Earth Science and Technology, Yokosuka, Japan. of a shallow symmetrical cone with a summit depth 2 of ~100 m. Monowai is one of the most active National Institute of Water and Atmospheric Research, Wellington, New Zealand. submarine volcanoes in the Kermadec arc, based on 3 visual reports from overflights, oceanographic Dept. of Geology, National University of Ireland, University College Cork, Ireland. surveys of hydrothermal plumes, and 4 seismoacoustic monitoring from French Polynesia Dept. of Terrestrial Magnetism, Carnegie and elsewhere. Since the late 1970’s, Monowai has Institution of Washington, USA.

50thKaikoura05 -98- Kaikoura 2005 5Dept. of Mineral Sciences, Smithsonian ORAL Institution, Washington, USA. 6Research School of Earth Sciences, Australian CYCLIC GROWTH AND DESTRUCTION OF National University, Canberra. STRATOVOLCANOES (richardw*jamstec.go.jp) Anke Zernack, Jon Procter & Shane Cronin Convergent margins, where oceanic lithosphere is INR, Massey University, Private Bag 11 222, subducted back into the mantle, form the key Palmerston North, NZ interface for large–scale element recycling between (a.v.zernack*massey.ac.nz) ocean, crust, mantle, and atmosphere. Recycling of elements in occurs as sediments and altered oceanic The last 150,000 years of volcanic activity of Mt crust (AOC) in the subducting slab dehydrate Taranaki are characterised by a series of alternating and/or melt, releasing water and mobile elements phases of edifice construction and collapse, with into the overlying mantle wedge, initiating melting the latter often producing catastrophic debris and the generation of arc magmatism. The avalanches. Repeated debris avalanche events from composition of arc magmas reflects these multiple unstable volcanic edifices have been inferred from sources and is further complicated by assimilation a number of long-lived stratovolcanoes, e.g. Mt of arc crust and hydrothermal fluids and brines as Rainier, Colima, Shiveluch, and St. Augustine. the magma ascends. Deconvolving the origin and However, in many of these locations it is transport mechanism of slab fluids and melts in impossible to study the oldest units because they subduction zones requires identifying tracer are deeply buried by more-recent volcaniclastic elements specific to a source and/or mechanism. deposits. Unusually, at Mt Taranaki an almost Fluid-mobile elements such as Cl, Ba, and Pb complete stratigraphic record of distal ring-plain provide the potential to investigate the composition successions is exposed due to continuous coastal erosion of the tectonically uplifted areas of southern and source of aqueous fluids derived from the Taranaki. This allows a detailed analysis of the subducting slab in arc systems. In the southern processes that are behind Mt Taranaki’s evolution Kermadec arc – Havre Trough (KAHT) pillow- and apparent cycles in behaviour. basalt glasses have water (~1.5 wt.%) and carbon (<16 ppm C) contents consistent with degassing to Previous work had split the volcaniclastic their pressures of eruption at 3000m bsl. By succession into an inferred edifice-construction contrast, Cl contents show strong correlations with sequence (Opunake Fm; 48-20 ka BP) and a fluid mobile elements (e.g. Pb and Ba) and sequence representing destruction (Stratford Fm; commonly used indices of aqueous fluids (e.g. 80-48 ka BP). However, more detailed mapping Ba/La). Simple modeling indicates that in excess of now reveals a greater complexity of packages of 80% of fluid mobile components in the mantle deposits representing higher frequency cycles of wedge are derived from addition of <1.5 wt.% of an growth and destruction, including two previously aqueous fluid from the descending slab. The unrecognised debris avalanche events between 23- proportion of aqueous fluid added to the mantle 29 ka BP. Accumulation during constructional wedge decreases westward into the back arc, phases is marked by massive sequences of consistent with the increasing volume of the predominantly monolithologic lahar and depleted mantle wedge. Correlations of aqueous hyperconcentrated flow deposits with intercalated fluid indices with Pb isotopic compositions indicate andesitic Taranaki and TVZ tephra beds. Intervals a sediment rather than AOC source for the fluids in of quiescence separating these eruptive periods are the southern KAHT, although in sediment-starved represented by paleosols and complex channels of areas such as the northern KAHT, fluids are reworked volcaniclastic sediments formed by probably derived from AOC. intense fluvial erosion. In contrast, destructional episodes are represented by coarse polylithologic We propose a single reservoir for the aqueous fluid debris flow and debris avalanche deposits which source of the arc magmas. This reservoir is most form due to partial or complete failure of the likely to be hydrated serpentinite formed above the edifice. Major debris avalanches bury extensive subducting slab by fluids derived from subducting areas of the ring plain and reshape the landscape, sediment and/or altered oceanic crust. Dehydration while those related to small events are confined to of the serpentinite occurs as it descends into the channels. mantle, transporting fluid mobile elements into the A general model of a cycle begins with edifice overlying mantle and triggering partial melting. The destruction, which is followed by long-term similarity of aqueous fluid compositions derived for production of ash - reflected in the formation of other oceanic arcs suggests that this process may thick paleosols or tephra layers within lignites at occur in arc systems worldwide, with the origin of aqueous fluids dependant on the volume and distal locations. This period represents the time composition of the sedimentary pile. taken for the cone to grow to a size at which

50thKaikoura05 -99- Kaikoura 2005 pyroclastic activity starts generating long-runout massflows. Edifice growth is ultimately limited to a critical point at which it fails. Past cones were probably similar to the current edifice, built primarily from voluminous unconsolidated pyroclastic deposits, making them susceptible to large-scale, deep-seated failures. Currently we appear to be near the end of the edifice growth phase. Understanding the cyclic nature of this record, including redefining the number of cycles will be critical for developing realistic probabilistic hazard models. Forecasting models can be refined by considering not just return periods of debris avalanches but also the preconditioning of the edifice to failure, and the type and nature of other hazards at different parts of the cycle.

ORAL

50thKaikoura05 -100- Kaikoura 2005 Author Index

Adams CJ...... 1, 18 Carter RM ...... 13, 14 Alexander C...... 64 Cashman KV ...... 68 Allibone A ...... 1, 89, 90 Cave M...... 14, 15 Alloway BV...... 4, 49 Chadwick WW ...... 98 Almond P ...... 4, 43, 86 Charley D...... 20 Amos C ...... 61 Clark M ...... 47 Arculus RJ ...... 31 Cleverley JS...... 63 Arnot M...... 23 Cochran UA...... 16, 35, 94, 95 Augustinus PC...... 4 Cole JW...... 32, 95 Baggs RA...... 2 Cole-Baker J ...... 16 Baldwin SL ...... 46, 67 Collot J-Y...... 39 Bani P...... 20 Cook C ...... 29, 70 Bannister JM...... 2 Cooke PJ ...... 16, 17, 57 Bannister S...... 8, 98 Cooper A...... 78 Barker D...... 3 Cooper RA...... 17 Barnes PM ...... 3, 8, 42 Cox SC...... 18 Barrell DJA...... 4, 5, 18 Crampton JS ...... 17, 19, 20, 35, 73, 77 Barrett PJ...... 5, 6, 55, 96 Crimp R...... 20 Bassett KN ...... 7, 10, 54, 76 Cronin SJ ...... 20, 21, 58, 68, 69, 71, 90, 99 Bateman L...... 60 Crouch EM ...... 22, 23, 27, 73 Beanland S ...... 55 Crundwell M...... 23 Bear T...... 7 Daczko N ...... 1 Beavan J...... 92 Dalbey K ...... 71 Bebbington M...... 90 Davies G ...... 56 Beck R...... 1 Davies TR ...... 10, 67 Beetham D ...... 55 Davis K ...... 61 Begg J...... 65 Dawson S ...... 50 Bennett E ...... 62 de Ronde CEJ ...... 31, 98 Bennett VC ...... 33 Dellow GD...... 24 Benson A...... 8 DeVaughn AM ...... 50 Berg JH ...... 33 Dickens GR...... 37 Berrill JB...... 10 Doyle LR...... 24 Berryman K ...... 5, 16, 24, 55, 83, 92, 94, 95 Dunbar G...... 55 Bertler N ...... 4 Duncan R ...... 43 Beu AG ...... 17 Dunkin M...... 47 Bland KJ ...... 2 Eagle MK...... 25 Bodger KL ...... 8 Eggins SM ...... 98 Bolhar R...... 9 Eusden JD ...... 26 Bradshaw JD...... 10 Ewig E...... 26 Bradshaw M...... 76 Faure K ...... 30 Brichau S...... 74 Field B...... 20, 22, 27, 91 Briggs C ...... 4 Finney B...... 29 Briggs RM ...... 75 Fitzgerald P...... 46, 67 Browne G...... 62 Flintoft M...... 60 Buech F ...... 10 Fohrmann M ...... 27 Bull WB ...... 11 Foley SF...... 69 Burbank DW...... 61 Fraser H...... 90 Burke R ...... 86 Funnell R ...... 91 Butland C ...... 60 Gaiger FJ...... 28, 60 Campbell HJ ...... 1, 12, 18, 85 Gamble J A ...... 33, 70, 98 Campbell K...... 62 George R...... 29, 70, 91 Carroll S...... 1 Gessner K...... 74 Carter L ...... 4, 12, 50, 55, 64, 96 Ghisetti FC...... 29 Carter R...... 35 Glodny J...... 74

50thKaikoura05 -101- Kaikoura 2005 Goff JR...... 93 Lea J ...... 60 Gollan MR ...... 30 Lebourg T ...... 39 Gómez JB...... 31 Lee DE ...... 2, 36, 43, 45 González Á ...... 31 Leith K ...... 68 Goodall A...... 18 Lever H ...... 44 Gorman AR...... 27 Lewis B ...... 44 Graham IJ...... 31 Leybourne MI...... 75 Grenfell HR ...... 32, 35, 40, 76 Lindqvist JK ...... 45 Guilderson TP...... 78 Lipps JH...... 35 Gutjahr M...... 10 Litchfield NJ...... 4, 45, 94, 95 Hampton SJ...... 32 Little T A ...... 46, 52, 55, 67, 88, 94, 95, 97 Handler MR ...... 33, 98 Love S ...... 15 Hansen RJ ...... 34 Lowe DJ...... 4, 16 Harper M...... 55 Lüer V ...... 36 Harrington HJ ...... 34 Luhr JF ...... 98 Harris C...... 30 MacFarlan DAB ...... 43 Hasegawa T ...... 20 Mackay K...... 47, 98 Hauri EH ...... 98 Mackey B...... 68 Hayward BW ...... 32, 35, 40, 76 Mackintosh A ...... 96 Hendy CH ...... 4, 16, 17 Manighetti B...... Henrys S...... 83 Manighetti B...... 4, 36 Herzer R...... 3 Mannering AA...... 48 Hikuroa DCH...... 35 Manville V ...... 44, 48, 49 Hiller N ...... 48 Marden M ...... 50 Hobbs BE...... 63 Marra MJ...... 49 Hocken AG ...... 36 Marsaglia KM...... 50 Hollis CJ ...... 27, 36, 37, 91 Marshall BA ...... 17, 50 Holt K...... 38 Martelli K...... 51 Hood SD ...... 2, 38 Martin SB...... 51 Horrocks M...... 32 Marx R ...... 49 Hudson K ...... 26 Marx SK...... 52 Hughes M ...... 86 Maslen G...... 91 Hyvernaud O ...... 98 Mason DPM...... 52 Jackson J ...... 62 Matcham I...... 73 James DE ...... 50 Mauffret A ...... 3 James NP...... 85 Maxwell PA...... 17, 50 Jarvis KDG ...... 27 Mazengarb C ...... 53 Joanne C...... 39 McCaffrey R...... 92 Johnston MR...... 74 McClintock M ...... 53 Jol HM ...... 60 McConnico T...... 54 Jones BJ ...... 85 McDonnell S...... 31 Jones CM ...... 17, 22, 39 McDowall RM...... 54 Jongens R...... 90 McGlone MS ...... 4 Jugum D...... 40 McGowan HA ...... 52 Kamber BS ...... 52 McKay R...... 55 Kamp PJJ ...... 2, 7, 34, 38, 62 McKean J ...... 68 Kapoutsos D ...... 7 McLellan J ...... 63 Kataoka K ...... 48 McSaveney MJ ...... 24 Kawagata S ...... 40 McVerry GH...... 83 Kear D ...... 41 Migeon S...... 39 Kennedy DM ...... 92 Milan L...... 1 Kennedy EM...... 23 Mitchell J ...... 47 King P ...... 62 Monteleone B ...... 46 Koons PO...... 26 Morgans HEG...... 22, 85 Kuehl S...... 64 Morley M ...... 32, 35 Lafoy Y ...... 3 Morrison B...... 73 Laird MG ...... 42, 77 Mortimer N ...... 3, 89 Lamarche G ...... 39, 42, 61 Mountjoy J...... 68 Landis CA...... 12 Mouslopoulou V...... 55 Langridge RM ...... 43, 55 Nairn IA ...... 24, 51, 80, 81

50thKaikoura05 -102- Kaikoura 2005 Naish T...... 55 Sabaa AT...... 32, 35, 40, 76 Naish T...... 85 Savage J ...... 76 Nalin J ...... 57 Schellenberg F ...... 62 Nathan S...... 56 Schiøler P...... 19, 42, 77 Neall VE ...... 56, 90 Scott GH ...... 36 Neil HL ...... 17, 47, 57, 76, 92 Scott J...... 78 Neil HM ...... 36 Shane PR...... 4, 24, 35, 51, 78, 80, 81 Nelson C ...... 2, 7, 17, 38, 57, 62, 66, 85 Shapiro SA...... 50 Németh K...... 21, 58 Sheridan M ...... 71 Newnham RM ...... 4, 49 Shulmeister J ...... 4 Nicholson H...... 59 Sibson RH...... 79 Nicol A...... 55, 59 91 Sikes EL...... 78 Nicolo M...... 37 Smith I...... 31, 69, 70, 80, 90 Nobes DC...... 60, 61 Smith M ...... 43 Nodder SD ...... 61 Smith VC ...... 80, 81 Norris RJ...... 40, 62, 88 Smith WD ...... 83 Nyman S ...... 62 Speed J ...... 81 O’Loan AG ...... 63 Spörli KB ...... 82 Okaya D ...... 83 Stern T...... 8, 26, 83, 84, 87 Oliver NHS ...... 63 Stewart RB...... 68, 69, 90 Oppenheimer C...... 20 Stirling MW...... 24, 83 Orpin AR...... 64 Stoffers P ...... 98 Pacheco AF...... 31 Stratford WR ...... 84 Palin JM ...... 30, 44 Strong CP...... 22, 37 Palin M...... 78 Suggate RP ...... 4, 84 Pallentin A ...... 3 Swanson K ...... 28 Palmer A ...... 4, 65 Sykes R ...... 27 Pantin HM...... 65 Tinto K ...... 85 Patra A ...... 71 Titjen JQ ...... 85 Pearson MJ ...... 66 Tonkin PJ ...... 4, 86 Pecher I ...... 27 Toulmin S ...... 87 Pere VH...... 67, 68 Townend J...... 87 Perez V...... 43 Townsend DB...... 65, 74, 88 Peters K J ...... 67 Toy VG ...... 88 Pettinga JR...... 8, 10, 12, 26, 54, 67, 68, 72 Tripathi A...... 38 Platz T ...... 68, 69, 71 Tulloch A ...... 78, 89, 90 Popham T...... 18 Turnbull I ...... 1, 90 Prebble WM...... 70 Turner M...... 90 Price R...... 29, 70 Turner S ...... 29, 91 Prior DJ ...... 88 Upton P ...... 26 Procter J ...... 71, 99 Uruski C...... 91 Proust J-N ...... 61 Van Dissen RJ ...... 5, 52, 86 Quinn A...... 71 Van Kranendonk MJ ...... 9 Rahiman T ...... 72 Vandergoes MJ...... 4 Raine JI ...... 22, 23, 73 Villamor P...... 55 Raisbeck G...... 62 Waikari C...... 92 Ramezani J...... 89 Wallace LM ...... 59, 92 Rattenbury MS ...... 74 Wallace RC...... 56 Read SAL...... 5 Walsh JP ...... 64 Read SE...... 96 Waterhouse JB...... 93 Reymond D...... 98 Watts P ...... 72 Ring Uwe ...... 74 Weaver SD...... 10 Rivera K...... 50 Wells A ...... 93 Robbins J ...... 71 White JDL...... 44, 49 Robertson DJ ...... 75 Wightman RH...... 97 Robertson KA...... 75 Wilkinson S ...... 60 Roest W...... 3 Williams PW ...... 4 Roncaglia L...... 19 Wilson CJN...... 63 Rother H...... 4 Wilson GJ ...... 22, 37 Rowland JV ...... 63, 82 Wilson GS...... 71, 85

50thKaikoura05 -103- Kaikoura 2005 Wilson K ...... 45, 65, 94, 95 Wilson TM...... 95 Wood JR ...... 96 Wood M ...... 96 Wright IC ...... 31, 47, 98 Wysoczanski RJ ...... 33, 98 Yiou F ...... 62 Youngson J ...... 62 Zernack A ...... 99

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