GEOSCIENCE SOCIETY OF ANNUAL CONFERENCE 2017

DYNAMIC NEW ZEALAND, DYNAMIC EARTH

Abstract Volume

University of Auckland November 28- December 1

ABSTRACT VOLUME

Chair Organizing Committee Michael Rowe

Extended Organising Committee Julie Rowland, Paul Augustinus, Martin Brook, Jon Tunnicliffe, Jennifer Eccles, Kathy Campbell, Joel Baker

Administration Stephanie Szmurlo

Fieldtrip Leaders Bruce Hayward, David Lowe, Julie Rowland

Abstracts are organised in alphabetical order by family name of first author

The bibliographic reference for abstracts is: Author, A.N. (2017). Title of Abstract. In: Baker, J. and Rowe, M. (eds). Abstracts, Geosciences 2017, Auckland, Geoscience Society of New Zealand Miscellaneous Publication 147A. p. x.

Co-Published by: University of Auckland, School of Environment & The Geoscience Society of New Zealand

ISBN 978-0-9922634-4-7 ISSN (print) 2230-4487 ISSN (online) 2230-4495

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under in situ conditions, with simulations that RECONCILING EXPERIMENTAL AND STATIC- account for micrometre-scale variations in DYNAMIC NUMERICAL ESTIMATIONS OF elastic properties of constituent minerals with SEISMIC ANISOTROPY IN ALPINE FAULT the MTEX toolbox and finite-element wave MYLONITES propagation on EBSD images. We observe that the sorts of variations in the distribution of L. Adam1, M. Frehner2, K. Sauer3, V. Toy3, S. micas and quartz+feldspar within any one of Guerin-Marthe4 & C. Boulton5 our real core samples can change the elastic 1 University of Auckland, New Zealand wave anisotropy by 10%. In addition, at 60 2 ETH Zurich, Switzerland MPa confining pressure, experimental elastic 3 University of Otago, New Zealand anisotropy is greater than modelled 4 Durham University, Earth Sciences, United anisotropy, which could indicate that open Kingdom microfractures dramatically influence seismic 5 Victoria University of Wellington, New wave anisotropy in the top 3 to 4 km of the Zealand crust, or be related to the different resolutions [email protected] of the two methods.

Quartzo-feldspathic mylonites and schists are the main contributors to seismic wave THE PHYSICAL PROPERTIES OF ALPINE FAULT anisotropy in the vicinity of the Alpine Fault CATACLASITES THAT DRIVE ITS ELASTIC (New Zealand). We must determine how the WAVE VELOCITIES physical properties of rocks like these influence elastic wave anisotropy if we want to L. Adam 1, S. Guerin-Marthe 2, S. J. Kanakiya unravel both the reasons for heterogeneous 1, C. Boulton 3, V. Toy 4 & D. Faulkner 5 seismic wave propagation, and interpret 1 University of Auckland, New Zealand deformation processes in fault zones. To study 2 Durham University, Earth Sciences, United such controls on velocity anisotropy we can: 1) Kingdom experimentally measure elastic wave 3 Victoria University of Wellington, New anisotropy on cores at in-situ conditions or 2) Zealand estimate wave velocities by static (effective 4 University of Otago, New Zealand medium averaging) or dynamic (finite 5 University of Liverpool, United Kingdom element) modelling based on EBSD data or [email protected] photomicrographs. Here we compare all three approaches in study of schist and mylonite Studying the Alpine fault, which is late in its samples from the Alpine Fault. cycle of stress accumulation, is a unique opportunity to understand the subsurface Volumetric proportions of intrinsically conditions ahead of a large earthquake. It is anisotropic micas in cleavage domains and the physical properties of the rocks in the comparatively isotropic quartz+feldspar in damaged zone around the fault that will microlithons commonly vary significantly control the mechanisms of rupture and within one sample. Our analysis examines the propagation. Here we present a effects of these phases and their arrangement, comprehensive study of the physical and further addresses how heterogeneity properties of Alpine Fault cataclasites and influences elastic wave anisotropy. We their relation to elastic wave speed and compare P-wave seismic anisotropy estimates moduli. We study 12 cataclasite samples from based on millimetres-scale ultrasonic waves core extracted from the DFDP-1A and -1B 1 wells from the first Alpine fault DFDP more closely match those likely to be campaign. encountered in future career opportunities. However, fieldtrips are also a stressful Sonic log P-wave velocities in the cataclasite experience, requiring students to work long sections in DFDP wells vary between 2000 and hours and to produce an integrated finished 6000 m/s and there is little quantitative product (e.g., a map) in a relatively short understanding on the nature of this variability. period of time. We have performed high (up to 100 MPa) and low (pressure at the core depth, 2-4 MPa) At the University of Canterbury, we identified pressure P- and S-wave ultrasonic velocity that students felt underprepared for fieldwork measurements on the water-saturated and that the current laboratory-based field cataclasites. Our laboratory velocities match training was not an adequate lead in for the well data at the pressures representative independent field mapping trips. Therefore, of the core depths, but as expected, velocities we developed a one-day fieldtrip “boot camp” at higher pressures do not agree with the log. to replace laboratory teaching. In the boot To understand which micro-scale physical camp, we introduced the students to basic properties affect the P- and S-wave velocities, field concepts in an authentic field setting, we have performed computerized which helped to improve their self-efficacy tomography scanning and analysis, semi- before attempting their first overnight quantitative XRD, XRF, porosity and grain independent field mapping course. density from pycnometry and fracture estimation from rock physics modelling. Here, we present our initial findings on Preliminary data indicate that fractures and student self-efficacy as a result of our fieldtrip porosity are not the principal controls on wave changes. We also present ongoing curriculum speed variability. Moreover, we will discuss development into the benefits of repeated the challenges of studying the physical field skills exercises as a preparation to further properties in cataclasite rocks in the context of learning in later degree fieldtrips which atmospheric vs. confining pressures. require more independence and critical thinking from undergraduate students. We then discuss implications of our data for the TRADITIONAL AND VIRTUAL FIELDTRIPS AS development of future real and virtual PREPARTION FOR FURTHER GEOSCIENCE fieldtrips. LEARNING

P.A. Ashwell1, A. Jolley1, J. Dohaney2 & B.M. Kennedy1 1 Dept. of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch 2 Swinburne University of Technology, PO Box 218, Hawthorn, Victoria, Australia [email protected]

Fieldtrips are often seen as crucial learning experiences for undergraduate students. In the field, students apply knowledge and skills from prior courses to real world scenarios that 2

INTEGRATED INTERPRETATION OF which broadly coincide with the surface AEROMAGNETIC AND GEOLOGICAL DATA TO geology, including: a) > 3 km deep andesite IMAGE THE SUBSURFACE GEOLOGICAL intrusives, b) 0.5 – 2 km deep andesite/dacite PATTERNS (DISCONTINUITIES) WITHIN THE intrusives and extrusives, and c) < 1 km deep COROMANDEL VOLCANIC ZONE (CVZ) andesite/dacite and rhyolite extrusives. Similarly, the data show prominent NW-SE, E.A. Bahiru1, J.V. Rowland1 & J.D. Eccles1 and NE-SW oriented, strong and linear to 1School of Environment, the University of semi-linear structural discontinuities and Auckland, Private Bag 92109, New Zealand anomaly boundaries, which we interpret as [email protected] deep-seated structural patterns that broadly reflect the control of regional basement The paucity of bed rock exposures due to structures. dense vegetation cover, and a lack of uniform coverage of high-resolution geophysical data in the Coromandel Volcanic Zone (CVZ) make SEDIMENTARY PROCESSES OF THE COOK imaging of the subsurface geologic patterns STRAIT CANYON SYSTEM difficult. We compile companies’ deposit scale high-resolution aeromagnetic surveys and S. Banks1, L. Strachan1, I. Pecher1, P. Barnes2, integrate with the surface geological data as A. Orpin2 constraints to illustrate the subsurface 1School of Environment, University of geologic features and their relationship with Auckland, Private Bag 92019, Auckland, New surface patterns. Despite the inherent Zealand ambiguity associated with aeromagnetic 2National Institute of Water and Atmospheric interpretation, the data provide an Research, 301 Evans Bay Parade, Wellington opportunity to recognise the occurrence of [email protected] magnetic source bodies at different subsurface depths by isolating the long and Submarine canyon systems provide a major short wavelength anomaly components. In conduit for transport of marine and terrestrial this regard, we particularly use the multiscale sediment from shelf to deep-ocean. Sediment edge detection (worming) technique on the flow processes and triggering mechanisms gradient enhanced aeromagnetic grid to that drive flow processes vary greatly from indicate locations where there exist maximum canyon to canyon. Variation of flow processes contrasts in the susceptibility of the is affected mainly by the canyon subsurface geology. The technique images the geomorphology and sediment type. This subsurface contrast interfaces retrieved at investigation was undertaken in the Cook different resolution by combining the Strait Canyon System, which includes horizontal gradient and upward continuation Opouawe, and Campbell canyons. This canyon techniques. system covers approximately 1800 km2, which consists of multiple branches incised into the Our integrated interpretation reveals the continental shelf. The Cook Strait Canyon spatial distribution, geometry and relative System is located in the eastern Cook Strait; a depth persistence of magnetic source bodies, body of water that separates the North and which are inferred to be associated with South Islands of New Zealand. This canyon known stratigraphic and structural features. transports sediment derived from the Cook For example, we interpreted three relative Strait off the shelf into the Hikurangi Channel. depth occurrences of magnetic source bodies, 3

A total of six sediment cores were collected siltstone, and weighs approximately 10-15 throughout the study site, high resolution tonnes. Sedimentological and physical visual core logging, CT scanning, Geotek volcanological evidence is used to identify the analysis and laser grain size analysis were original in-situ position, indicating that the done on the suite of cores. 3 radiocarbon block was transported 42 m across the rock dates were derived from basal sediments platform and rotated 110o. More movement within 3 cores in order to define a maximum has occurred within the past few years, of age for the overlying sediments. about 1 m sideways whilst being rotated back 50o. Another larger block weighing at least 30 From the data attained through these analyses tonnes at another location has been observed 5 facies have been described with six sub- to move at least 10m upslope of the platform facies within these. The facies were and rotate approximately 45o, during the last determined based on depositional 5 years. The movement is attributed to large characteristics in order to define the varying storm waves. No scraping across the flow processes within the canyon system. The underlying rock is evident, suggesting that canyons exhibit a variety of flow processes as they may have been lifted, or floated, the sediments vary in size from pebble to silt. indicating the potential energy of the wave Low clay content in the canyons cause all flows after travelling 40 to 50 m across the rock to remain non-cohesive. Smaller grain-sized platforms. Calculations suggest that a wave of beds normally graded from sand to silt are considerable height and wave length is interpreted as turbidity currents. Larger grain required to detach, lift and displace the block flow beds were found to contain a mixture of across the platform in one event, however, high density turbidity currents and grain flows. results are problematical due to the errors Most beds exhibit waning flow characteristics associated with the factors concerned. An and are likely triggered by seismic sources inversion algorithm may assist with producing making the area a potential site for a meaningful scenario. Other examples of paleoseismic investigation. both recent and less recent block movements are shown. The findings indicate that shore platforms along the New South Wales south DISPLACEMENT OF LARGE BOULDERS coast are prone to occasional large storm ACROSS COASTAL ROCK PLATFORMS SOUTH waves capable of moving large heavy blocks OF WOLLONGONG, NSW, BY LARGE STORM and boulders. The research contributes to the WAVES OR TSUNAMI? growing body of information regarding erosion and natural hazards at coastlines, Glen R. Bann and Brian G. Jones particularly applicable to climate change and School of Earth and Environmental associated sea level rise. Sciences, University of Wollongong, NSW, [email protected]

This research reports large boulders, or blocks, that have been displaced across coastal rock platforms south of Wollongong, Australia. In some cases imbrication of the blocks is evident. One block in particular measures approximately 1.5x2x4 m in size, is composed predominantly of fine-grained sandstone and 4

TUFFS, DYKES, FLOWS, FOSSILS, throughout the sedimentary units, especially DROPSTONES AND GLENDONITES; the tuffs, often exhibit very different EARLY VOLCANISM AND SEDIMENTATION IN morphologies, possibly due to the local heat THE MID- regime during or post formation. Evidence SOUTHERN SYDNEY BASIN suggests that the sources for these eruptions and intrusions were from volcanoes situated G.R. Bann1, B.G. Jones2 and I. Graham3 initially off the present day coastline to the south east, followed by at least one island 1Sanctuary Point, NSW, Australia volcano at Jervis Bay, with later development 2School of Earth and Environment Sciences, of a volcanic arc to the north east, also off the University of Wollongong, NSW, Australia present day coastline, which was responsible 3School of Biology, Earth and Environment for the later GV latite flows. It is likely that Sciences, UNSW, Kensington, Australia these volcanoes were associated with stress [email protected] and tension related to subduction and foreland loading from the Currarong Orogen This research investigates the volcanology and to the east, the south-easterly extension of sedimentation of the Mid Permian Southern the New England Orogen. Sydney Basin. A number of newly identified tuffs interspersed with the shallow marine sediments are described. These tuffs are LATE RIFTING OF THE laterally extensive, hence chronostratigraphic CANTERBURY BASIN DURING markers and are both mafic and felsic. Trace INTRA-CONTINENTAL EXTENSION and body marine fossils are associated with some of them, including death assemblages. A. Barrier1, A. Nicol1, K. Bassett1, G. The dykes along the coast south of Sydney Browne2, T. Sahoo2 have been reported as being generally 1University of Canterbury, Department of to Tertiary in age, however, many dykes are Geological Sciences, Christchurch 8140, New found intruding unconsolidated wet Zealand sediments, hence being 2GNS Science, PO Box 30368, Lower Hutt penecontemporaneous with sedimentation. [email protected] These are more likely associated with the proximal volcanoes responsible for the early Zealandia comprises continental crust that latite eruptions of the Gerringong Volcanics rifted from Gondwana during Cretaceous (GV). At least one of these Permian dykes breakup. The Canterbury Basin is one of contains xenoliths, with at least one syenitic Zealandia’s rift basins formed during intra- type originating from a lower crustal source continental extension initiated around beneath the Basin. Dropstones, which 105Ma. By ~86.5 Ma, the locus of the primary sometimes exceed 1 metre in cross section, of extension shifted to the West Antarctica and extrusive igneous material, both mafic and South Zealandia spreading centre. Extension felsic, from eruptions prior to the first in the basin was active for over ~20 Ma. recognized flows of the GV are also described. Typically in Canterbury, the extensional basins These dropstones usually occur in are under-filled with sediments, as the rate of conglomerate horizons, probably transported sediment supply was lower than the rate of from coastal sea ice due to short and long accommodation space creation. term climatic cycles. Intercalated glendonite and concretion horizons which occur Interpretation of mainly 2D seismic reflection 5 lines and petroleum wells indicates that mid- The Mid-Miocene Climatic Optimum (MMCO) Cretaceous rifting (~105-86.5 Ma) formed in was an interval of high global temperatures association with NE-SW, E-W and NW-SE that lasted from 17-15 Ma. Palaeoclimate striking normal faults that accrued evidence for this period has primarily come displacement synchronously. These faults from deep marine sediment cores with formed due to distributed extension prior to minimum resolution of thousands of years. Gondwana breakup, with maximum throws of The Hindon Maar Complex (HMC), located ~22 2-3 km typically greatest on NE striking faults km NW of Dunedin CBD, consists of four maar sub-parallel to the subsequent mid-ocean craters of mid-Miocene age (~15 Ma), ridge system that formed between New coinciding with the end of the MMCO. Zealand and Antarctica. Laminated lake sediments are found in Maar 1, and in a depression between Maar 2 and E-W and NW-SE faults are mainly located in Maar 3. These sediments are composed northern parts of the basin where deep almost entirely of organic matter and biogenic seismic reflectors within basement highlight E- silica. Due to the high organic matter content, W trending thrust faults and folds. These laminae are hard to discern; however, maar contractional structures are interpreted to lake sediments are frequently characterised have formed during Mesozoic subduction by seasonal to annual layers, and we assume along the eastern Gondwana margin and were that the Hindon deposits are very highly reactivated during mid-Cretaceous extension. resolved compared to contemporary marine deposits. Sediments in the HMC thus provide In the offshore Canterbury Basin top lap of a unique opportunity to reconstruct climate syn-rift reflectors onto post-rift reflectors is and environment in New Zealand at an consistent with erosion of syn-rift growth- unusually high resolution during a period of strata. In the Clipper-1 well an unconformity high global temperatures. between syn-rift terrestrial strata and Lower Haumurian post-rift marine sedimentary rocks This project aims to characterise represents a 10 Myr hiatus. An unconformity compositional and ecological variability in one of similar age has been described in the of the Hindon Maar lake deposits and use and could record regional uplift these to infer climatic and environmental of Zealandia following Gondwana break-up. conditions. Microfossil assemblages are composed of freshwater diatoms, sponge spicules, and chrysophycean cysts. Biogenic SEDIMENTOLOGY & silica and total organic carbon contents are MICROPALAEONTOLOGY OF A MID- estimated using Fourier transform infrared MIOCENE MAAR LAKE SEDIMENT spectroscopy (FTIRS) and verified using wet chemistry. Here we present preliminary Noel Bates1, Beth Fox1 & Christina results and palaeoenvironmental inferences. Riesselman2 1School of Science, University of Waikato, Private Bag 3105, Hamilton 2Dept. of Geology, University of Otago, PO Box 56, Dunedin [email protected]

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EVOLUTION OF THE DUNEDIN VOLCANIC occurring during the onset of a long-lived COMPLEX: INSIGHTS FROM ALLANS BEACH intraplate complex.

R.J.M. Baxter & J.D.L. White Dept. of Geology, University of Otago, PO Box A RECORD OF NATURAL AND HUMAN- 56, Dunedin INDUCED ENVIRONMENTAL CHANGE FROM [email protected] PUNAHAU (LAKE HOROWHENUA)

Intraplate volcanism is a widespread C. Bevins1, K. Holt1, J. Procter1, P. Verburg2, phenomenon throughout the world with the M. Gibbs2 Auckland Volcanic Field being a currently 1Massey University, Private Bag 11 222 active example in the New Zealand region. The Palmerston North, 4442 onset of such volcanism is poorly understood. 2 NIWA, Gate 10 Silverdale Road, Hillcrest, An understanding of the evolution of small Hamilton, 3216 eruptive centres has been attained through [email protected] sampling of their entire sequences. However, studying the evolution of long-lived complexes Lake sediment records provide invaluable is more difficult as their earliest products are archives of the environmental changes both often inaccessible. The Dunedin Volcanic within the lake, and the surrounding Complex (DVC) was a long-lived volcanic catchment. Such archives are now increasingly centre, active from 16 Ma to 10 Ma, within an being used to provide baseline data for intraplate setting. Allans Beach on the informing environmental restoration efforts. southeastern coast of Otago Peninsula is one Lake Horowhenua (Punahau) is a shallow dune of the oldest known exposed sections of the lake located in the Horowhenua District. The DVC. This exposure offers a unique window lake is owned privately by the Muaūpoko into the eruptive and magmatic processes people who have a special cultural and taking place during the onset of volcanism in spiritual connection to the lake. Punahau has the Dunedin area. Intraplate volcanism is poor water quality, high turbidity and is known to produce chemically primitive hypertrophic due to agricultural and magmas, with few examples of evolved horticultural runoff, groundwater transport, compositions. At Allans Beach, however, a and storm water overflow. However, wide spectrum of compositions (basanitic to knowledge of the lakes’ inception and phonolitic) and textures are observed within evolution, changes in vegetation of the the volcaniclastic and intrusive material. surrounding catchment and sedimentation These units have complex cross-cutting rates due to land-use change are poorly relationship, in a small area (< 1 km). Field and quantified. In order to rectify this, sediment petrographic analysis has enabled re- cores have been collected from Punahau. interpretation of the events that led to their Stratigraphy and initial radiocarbon dating formation. A phonolitic pumice host is cross- results indicate that the modern lake began to cut by diatremes, cross cut further by dikes form at approximately 7100 cal yr BP following ranging from alkaline basalt to phonolite. a marine incursion, which may be attributed Some of these diatremes formed to the Holocene high sea level stand, or penecontemporaneously with intruding dikes. possibly a tidal surge associated with a A wide range of magma compositions tsunami. Ongoing research involves emplaced in a relatively short time span is an palynology, charcoal analysis, indication of complex magmatic processes sedimentology/grain size, XRF geochemistry, 7 radiometric dating (14C, 210Pb and 137Cs) and insights have been combined with data from other elemental analyses to construct a the literature to evaluate the role of allogenic detailed history of the lake to assess the and autogenic processes that control the impact of human-induced environmental stratigraphy of the northern Canterbury basin. change resulting from Polynesian and European settlement. The archive of Although the current literature indicates that information retrieved from the sediments of self-slope construction and the associated Punahau will be a key resource informing lake stratigraphic sequences of Canterbury basin restoration efforts currently underway as part are exclusively controlled by eustatic cycles of the Lake Horowhenua Accord as well as Te and tectonic pulses, we observed that two Mana O Te Wai projects. important magmatic events strongly influenced progradation of the shelf: 1) a group of volcanic cones, lavas (?) and THE INTERPLAY OF TECTONIC, VOLCANIC pyroclastic deposits erupted during the AND EUSTATIC FLUCTUATIONS DURING THE Middle Miocene, here referred to as NEOGENE SEQUENCE OF NORTH Resolution Volcanic Field, which is located 50 CANTERBURY BASIN, NEW ZEALAND km offshore of Ashburton. 2) Banks Peninsula Volcanic Complex a trachytic/andesitic Alan Patrick Bischoff1, Andrew Nicol1 volcanic group composed of three large shield and Andrea Barrier1 volcanoes and several minor eruptive centres, 1University of Canterbury, Department of which were active during the Late Miocene. Geological Sciences, Christchurch [email protected] The area beneath the edifices was intensively deformed, uplifted by magma emplacement The Neogene sequence of northern and experienced local subsidence due to the Canterbury basin is dominated by thick weight of the volcanoes compacting siliciclastic deposits formed as a consequence underlying marine siltstones. The presence of of uplift and erosion of the Southern Alps. the volcanoes form elevated areas of more Throughout the eastern basin these than 4000 km2 and produce distinctive sequences are locally pierced and intercalated retrogradation migration of the shelf slope not with volcanogenic rocks, which include the observed elsewhere in the basin. volcanoes of Banks Peninsula.

We aim to understand how the interplay of DISTRIBUTION OF SURFICIAL SEDIMENTS IN tectonic events, eustatic fluctuations in sea THE OCEANS AROUND NEW ZEALAND level and volcanism controls the Neogene morphology and progradation of the shelf- H. Bostock1, K. Mackay1, C. Jenkins2, L. slope along the eastern margin of New Carter3 Zealand’s South Island. We use a large 1National Institute of Water and Atmospheric collection of onshore and offshore seismic Research, Wellington reflection lines calibrated with logs, 2INSTAAR, University of Colorado, Boulder, biostratigraphic, radiometric and lithological USA data from exploration wells and outcrops. 3 Antarctic Research Centre, Victoria These data constrain the architecture of five University, Wellington chronostratigraphic sequences proximal and [email protected] distal to volcanic centres. The resulting 8

New Zealand has a large marine territory. Data likely governs the mode of fault slip. We from >300 published, unpublished, national sampled gouges, cataclasites, and protolith and international databases covering metabasite and serpentinite from three approximately 30,000 sediment datasets was exposed normal faults: the active Mai’iu Fault, compiled to produce a series of maps an abandoned part of the Mai’iu Fault, and the characterising the surficial sediments of the Gwoira splay fault in the hanging wall of the entire New Zealand Exclusive Economic Zone Mai’iu Fault. Quantitative XRD results indicate for the first time. Sediment grain size and that all three faults formed primarily within carbonate distributions around New Zealand footwall Gorupu metabasalts. Significantly, show some distinct spatial patterns. We also the active and abandoned Mai’iu Fault discuss other sedimentological features such localities accommodate slip within fault as the presence of nodules of various types. gouges comprise up to 65% corrensite and The sedimentary patterns can primarily be saponite. Hydrothermal friction experiments explained by past and present climate, were conducted on six different fault rocks at onshore geology and terrigenous flux, varying values of sliding velocity (v=0.3-100 tectonics and volcanic activity, complex µm/s), normal stress (σn=30-210 MPa), and bathymetry, oceanographic circulation, and temperature (T=50-450°C) to simulate diagenetic alteration. The interaction between progressively deeper levels of fault activity. these various facets permit recognition of Saponite-bearing fault gouges exhibited distinct regions of deposition such as the east extremely low friction coefficients (µ=0.13- of the North Island where tectonism, source 0.15 and µ=0.20-0.28) and velocity- rocks and climate collectively produces strengthening behaviour conducive to fault extreme sediment fluxes so that the shelf is creep. At the highest temperatures (T≥150°C) mantled by modern sands and muds. and lowest sliding velocities (v=0.3-3 µm/s) tested, the frictional velocity dependence of the saponite-bearing gouges transitioned to FLUID-ROCK INTERACTIONS AND FAULT- velocity-weakening, indicating the potential ZONE WEAKENING ALONG THE ACTIVE for unstable slip. Hydrothermal friction MAI’IU LOW-ANGLE NORMAL FAULT, experiments conducted on frictionally WOODLARK RIFT, PAPUA NEW GUINEA stronger (µ=0.37-0.78) cataclasite, ultracataclasite, and protolith metabasalt and 1 2 1 C. Boulton , A.R. Niemeijer , T.A. Little , M. serpentinite samples similarly showed a 1 3 1 Mizera , S. Ellis & S. Webber temperature-dependent transition to 1 Victoria University of Wellington, PO Box velocity-weakening behaviour with simulated 600, Wellington, New Zealand depth; the potential for unstable slip was most 2 HPT Laboratory, Utrecht University, Utrecht, pronounced in the temperature range of 200 the Netherlands to 350°C. Our experimental results support 3 GNS Science, Lower Hutt, New Zealand geodetic, seismological, field, and [email protected] microstructural evidence for both seismic and aseismic slip on the long-lived Mai’iu Fault. Field observations indicate that a majority of fault slip on the low-angle Mai’iu Fault, Woodlark Rift, Papua New Guinea, occurred along fault rocks comprising a narrow (< 2 m) core. The frictional properties of these fault rocks, in large part predicated by mineralogy, 9

velocity-strengthening (+a-b) materials are FRICTIONAL PROPERTIES OF HIKURANGI prone to aseismic creep. At every temperature PLATEAU SEDIMENTS AND APPLICATION OF tested, the highly calcareous sediments are THE RESULTS TO SLOW-SLIP PHENOMENA predominantly velocity-weakening. The smectitic sediments are predominantly C. Boulton1, A.R. Niemeijer2, J. Townend1, velocity-strengthening. However, when tested C.J. Hollis3, T.A. Little1, & S. Ellis3 at sliding velocities equal to, and slightly faster 1Victoria University of Wellington, PO Box than, the plate convergence rate (v=0.001- 600, Wellington, New Zealand 0.003 µm/s) at 25°C, the smectitic sediments 2HPT Laboratory, Utrecht University, Utrecht, exhibit velocity-weakening behaviour. The the Netherlands experimental results are significant because: 3GNS Science, Lower Hutt, New Zealand (1) pore-fluid overpressures may not be [email protected] required for fault-zone weakness or slow slip; and (2) the smectitic sediments overlying the The North Island of New Zealand overlies the demonstrate the capacity Hikurangi Subduction Zone (HSZ), which for hosting an instability at conditions accommodates westward subduction of the comparable to those along the shallow Pacific Plate at a convergence rate that varies décollement. from 50-60 mm/yr in the North to around 20 mm/yr in the South. The Hikurangi Subduction Zone décollement occurs within Late A VIOLENT PHREATOMAGMATIC ERUPTION Cretaceous-Paleogene (70-32 million-year- THAT FORMED A MAAR IN AN INTRA- old) marine sediments. We measured — for MOUNTAIN BASIN AT ARXAN-CHAIHE the first time — the frictional strength and VOLCANIC FIELD, INNER MONGOLIA, CHINA stability of Paleocene and Eocene marine sediments deposited on the Hikurangi Plateau L. Boxin & K. Németh and recovered from 419.3 m to 434.56 m Massey University, CS-IAE, Volcanic Risk below the sea floor during IODP Leg 181 at Site Solutions, Turitea Campus, Palmerston North 1124 (Hole 1124C; -39.4984°S, -176.5316 °E). [email protected] Hydrothermal friction experiments were conducted on nine different samples at a The Arxan-Chaihe volcanic fields (ACVF) in NE constant effective normal stress of 60 MPa China consist of about 30 young scoria cones with hydrostatic pore fluid pressure and with pahoehoe to aa-type basaltic lava flows varying sliding velocities (v=0.001-30 µm/s) and at least 4 maars, together covering an and temperatures (T=25-225°C). Highly area of c. 1000 km2. Volcanism initiated in the calcareous sediments are frictionally strong Pliocene and continued through the Late (µ=0.48-0.66). Calcareous and noncalcareous Pleistocene to Holocene (c. 2000 cal yrs BP). clayey sediments are frictionally weak Recently, tephra of 14,200 cal yrs BP age has (µ=0.18-0.30) and contain the mineral been identified, preserved in a crater lake, smectite. The HSZ décollement likely localises suggesting a Holocene violent in the weakest, smectitic sediments. The phreatomagmatic explosive eruption from an friction rate parameter (a-b) was determined unknown source. This has intensified the from velocity steps conducted at search for potential phreatomagmatic temperatures of 25°C, 75°C, 150°C, and 225°C. volcanoes in the ACVF. Tongxin Tianchi Whereas velocity-weakening (-a-b) materials volcano in the eastern ACVF forms a steep- may nucleate earthquakes or slow-slip events, walled, flat floored basin filled with a lake and 10 is suspected to be a maar. The depression is shale oil and gas exploitation: the initial surrounded by a c. 400 m high escarpment of resource assessment by the BGS and the way Mesozoic crystalline rocks that gradually politicians swallowed the big numbers : the drops toward the south. Dune-bedded base- response of the regulatory authorities in surge-dominated successions are at least 40 m allowing exploration by a few minor oil thick in the south and diminish toward the companies: and the public protests arising higher cliffs in the north. Abundant from environmental concerns so freely accretionary lapilli beds, accidental lithic-rich promulgated on social media. tuffs with impact sags, cored bombs, blocky pyroclasts, as well as glassy, non-to-low Shale oil and gas is recognised as an vesicular juvenile particles, all point to a ‘unconventional’ energy source since it sustained and energetic phreatomagmatic doesn’t conform with the science as practised explosive eruption forming this volcano. The (and taught) by most active petroleum uniform basaltic composition of the juvenile geologists. Without a conventional database it pyroclasts indicates that phreatomagmatism begs the question as to how trustworthy and played a key role in the eruption and the independent is the geoscientific opinion volcano likely was capable of producing a large (including my own) ? volume of ash, which could have accumulated in other crater and maar lakes in the ACVF. The The fracking story characterises many other pyroclastic deposit characteristics, resource developments (deep sea oil, gold & stratigraphy and microtextures suggest that iron sand mining, freshwater dams) and is Tongxin Tianchi is a maar volcano; however, symptomatic of an ever increasing and hungry the present day depression is not necessarily population. The need to conform can easily be identical to the structural margin of the maar driven by political, economic and social crater. pressures; as such it is suggested that technical discussion take place within the informed geoscience community prior to it’s SOCIAL RESPONSIBILTY FOR GEOSCIENCE IN airing within the world that includes THE UNCONVENTIONAL WORLD Government, Resource and Environmental Court Proceedings, Facebook etc. Roger Brand Inter Est, Waimamaku, Hokianga, Northland However I suspect the polemic is well [email protected] established and the time for dialogue has passed. But in New Zealand we are fortunate The very mention of FRACKING can elicit an not to have ‘academic freedom’ bills before emotional response, polarising attitudes for legislature and can educate and engage the and against. In the USA the advent of hydraulic ‘public’ with grassroots geoscience as with the fracturing (aka. fracking) has meant for some GNS Science initiative. economic salvation, while to others it spells environmental doom. In France and Germany fracking has been banned while in the UK (and New Zealand) the waters are being still tested amongst considerable public outrage.

Here I look at the UK’s hydraulic fracturing issue and how geoscience lies at the foot of 11

THREE KINGS OR A WHOLE DYNASTY? A The eruption at Three Kings began with COMPLEX VOLCANO IN THE HEART OF basanitic magma feeding phreatomagmatic AUCKLAND volcanism. As eruption proceeded magma became progressively less strongly alkaline M. Brenna1, S.J. Cronin2, I.E.M. Smith2, K. (tending to sensu stricto alkaline basalt) and Nemeth3, J.D.L. White1, & R. Baxter1 more magmatic (strombolian) in character. 1Department of Geology, University of Otago, The last phase of the eruption formed spatter PO Box 56, Dunedin. mounds/lava flows with the least alkaline 2School of Environment, University of composition distinct from preceding products. Auckland, Private Bag 92019, Auckland. Three Kings illustrates another example of 3Volcanic Risk Solutions, Massey University, complex monogenetic volcanism fed by Private Bag 11222, Palmerston North. distinctly stored magma batches within the [email protected] mantle.

The city of Auckland is situated within the confines of the omonimous intraplate volcanic RAPID MAGMA ASCENT FOLLOWING field, which consists of at least 53 individual COMPLEX STORAGE AT PUPUKE MAAR, volcanoes. Understanding the mechanisms AUCKLAND VOLCANIC FIELD driving magmatic activity and the impact of the resulting volcanic processes is essential to M. Brenna1, I.E.M. Smith2, S.J. Cronin2, E. prepare for a potential future eruption. The Smid2, J.M. Scott1 & D.J. Prior1 Three Kings volcano is situated in the central 1Department of Geology, University of Otago, portion of the volcanic field and can therefore PO Box 56, Dunedin yield crucial information on the core of the 2School of Environment, University of magmatic system. It consists of a tuff Auckland, Private Bag 92019, Auckland sequence that formed a ring surrounding a [email protected] crater subsequently infilled by scoria and lava flows (mostly quarried away), which tipped Eruptions in monogenetic volcanic fields are out of the crater and formed some lava tubes. unpredictable both spatially and temporally. Nonetheless as magma makes its way to the We collected stratigraphically controlled surface to erupt seismic signals are produced, samples from the tuff sequence in both which can give some indication of unrest. The proximal and distal deposits for chemical and timescale between initiation of unrest and physical analyses, as well as samples from the eruption onset is not clear, and depends on scoria and lava in the central portion of the magma ascent rates. Understanding these volcanic complex. The composition ranges relationships is paramount when eruptions from basanite to alkaline basalt. The tuff may occur within densely populated areas sequence is more strongly alkaline showing a such as the Auckland Volcanic Field. stratigraphic trend towards decreasing alkalinity. The subsequent lava and scoria Magma ascent rates can be estimated in deposits have a distinct composition with monogenetic basaltic volcanoes by higher MgO, Cr and Ni, and lower P2O5, Ba and investigating their crystal cargo. Olivine Zr. Tephra consist of mostly (>60%) juvenile xenocrysts from the mantle lithosphere that glass components (2phi fraction) with a broad have been entrained by the ascending basaltic decrease of lithic fragments up-stratigraphy. magma are not in equilibrium with the melt, 12 and will therefore exchange chemical elements with the host melt through diffusion. DEVELOPING THE LINK BETWEEN ELASTICITY The time necessary for this process to occur AND CONTROLLING PHYSICAL PROPERTIES can be quantified through element diffusion IN NEW ZEALAND’S COALS AND modelling. CARBONACEOUS MUDSTONES

We sampled a suite of olivine xenocrysts from S. Brennan1, L. Adam1, R. Sykes2, D. a strombolian fall deposits at Pupuke Maar to Mohnhoff2, and L. Strachan1 understand the magma ascent duration and 1University of Auckland, School of mechanisms from mantle depths. Olivine Environment, Auckland xenocyrsts have forsteritic cores (Fo#91-92) 2GNS Science, Lower Hutt and Cr-spinel inclusions indicative of their [email protected] upper mantle origin. Diffusion profiles length ranges from few tens of microns up to ~200 Coals and carbonaceous (“coaly”) mudstones microns. Fe-Mg, Ca, Ni and Mn diffusion are the primary sources of oil and gas in most modelling of the observed profiles results in of New Zealand’s sedimentary basins. These residence times for the mantle derived types of petroleum source rocks are regionally xenocrysts of mostly less than a week. A few significant, however; they are less common crystals have more complex diffusion profiles globally. Our ability to identify and that may indicate longer periods of storage up characterize them in the subsurface is a critical to two years and interaction with magmas component of prospecting for new oil and gas with different compositions. accumulations. Predicting their nature from geophysical measurements (i.e., seismic and We propose a model for the plumbing system wireline logs) is constrained by a lack of of Pupuke volcano, in which magmas ascend calibration between the geophysical from their mantle source and interact with attributes of coaly rocks and their physical magmas with variable composition derived properties. These results are part of a broader from different levels within the mantle. project, which aims to characterize the Trigger for ascent is given by the arrival of a inorganic and organic constituents of coaly final magma batch, generally more alkaline, source rocks based on indirect geophysical which raises rapidly and promotes ascent of field observations. other ponded magmas. This study will construct models specific to coaly source rocks for correlating their physical properties, geophysical signatures, and petroleum potential. New Zealand is an excellent location to conduct such a study as it hosts a near complete spectrum of coal ranks (peat through anthracite). Samples will be collected from each of these as well as adjacent lithologies (i.e., shaly coals and coaly mudstones) to experimentally measure and model the seismic signatures resulting from variations in organic versus inorganic sediments, coal rank, and wave anisotropy.

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smoothed internal surfaces caused by ENGINEERING GEOMORPHOLOGY OF AN scouring from rapid sediment discharge. The ACTIVE SUBURBAN LANDSLIDE: WALLIS channelized flow then descends the 70° cliff, ROAD LANDSLIDE COMPLEX, KAITI HILL, prior to forming a scoured parabolic channel GISBORNE through the fan at the cliff base. Repeat surveys show creep-rates increase following M.S. Brook1, M. Cave2 & T. Rishworth1 heavy rainfall. Hence, the Tunanui Fm 1School of Environment, University of mudstones are acting as an impermeable Auckland, Auckland 1010 barrier to groundwater infiltration from the 2Gisborne District Council, 39 Gladstone Rd, overlying (deforming) Mangatuna Fm. Gisborne, 4010 Slumping retrogressively extends the complex [email protected] inland along Wallis Road, visible from warping and scarplets around No. 3 Wallis Road. The geomorphological character of the Wallis Road coastal landslide complex, Gisborne, is presented here from site investigations, LiDAR ENGINEERING GEOLOGICAL ROCK MASS and UAV-acquired imagery. Instability at the CLASSIFICATION OF UNDERGROUND COAL eastern end of Wallis Road (80 m asl) has been MINES: CARBOROUGH DOWNS MINE, recognised for several years, resulting in No. 1 QUEENSLAND, AUSTRALIA Wallis Road being demolished in 2015. Within the complex evidence for prior instability M.S. Brook1, B. Hebblewhite2 & R. Mitra3 includes relict slump-blocks and revegetated 1School of Environment, University of hummocky paddocks marking former Auckland, Auckland, New Zealand earthflows are visible. However, the historic 2School of Mining Engineering, University of nature of instability is unknown. Recent New South Wales, Sydney, Australia deformation has occurred throughout the 3School of Mining Engineering, University of 2017 winter, culminating in an earthflow from the Witwatersrand, South Africa the complex depositing a 100 m × 60 m fan [email protected] onto Kaiti beach, below. The upslope extent of the landslide forms a broad headscarp, and Developing an accurate engineering geological lateral scarps, with back-tilted blocks, ponded model and realistic delineation of variation in surface water, and tilted telegraph poles rock mass conditions are important indicating rotational slumping. Cone prerequisites for slope stability analyses, penetrometer testing and boreholes indicate tunnel design, mine planning and risk the slip base at c. 6 m depth in the upper management. In coal measures rocks, section, marking the boundary between the knowledge of discontinuities may yield surficial early Pleistocene Mangatuna Fm improved understanding of coal seam (estuarine, river sediments, ignimbrite) and permeability, which is important for coal seam underlying mudstone of the Miocene Tunanui gas (CSG) reservoir behaviour. Rock mass Fm. A photographic time-series indicates classification schemes such as Rock Mass slumping and subsidence at the end of Wallis Rating (RMR), Coal Mine Roof Rating (CMRR), Road proceeds at up to 0.35 m d-1. Below the Q-system and Roof Strength Index (RSI) have upper area of rotational-slumping, a transition been used for a range of engineering zone occurs, and below this, a channelized geological applications, including transport earthflow c. 10 m wide has formed. This is tunnels, “hard rock” mining and underground characterised by levees on each side, and and open-cut coal mines. Often, rock mass 14 classification schemes have been evaluated on Palmerston North subaerial exposures, where weathering has 4INGV Pisa, Via della Faggiola 32, 56126 Pisa, affected defect characteristics and intact Italy strength. The focus of this evaluation of the [email protected] above classification schemes is an underground coal mine in the Bowen Basin, Pyroclastic surges are fast, variably hot and central Queensland, Australia, 15 km east of highly destructive mixtures of particles and the town of Moranbah. The mine targets the gas, which constitute one of the most frequent Late Permian Rangal Coal measures. Rock hazards at volcanoes worldwide. Their highly mass classification was undertaken at 68 sites variable thermal energy, dynamic pressures as across the mine. Both the target coal seam well as their ability to surmount topography (Leichhardt Seam) and overlying rock show make hazard prediction extremely marked spatial variability in terms of rock challenging. mass properties, and this is reflected in their RMR, CMRR and Q classification results. Previous studies have been carried out to However, RSI showed limited sensitivity to understand the surge hazard potential by changes in rock mass condition. Relationships analysing their deposits, by direct were developed between different observations from distance or through parameters with varying degrees of success. A numerical modelling. However due to the lack mine-wide analysis of faulting was of data of the inner flow structure and undertaken, and compared with in situ stress dynamics, assessment of hazard potential field and local-scale measurements of joint from field data and current numerical models and cleat. While there are no unequivocal remains mostly qualitatively and involves relationships between rock mass classification large uncertainties. parameters and faulting, a central graben zone shows heterogeneous rock mass Large-scale experimental simulations properties. The corollary is that if geological conducted at the eruption simulator PELE in features can be accurately defined by remote New Zealand produced first insights into the sensing technologies, then this can assist in inner structure of pyroclastic surges, which predicting rock mass conditions and risk were synthesized with a number of invariable management ahead of development and and variable initial- and boundary conditions. construction. During the experiments space- and time- variant gas-particle transport and sedimentation characteristics were recorded FIRST VIEWS INSIDE PYROCLASTIC SURGES as well as time- and space-variant REVEAL NEW MECHANISMS BEHIND THEIR temperature, turbulence, velocities, THERMAL AND DYNAMIC PRESSURE concentrations and deposit characteristics. HAZARD POTENTIALS First results reveal strong pulsing in the flow E. Brosch1, G. Lube1, E. Breard2, K. Kreutz3, J. which is associated with the passage of the Jones3, T. Esposti-Ongaro4 head and rear of the head flow regions. These 1Volcanic Risk Solutions, Massey University, pulses of dynamic pressure are not only Private bag 11 222, Palmerston North recorded in the frontal and fastest part of the 2Georgia Institute of Technology, North Ave flow, but they also occur inside the flow. The NW, Atlanta, GA 30332, USA occurrence of multiple pulses of high dynamic 3SEAT, Massey University, Private bag 11 222, pressure, quite similar to multiple seismic 15 shocks during Earthquake events, strongly the central STB, preceding (3) rapid northward increases the destruction potential of surges progradation of the shelf break between 14 on infrastructure. Thermal imaging of the and 7 Ma. Episodes (2) and (3) reflect internal structure of the experimental surges increasing terrigenous input. Sedimentation shows strong time-variance in thermal energy patterns in the STB during episode (3) are during flow passage, which is currently not temporally consistent with conglomerates captured in volcanic hazard models. deposited in West Coast basins, which are interpreted to be derived from the proto In this talk we will illustrate internal velocity, Southern Alps located ~300 km south of the density, dynamic pressure and thermal STB. Furthermore, the Mid-Late Miocene structure of experimental pyroclastic surges (~16-7 Ma) was dominated by sediment and discuss space- and time variant hazards transport directions perpendicular to the shelf with regards to updating existing hazard break in the STB where sedimentation rates models. exceeded fault-displacement rates. (4) Latest Miocene (~7-5 Ma) saw widespread erosion and uplift in the STB. Increasing sedimentation TECTONIC CONTROLS ON SEDIMENTATION and erosion rates observed in this study are IN THE SOUTHERN TARANAKI BASIN DURING temporally aligned with increases in plate THE MIOCENE: IMPLICATIONS FOR PLATE boundary convergence and tectonic BOUNDARY DEFORMATION shortening rates.

S. Bull1, A. Nicol2, K. Kroeger1 & H. Seebeck1 1GNS Science, 1 Fairway Drive, Avalon, Lower FAULT RUPTURE PATTERNS DURING THE Hutt Mw7.8 2016 KAIKOURA EARTHQUAKE IN THE 2Geological Sciences, Private Bag 4800, REGION BETWEEN THE LEADER AND University of Canterbury, Christchurch CHARWELL RIVERS, NORTH CANTERBURY, [email protected] NEW ZEALAND

The rate of sediment deposition and its T. Bushell, A. Nicol, C. Fenton, N. Khajavi, J. distribution in the southern Taranaki Basin Pettinga, T. Stahl, N. Brook (STB) during the Miocene record both local Department of Geological Sciences, and New Zealand plate boundary scale vertical University of Canterbury, Christchurch deformation. Evidence from up to 3 km of [email protected] Miocene strata, examined using 2D and 3D seismic reflection data tied to exploration well Surface rupture and slip during the Mw 7.8 stratigraphy, indicate four main phases of 2016 Kaikōura Earthquake have been mapped basin development: (1) The Early Miocene (24- in the region between the Leader and 18 Ma) featured bathyal water depths and Charwell rivers using field mapping and LiDAR deposition of local clastic fans proximal to the data. The eastern Humps, northern Leader Taranaki Fault System (TFS) along the eastern and Conway-Charwell faults ruptured the basin margin, strongly influenced by vertical ground surface in the study area. The ENE-NE motion on the TFS and regional subsidence striking Humps Fault runs along the base of produced by subduction of the Pacific Plate the Mt Stewart range front, appears to dip beneath northern New Zealand. (2) In the Mid steeply NW and intersects the NNW-NNE Miocene (~16-14 Ma) sand-rich basin floor Leader Fault which itself terminates fans of the Moki Formation were deposited in northwards at the NE striking Conway- 16

Charwell Fault. Although the Mt Stewart range temperature gradients, from near-boiling front is bounded by the Humps Fault, in the spring-vents and mounds, to cooler apron study area neither this fault nor the Leader terraces, pools and geothermally influenced Fault were known to have been active before marsh, fluvial, and lacustrine settings. the earthquake. The eastern Humps Fault is up Furthermore, thermal spring discharges to the NW and accommodates oblique slip contain relatively high concentrations of with reverse and right lateral displacement. dissolved ions and thus may fossilise microbial Net slip on the Humps Fault is ≤5 m and remains in situ within mainly siliceous sinter produced ≤4 m uplift of the Mt Stewart range and travertine deposits, as well as in less during the earthquake. The Leader Fault common iron-silica occurrences. Therefore, strikes NNW-NNE with dips ranging from ~10° they represent an array of distinct microbially west to 80° east and accommodated ≤4 m net dominated textures encompassing the upper slip comprising left-lateral and up-to-the-west temperature limit for life on land, with a vertical displacement. Like the Humps west of geological record recently extended back to at the study area, surface-rupture of the Leader least the early Archean (ca. 3.5 billion years). Fault occurred on multiple strands. The Early mineralisation, particularly by complexity of rupture on the Leader Fault is in silicification, is paramount for preserving high- part due to the occurrence of bedding-parallel quality biosignatures in ancient hydrothermal slip within the Cretaceous-Cenozoic sequence. settings because the fluids effectively infiltrate The earthquake produced both faulting and sediments and entomb microbes to folding at the ground surface. sometimes form lagerstätte-style (exceptional) preservation of textural biosignatures. Recent detailed comparisons HOT SPRINGS AND THE SEARCH FOR EARLY between unusual silica deposits discovered by LIFE ON EARTH AND MARS the Spirit rover in Gusev crater and terrestrial hot springs at El Tatio, Chile, indicate that K.A. Campbell1, M.J. Van Kranendonk2, F. distinctive nodular digitate fabrics may Westall3, D.M. Guido4, J.D. Farmer5, T. represent stromatolites and warrant further Djokic2 & K.M. Handley1 study as well as potentially a Mars sample- 1School of Environment, University of return mission in the coming decades. Similar Auckland, Private Bag 92019, Auckland features have been recognised in modern hot 2Australian Astrobiology Centre, U New South springs of the Taupo Volcanic Zone, and are Wales, Kensington, NSW 2052, Australia currently under detailed assessment. 3Centre de Biophysique Moléculaire, CNRS, Quaternary sinters of the TVZ and Jurassic 45071 Orléans, France sinters of Patagonia contain parallel features 4FCNyM UNLP and CONICET, INREMI, La Plata to those of the 3.48 Ga Dresser Formation, 1900, Buenos Aires, Argentina Pilbara craton, Western Australia, and 5School of Earth & Space Exploration, Arizona therefore provide opportunities to examine State U, Tempe, AZ 85287, U.S.A. processes of formation and diverse [email protected] paleoenvironmental conditions of the oldest life thus far discovered on land. Continental hot springs are key ‘extreme environments’ utilised in the search for early life (>3 billion years, Ga) on Earth and Mars as they harbour diverse microbial communities in varied habitats with well-defined pH- 17

comparison. Distal to the fault trace, the THE PAPATEA FAULT RUPTURE, NOV 14 M7.8 hanging wall moves south, raising the KAIKŌURA EARTHQUAKE: WAS IT PULLED possibility of additional fault activity west OR WAS IT PUSHED? of the mapped rupture. The inclination of surface displacement vectors varies from A. Canva1, J.Rowland1, R. Langridge2 & C. 41° to 74°, perhaps reflecting the Madugo3 geometry at depth. Here we consider the 1School of Environment, University of context of the Papatea fault and explore Auckland controls on its rupture. 2GNS Science, Wellington 3Pacific Gas & Electric Company, San Francisco STRUCTURE AND ALTERATION IN THE [email protected] BROKEN HILLS DISTRICT, COROMANDEL PENINSULA The Papatea fault ruptured spectacularly during the Kaikōura earthquake, Lucy Carson1, Julie Rowland1 & Michael producing vertical displacements of the Rowe 1 hanging wall >8 m (average = 7.4 m) and Dept. of Earth Sciences, The University of left-lateral strike-slip of >5 m (average = Auckland Private Bag 92019. Auckland Mail 3.5 m) on a single and in places double Centre Auckland 1142 fault strand. In association, fault-triggered [email protected] landslides (Seafront slip and Limestone Hills slip) occurred where the west- The Broken Hills District is located in the dipping fault cut a series of limestone hills Puketui Valley, on the Coromandel Peninsula, with east-facing hillslopes. The surface and encompasses the Broken Hills and Golden rupture extends 13 km along-strike where Hills prospects, as well as the smaller Triumph, the fault is exposed on land, and a further Monarch, Coronation and Golden Bug 6 km offshore. Strike varies from WNW to prospects. The discovery of gold occurred in NNW, with the greatest contraction outcropping breccia pipes near the Tairua across a NNE striking section where the River in 1893 and the prospects were mined fault crosses the Clarence River and dips intermittently until 1952 with varying success. steeply west (75°). In places the fault trace During this time, over 43 million ounces of follows or closely parallels geological bullion was recovered. The Broken Hills mine contacts in Cenozoic cover sequences but was then restored in 1999 and has been active this relationship does not persist proximal since. to the NE-striking Kekerengu Fault, which was also active during the earthquake (up The region was volcanically active to 10 m right-lateral strike slip). Fault approximately 6 to 7 million years ago, and the kinematics and surface trace morphology local stratigraphy consists of andesite flows defined from field mapping, orthophoto overlain by flow-banded, spherulitic and interpretation and differential LiDAR, vary pyroclastic rhyolites. Various faults are according to strike. These patterns are in present in the district, dominated by the NNE- accord with SE migration of the hanging trending Tairua fault; this faulting localised wall block as defined by displacement hydrothermal fluid flow, causing widespread vectors constructed proximal to the fault clay alteration, strong silicification and quartz trace using differential LiDAR and image veining. In the past, mapping has been carried 18 out at various scales. A number of drillholes size have been identified, and at least one have been obtained, particularly in the Broken rising diapir has been identified in seismic Hills prospect area, and various geochemical lines. and geophysical surveys have been carried out across the district. The mud volcanoes are distributed across the region from Hangaroa in the south to the We have undertaken new surveys in this Waikura Valley in the north. There is a region and produced new geological maps, concentration of features in an east-west line which both integrate and improve upon on the northern edges of Gisborne City, a previous mapping. Samples collected during further concentration in the Waimata Valley. our field studies are to be analysed using New mud volcano fields have been identified TerraSpec, x-ray fluorescence, 4-acid digest at Te Puia, while the Otopotehetehe Mud lake ICP-MS, petrography and other techniques (Waikura Valley) is now also classed as a based on the results obtained from these substantial diapir and mud volcano field. The analyses. These will be integrated with Otopotehetehe diapir is around 2.8km long historical data and mapping to produce an and around 100m above the Waikura River. overall conceptual model of the hydrothermal New unerupted diapirs have been identified system and footprint in the Broken Hills near Tolaga, and adjacent to Gisborne City. District. The findings of this study will add Locally, the mud volcanoes are a natural substantial value to the previous work hazard and do not present a good building undertaken in the area, and contribute to the platform despite providing an elevated vista. broader scale understanding of the regional tectonic structure. A number of the mud volcanoes have exhibited renewed activity following the September 2016 Te Araroa Earthquake with THE MUD VOLCANOES OF TAIRAWHITI uplift and rupturing occurring at the Hangaroa and Waimata fields (Halls, Savages and Uttings Murry Cave mud volcanoes), with the earthflow Principal Scientist Gisborne District Council associated with the Savages Mud Volcano field Box 747 Gisborne displacing 11.2m within a 24 hour period. The [email protected] Gisborne mud volcanoes (Kirkpatrick, Knapdale, Wheatstone Road, Goodwins, The world is a big place, so the mud volcanoes Taumotu) on the other hand, remained of the East Cape Tarawhiti region are not quiescent. unique, with some known from Azerbaijan, Romania, Trinidad, Iran, Java, India, Pakistan, Venezuela, Columbia, and Yellowstone USA. DETECTING REAL EARTHQUAKES USING They are not even unique in New Zealand with IMAGINARY EARTHQUAKES: MATCHED- one reported from Coalgate, one in Northland FILTER DETECTION WITHOUT A-PRIORI and another from Hawkes Bay. The mud INFORMATION volcanoes of Tairawhiti have been previously studied but this study is probably the most C. J. Chamberlain1, J. Townend1, L.-M. comprehensive and has resulted in poorly Baratin1 reported features being located and 1SGEES, Victoria University of Wellington, significant new mud volcanoes located. Wellington, PO Box 600 Diapiric features, some quite substantial in [email protected] 19

Matched-filter techniques are demonstrably SEISMIC IMAGING OF STATIONARY MESO- the best way of detecting repeating and near- SCALE EDDIES EAST OF COOK STRAIT repeating earthquakes in noisy data, but they rely on a-priori knowledge of the source. S. Clar1, A.R. Gorman1 and R. Smith2 Matched-filter methods rely on the cross- 1Dept. of Geology, University of Otago, PO correlation of previously determined Box 56, Dunedin waveforms with continuous data; detections 2Dept. of Marine Sciences, University of are made when the cross-correlation is Otago, PO Box 56, Dunedin significantly above the background correlation [email protected] level. Therefore, they are able to detect events with overlapping waveforms, and events Meso-scale (10 to 300 km) eddies contribute below the noise-level, settings where significantly to the exchange of heat and standard detection methods fail. Matched- nutrients in the world’s oceans and can also filter techniques have been applied enhance biological production. In a few successfully to a range of settings, including locations, meso-scale eddies have been detection of: repeating earthquakes, low- imaged using multi-channel seismic reflection frequency earthquakes, explosions, and data. While these eddies are generally moving aftershocks. In all cases, pre-defined unrestricted in the open ocean, New Zealand templates have to be constructed of the waters host several relatively stationary waveforms of the events to be detected, eddies, which provide the opportunity for which limit their application to only finding longer-term or repeat surveys of their detailed signals from previously known sources. In this internal structure. presentation, we will demonstrate the use of synthetic templates to detect real In this study we present multi-channel seismic earthquakes in a range of settings. By images of three stationary eddies located in generalising the templates, the matched-filter the vicinity of the east of method can be applied to seismicity Cook Strait. We briefly explain the differences throughout the crust and does not need to be in the data processing sequences between restricted to near-repeating earthquakes. By conventional and water column marine using such synthetic templates, we are able to seismic reflection data. Aided by hydrographic detect earthquakes within swarms that were and satellite data we then explore the fine- otherwise missed by standard detection scale structures of these three eddies and techniques and extend the catalogue of low- their interaction with each other. We also frequency earthquakes beneath the central examine similarities and differences between Southern Alps to better characterise where eddies in the Hikurangi Trench and those slip is occurring on the deep-extent of the previously studied in other settings. Alpine Fault. The largest and best known eddy in the Hikurangi Trench is the Wairarapa Eddy. Its fringe has been imaged in several of the seismic lines examined here. One surprising feature of the Wairarapa Eddy is the existence of sharp continuous reflection at its lower boundary. This is uncommon in other eddies from the same region or those imaged in 20 previous work outside this region. fracture networks in cylindrical rock core EXPLORING LABORATORY SCALE, FLUID samples and detected by an array of 18 INDUCED VOLCANIC EARTHQUAKES ultrasonic transducers. We fracture samples of two lithologies: 1) low porosity J. Clarke1, L. Adam2, K. van Wijk1, J. Sarout3, impermeable granite samples and 2) a J. Dautriat3, B. Kennedy4 permeable volcanic ash tuff sample. 1Dept. of Physics, University of Auckland, Permeability and porosity in the granites are Auckland due to a fracture network, while in the tuff a 2Dept. of Environment, University of high porosity matrix (~40 %) and a fracture Auckland, Auckland network interact. 3CSIRO Earth Science and Resource Engineering, Perth, Australia We generate and detect a myriad of seismic 4Dept. of Geological Sciences, University of event types, some of which resemble well- Canterbury, Christchurch known families of volcano-tectonic, low- [email protected] frequency, hybrid and tremor-type seismicity. Samples with fluids of lower density and Low frequency volcanic seismicity has long viscosity generate a higher number of seismic been associated with resonance in fluid-filled events. We will present an integrated analysis cracks or conduits driven by pressure of event types, frequency content, source perturbations at depth. In volcano monitoring, locations and mechanisms. In addition, we fluid movement, fracturing and the conduit explore the importance of seismic wave geometry are interpreted based on field attenuation by studying the relationship observations, laboratory experiments, and between wave path and event frequency numerical models. Fluids in a volcanic content. environment include gasses, brine and magmas with different viscosities. Magma viscosity is a key influence on eruptive A BIT OF STRIFE: RISK IN behaviour. For example, increasing magma ANCIENT AND MODERN SEAS viscosity is known to favour explosive eruptions. How different fluids affect volcano K. S. Collins1, S. M. Edie1, G. Hunt, K. Roy3 seismicity is not well understood. and D. Jablonski1 1University of Chicago, 5734 South Ellis Ave, Here, we explore the effects of fluid type on Chicago, Illinois, USA volcano seismic signals. Frequency content in 2Smithsonian Institution, National Museum of the signal, frequency of the events, source Natural History, Washington DC, USA mechanism and quality factor are studied. We 3University of California, San Diego, simulate volcano tectonic (fracturing) and California, USA. volcano seismic (fluid movement) signatures [email protected] in a controlled laboratory environment using a range of rock samples, fluid types and A major hurdle to conservation effort is the pressure conditions. The viscosity of the fluids patchy coverage of extinction risk estimates spans six orders of magnitude, representing for living taxa. The International Union for the realistic volcanic fluids. Conservation of Nature assesses risk level, but their process is necessarily slow, and Microseismicity is generated by venting at present less than 5% of the world’s biota pressurised fluids through pre-generated has been classified under their scheme. 21

However, the ability to identify both at-risk taxa and geographic hotspots where many at- MORPHOTECTONICS AS A LANDSCAPE risk taxa occur is essential to our ability to TEMPLATE FOR ASSESSING SEDIMENT mitigate potential biodiversity loss, in New TRANSFERS AND FLOOD VULNERABILITY Zealand and around the world. Many factors, biotic and abiotic, contribute to a species’ Will Conley1, Sam T. McColl1, Ian C. Fuller1, vulnerability to extinction, and the pattern of Mark Macklin1,2, Jon F. Tunnicliffe3 past in the fossil record, to a first 1 Physical Geography Group, Massey order, acts as a summary of those factors and University, Palmerston North, New the resulting propensity of a clade towards Zealand extinction. We present a method of 2 School of Geography, University of Lincoln, quantifying Extinction Risk In Species (ERIS) United Kingdom based on modern geographic distribution 3School of Environment, University of patterns and paleontological data on clade Auckland, Auckland, New Zealand extinction rates, built and tested on the [email protected] marine Bivalvia. This large group mirrors many global shallow-marine diversity patterns and While most flood risk assessments are has an excellent fossil record. We test the founded on hydraulic and hydrologic models, metric using survivorship analyses of Pliocene a review of high-resolution digital topography bivalve faunas from New Zealand, California, in the upper Ruamahanga catchment, and the Southeastern United States. Across all Wairarapa, implicates tectonism as a template three faunas, species with high ERIS scores in for structuring flood risk assessment. Multiple, the Pliocene are increasingly likely to have active oblique strike-slip faults cross river gone extinct in the Pleistocene, suggesting valleys, and geomorphic analysis has that ERIS captures extinction dynamics well identified subcatchment, channel, floodplain, and may approximate extinction risk in the and terrace forms that suggest ongoing modern fauna. influence of the southern North Island Fault System on channel and catchment behaviour. When ERIS is calculated for the modern Contemporary river paths on inhabited Bivalvia, New Zealand is one of the highest-risk floodplains draining the Tararua Ranges differ areas of the globe. We discuss the implications from prevailing prehistoric river alignments, of a high or low ERIS score in the context of the and paleofluvial signatures suggest changes Plio-Pleistocene extinction, and its may have been abrupt (i.e. avulsion). Overfit applicability to Recent faunas given the and underfit valleys suggest coseismic land potential mechanisms of modern biodiversity deformation may selectively predispose loss. certain communities to avulsion or break-out flooding. In addition, headwater drainage captures, initiated by faulting, have likely altered discharge regimes and, possibly, sediment dynamics. Several fluvial process zones are identified where reach-scale form (e.g. confinement and channel pattern) and dominant processes (e.g. erosion or deposition) and behavioural tendencies (e.g. lateral movement or incision) can be expected to differ. Subreach 22 fluviotectonic signatures in proximity to pressures associated with periods of mapped faults are also observed away from prolonged and heavy rainfall. The novel DBPSB mapped geologic structures, but along is based on a standard direct shear device, but lineaments, implicating a potentially more modified to allow the measurement and extensive network of geologic structural control of pore water pressure whilst control than presently published. We believe controlling both the normal and shear differentiating tectonically-forced features stresses. Here we have used the DBPSB to from landforms that are purely fluvial in origin replicate stress conditions within slopes will help estimate sediment transfer dynamics comprised of fills with different particle size and predict channel behaviour, particularly at characteristics, and subjected them to varying reach and sub-reach scales. pore water pressure scenarios anticipated These more detailed, localised investigations during rainstorms. We measured the are nested within the fluviotectonic deformation of the shear surface during each assessment template hierarchy. Repeat high- test to analyse when and how landslide shear resolution (structure-from-motion) surveys zones form and develop within fill-slopes. are in progress along four valley segments that will inform geomorphic differencing for Our study provides new knowledge on the sediment budgeting and hydraulic modelling landslide failure potential of Wellington fill in support of Greater Wellington Regional slopes during rainstorms and the hazard they Council’s (GWRC) flood protection planning. may pose.

MECHANISMS OF RAINFALL-INDUCED WHAT ROLE FOR TUSKS IN AN LANDSLIDING IN WELLINGTON FILL-SLOPES DOLPHIN (LATE OLIGOCENE, AWAMOKO VALLEY)? B. Cosgrove1, J. Carey2 & K. Norton1 1SGEES, Victoria University of Wellington, PO A. Coste1, R.E. Fordyce1, C. Loch2 Box 600, Wellington 1Department of Geology, University of Otago, 2GNS Science, 1 Fairway Drive Avalon, PO Box PO Box 56, Dunedin 30368, Lower Hutt, New Zealand 2Department of Oral Sciences, University of [email protected] Otago, PO Box 56, Dunedin [email protected] Large rainfall-induced landslides in poorly compacted fill-slopes are a global hazard. Several extinct Oligo-Miocene dolphins from Engineered fill-slopes are common across New Zealand have delicate, tusk-like, Wellington, and have been constructed at procumbent teeth, unlike any living dolphins. various scales through varying engineering Previously described tusked specimens practices during the cities development. include species of Kentriodontidae and Whilst the regions topography, climate and Waipatiidae, however, other undescribed seismic activity makes its slopes susceptible to fossils, including key specimen OU 22397 from landsliding, limited research has considered Awamoko Valley, may belong to a new clade. how different fill-slopes may perform in OU 22397 is from the transitional Kokoamu response to rainstorms. Our study uses a Greensand - Otekaike Limestone, in a mid- dynamic back-pressured shear box (DBPSB) to shelf setting, upper Duntroonian stage study shear surface development in fill ( stage), at about 26 Ma. Key materials subject to elevated pore water elements include a well-preserved long-jawed 23 skull, mandible, teeth and earbones. and procedure within Local Government in Vertebrae and ribs are also present. New Zealand. As such, the project studies the Preliminary phylogenetic studies indicate that interface between: OU 22397 belongs in the Platanistoidea, a • tsunami – a severe but unlikely hazard clade which includes the endangered modern that has limited public risk South Asian river dolphin Platanista understanding; gangetica. • risk modelling – a more modern tool for assessing and communicating risk, What did OU 22397 use its teeth for, and how beset with its own assumptions and did they work? The dolphin has ten double- uncertainties, and; rooted triangular posterior teeth in the upper • Local Government policy and jaw, grading forward into more horizontally procedure – the coal-face for procumbent conical tusks. Five of the seven managing natural hazard risk for New tusks are very prominent. The right anterior Zealand communities, challenged by tusk-like tooth shows significant wear at an ignorance of natural hazard risk data angle of about 20° to the tooth’s long axis. This within councils, abstracted and jargon- unusual wear pattern could shed light on the filled risk terminologies, subjective and use of the tusks. Options include feeding (by varying risk perceptions, little spearing), foraging for buried prey species, appreciation of low probability risks, and display. Apart from the narwhal, with its and a disconnect between science and prominent tusk used in display, there are no practice. modern cetacean species with similarly This research uses qualitative methods to prominent teeth. engage with local government natural hazard risk managers (e.g., emergency managers, resource planners and policy developers) HOW RISK MODELLING FOR TSUNAMI within councils at risk of tsunami originating in INUNDATION INFORMS LOCAL the Hikurangi Subduction Margin. Participants GOVERNMENT NATURAL HAZARD are presented with a tsunami impact MANAGEMENT POLICIES AND PROCEDURES. consequences using ‘RiskScape’ – a New Zealand centric risk modelling tool, using an M. Crawford ‘all of boundary’ scenario along the Hikurangi Joint Centre for Disaster Research, Massey Subduction Margin. Participants are asked to University, Wellington 6140 collaborate with the researcher, using an [email protected] action research approach, to co-produce a better understanding of where the barriers to Whilst it is generally understood that risk risk communication, perception, and efficacy management can reduce the likelihood and lay, how the use of risk modelling can consequences of natural hazards, it continues overcome those barriers, and enable to hit barriers relating to communication, improved policy and procedures for tsunami perception, and efficacy. This in turn affects risk management. the value and success of policies and procedures employed for its application. This research focuses on those barriers to natural hazard risk management, specifically on how risk modelling for tsunami inundation informs the development of risk management policy 24

RISK MODELLING AS A TOOL TO SUPPORT MORPHOLOGY AND STRUCTURE NATURAL HAZARD RISK MANAGEMENT IN ASSOCIATED WITH ROUGH SUBDUCTION – NEW ZEALAND LOCAL GOVERNMENT NORTHERN HIKURANGI, NEW ZEALAND

Crawford, M.1, Johnston, D. 1, 2, Hudson- S. Davidson1, P. Barnes2, J. Pettinga1, A. Doyle, E.1, Saunders, W.2, Leonard, G.2 Nicol1, S. Henrys3, R. Harris4, A. Trehu4 D. 1 The Joint Centre for Disaster Research, Barker3, J. Mountjoy2 Massey University, Wellington, 6021 1Dept. of Geological Sciences, University of 2 Institute of Geological and Nuclear Sciences, Canterbury, Private Bag 4800, Christchurch Lower Hutt, 5040 2National Institute of Water and Atmospheric [email protected] Research, Private Bag 14901, Wellington 3GNS Science, PO Box 30-368, Lower Hutt. Demand for natural hazard risk modelling has 4Oregon State University, College of Earth, significantly increased over the last few Ocean, and Atmospheric Sciences, USA decades as we seek to use risk modelling to [email protected] assess the consequences for hazard scenarios we have little historical information about. By The subducting basement of the Pacific Plate giving an estimate of loss, risk models provide along the obliquely convergent Hikurangi policy makers and decision makers with a subduction margin comprises the Hikurangi starting point for the risk communication Plateau, a Cretaceous large igneous province process and decisions for natural hazard of anomalous oceanic crustal thickness and management. However, while local topographic roughness. Subducting government can see the value in risk associated with the plateau have modelling, some fundamental challenges limit had a profound impact on the structure and its use related to: uncertainty over council morphology of the accretionary wedge. They natural hazards management, limited use of have also previously been proposed to ‘knowledge brokers’ and ‘gate keepers’, and influence the nature of subducting sediments immaturity of risk modelling and its data. This beneath North Hikurangi, and to possibly poster provides some recommendations to relate to spatial variations in fault slip circumvent these barriers and enable risk behaviour. In support of several on-going modelling in local government: legislate research initiatives, including upcoming IODP greater mandate for natural hazard risk (International Ocean Discovery Program) management; adopt effective and meaningful drilling expeditions (372 & 375) to study slow participatory approaches; enable the slip fault behaviour, we investigate the movement of knowledge through the impacts of rough crust subduction, including development of ‘knowledge broker’ and ‘gate the interplay between accretionary wedge keeper’ roles; and enable greater capacity and morphology, fault structure, subducting capability building for collecting, managing seamounts, and trench sediment thickness. and using natural hazard risk data. We use regional multi-channel seismic reflection and 30 kHz multibeam bathymetric survey data to characterise the northern , between Hawkes Bay and East Cape. This 250 km long section of the margin is characterised by (1) a generally 25 steep (~10o) lower continental slope, (2) a land-use planning, calculating set-back narrow, discontinuous frontal accretionary distances, as well as excavation design. Here, wedge, (3) evidence of subduction we applied a selection of established rock including large seamount impacts scars that mass classification schemes to the East Coast reflect frontal tectonic erosion, and (4) Bays Formation at coastal cliff exposures at sediment thickness in the Hikurangi Trough of Waiake Beach, Stanmore Bay, and Bucklands about 1.0-1.5 km. Detailed mapping of the Beach. This study utilized the Rock Mass tectonic structure and morphology of the Rating (RMR) and Rock Mass Strength (RMS) margin allow us to identify the ephemeral and classification schemes. The two classification overprinting nature of deformation, together schemes were used in conjunction with the with the characteristics of deep-seated mass slope angle of the exposed outcrop in order to failure, that are associated with the passage of determine the strength-equilibrium state of subducting seamounts of various scale and the exposed rock mass. This theoretical relief. We compare this section of the margin relationship can be used to determine with offshore northern Wairarapa, where a whether the exposed slope is likely to fail, and relatively smooth plateau basement overlain is useful when compared with kinematic by thick (3-6 km) trench sequences has analyses of possible failure mechanics. Results allowed the formation of a wide, low taper indicate, firstly, that the East Coast Bays (<4o) accretionary wedge. Formation are of ‘weak’ to ‘moderate’ engineering strength. Second, at most sites, the rock mass exposures are oversteepened ENGINEERING ROCK MASS CLASSIFICATION with respect to the slope angle, and given the OF THE EAST COAST BAYS FORMATION, likely friction angles. Third, kinematic analyses AUCKLAND show that a range of failure mechanics are possible, as a result of the combination of M. R. Davis1, M. S. Brook2, B. Fleetwood bedding-plane defects, pervasive subvertical 155 King George Ave, Epsom, Auckland defects, and local-scale faulting. Given the 2Dept. of Earth Sciences, University of engineering properties and failure mechanics, Auckland, Private Bag 92019 we conclude that many residential properties [email protected] lie within theoretical set-back distances, are sited too close to cliff edges, and are therefore The East Coast Bays Formation (ECBF) is one of within zones where loss to property and life is the most prominent rock formations in at an elevated risk. Auckland and covers a large proportion of Auckland’s East Coast. The formation consists of weak interbedded sandstone, siltstone and claystone with lenses of Parnell Grit throughout, and has previously been characterised as a “flysch” deposit. Recent slope failure events and damage to infrastructure and housing, along with transport tunnelling projects has drawn attention to the engineering properties and failure mechanisms of the Formation. Hence, classifying the engineering characteristics and likely failure mechanics is of importance for 26

Terrace, guided by multibeam swath data. THE CRUSTAL STRUCTURE OF THE EASTERN GNS Science operated their gravity meter and REGION - RESULTS OF THE magnetometer throughout most of the 2016 GEOPHYSICAL SURVEY SO246 BY THE survey. R/V SONNE The initial results from the survey will be Bryan Davy1, Karsten Gohl2, Reinhard presented and linked with existing data and Werner3, Rachel Barrett4 and Florian concepts on the structure of the Chatham Rise Riefstahl2 accretionary prism structure (Rakaia versus 1GNS Science, PO Box 30368, Lower Hutt Pahau) and its onshore South Island 2Alfred Wegener Helmholtz Institute for Polar prolongation. The nature of the West and Marine Research, Am Handelshafen 12, Wishbone Ridge and similar Cretaceous fault 27570 Bremerhaven, Germany structures and their role in Gondwana 3GEOMAR – Helmholtz Centre for Ocean breakup will also be discussed. Research, Wischhofstraße 1-3, 24148 Kiel, Germany 4 Victoria University of Wellington INFLUENCE OF THE EARTH TIDE ON GROUND [email protected] MOVEMENTS AT OMOKOROA

The easternmost Chatham Rise is a key focus W.P. de Lange1, T. Manderson2 & V.G. area for understanding the Cretaceous Moon1 tectonics of the New Zealand region. It is the 1School of Science, University of Waikato, region where seafloor spreading between Private Bag 3105, Hamilton New Zealand and Antarctica first initiated. The 2CMW Geosciences: Level 4, 3 Bowen West Wishbone Ridge, a major 1200 km long, Crescent, Melbourne, Australia northeast trending, gravity and bathymetry [email protected] lineament intersects the Chatham Rise immediately east of where the Hikurangi Diurnal ground movement may contribute to Plateau LIP abuts the northern Chatham Rise, slope failure at Omokoroa due to cyclic and 150 km east of the Chatham islands. The loading of a sensitive layer within southeast Chatham Rise was once adjacent to volcaniclastic deposits. Inclinometer Marie Byrd land in Antarctica, a key research measurements indicate that differential focus area for the Alfred Wegener Helmholtz movement of the main stratigraphic units (Te Institute (AWI), Germany. Puna Ignimbrite, Pahoia Tephras, Hamilton Ashes, and Rotoehu and younger tephras) A seven-week seismic reflection/refraction occurs in response to the Earth tide. Other and volcanic rock-dredging survey was processes also contribute to the observed conducted across the eastern Chatham Rise by deformation of the inclinometer borehole, the Alfred Wegener Helmholtz Institute in including temperature, rainfall and early 2016 using the new R/V Sonne research microseisms. A monitoring programme has vessel. The survey collected four crustal scale been run at the landslide at Bramley Drive seismic reflection and refraction lines across since 2013 to assess the effects of cyclic the eastern Chatham Rise, two seismic loading. This includes a 3-axis accelerometer reflection lines across the Wishbone Ridge to measure ground movements at the surface. complex, and numerous dredges of seafloor Although microseisms induced by ocean volcano structures on the southeast Chatham waves breaking on the open coast of 27

Matakana Island are present, they do not past earthquakes so as to infer (under appear to have a significant effect on ground uncertainty) the values of underlying stress movement or slope stability. The uppermost and poroelastic parameters. This exercise stratigraphic unit (Rotoehu and younger suggests that the pre-1960 reservoir was not tephras) shows a strong diurnal response to critically stressed prior to exploitation. It soil temperature, which is attenuated by further reveals an instance of parameter increasing water content. However, the surrogacy, wherein the stress path coefficient largest ground movement affecting the upper takes on a physically unrealistic value to 3 units occurs when the Earth tide peak compensate physics missing from the model. vertical displacement occurs close to the maximum horizontal displacement. The timing Extrapolating the calibrated model 7 years of both maxima is a function of the Moon’s into the future yields a spectrum of possible declination, while the amplitude of the outcomes – a forecast – for each of three displacements depends on the distance different operating scenarios. Accounting for between the Earth and the Moon. For both epistemic (parameter) and aleatoric Omokoroa, the combination of Earth tide (random-process) uncertainty, it can be maxima coincides with landslide initiation, shown that the likelihood of an earthquake consistent with previous studies linking the exceeding the previous largest event (an M 3.6 occurrence of small landslides with the orbital in 2012) is between 17 and 25%. The likelihood motion of the Moon. that the largest event exceeds M 4 is approximately 5%. Earthquakes of these magnitudes are concerning given their shallow USING A WRONG MODEL TO OBTAIN depth (~3 km) and a building stock that largely USEFUL INSIGHTS: FORECASTING INDUCED comprises unreinforced masonry. Weighing SEISMICITY IN THE NETHERLANDS the impact on local communities against the economic value of the remaining gas is an D. Dempsey ongoing challenge for the Dutch government. Dept. Engineering Science, University of Auckland, PO Box 30368, Auckland [email protected] PHYSICAL ROCK PROPERTIES AT IN-SITU CONDITIONS OF PYROCLASTIC ROCKS FROM The statistician George Box famously wrote NGATAMARIKI GEOTHERMAL FIELD, NEW “All models are wrong but some are useful.” I ZEALAND will try to demonstrate how this can be the case, using for illustration a model of E. Duran1, L. Adam1, I. Wallis1, A. Barnhoorn2 earthquakes occurring at Western Europe’s 1School of Environment. The University of largest gas field, Groningen, in the Auckland. Auckland 1142 Netherlands. [email protected], [email protected] This model makes several simplifications in its 2Faculty of Civil Engineering and Geosciences, attempt to capture earthquake physics TU Delft, PO-box 5048 (nucleation, rupture, arrest), subsurface [email protected] heterogeneity, and the interactions between [email protected], an evolving gas reservoir and the surrounding rock. A Markov-Chain Monte Carlo method A better understanding of the seismic was used to calibrate this model against 600 properties of volcanic rocks will benefit 28 geothermal exploration and volcanology in DETAILED ANALYSIS OF THE HAUTAWA general. Little experimental analysis of the in- SHELLBED situ rock elasticity and its correlation to the rock physical properties exists. We study J.E.G. Elliott & M.J. Hannah volcaniclastic and pyroclastic rocks from Victoria University of Wellington, PO Box 600, Ngatamariki Geothermal Field. P- and S-wave Wellington velocities, CT scans, pycnometer and [email protected] Archimedes porosity, SWIR data, and XRD/XRF measurements are used to recognize mineral Charles Fleming’s foundation work recognised assemblages and alteration, degrees of fluid the Hautawa Shellbed as a marker of cooling saturation, and pore micro-structure of the conditions expressed by the influx of a sub- rocks. This information helps define rock Antarctic molluscan assemblage into physics models to match the elastic Whanganui Basin. The major index fossil of measurements made at in-situ confining and this cold assemblage is the queen scallop fluid pressures. Zygochlamys delicatula. It has previously been shown that outcrops of the Hautawa Shellbed CT scans reveal lithic fragments and cracks in adjacent to the Whanganui River were volcaniclastic rocks. Some of these fragments deposited in a shallower environment than are high porosity tuffs which significantly those proximal to the Rangitikei River – a decrease the elastic wave velocities. XRD and result of the basin depocenter being closer to SWIR are combined to get a finer quantitative the modern Rangitikei catchment. Although representation of the mineral constituents. outcrops of the shellbed are known to extend Rock alteration is the second dominant over 50 kilometres laterally, there has been parameter on the elastic wave velocities, with little focus on investigating the preserved alteration to chlorite resulting in an increase in paleoenvironmental variation beyond relative wave velocities. We will also present results water depth. on estimates of elastic wave attenuation for these volcaniclastic samples. We interpret The Hautawa Shellbed is a compound shellbed these experimental data by testing several made up of lower and upper shellbed units. rock physics theories and models, which have The majority of specimens in the lower seldom been studied for volcanic rocks. shellbed have been, to varying degrees, transported prior to deposition. This lower These results add to the existing knowledge shellbed formed a stable substrate which gap in the rock physics literature on the supported development of the upper properties of volcaniclastic/pyroclastic rocks shellbed. Accordingly, the assemblage of the for which empirical and theoretical models upper unit is dominated by colonizing developed for clastic sedimentary rocks must epifauna of brachiopods and bryozoa likely be judiciously applied. Finally, free software to deposited in situ. aid the velocity picking of ultrasonic P and S waves with their respective uncertainties is This study focuses on findings from one site of made available. a MSc research project which aims to capture lateral paleoenvironmental changes observed in the Hautawa Shellbed shown by detailed analysis of sedimentary, taphonomic, and macrofaunal assemblage variability. Previously, paleoenvironmental 29 interpretations have been largely based solely technique to estimates of the Rayleigh wave on the macrofaunal content. Foraminiferal Greens Functions estimated from ambient assemblages preserved in the silty units seismic noise and validate this method using directly below and overlying the condensed earthquake sourced p-wave polarisation. shellbed provided further restriction on paleo- water depths in this study. LAKE KANONO: INVESTIGATING CLIMATE OSCILLATIONS USING HIGH RESOLUTION ESTIMATING BOREHOLE SEISMOMETER WIND AND PRECIPITATION ITRAX PROXIES ORIENTATION USING AMBIENT NOISE FOR AMBIENT NOISE TOMOGRAPHY OF THE Gianna Evans1, Paul Augustinus1, Patricia AUCKLAND VOLCANIC FIELD USING MULTI- Gadd2 COMPONENT DATA 1University of Auckland, New Zealand 2Australian Nuclear Science and Technology J.X. Ensing1 & K. van Wijk1 & K.B. Spörli2 Organisation (ANSTO) 1Dept. of Physics, University of Auckland, Private Bag 92019, Auckland 1142 The South Westerly Winds (SWW) are a belt of 2School of Environment, University of winds that are the driving force of wind and Auckland, Private Bag 92019, Auckland 1142 precipitation in New Zealand and shift north or [email protected] south with temperature changes. An annually resolved Itrax record spanning 2200 years was In the active Auckland Volcanic Field, constructed from sediment core stratigraphy earthquake-generated seismicity is low and a from Lake Kanono, Northland to investigate high ambient noise level hinders the the correlation of shifts in the SWW on inter- investigation of structural eruption controls by annual, decadal, and centennial time scales most passive seismic imaging. There have thought to be caused by cyclic climate been only a few studies using active sources. patterns such as El Niño Southern Oscillation We applied ambient noise tomography using (ENSO). the vertical seismic waveform data from pairs of seismometers to compute 1D crustal shear- Previous work shows that there is a good wave velocity models beneath the Auckland correlation between temperature and ENSO in Volcanic Field, and interpolated data onto a New Zealand and that the link between grid to obtain pseudo-2D models. These shear precipitation anomalies and ENSO in New velocity models penetrated 25 km deep, Zealand vary by region. Specifically, there is a almost to the Moho. The resulting overall positive rainfall anomaly associated with the velocity variations in the crust correspond well La Niña phase of ENSO in the Northland region with previous models, major known surface where Lake Kanono is located. Various Itrax geological features, and tectonostratigraphic proxies representing organic processes, terranes deeper. We are currently working to nutrient fluctuation, and detrital changes increase the resolution and the penetration were compared with regional wind gust data, depth to include the entire crust by using rainfall data, and the Southern Oscillation multi-component ambient noise. This requires Index (SOI) in order to verify which Itrax estimating the orientation of the horizontal proxies are best suited as wind and/or components of 8 borehole seismometers from precipitation proxies. The Itrax proxies with the Auckland Volcano Seismic Network. We do the best correlations were analysed with a this by applying a Rayleigh wave polarisation wavelet transform to identify periodicities. 30

In general, even though the 3 categories of We have specifically targeted a limited data have different results, there are number of surge/fall deposits for analysis periodicities present in these data sets at which track changing interactions with inter-annual, decadal, and centennial external water to test the impact on clast oscillations, although the timing of the characteristics. Sample cleaning and periodicities in the sequence is different separation is particularly challenging for surge depending on what type of proxy is analysed. deposits where materials are well cemented, Land use changes associated with different requiring multiple round of ultrasonic phases of human settlement in New Zealand cleaning, scraping, and treatment in weak HCl complicate the environmental signal and solutions- this intricate cleaning procedure affect the wavelet results – which is most however is necessary for isolation of the evident in the raw detrital proxy. juvenile clasts for analysis. Juvenile clasts were characterized texturally and analysed by X-ray diffraction (XRD) to determine mineralogy and USING PYROCLASTIC COOLING HISTORIES TO crystallinity. XRD diffraction patterns were UNDERSTAND DYNAMIC ERUPTIONS: analysed using the AMORPH software for CASE STUDIES FROM THE AUCKLAND determining the crystallinity and VOLCANIC FIELD characteristics of the amorphous material. Sample sizes range from <250 micrometers to M. M. Ferguson1, M. C. Rowe1, M. Tost, & K. ~ 2 cm. Multiple clasts were analysed per Nemeth2 sample (up to 15) to better characterise the 1School of Environment, The University of heterogeneity of each sample. Interestingly, Auckland, Auckland 1142, New Zealand preliminary results from Motukorea suggest 2CS-INR, Volcanic Risk Solutions, Massey the opposite characteristics, that for the University, Palmerston North, New Zealand smallest clast sizes (250-600 micrometers), [email protected] juvenile clasts from the surge deposits uniformly contain higher crystallinities During the transition from phreatomagmatic compared to “magmatic” units. These initial to predominately magmatic eruptions, the results point to the complexity of processes alleviation of external water from the process involved in phreatomagmatic eruptions and changes the eruption style. A proposed model the need for high sampling density to properly for the crystallinity values associated with investigate these dynamic systems. both phreatomagmatic and magmatic eruptions is that of an inverse relationship with respect to magmatic cooling rate. Thus, THE GEOLOGICAL ORIGIN OF THE we propose that as cooling rates decrease, CHOCOLATE HILLS OF BOHOL associated with the mitigation of external water sources, the groundmass crystallinity P.T. Finlay should increase. Groundmass from juvenile Holy Name University, Bohol pyroclasts collected from Motukorea (Brown’s [email protected] Island) and Maungauika (North Head volcano), New Zealand, can yield insight into the The 1776 approx. and possibly counting, availability of external water, complexity of Chocolate Hills of Bohol are outstanding eruption processes, and changing eruptions geological features. The Chocolate Hills are 66 styles. Ma years in age. This paper examines their 31 geological, hydyrological and rate of tectonic resulting in low pH conditions and high uplift responsible for the harmony in their dissolved metal concentrations. This has led to formation. The recent September 2017 poor stream ecosystem health and low discovery, by the author, of densely forested, aquatic biodiversity. Diversion wells are a forming younger Chocolate Hills on the method of passive treatment of acid mine isolated Anda Peninsula, of East Bohol, is drainage. A typical well consists of a cylinder- presented. shaped container filled with limestone After the M7.2 Bohol Earthquake of 15 aggregate, and a pipe centred down the well October 2013, two scientific expeditions were to allow water from an upstream dam to made on the palaeontology of the Wahig River provide hydraulic head and entry to the in central Bohol. Paleo earthquake induced system. Dissolution of the calcium carbonate landslides were located. Earthquakes have raises the pH of the acidic drainage, adds also had a profound scientific effect on the alkalinity, and allows for precipitation of metal formation of the morphology of the Chocolate contaminants out of solution. Mussel shells Hills. Paleo evidence exists with the runout are an alternative source of calcium carbonate distance of earthquake induced fallen and method of passive treatment: this is to be boulders from the Chocolate Hills. used in a mussel shell reactor at the Bellvue Research is slowly continuing and invitational site later this year. Because the reactor is overseas (from Philippines) research unable to treat acidic discharge during high opportunities are presented. flow events, a diversion well will allow for Keywords: Karst landscape, Chocolate hills, treatment of excess acidic discharge during geological harmony, earthquake damage, high precipitation events. The use of a research opportunities. diversion well, and mussel shells as a diversion well substrate, has not previously been trialled in New Zealand. This research involves the COMPARISON OF DIVERSION WELL installation of a diversion well at Bellvue Mine, SUBSTRATES FOR THE TREATMENT OF ACID and chemical analysis of treated waters, to MINE DRAINAGE, BELLVUE MINE, WEST determine the effectiveness of a diversion well COAST, NEW ZEALAND using mussel shells in treating acid mine drainage in comparison to the more E. Forbes1, D. Trumm2, D. Bell1 & J. Pope2 traditional diversion well using limestone. 1Dept. of Geological Sciences, University of Canterbury, Christchurch, New Zealand. 2CRL Energy Ltd, PO Box 29 415, Christchurch, A TOOTHLESS SUCTION-FEEDING DOLPHIN New Zealand. FROM THE OTEKAIKE LIMESTONE [email protected] (WAITAKIAN STAGE, LATEST OLIGOCENE), HAKATARAMEA VALLEY Acid mine drainage is a significant environmental problem globally. Sulphide R.E. Fordyce bearing minerals, exposed as a result of Department of Geology, University of Otago, metalliferous and coal mining, interact with air PO Box 56, Dunedin and water to produce acidic run-off, a [email protected] considerable pollutant of many surface water systems. Bellvue Mine, an abandoned coal A new species of large dolphin from the mine north of Greymouth, West Coast, is Otekaike Limestone, Hakataramea Valley, has discharging acidic run-off into Cannel Creek, specialised jaws and reduced teeth, consistent 32 with a suction-feeding life mode – the first such fossil from the New Zealand mid- SPELEOTHEM MAGNETISM AND Cenozoic. The dolphin is convergently and HYDROCLIMATE: AN INVESTIGATION OF remarkably similar in skull form to the HYDROLOGICAL PROCESSES IN WAIPUNA unrelated living, suction-feeding, beaked CAVE, WAITOMO DISTRICT whales (Ziphiidae). B. R. S. Fox1, I. Lascu2,3, R. Harrison2, S.F.M. The dolphin, OU 22540, is from the upper Breitenbach4, and A. Hartland1 Otekaike Limestone, just above a diffuse macrofossil rich mollusc and Protula shellbed 1. School of Science, University of Waikato (Waitakian, Globoturborotalita woodi zone, 2. Department of Earth Sciences, University latest Oligocene). Massive bedding, well- of Cambridge preserved para-autochthonous 3. Department of Mineral Sciences, macroinvertebrates, and associated skeletons Smithsonian Institute of vertebrates suggest limited traction 4. Ruhr-Universität Bochum, Geology, currents in a mid-shelf setting. Mineralogy & Geophysics, Sediment- and The dolphin has a beak-like upper jaw with Isotope Geology, Bochum, Germany massive maxillae, but no alveoli for upper [email protected] teeth. The lower jaw is straight-edged with an alveolar groove possibly for small teeth; two Speleothem science is a fast-growing tiny conical teeth were found with the skull. subdiscipline of geosciences, with the The face around the nasal passages is strongly potential to produce high-resolution, long- asymmetrical and elevated, implying the duration, well-dated proxy records for presence of well-developed soft tissues used terrestrial climate, environment, and surface in echolocation. Similar features occur in processes. Traditional speleothem science is beaked whales (Ziphiidae), albeit constructed based largely on measurement of oxygen and differently. All the neck vertebrae are carbon isotopes in speleothem calcite. preserved, unfused. The earbones (periotic, However, a raft of novel techniques are tympanic bulla) show features important in currently under development to exploit phylogenetic placement. Notably, the curved speleothem archives in more detail. One of parabullary sulcus on the periotic may these is speleothem magnetism. characterise archaic platanistoids. Further, the dolphin lacks the enlarged posterior process Allogenic particles are often incorporated into on the bulla, and enlarged pterygoid sinus speleothems as they grow. These particles fossa – features diagnostic for Ziphiidae. may be sourced from overlying soils via infiltrating waters, or from flooding of Otekaike Limestone cetaceans continue to subterranean passages. In both cases, the expand the diversity of early species in the two concentration of allogenic particles is living groups, Odontoceti (dolphins) and indirectly linked to precipitation. The Mysticeti (baleen whales). The ziphiid-like concentration of allogenic particles in dolphin is one of several such fossils globally speleothems is generally extremely low, that mimic beaked whales. Does skull making them difficult and time-consuming to structure in OU 22540 reflect largely pelagic quantify by traditional microscopic methods. deep-diving habits, or did the dolphin live and However, if the allogenic fraction includes feed in shelf settings? ferrimagnetic particles, these can be detected and characterised quantitatively using state- 33 of-the-art non-destructive magnetic methods. elements be potentially ecotoxic, thus Magnetic particles in speleothems thus affecting the suitability of a deposit for use as potentially represent a high-quality proxy for an agricultural fertiliser. hydroclimatic variability. The geochemical diversity of significant New Here we present the initial results of an Zealand phosphorite deposits outside of the environmental magnetic investigation of a Chatham Rise is poorly characterised. This flowstone from Waipuna Cave, Waitomo study addresses this gap in geochemical District. First-order reversal curve analysis information for deposits from Bollons indicates the presence of two populations of Seamount and offshore South Island, as well magnetic grains which make varying as providing new geochemical data for the contributions to the magnetic fraction of the extensive Chatham Rise phosphorite deposit. speleothem over time. We interpret one of Major element contents were measured using these as representing periodic flooding of the X-ray fluorescence (XRF), and trace element flowstone site, and the other as representing contents by inductively coupled plasma mass transport of allogenic particles by dripwater spectrometry. Micro-XRF and scanning (and therefore precipitation). New statistical electron microscope energy dispersive software allows us to quantify the spectroscopy maps detail the distribution of contribution of each of these processes at major and minor elements within nodules. each time step, and thereby build a picture of North Island hydroclimate over the last 35,000 Chatham Rise and offshore South Island years. nodules are characterised by enrichments in Sr, Y, Mo and U with depletion in Sc, Cr, Cu, Rb, Cs, Ba, Ta, Pb, and Th relative to average upper GEOCHEMICAL CHARACTERISATION OF continental crust (AUCC). Bollons Seamount OFFSHORE NEW ZEALAND PHOSPHORITES nodules show significant (two to five times) enrichments in first row transition metals; Ni, G.E. Frontin-Rollet1, M.R. Handler1, R.J. Co, Cu, Zn, in addition to Sr, Y, Mo, U and 2 3 4 Wysoczanski , M.F. Gazley & C. Hickey depletion in Sc, Cr, Ga, Rb, Cs, and Th relative 1 School of Geography, Environment & Earth to AUCC. Low Cd contents (3x AUCC) in all Science, Victoria University of Wellington. deposits suggests good suitability for use as a 2NIWA, Greta Point, Wellington. fertiliser, as contribution to already high Cd 3CSIRO, Perth, Australia. contents in New Zealand soils would be 4NIWA, Hamilton. minimal. [email protected] This study was conducted as a part of the Seafloor mineral resources are becoming Enabling Management of Offshore Mining increasingly attractive for exploitation as land- (EMOM) project awarded to NIWA through a based resources begin to decline. Ministry of Business, Innovation and Phosphorites are a rich source of phosphorus, Employment (MBIE) grant (2012-2016). an invaluable ingredient in agricultural fertilisers which are in high demand globally. Whilst high phosphate content is one of the most important qualities of a phosphorite deposit, knowledge of the associated trace elements is important should some of the 34

AUCKLAND VOLCANIC FIELD: SEISMIC FLOW PROCESSES AND PROVENANCE OF TRAVEL-TIME TOMOGRAPHY WITH FAST SEDIMENT IN THE HIKURANGI CHANNEL: MARCHING METHOD APPROACH LINKS TO SEISMIC ACTIVITY

G. Ganefianto1 & K. van Wijk1 A. Ganguly1, L. J. Strachan1, H. C. Bostock2, I. 1Department of Physics, University of Pecher1, J. Howarth3, A. R. Orpin2 & P. M. Auckland, Auckland, New Zealand Barnes2 [email protected] 1School of Environment, University of Auckland, Private Bag 92019, Auckland The Auckland Volcanic Field (AVF) is a 2National Institute of Water & Atmospheric monogenic intraplate volcanic field, located Research, Private Bag 14901, Wellington right beneath one of New Zealand’s main city, 3School of Geography, Environment and Earth Auckland. However, despite the potential Sciences, Victoria University of Wellington, hazard it imposes, much of the structure and PO Box 600, Wellington driving cause with regards to the AVF are [email protected] remain to be known. Furthermore, geophysical studies (particularly 3-D) for the The Hikurangi Channel lies east of New deeper structure of the AVF generally lack in Zealand and is one of the longest submarine resolution. This research looks on this three- channels in the world. The channel runs dimensional geophysical structure of the parallel to the Hikurangi subduction margin, Auckland Volcanic Field, focusing on the where the Pacific Plate subducts beneath the velocity structure deduced from seismic Australian Plate. It connects submarine travel-time tomography. Fast marching canyons that incise and nourish the method, a grid based eikonal solver is continental slope east of New Zealand, implemented. This method has low computing especially Kaikoura and Cook Strait canyons, cost, stable, and robust. The main aspect of with the abyssal basin of the South Pacific. This this method is that it will converge to one true study analyses a series of sediment cores from two-point path between the source and within the Hikurangi Channel and adjacent receiver, consistently computing the first levee to determine sediment provenance, arrival travel-time. flow processes and deposits, and whether these are linked to seismic events along the The first part of this research is to perform Hikurangi subduction zone, such as the synthetic tests, to see at the potential Kaikoura Earthquake in November 2016. Can resolution that can be achieved from this we use these sediment events to investigate study. The synthetic test that we implement the frequency of large earthquakes along the here is the checker-board test, where the size Hikurangi subduction zone? and geometry of the recovered checker pattern will infer the scale and coverage of the To characterise the cores, we used a range of resolved features. The second part is to use different analytical methods including visual the first arrival P-wave travel-time data; logging, laser grain size, carbonate content, observed, and predicted using ak135 1-D Earth total organic matter, X-Ray diffraction (XRD), velocity model. By performing the relative X-radiography, Computerized Tomography travel-time tomographic inversion, we can (CT) Scans, magnetic susceptibility, and bulk produce the 3-D velocity structure beneath density. the AVF, constructed as positive and negative deviation from the reference model. 35

The cores show turbidity current deposits, (Pomahaka), near-shore sheltered bay with those in the channel significantly thicker (Brydone), rocky shore (Cosy Dell), shallow than those in the levee cores. Levee cores shelf (Chatton, Hedgehope) to a deep marine show grain sizes ranging from very fine silt to offshore environment (Grindstone Creek). fine sand, while channel cores are relatively Species include several eel-like predators coarser grained, with grain sizes up to medium (Moringua, Gnathophis, Pseudophichthys, sand. XRD analyses on these cores show Rhynchoconger), a garden eel presence of minerals such as quartz, micas, (Heteroconger?), sardines (Sardinops), a and feldspars, and a very small proportion of lantern-fish (Diaphus), rock cod and codlets other minerals which change in proportion (Lotella, Bregmaceros), rattails (Trachyrincus, and composition going along northwards, Coelorinchus), hake (Macruronus), pearlfish down channel. Using these data will improve (Eurypleuron), alfonsino (Centroberyx), roughy our understanding of the origin of these (Optivus), flathead (Platycephalus), grouper sediments, and the flow processes that have (Serranidae), whiting (Sillago), seabream carried them to the various locations. (Dentex), grunt (Pomadasys?), sandperch (Parapercis), opalfish (Hemerocoetes), stargazers (Lesueurina, Uranoscopus), sleeper OTOLITHS, TEETH AND SCALES REVEAL goby (Micropercops) and flatfish DIVERSE FISH COMMUNITIES IN LATE (Arnoglossus). In addition, one incomplete but OLIGOCENE ESTUARINE TO DEEP-WATER articulated percidiform fish, odontaspid (sand PALEOENVIRONMENTS IN SOUTHERN tiger) teeth, isolated teleost bones, and ZEALANDIA cycloid? scales have been uncovered at Pomahaka and an array of fish teeth, including Henry JL Gard1, Werner Schwarzhans2 & probable seabream (?Diplodus) and Daphne E Lee3 myliobatiformes (stingray) crushing plates, are 1GNS Science, PO Box 30368, Lower Hutt found at Cosy Dell. The otolith faunas show 2Ahrensburger Weg 103, 22359 Hamburg, considerable continuity with the extant Germany marine fish fauna of New Zealand with 50% of 3Department of Geology, University of Otago, species belonging to genera present in New PO Box 56, Dunedin Zealand waters today. Endemism in the Late [email protected] Oligocene was high at ca. 45% including putative extinct endemics. Significant fossils Although fish macrofossils are rare, otoliths include the first Southern Hemisphere are common in Cenozoic marine sediments of representative of a basal gobioid family New Zealand and are essential tools for (Odontobutidae) now restricted to fresh- and reconstructing fossil teleost faunas. Here we brackish waters of eastern Asia. We compare describe the , paleoecology and and contrast the faunas of each site with one paleogeography of mainly otolith-based fish another and with the extant marine fauna of faunas from six sites of Late Oligocene age New Zealand and discuss their phylogenetic (Duntroonian - Waitakian) in southern and biogeographic significance. Zealandia spread across the Pomahaka, Chatton and Waihoaka Formations. The otolith associations comprise 46 species (14 new) in 9 orders and 24 families, and represent a remarkably diverse range of environments from brackish to estuarine 36

COMPARISON OF GEOTECHNICAL analysis, in-situ moisture content, and skeletal PROPERTIES OF TAUPO VOLCANIC ZONE and bulk density. Initial results suggest that TEPHRA AND SURROUNDING SEDIMENTS OF fundamental differences exist in the THE TAURANGA GROUP IN THE AUCKLAND geotechnical index and shear strength AREA properties between the tephra and surrounding sediment which are contributing R. Garrill & N. Richards factors causing instability at the two sites. School of Environment, University of Auckland, Private Bag 92019, Auckland [email protected] MODELLING BALLISTIC HAZARD AT NEW ZEALAND’S MOST VISITED ACTIVE Tephra deposits originating from the Taupo VOLCANOES; WHITE ISLAND AND RED Volcanic Zone (TVZ) are exposed as beds of CRATER, TONGARIRO. variable thickness with fine-grained sedimentary sequences around the Auckland Stephanie Gates1, Ben Kennedy1, Thomas coast. These sequences, also of considerable Wilson1, Geoff Kilgour2, Ame McSporran1 thickness variability, are included in the 1 Dept. of Geology, University of Canterbury, Tauranga Group of sediments which overly the PO Box 4800, Christchurch Miocene East Coast Bays Formation. Cliff 2 GNS Science, PO Box 2000, Taupo sections composed of the Tauranga Group are [email protected] prone to rotational failures, with evidence of past landslides existing at Pohutukawa Bay Volcanic ballistics are a major hazard in areas and Sunkist Bay in the Beachlands area of East proximal to volcanic eruptions. The high Auckland, and along the edges of the Tamaki kinetic energy of volcanic ballistics constitutes Estuary. In January 2017, following an a significant threat to life and property within unusually large amount of rainfall, a landslide the ballistic hazard zone. New Zealand has a of significant size occurred at Sunkist Bay, large volcano-tourism industry with the resulting in the loss of a section of residential country’s two most visited active volcanoes, property. Given the unstable nature of these White Island and Tongariro, attracting a cliffs and the threat posed to infrastructure it combined total of >150,000 tourists annually. is important that the geotechnical properties Visitors to these volcanoes walk within of the Tauranga Group sediments exposed at volcanic ballistic fields emplaced during recent both Beachlands and the Tamaki estuary be phreatic and phreato-magmatic eruptions. determined to assess their influence on slope Ballistic hazard assessments of White Island instability. Two tephra units from the and Red Crater, Tongariro are needed due to Beachlands area, including one from the near their rising popularity and histories of ballistic the base of the 2017 Sunkist Bay landslide and producing phreatic eruptions, which occur the underlying fine-grained sediments were with little, if any, warning. investigated. In addition, one tephra and a sample of underlying sediment from a coastal An unheralded, phreatic eruption at White exposure near Saint Kentigerns School were Island on the night of the 13th of April 2016 investigated. Undisturbed intact block produced ballistics and a surge. The ballistics samples were taken for shear strength testing heavily impacted the path used by tourism and scanning electron microscopy analysis. operators. Had the eruption occurred during Each sample was also tested for a variety of operational hours, casualties would have been index tests including laser particle size likely. Red Crater is an active vent of Tongariro 37

Volcano which has erupted at least 16 times Tauranga Group sediments exposed around within the last 300 years in Strombolian and coastal southern Auckland. Fluvial, estuarine phreatic styles. It lies directly adjacent to the and near shore sediments yield organically Tongariro Alpine Crossing (TAC), which hosts preserved fossil fruits (and stones, seeds and >140, 000 visitors annually. Recent fieldwork cones), vascular and non-vascular leaves, has elucidated the extent of a composite wood, amber, pollen, spores, bracket fungus ballistic field surrounding Red Crater and the basidiocarps, mites and other arthropod Emerald Lake, which the TAC passes though. fragments.

We present phreatic ballistic hazard maps and The fossil fruit and leaf assemblages are insights into eruption source parameters at indicative of a diverse vascular plant flora. A each volcano, informed by field mapping and high proportion of the currently identified 3D modelling. Detailed field mapping of White fossil fruit morphotypes belong to locally Island’s April 2016 ballistic field and Red extinct groups, such as Vitaceae, Crater’s remnant ballistic field, following UAV Menispermaceae, Casuarinaceae, image collection, is used to inform model Brassospora-type Nothofagus and locally inputs. Ballista, a semi-probabilistic 3D extinct species of Cupressaceae and volcanic trajectory model, is calibrated using Elaeocarpus. In contrast, a few fossil fruit field data to determine eruption source morphotypes including Prumnopitys, parameters. This study is the first step towards Passiflora and another Elaeocarpus species production of probabilistic ballistic hazard share possible affinities with extant taxa. maps for White Island and Red Crater, Tongariro. Non-vascular plant fossils, such as moss (Bryophyta) stems and leaves are an exciting addition to the list of fossils known from these PLIOCENE MACRO- AND MICROFOSSIL localities. Mosses are only encountered or PLANTS AND FUNGI OF AUCKLAND reported rarely in the fossil record and few moss fossils are known from New Zealand. The I.J. Geary1,2, J.E. Beever3, B.W. Hayward4, fossil mosses of the Tauranga Group D.E. Lee1, J.G. Conran5, J.M. Lord2, A.G. Beu6 sediments form a diverse assemblage with & D.C. Mildenhall6 more than 15 taxa recognised to date. The 1Dept. of Geology, University of Otago, PO preservation of the mosses is excellent and Box 56, Dunedin leaves retain fine cellular structure. One fossil 2Dept. of Botany, University of Otago, PO Box moss morphotype is indistinguishable from an 56, Dunedin extant species, Calyptrochaeta cristata. Other 3c/o Landcare Research, 231 Morrin Rd, St specimens belong to extant genera/families, Johns, Auckland 1072 such as Hypnodendraceae, Neckeraceae, 4Geomarine Research, 19 Debron Ave, Sematophyllaceae, Pyrrhobryum and Remuera, Auckland Ptychomnion. Some fossil mosses represent 5School of Biological Sciences, The University locally or globally extinct species, such as a of Adelaide, PO Box 5005, Australia morphotype attributable to Rhizogonium. 6GNS Science, PO Box 30-368, Lower Hutt. [email protected] The sediments yielding these fossils are not yet dated precisely, but a macro-mollusc Well-preserved fossil plants, fungi and fauna suggests that sediments at one locality arthropods are frequently recovered from are Pliocene (Waipipian) in age. These plant 38 fossils provide unique insights into relatively Structural High (IMSH), buried below the recent, northern New Zealand ecosystems and gravel cover, but penetrated by the Ruby Bay- highlight some plant taxa that have only 1 exploration well, close to the coastline. become extinct in New Zealand since the However, a reconstruction of the IMSH has Pliocene. never been attempted. This structure can be linked to the Surville reverse fault offshore, and is continuous along-strike to the south for MORPHOTECTONIC EVIDENCE OF BLIND > 60 km. Evidence for surface faulting is not ACTIVE FAULTS IN THE MOUTERE preserved in the unconsolidated cover DEPRESSION (SOUTH ISLAND, NEW sequence, but there is arguably a strong ZEALAND) control exerted by the IMSH on a domal bulge in the surface topography, the development of F.C. Ghisetti1, R.H. Sibson2 & P. Wopereis3 an intra-basin divide, the deflected 1TerraGeoLogica, 60 Brabant Drive, 7005, hydrographic network, and the aggradational Ruby Bay, New Zealand vs. erosional pattern along the major river 2University of Otago, PO Box 56, Dunedin, valleys. New Zealand 3Beca, 105 Trafalgar St., 7010, Nelson, New All these elements point to a growing blind Zealand anticline connected to a set of reverse faults [email protected] sub-parallel to the Waimea fault system, potentially posing significant hazard for the Active, but undetected “blind” faults pose wider Nelson-Motueka urban area if significant hazard because active fault reactivated with a M>6 earthquake. inventories and seismic codes do not account for their presence. The Darfield fault which started the 2010-2011 Canterbury earthquake AN UNUSUALLY COARSE BASALTIC LAVA sequence is a recent example, so two WITH EXTREMELY COARSE SEGREGATION questions arise: (1) how many faults capable STRUCTURES, SWINBURN, WAIPIATA of a M>6 earthquake are still unaccounted for VOLCANIC FIELD, OTAGO, NEW ZEALAND in New Zealand, and (2) are there cases where the geologists are blind rather than the faults? E. Giacalone, J.D.L. White, J.M. Palin, M. Brenna The case made here concerns the Moutere Dept. of Geology, University of Otago, PO Box depression, described in the past as an 56, Dunedin “aseismic corridor”, though bounded by the [email protected] active Alpine-Wairau Fault to the south and the Waimea-Flaxmore reverse Fault to the The Miocene Waipiata Volcanic Field, South east. Island, New Zealand, is an eroded Miocene volcanic field (c. 25 – 9 Ma), belonging to the The structural geometry of the Moutere broader Dunedin Volcanic Group. The largest region is indeed poorly understood, given its Waipiata volcano is represented by the little- subdued topography and the infilling of > 2 km known Swinburn Volcanic Complex, in Central thick Pliocene-Quaternary clastic cover. Otago. Here we present new petrographic and Seismic lines of the Survey MD87, together geochemical results of an unusually coarse with magnetic and gravity surveys hint at the type of lava common at Swinburn and its presence of a N-S elongated, Intra-Moutere extremely coarsely crystalline segregation 39 structures. Lava flows at Swinburn are PRELIMINARY ANALYSIS OF SEISMIC underlain by bedded, bomb-bearing ANISOTROPY CHANGES ASSOCIATED THE scoriaceous pyroclastic rocks. Highly vesicular KAIKOURA EARTHQUAKES IN NEW ZEALAND basalt at the basal contact and equivalent- aged sediment depositionally overlying it, Kenny Graham1, Martha K Savage1 & Richard confirm an effusive origin. Swinburn lava has Arnold2 crystals of augite and olivine that enclose 1Institute of Geophysics, SGEES, VUW, NZ random plagioclase laths. Crystal sizes average 2School of Mathematics and Statistics, VUW, 0.5 – 1 mm, with some bigger crystals reaching NZ 2 mm. Centimetric domains crystallised from [email protected] residual liquid and metre-scale pegmatitic segregation veins have been found at the The M7.8 Kaikōura Earthquake, occurred in a bottom and at different heights inside the lava complex tectonic regime. It is the largest and flow, respectively. They show the same most complex earthquake recorded on land mineralogy and ophitic texture of their host since the digital seismological age. A basalt but are much more coarsely crystalline remarkable number (more than 20) shallow (crystals 0.5 – 2 cm long). Inside the crustal fault segments ruptured. It ruptured segregations, plagioclase compositions are the surface over a distance of 150 km. The more sodic, also olivine and augite crystals main shock was followed by more than 20,000 have enriched FeO and depleted MgO and CaO aftershocks clustered with three unique compared to host basalt crystals. There is also spatial patterns. The Kaikōura earthquakes an enrichment in incompatible elements such provide a unique dataset to test the use of as Ba, REE, Zr, Nb, Th and a depletion in shear wave splitting (SWS) for measuring compatible ones (e.g. Cr, Ni). Field and variations in stress, because clusters of textural observations along with geochemical closely-spaced earthquakes occurred both features of the Swinburn lavas suggest that before and after the main shock. The study they had an effusive emplacement. During aims to measure any appreciable changes in cooling, within the partially solidified lava, a stress, before and after the Kaikōura slighter more evolved and less dense residual earthquake. We determine SWS, during the liquid moves from the bottom to upward, period of 2015 to August 2017, for over 5,000 through the flow, forming segregation veins crustal earthquakes which were located close and domains. A higher water content inside to each other and near the previous Seddon the residual melt and destruction of the earthquake sequence. We used the majority of crystal nuclei during the ascent, automatic, objective splitting analysis code could explain the extremely coarse crystals MFAST and an automatic S-phase picker to forming the segregation structures. speed the processing and to minimize observer bias. We made preliminary SWS measurement for two GeoNet stations around the Cape Campbell (CMWZ) and Seddon region (BSWZ) which released the most energy during the earthquake (Hamling et al., 2017). The mean fast orientation at both stations for events before the Kaikōura earthquake are parallel to NE-SW tectonic structures of the area. Station BSWZ showed similar NE-SW orientation after the earthquake. For station 40

CMWZ, there is bimodal fast orientation after Meteoric fluids circulate and are heated the earthquake, with a NE–SW mode and a throughout the seismogenic zone in the NW-SE mode, which could be an indication of hanging wall, while the higher permeability of stress changes. These changes may be related a damage zone near the fault allows upwelling to crack opening and closing and to the fluids of hot fluid parallel to the fault. Upwelling fluid contained in the cracks. Further analysis is flows preferentially into valleys due to a planned for stations around the Marlborough higher water table height in the mountains of region, particularly in areas where most of the the Southern Alps. The presence of the low surface ruptures occurred. permeability fault gouge and the difference in water table height across the fault results in the elevated pressures observed in the A MODEL OF DEEP HYDROTHERMAL hanging wall. Uplift of rock and shear heating CIRCULATION ON A PERMEABLE ALPINE contribute to the heat budget but are FAULT insufficient to explain the high temperatures on their own. T. Gray1, D. Dempsey1, J. P. O’Sullivan1 1Dept. Engineering Science, University of Auckland, PO Box 30368, Auckland PRELIMINARY INVESTIGATION INTO [email protected] LIQUEFACTION OF THE MANUKAU LOWLANDS, AUCKLAND, USING SETTLE3D Drilling into the hanging wall of the Alpine MODELLING Fault in the Whataroa Valley by the DFDP-2 borehole has revealed an unusually high L.J. Green, M.S. Brook & B. O’Connor geothermal gradient and pore fluids in excess School of Environment, University of of hydrostatic pressure. A recently presented Auckland, Private Bag 92019, Auckland thermal model (Sutherland et al. 2017) [email protected] considered convection of groundwater within the hanging wall and tectonic uplift of hanging It is often assumed that Auckland has a low wall rocks to account for the high fluid seismic hazard compared with the rest of New temperatures. However, this model did not Zealand, but there is the possibility of large consider fault parallel fluid flow within a high earthquakes from mapped and unmapped permeability damage zone, nor periodic shear faults. The near-surface stratigraphy of the heating due to great (M 8) earthquakes every Manukau Lowlands is typically mapped as ~300 years. Puketoka Formation, a range of soil types including volcanic deposits, soft alluvial and We have constructed an alternative thermal swamp deposits, as well as reclaimed land. model of the Alpine Fault to extend our Despite the liquefaction potential of these understanding of the physical processes that soils, under the Auckland Unitary Plan the area contribute to such high temperatures. will be developed, in-part, as greenfield sites. Incorporating fluid flow driven by local This study carries out a preliminary topography, uplift of hanging wall rock, and investigation into potential liquefaction at periodic shear heating, we find that the three sites within the Manukau Lowlands thermal anomaly can be accounted for as the located at Kingseat, Drury and Takanini, by product of cold downwelling in the hanging using site-specific standard penetration test wall far from the fault and focused hot upflow (SPT) data and liquefaction analysis software, in and around the fault damage zone. Settle3D. Two seismic scenarios adapted from 41 the National Seismic Hazard Model for New suitability of the Waipawa and Whangai Zealand are modelled for each site with formations as unconventional shale oil/gas estimated return periods of 500 and 2,500 plays in the onshore part of the southern East years. A further hypothetical seismic scenario Coast Basin. Drillcores and borehole image is modelled with an estimated return period of logs (acoustic and resistivity) were acquired in 10,000 to 20,000 years. the wells. These datasets provide a unique opportunity to directly calibrate image logs to The investigation reveals the uncertain nature observations in the core, allowing us to of liquefaction occurrence subject to the enhance our understanding of the fractures complex relationship between earthquake and in-situ stress in the boreholes, and relate magnitude and peak ground acceleration these to outcrop at a regional scale. (PGA) with localised geological conditions. This uncertainty is amplified by a lack of Structural data obtained from image logs standardised protocols for liquefaction show that the fracture strike orientations vary modelling. Following the methods established between formations within the wells, and by Idriss and Boulanger (2008), results show between the wells themselves. The that there is a likelihood of liquefaction Paleocene–Eocene Wanstead Formation has a occurring at the Takanini site for the 500 year general NW–SE fracture strike direction in return period scenario. At both the Takanini Orui-1A, whereas in Te Mai-2 the fracture and Drury sites, there is a likelihood of strike direction is more N–S. The Late liquefaction for the 2,500 year return period Paleocene Waipawa Formation was scenario, and a likelihood of liquefaction intersected by Orui-1A and Te Mai-2, and has occurring across all sites under the 10,000 to a similar fracture strike direction of NE–SW in 20,000 year return period. This study also both wells. Late Cretaceous–Paleocene highlights the need for detailed engineering Whangai Formation was imaged in both classification of sites in the Auckland region Ranui-2 and Te Mai-2, with approximate NE– logged as “Puketoka Formation”, as well as SW and variable fracture strike directions, detailed dynamic site characterisation. respectively.

Reference: Idriss, I., & Boulanger, R. W. (2008). The image logs show that in-situ stress varies Soil liquefaction during earthquakes: between the same formations encountered in Earthquake Engineering Research Institute. different wells, and between the three wells. Orui-1A has an overall SHmax of approximately N-S for the entire imaged interval, whereas Te INSIGHTS INTO SUBSURFACE STRESS AND Mai-2 has a low confidence SHmax of NE-SW. STRUCTURE IN THE SOUTHERN EAST COAST Ranui-2 has two directions of SHmax, NW–SE BASIN, NEW ZEALAND and W–E. When comparing these in-situ stress trends to the regional stress regime, other Angela G. Griffin factors such as faults and topography need to GNS Science, PO Box 30368, Lower Hutt be considered. 5040. [email protected]

In 2011-2012, New Zealand Energy Corp drilled the Orui-1A, Te Mai-2, and Ranui-2 stratigraphic holes, to determine the 42

VARIATIONS WITHIN THE FOSSILISED fluid temperature, volume, pH and change in SILICEOUS SINTERS OF THE COROMANDEL the system over time. VOLCANIC ZONE

A.R. Hamilton1, K.A. Campbell1, J.V. TRACE METALS IN CRUSTACEA: Rowland1, S. Barker2 BIOMONITORING OF THE MARINE 1School of Environment, The University of ENVIRONMENT Auckland, Private Bag 92019, Auckland 2Earth Sciences, University of Waikato, M.R. Handler1, R.J. Wysoczanski2, R. Peart2, Private Bag 3105, Hamilton K. Schnabel2 & G.E.Frontin-Rollet1 [email protected] 1 School of Geography, Environment & Earth Science, Victoria University of Wellington The Coromandel Volcanic Zone (CVZ) hosts 19 2National Institute of Water & Atmospheric fossilised siliceous sinters or hot spring Research, Greta Point, Wellington deposits. Siliceous sinters are surface [email protected] expressions of geothermal systems where fluids up to 100 °C are expelled at the The state and health of New Zealand’s marine intersection of the water table with the Earth’s environment is paramount to our societal and surface from deep reservoirs with economic wellbeing. An important factor in temperatures >175 °C. Upon cooling, these being able to preserve our unique marine fluids, oversaturated in silica, depositing non- estate is understanding the chemistry of our crystalline opal-A precipitates onto biotic and marine environment in order to monitor any abiotic surfaces. Overtime this silica change that might occur, such as changes in diagenetically matures to quartz, to form levels of metals resulting from offshore mining erosion-resistant sinter mounds and sheet activities, urban development, or ocean deposits with identifiable textures, which are acidification. Crustaceans, such as crabs and produced by extremophiles and diagnostic amphipods, take up potentially toxic trace taxa that live within the sinter during metals into their tissue and carapace, and formation. The CVZ is a Miocene-Pliocene sub- hence become recorders of their chemical aerial calc-alkaline volcanic arc, overlying environment. Jurassic meta-sedimentary basement. Within the CVZ the Hauraki Goldfield consisting of 50 We will present preliminary trace element known epithermal veins, also produced by data for marine amphipod and decapod geothermal activity within the upper parts of specimens from several New Zealand the Earth’s crust, some of which are directly locations, as a first stage in developing associated with siliceous sinters. Analysis of geochemical analysis of crustacea as a lithological, textural and geochemical biomonitoring tool for tracing chemical variation within the CVZ siliceous sinters show change in the marine environment. Thirty similarities to deposits in the Recent and trace elements have been analysed in four actively forming Taupo Volcanic Zone deposits amphipod species (Ampelisca chiltoni, and the siliceous sinters of the Jurassic Podocerus sp., Ischyrocerus sp., Apohyale sp.) Deseado Massif, Argentina. Comparisons of and in the decapod species Jasus edwardsii these 19 siliceous sinter deposits to the (crayfish). The trace element data allow us to modern and fossilised hot spring deposits evaluate natural variations among specimens reveals proximal, middle and distal facies from single localities, compare uptake of assemblages, allowing inferences of paleo elements among different amphipod families 43 from the same environment, compare uptake and groundwater interactions. of elements into decapod tissue versus shell, and between decapod and amphipod species The proximal sequence of the tuff ring consists from the same general locality. of a coarse massive-to-weakly bedded pyroclastic breccia and lapilli tuff that These results are the first of a 3-year alternates with a well-bedded, cross- and/or Endeavour funded programme to measure dune-bedded tuff. The clast-supported nature trace element contents in crustaceans of juvenile lapilli layers and the presence of throughout New Zealand’s waters. The data scoriaceous bombs within the tuff ring will provide baseline values of trace elements deposits suggest repeated magma discharge from which any future changes in the marine through an open but slurry-laden vent. The environment can be assessed. The data also irregular and flame-like boundaries of lithic provide a means to test the quality of clasts within magmatic bombs indicate that kaimoana, as any increase in toxic elements coarse mixing occurred between intruding above natural values will affect the quality and magma and water-saturated sediments (e.g., health of the food chain ultimately consumed peperitic domain). Juvenile scoria fall and by us. spatter deposits within the tuff ring crater provide evidence for a more sustained magmatic phase towards the end of MULTIPLE VENT ERUPTIONS AT Waitomokia’s eruption leading to a scoria MONOGENETIC VOLCANOES: WAITOMOKIA cone building phase. Several lines of evidence VOLCANO, AUCKLAND VOLCANIC FIELD, suggest that the tuff ring was formed by NEW ZEALAND volcanic activity at multiple, closely-spaced vents with some aspect of vent migration H. Handley1, R. Griffis1, L. McGee1, R. through time. Didonna1, K. Németh2, M. Turner1 1Department of Earth and Planetary Sciences, This eruption model is in good concert with Macquarie University, Sydney, Australia inferred eruptive histories of other large tuff 2Volcanic Risk Solutions, Massey University, ring complexes from the AVF, especially those Palmerston North, New Zealand formed in the low-lying coastal areas of the [email protected] field, suggesting the influence of the external environment on volcano growth and the Waitomokia volcano is a basaltic tuff ring and potential volcanic hazards involved in such scoria cone complex located in the southern type of evolution can be associated with vent lowlands of the Auckland Volcanic Field (AVF). migration and unstable vent/crater and Extensive quarrying and urban developments conduit conditions. have resulted in the near-complete removal of three intra-tuff ring scoria cones, incision of the tuff ring rim and some degree of infilling of the crater floor, hindering a full understanding of the volcano’s formation. In this work, historical records are combined with detailed field studies of the remaining pyroclastic deposits to reconstruct the formation and evolution of Waitomokia, with special reference to the nature of explosive magma 44

SEDIMENTARY GEOLOGY OF A PORTION OF depositional environment and age control. THE EAST COAST BASIN, WEBER TO AKITIO, Sedimentological and petrographic analysis of NEW ZEALAND major units also indicate variability in depositional environments such as abyssal to H. Harvey¹, J. Procter¹, J. Palmer¹, K. Bland², shallow marine. Key sections have been D. Strogen² identified to provide accurate ages ¹Volcanic Risk Solutions, IAE, Massey throughout the depositional sequence. This University, PO Box 11 222, Palmerston North project will contribute to current research on ² Geological and Nuclear Science, Oil and Gas the petroleum reservoir potential of the East Team, PO Box 30-368, Lower Hutt Coast Basin.

Geological mapping of the East Coast Basin has tended to be at a broad scale with detailed DARWIN’S GEOLOGICAL OBSERVATIONS IN mapping confined to a few specific areas of NEW ZEALAND, 1835 interest. East Coast Basin is a petroliferous region and therefore of interest for petroleum Bruce W. Hayward exploration, however, further detailed Geomarine Research, 19 Debron Ave, mapping and sedimentological research is Remuera, Auckland needed to have a better appreciation of the [email protected] reservoir potential of the basin. The Weber district, 35km southeast of Dannevirke, has Charles Darwin, arguably the world’s best received minimal attention. Mapped known geologist, visited the Bay of Islands, geological boundaries are inferred based on New Zealand, on HMS Beagle in December broad tectonic features and structures and 1835, 22 years before the arrival of the fathers little sedimentology has been undertaken. The of New Zealand geology Ferdinand von current geological understanding is that this Hochstetter and Julius von Haast. During his area contains a succession of Late Cretaceous visit Darwin wrote nine pages of geological (66ma) to Late Miocene (10ma) sandstone, notes in his unpublished geological diary. Until limestone, marl, flysch and mudstone facies. recently these were relatively inaccessible in Few potential reservoir units are mapped or the Cambridge University archives but now received detailed analysis and source rock has the original diary and transcript are available been an ongoing enigma. on the web at Darwin on-line. Thus New Zealand geologists (including Hochstetter) The purpose of this research is to produce a have been mostly unaware that Darwin was high- resolution 1:25 000 geological map and the first to make substantive geological undertake sedimentological, observations in New Zealand. His notes biostratigraphical, petrological, structural and include descriptions of the puzzling weathered paleo-environmental studies to help better Waipapa Terrane greywacke that forms the understand the petroleum potential of the Bay of Islands coast and the young basalt area. volcanoes of the Kaikohe Volcanic Field. He described Oligocene Whangarei Limestone Initial findings indicate the area is structurally and some of the rocks that we now recognise complex with numerous faults, folds, including as having been displaced by the Northland the Akitio Syncline, and local unconformities. Allochthon. He also documented discussions Within the stratigraphic sequences identified with the local missionaries on the lack of both macro and micro fauna provide earthquakes in Northland compared with 45 further south; the active volcanoes of the ability of the gas to separate from the magma central North Island, White Island, Mt Egmont and travel through connected bubbles. Data and Rangitoto; and lignite, conglomerate and will be presented from 2D and 3D glauconitic marl from Northland’s west coast. visualizations for several of the Mangamate He uses some of his observations to affirm his lapilli units. Unusually fine-vesicle textures growing conviction that most lands had been observed are suggestive of a late-stage bubble uplifted by earthquakes; that New Zealand nucleation event, followed by rapid rise to was at the southwestern end of the Pacific eruption. This contrasts with the textures and Ring of Fire; and that coal existed because of a eruptive processes identified in the favourable environment for accumulation and neighbouring Ruapehu Plinian eruptions. The not because of its age. Mangamate textures seem consistent with the sudden rise of a deeply stored and gas-poor magma to eruption. This work will be DRIVERS, DYNAMICS AND HAZARDS OF THE extended alongside geochemical and LARGEST ERUPTIONS OF MT. TONGARIRO petrological studies to delve further into the triggering mechanisms and dynamic M. Heinrich and S. J. Cronin properties of the maximum likely eruption School of Environment, University of scenarios at Mt. Tongariro. Auckland, Auckland 1010 [email protected]

Mt. Tongariro is an unusual composite VAPOUR PHASE ALTERATION AND COOLING volcanic complex made up of many widely OF COMPOUND IGNIMBRITE SHEETS: THE dispersed vents, associated along fault-zone SILICA STORY lineaments within the Tongariro graben. The eruptive history of Mt Tongariro is Y. Heled1, M.C. Rowe1, I. Chambefort2 & characterized by a bimodal distribution in C.J.N. Wilson3 eruption size and frequency. Small-scale 1School of Environment, Auckland University, eruptions of <0.01 km3 are regular, but very PB 92019, Auckland 1142 large eruptions (0.5-1 km3) are also 2GNS Science, Private Bag 2000, Taupo 3352 documented. These large events were 3SGEES, Victoria University, PO Box 600, attributed to tectonic drivers, but firm Wellington 6140 evidence for this is lacking. In this study we [email protected] examine in detail an unusual flare-up of activity at ~11 000 years ago when Mt. Many welded ignimbrites show vapour-phase Tongariro produced at least 4 Plinian alteration, overprinting initial crystallisation of eruptions, (mapped within the Mangamate the formerly glassy matrix. We present data Formation). In less than 400 years 5.3 km³ of on silica polymorphs formed during glass pyroclastic material was deposited over many crystallization accompanying cooling of hundreds of square kilometers around the compound ignimbrites. Previous work has volcano. In the first phase textures of the indicated that ignimbrites can record a change juvenile lapilli were examined. Bubble-growth in silica polymorphs and associated in the rising magma foam drive the magma to groundmass textures consistent with cooling rise either by increasing buoyancy or by profiles from numerical modelling. X-ray increasing magma chamber overpressure. The diffraction and SEM imaging is used to resulting magma ascent is controlled by the examine changes in groundmass texture and 46 mineralogy through selected sections in the Bishop Tuff (USA) and Whakamaru ignimbrite URBAN MAPPING IN SOUTH AUCKLAND (New Zealand). Two transects through the Bishop Tuff, linked to documented M.P. Hill, J.G. Begg, J.M. Lee, K.E. Jones, R. stratigraphic packages and welding zones, Morgenstern provide a basis for comparison to the GNS Science, PO Box 30-368, Lower Hutt Whakamaru ignimbrite at Maraetai Dam on 5010, New Zealand the Waikato River. Samples from both [email protected] localities generally contain only 10-30% amorphous material, consistent with their The current rate of city expansion means welded nature. Silica polymorphs reflect a better understanding of urban geology, such change from cristobalite to tridymite at, and as landforms, subsurface geology, hazards and just above, the contact between the major resources, has become increasingly flow packages for two of the three sections important. A GNS Science geological mapping investigated. No tridymite is observed within project has commenced in South Auckland the Bishop section containing a fall deposit and extends from the Waikato River in the intercalation. A density profile through the south to the Manukau Harbour in the north. Whakamaru section shows no significant This map is the start of our urban geological variation in the presence of tridymite. In research in the Auckland region; our future contrast, for the Bishop, there is a significant intent is to continue mapping north through variation in density at the contact between the city. Initial compilation of published and ignimbrite packages. The systematic unpublished geological data in the region and stratigraphic location of the tridymite at an evaluation of the stratigraphy and volcanic package boundaries suggests that the evolution has been completed. South presence of tridymite is not related to cooling Auckland is particularly data-rich and includes rate. For Whakamaru, the presence of many university mapping studies; tridymite corresponds to a distinctive aeromagnetic and radiometric geophysical horizontal fracture pattern. We propose that data; LiDAR digital elevation models (DEMs); groundmass tridymite is related to localised and several thousand borehole records. We vapour phase alteration under a cap of the less have compiled ca. 28,000 lithological permeable upper flow materials, resulting in descriptions from more than 2,000 boreholes tridymite formation only where the two in the region that provides an extensive sheets are in contact. Correlations between database of subsurface geological compound ignimbrite structures and silica information. Aeromagnetic data has been polymorphs may help mapping of used to create inversion models of areas with hydrothermal fluid flow pathways in magnetic anomalies that represent volcanic ignimbrite hosts. intrusions, and these enhance our understanding of the subsurface volcanology. Using a 1 m LiDAR DTM we are mapping geomorphic features, many of which constrain the location of geological boundaries, and along with subsurface data and historic geological observations, will provide a robust foundation for our urban geological map. In addition to a surface geological map, the wealth of subsurface information allows the 47 construction of a 3D geological model that will stability studies, and the calculations of vital provide constraints on the distribution of data such as porosity and permeability from volcanic rocks, sedimentary formations and wireline logging. groundwater systems. We aim to quantify the geomechanical properties of key reservoir and seal horizons in GEOMECHANICAL CHARACTERISATION OF the Maari and Maui Fields, including porosity, RESERVOIR AND SEAL ROCKS IN THE permeability, ultrasonic wave velocities TARANAKI BASIN (Vp/Vs), and uniaxial compressive strength (UCS). Laboratory testing is undertaken on S. Hill1, M.C. Villeneuve1, D.D. McNamara2, samples of drill core and outcrop analogues to K. Bassett1 generate this data, which will then be used to 1 Dept. of Geological Sciences, University of refine stress data inputs into field Canterbury, Christchurch, New Zealand geomechanical and migration models. 2 Dept. of Earth and Ocean Sciences, Natural Furthermore, following a practical approach, Sciences, NUI Galway, Galway, Ireland empirical relations will be determined [email protected] between the rock properties, specific to the region, allowing for correlation between laboratory, wireline, and possibly field wide Around the world, extensive work has been geophysics scales which open up enhanced undertaken to understand the geomechanical analysis of existing and future exploration and properties of sands and shales, for application development data in the Taranaki Basin. to the modelling of petroleum reservoirs. Geomechanics provides vital information on the in-situ stresses within a basin and how FILLING THE GREAT BLANK WEDGE OF they impact the flow of fluids through ZEALANDIA: CRETACEOUS TO PALEOGENE reservoirs and movement of geological PALINSPASTIC RECONSTRUCTION OF THE structures. This information is pivotal when EAST COAST BASIN considering petroleum migration, reservoir compaction, sealing quality of cap rocks, B. R. Hines1,2, H. Seebeck2, J. S. Crampton1,2 hydraulic fracturing, and fault reactivation; all & K. J. Bland2 considerations that need to be accounted for 1SGEES, Victoria University of Wellington, when considering the overall condition and P.O. Box 600, Wellington viability of a petroleum play. 2GNS Science, P.O. Box 30368, Lower Hutt [email protected] This study focused on the Maui and Maari Fields in the Southern Taranaki Basin, which The East Coast Basin is a Cretaceous-Cenozoic contain substantial petroleum reserves for sedimentary basin that originally formed New Zealand. Despite development and within a late Cretaceous–Oligocene passive interest in the resources hosted here, industry margin setting, and has subsequently relies on non-site specific geomechanical developed within a convergent margin setting properties of reservoir and seal rocks which throughout the Neogene. The position of the has downstream implications for any decisions East Coast Basin prior to the inception of the that need to be made on well design and field modern boundary between the Pacific and planning, as these rock properties impact Australian plates has, for many decades, been stress field calculations needed for well a contentious issue in palinspastic and 48 paleogeographic reconstructions of Zealandia SEISMIC INVESTIGATIONS OF FLUID FLOW and the broader southwest Pacific region. RELATED STRUCTURES ON THE SOUTH Many previous reconstructions of Zealandia CANTERBURY SLOPE either omit the region entirely, or depict it as a broad wedge-shaped zone of unconstrained J. Hoffmann1, A.R. Gorman1 & G.J. Crutchley2 and unspecified deformation. 1Dept. of Geology, University of Otago, PO Box 56, Dunedin Applying recently developed rigid-plate 2GNS Science, PO Box 30-368, Lower Hutt reconstructions for Zealandia, we have used [email protected] geological and geophysical datasets to emplace constraints on the deformation, Crescent shaped pockmarks are abundant on horizontal movement, and paleogeography of the marginal extent of the Otago canyon the East Coast Basin. The outcome is a series system in water depths between 500 and 1100 of palinspastic reconstructions. These m. Fluids seeping through the seabed, palinspastic reconstructions are then potentially forming pockmarks, play a crucial translated into a suite of paleoenvironmental role in seabed ecological systems and can be maps through the integration of various used to investigate the distribution of datasets, including stratigraphic and hydrocarbons in underlying geological units. sedimentological measurements, fossil record Buried pockmarks revealed by 3D seismic data from the fossil record electronic database datasets indicate repeated fluid expulsion (FRED), and heavy mineral and detrital grain along the Canterbury slope triggered by studies. These data provide insight into paleo- different processes. Recent and buried slope and current directions, paleo-water seafloor depressions along the shelf exhibit depth, and sediment provenance. Maps have the same north-eastward facing crescent form been developed for several key time-slices that we associate with water current through the late Cretaceous to late Eocene, modification. High-resolution seismic namely the Ngaterian, Piripauan, Haumurian, investigations near the Waitaki Canyon K-Pg boundary, Teurian, Heretaungan and combined with recently acquired 3D seismic Runangan stages. data give the first evidence of shallow gas accumulations in the region. No active fluid Information derived from these palinspastic seepage was observed in water column maps has implications not only for the better imaging data above the shallow gas but understanding the petroleum prospectivity of pockmarks on the seafloor indicate past fluid the Raukumara-East Coast-Pegasus basins, flow. Analysis of the amplitude variation with but also has broader applicability to angle (AVA) in seismic common depth point paleotectonic, paleoclimate, and gathers reveals a class 3 AVA anomaly around paleoceanographic research. In addition to bright spots and a near vertical structure providing basin-wide temporal and spatial beneath them. We assume this vertical perspectives of ancient depositional structure to be a recent or ancient fluid environments, they can be presented in migration pathway feeding the shallow gas tandem with correlative time-slice maps from pockets beneath the seafloor. Continuous the Reinga-Northland-Deepwater Taranaki- reflections in the seismic section around the Taranaki, and Canterbury-Great South basins vertical structure visible in the AVA attribute to provide regional context for the Zealandia suggests that fluid migration causes only region in a consistent and reproducible minor modifications of the original format. sedimentary fabric. In a succession of dense 49 polygonal faulting, two near vertical faults the Alpine Fault in the southeast corner of create slightly uplifted cylindrical shapes with Northwest Nelson. Progressive truncation of diameters of 4 and 6 km, respectively. cave passages by faults in the upper levels of Polygonal faults around these cylindrical the cave suggests the system is of at least features create structures less than 500 m in Miocene age. diameter. Seismic sections through these circular features reveal upward-bent Cosmogenic nuclide burial dating of cave reflections in their centres that we interpret as sediments can be used to infer the age of ancient fluid migration pathways. They are abandonment of cave stream passages, and in confined to strata below the Marshall multi-level cave systems these abandonment paraconformity where they terminate and ages can be used to reconstruct the rate of the create a mound and a depression, lowering of hydrologic base level and hence respectively. regional uplift.

Initial results of applying 10Be/26Al burial COSMOGENIC NUCLIDE DATING OF THE dating to quartz in sediments in Bulmer SEDIMENTS OF BULMER CAVERN: Cavern suggests that Eye in the Sky passage, IMPLICATIONS FOR THE UPLIFT HISTORY OF which is located approximately 250m above SOUTHERN NORTHWEST NELSON, NEW the present day cave stream level was ZEALAND abandoned by 2.9Ma. This suggests a regional uplift rate of 0.1mm/yr since the late Pliocene. Gavin Holden The abandonment age is supported by the SGEES Victoria University of Wellington. PO observation that the sediments infilling Eye in Box 600 Wellington the Sky passage are similar to the upper parts [email protected] of the Glenhope Formation, which are also of late Pliocene age. Not much is known about the timing of the tectonic history of the Northwest Nelson area since the early Miocene inception of the THE VERY PECULIAR CONDITIONS THAT Alpine fault, which lies to the south. CREATED THE WAIPAWA FORMATION, ~59 Radioactive cosmogenic nuclides such as 10Be MILLION YEARS AGO and 26Al which have half-lives of 1.34 Ma and 0.72 Ma respectively accumulate in minerals C.J. Hollis, S. Naeher, C.D. Clowes, E.M. such as quartz on the Earth’s surface. In karst Crouch, C.L. Shepherd & X. Li terranes, these minerals can be transported GNS Science, PO Box 30368, Lower Hutt by fluvial processes into cave systems and [email protected] preserved in sediments that infill cave passages. After deposition in the cave, The Waipawa Formation is an organic-rich sediments are shielded from cosmic rays by marine mudstone that is a proven source of the overlying rock, and the difference in decay petroleum. Total organic carbon (TOC) rates of the cosmogenic nuclides allows the content is commonly 1–3% and ranges up to calculation of the age of burial. 12%. The unit and facies equivalents are widely distributed in the southwest Pacific but Bulmer Cavern is an extensive multi-level cave their thickness and distribution within system located within the Mt. Owen massif, individual basins is highly variable. which is located approximately 30km north of Biostratigraphic studies indicate that the 50 formation was deposited within a relatively regional vegetation patterns, particularly short period of time (0.5 to 1.0 million years) since the last glacial maximum, there are still about 59 Ma, at varying depths from outer some unresolved questions. We report some shelf to upper slope. Palynofacies and preliminary results from an ongoing study in biomarker studies reveal that, despite the which we seek to integrate pollen records with marine setting, the bulk of the organic matter plant macrofossils to help resolve some of (OM) is derived from land plants. The these problems. conditions that led to a massive influx of terrestrial OM into widely separated Three sites in north Taranaki form the basis of sedimentary basins are a matter of much the first stage of this study. Two coastal conjecture and debate. A possible answer lies sections, at Bell Block and Airedale Reef in the strongly positive δ13C signature of the include seams of dirty lignite that have yielded terrestrial OM: a mean value of -17.5 ‰, pollen, macrofossils, tephra and charcoal. which is ~10 ‰ heavier than associated Together with a third, inland section at Colson marine OM. We suggest that this excursion Road, sampled for pollen alone they will allow signals a major decrease in atmospheric CO2, comparison with other sites, both onshore linked to global cooling and a eustatic fall in and offshore. Initial results from this sea level. Erosion of well-vegetated coastal integrated approach suggest that during both regions, led to the accumulation of abundant MIS 7 and MIS 5, the coastal plain of northern terrestrial plant matter in marginal basins of Taranaki was covered by a complex of dunes Zealandia, eastern Australia and perhaps backed by swampy podocarp/broadleaf further afield. This short-lived event marks the forests, lakes and more open areas of swamp termination of long-term Paleocene cooling in and oligotrophic restiad bog. Both volcanicity which deep sea temperatures cooled by 3°C and fire seem to have affected the vegetation over 4 million years. Within the event itself, rather more than previous authors have local sea surface temperatures cooled by a suggested. further 4°C. This peculiar event was followed by a global warming trend of similar magnitude and duration that culminated in MICROSEISMIC RESPONSE TO DEEP the Paleocene-Eocene thermal maximum. INJECTION AT NGATAMARIKI GEOTHERMAL FIELD, NEW ZEALAND

VEGETATION CHANGE, CLIMATE AND Chet Hopp1, Stefan Mroczek1, Steven VOLCANISM IN TARANAKI OVER THE LAST Sewell1,3, Martha Savage1, Steven Sherburn2, THREE GLACIAL/INTERGLACIAL CYCLES – A John Townend1 MULTI-PROXY APPROACH 1Victoria University of Wellington, SGEES, PO Box 600, Wellington 6140 Aline Homes, Matt Ryan 2GNS Science, Wairakei, Private Bag 2000, School of Geography, Environment and Earth Taupo 3352 Science, Victoria University of Wellington, NZ 3Mercury, 283 Vaughan Rd, Rotorua 3010 [email protected] Email: [email protected]

Previous studies of past vegetation patterns in Fluid-induced seismicity (FIS) is a useful Taranaki over the past ~250,000 years have indicator of thermal and pressure changes concentrated almost entirely on palynology. within a geothermal reservoir. Given the While this has given considerable insight into difficulty of making measurements in the 51 space between wells, FIS provides one of the only direct observations of fluid-related A major source of error in volcanic ash reservoir processes. Understanding exactly forecasting is the wind pattern above and why and how these microearthquakes occur around the volcano. Our current operational helps us unravel the interaction between the forecasts are produced by the program movement of fluid and heat at depth and ASHFALL (Hurst 1994), which uses a 1- could allow for a better understanding of the dimensional model wind profile, and neglects creation and destruction of permeability in the horizontal variation in the wind field. Given reservoir. We begin with an earthquake New Zealand’s dynamic meteorology, this is a catalogue of 1171 events which occurred major limitation. GNS Science, in conjunction between May 2012 and November 2015 at the with New Zealand’s MetService, is working to Mercury geothermal field at Ngatamariki. We move its operational ash forecasts to HYSPLIT, expand this catalo using matched filter which uses a full 4-D atmospheric model. We detection to include ~77,000 are now routinely using HYSPLIT to produce microearthquakes. Earthquakes at the field forecasts of where ash would be deposited if a are densely clustered in areas of active fluid given volcano erupted. injection and the rate of seismicity is highly correlated with injection rate. We present Because of the simple 1-D wind assumption, high-precision locations as well as frequency- and the way ash diffusion is treated, ash magnitude distributions and source contours produced by ASHFALL are ellipses mechanisms for significant events and discuss which usually cover a much wider area than their relation to injection and production rates more sophisticated models forecast. at the fields. In particular, we focus on specific Conversely, HYSPLIT sometimes forecasts periods of interest including the stimulations narrower deposited ash distributions with of well NM08, NM09 and NM10 in June 2012 detailed contours with small scale features, so and the Ngatamariki plant start-up in April minor errors in input wind conditions cause 2013. precise but inaccurate forecasts. This higher level of detail can give a false impression of accuracy. This problem is apparent in USING MULTIPLE ATMOSPHERIC MODELS TO hindcasting ash deposition from the 6 August ASSESS AND DISPLAY UNCERTAINTIES IN 2012 Te Maari eruption from Tongariro VOLCANIC ASH FORECASTS FROM HYSPLIT volcano (Hurst & Davis, 2017).

Tony Hurst1, Cory Davis2 & Natalia Deligne1 Prior to making these new forecasts 1GNS Science, PO Box 30368, Lower Hutt operational, we will explore ways of displaying 2MetService, PO Box 722, Wellington the uncertainty in the atmospheric modelling [email protected] to avoid inappropriate reliance on deposit forecast details. This includes using multiple Since the 1995 eruption of Ruapehu, GNS atmospheric models to make our ash forecasts Science runs daily forecasts of where volcanic take better account of the uncertainties in the ash would be likely to land if there was a atmospheric modelling. volcanic eruption. When a volcano is erupting, ashfall forecasts for that volcano are distributed to relevant organisations and the public; at times these daily forecasts are also published for volcanoes in heightened unrest. 52

PRELIMINARY INSIGHTS INTO THE FAULT fault-traces with left-lateral and right-lateral GEOMETRIES AND KINEMATICS OF THE strike slip. Similar distributed fault SURFACE RUPTURE ALONG THE SOUTH intersection zones are widely documented in LEADER FAULT DURING THE MW 7.8 the literature, but in this case would be KAIKOURA EARTHQUAKE difficult to assess in the absence of the earthquake. N. Hyland-Brook1, A. Nicol1, N. Khajavi1, C. Fenton1, T. Bushell1 1Department of Geological Sciences, GEOLOGICAL STRESS EVOLUTION OF WEST University of Canterbury, Christchurch JAVA, INDONESIA [email protected] A.F. Ismayanto1,2, J.V Rowland & J.D Eccles1 1School of Environment, the University of The South Leader Fault (SLF) ruptured the Auckland, Science Centre 302 - Bldg 302, 23 ground surface during the Mw 7.8 Kaikoura Symonds St, Auckland 1010 earthquake. Part of the SLF had been 2Research Centre for Geotechnology, previously mapped in bedrock, although the Indonesian Institute of Science, LIPI Campus, fault was not known to be active prior to the Bandung, Indonesia earthquake, and does not have a strong [email protected], topographic expression. The fault is a NNE [email protected] trending oblique left lateral fault that links the predominantly right lateral ‘The Humps’ and Block collision, amalgamation and rotation Conway-Charwell faults. Field mapping and have affected all parts of Sundaland, including terrestrial LIDAR at 0.5m resolution have been West Java, which is situated at a bend on the used to assess the factors influencing the Sunda-Banda Subduction Margin (SBSM). This surface geometries and kinematics of the SLF ‘corner’ marks the transition between oblique ruptures at the ground surface. The SLF and orthogonal convergence along the margin deformation zone is up to 2km wide, and and coincides with the Sunda Strait between comprises a series of en echelon NE-striking West Java and Sumatra. The opening of Sunda thrusts linked by steeply dipping (65° west- Strait suggests a possible counter clockwise 85° east) N-S striking faults. The thrusts are rotation of West Java relative to Sumatra. We generally upthrown to the west by up to 1 m tested this notion by analysing the temporal and dip 35-45°. Thrusts are parallel with evolution of regional stress orientations, Cretaceous-Cenozoic bedding in the Greta SHmax in particular, using available geological Siltstone, Waikairi, Motunau and Amuri data and the World Stress Map. For this Limestone formations. These displacements analysis, the direction of paleo- SHmax is may reflect flexural slip folding and off-fault defined by the orientation of igneous dikes deformation during the earthquake. By and the elliptical shape of constructional contrast, the northerly striking faults volcanic edifices, based on the assumption accommodate up to 3m of oblique left lateral that magma propagation through the brittle displacement at the surface and displace crust is sensitive to regional stress. The Cenozoic bedding. The surface expression of Cenozoic magmatic intrusions and edifices in both steep oblique slip and thrust faults is West Java range from Middle Oligocene to particularly complicated in the north of study Early Holocene in age. Those that have a area where they intersect with the right- clearly preferred orientation have been lateral Humps to form a ~2 km widely zone of digitised from 19 map sheets at a scale of 1: 53

100,000. For the volcanic edifices, the SHmax Analysis of the water chemistry of the AMD, trend is parallel to the major axis of each including trace elements and major ions has ellipse. The ellipses of 544 Cenozoic intrusions been undertaken to allow quantification of the depict two major maxima trends at NW-SE and dilution occurring during mixing of waters in NE-SW. The SHmax trend analysis based on Cascade Creek catchment. Determination of age clustering indicates 3 major groups: 1) dissolved loads in the AMD runoff is being NW-SE trend from Middle Oligocene to Middle quantified using a data-logger attached to a V- Miocene, 2) NW-SE and NE-SW trend from notch in a runoff stream. Correlation with pH Late Miocene to Pliocene; and 3) NE-SW trend and specific conductance measurements from Pleistocene to Early Holocene. The through flood events has been undertaken to bimodal trend from Late Miocene to Pliocene allow the determination of the flux of acidic reflects a transitional period waters during these flood events. Preliminary contemporaneous with opening of Sunda results show a minor increase in pH during Strait at 10 Ma and associated counter- flood events coupled with a decrease in clockwise rotation of West Java. specific conductance correlating to a decrease in metals. The ultimate aim of the project is to define the parameters for dilution and/or WATER QUALITY AND GEOCHEMISTRY OF passive treatment of the AMD to ensure HISTORIC CASCADE MINE DISCHARGE ON enhanced environmental outcomes in the THE DENNISTON PLATEAU, NEW ZEALAND impacted streams.

C. Jewiss1, J. Pope2 and D. Craw1 1University of Otago, PO Box 56, Dunedin, NZ DETAILED LITHOFACIES ANALYSIS OF THE 2CRL Energy, Christchurch LATE CRETACEOUS NORTH CAPE Contact Details: FORMATION, SOUTHERN TARANAKI BASIN [email protected] R. Joyce1, K.N. Bassett1, G. H. Browne2 New Zealand’s largest coal resources are 1Dept. of Geology, University of Canterbury, located on the West Coast of the South Island. Private Bag 4800, Christchurch One particular coal measure of interest is the 2GNS Science, PO Box 30-368, Lower Hutt pyritic Eocene Brunner Coal Measures due to [email protected] their high acid producing potential. This is attributed to their pyritic nature, allowing the The Whanganui Inlet, northwest Nelson, production of pH 3 acid mine runoff on provides a unique opportunity for interaction with meteoric water. Historic sedimentary analysis of onshore expressions mining on the Denniston Plateau in the 1900s of Late Cretaceous units of the southern has caused an increase in the surface area of Taranaki Basin. Previous sedimentary the pyritic coal. This allows the discharge of investigations of the North Cape Formation acid mine drainage (AMD) through a series of have assigned 3 lithofacies associations that adits located above the current mine’s high represent estuarine, fluvial and swamp wall. These adits drain into the Cascade Creek, successions. These investigations have allowing the acidic water to mix with an focussed on interpretation of depositional unimpacted tributary, enabling partial settings providing the framework for this neutralisation producing waters of pH ca. 5.5. detailed investigation of lithofacies and their Iron and aluminium oxide precipitates are lateral variability in order to define reservoir present in this Cascade Creek mixing zone. characteristics. 54

GEOCHEMISTRY OF BIOLOGICALLY- Detailed sedimentological assessment of 8 MEDIATED GOLD MOBILISATION new stratigraphic sections in addition to those IN A SEMIARID CLIMATE, SOUTHERN NEW previously investigated has identified 9 key ZEALAND lithofacies that comprise the depositional environments of the North Cape Formation. G. Kerr & D. Craw Conglomerate lithofacies are limited to Dept. of Geology, University of Otago, PO Box northern outcrops, while the remaining 56, Dunedin lithofacies can be observed throughout the [email protected] area. Lithofacies range from high-energy, tidally influenced distributary systems in the Alluvial gold in Quaternary placers has northwest, to low-energy inter- and supra- undergone mobilisation and re-deposition at tidal environments in central portions, to the micron scale during biologically-mediated mixed-fluvial and tidal environments the interactions within groundwater. These southern areas. The recognition of cyclical processes have been occurring in a shifts from supra- to intra-tidal environments tectonically active semiarid region of southern within the central and southern regions New Zealand and are likely to be suggests influence from base-level representative of this environment elsewhere fluctuations over the Late Cretaceous, this in the world. The geochemical environment is may be the result of local subsidence dominated by authigenic sulphur minerals variations within the basin and/or sea level such as pyrite. Detrital and authigenic pyrite changes. Tidal signatures such as ripple forms commonly occur below the water table, and and rhythmic interbedded sandstones, in evaporative sulphate minerals are common addition to unique bioturbation from both above the fluctuating water table. Oxidation marine fauna and large herbivorous dinosaurs of pyrite is widespread but any acid generated are present throughout the study area. These is rapidly neutralised by abundant calcite in structures and their relationships with sediments, and pH remains circumneutral surrounding lithofacies have aided except in highly localised (centimetre scale) paleogeographic reconstruction. zones around pyritic material. Pyrite oxidation produces metastable thiosulphate ions, Our analysis has established distinct tidally- enhanced by bacterial mediation. This influenced depositional modes that vary bacterial mediation also forms authigenic laterally and stratigraphically across the pyrite in reducing conditions below the water region. Further analysis will enable the table. Gold has been mobilised chemically in interpretation of the reservoir quality in the this groundwater environment as Au- onshore facies. Ultimately, it is hoped this thiosulphate complexes. Subsequent research could be used to inform the deposition of this mobilised gold resulted from petroleum reservoir potential of the offshore localised variations in redox and/or pH near to North Cape Formation. the fluctuating sulphide-sulphate redox boundary.

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VOLATILE EXCHANGE DURING MAGMA to show the variability of volatiles within and MIXING: INVESTIGATING THE VERY SHORT across these zones to investigate the TIMESCALES BEFORE ERUPTION heterogeneous nature of silicate glasses.

G. Kilgour1, G. Zellmer2, N. Sakamoto2, H. We then use a physically constrained model to Yurimoto calculate the time required to achieve 1GNS Science, Private Bag 2000, Taupo complete homogenisation. This independent 2Massey University, PO Box 11222, method provides a maximum time between Palmerston North magma mixing and eruption. Our combined Isotope Imaging Laboratory, Hokkaido results show that magmatic processes can be University, Sapporo, Japan very rapid and through careful petrological [email protected] analysis and modelling, we can quantify processes that are directly relevant to near- Significant evidence shows that magma mixing real time volcano monitoring. occurs throughout the lifespan of a magma reservoir; in some cases, this process has been used to explain the triggering of an eruption. SPELEOTHEM RECORDS OF NEW ZEALAND'S To constrain the timing of these events, a EARTHQUAKE HISTORY growing number of studies have analysed the outer rims of zoned crystals to determine the J. Lang1, S. Suresh1, S.J Barker1, P. Williams1, time between magma interactions and ascent O. Buchanan1, K. Sutton1, N. Gampbell1, J. to eruption. This often requires a good Howarth2, T. Cross3, J. Hellstrom4, K. Clark5, understanding of the major and minor D. Hikuroa1, J.V. Rowland1, A. Hartland6, J.A. element transfer between two magmas. While Baker1 such element transfer has been well studied 1University of Auckland, PB92019, Auckland and applied over a range of magmatic 2Victoria University of Wellington, P.O. Box compositions, very little work has explored the 600 3 transfer of volatiles (H2O, CO2, Fl, Cl, S) Waitomo Gloworm Caves, Waitomo between two magmas. This is important 4University of Melbourne because one of the first and least equivocal 5GNS Science, PO Box 30368, Lower Hutt signs of an impending eruption are derived 6University of Waikato, PB3105 from active fumaroles. Therefore, we must [email protected] understand the effect of mixing on degassing, which in turn will significantly aid in eruption A record of past large earthquakes in NZ is forecasting. essential for robust forecasting of future events. Current records are limited to the To examine the transfer of volatiles between recent past (last few thousand years) due to magmas, we analyse a sample from the 1976- imperfect preservation of paleoearthquake 2000 eruption episode at White Island where evidence in NZ’s dynamic landscape. Many there is clear evidence of mixing between a uncertainties remain around long-term basalt and the volumetrically dominant dacite earthquake recurrence intervals, as well as magma. Using a novel SIMS measurement temporal sub-centennial clustering of large approach that scans across an area of ~ 30 earthquakes. We will develop a new tool for µm2, we measure the volatile content of each detecting and dating paleo-earthquakes that major volatile element across many disparate should extend records back in time by more mingled glass patches. We then use these data than an order of magnitude, and to places of 56 low modern-day seismicity, where the Detrital thermochronology is a novel approach likelihood of large earthquakes remain to interpret the pace, pattern and history of unknown. The tool is based on field, rock exhumation in sedimentary source areas geochronological, and geochemical from the cooling history of detrital minerals in investigations of cave deposits (i.e., sedimentary samples. Extensive speleothems) found throughout NZ. We thermochronologic analyses of bedrock hypothesize that speleothems will record terranes make the Southern Alps an ideal large earthquakes by: (1) strong shaking either setting to apply detrital thermochronology in causing speleothems to break, fall to the cave exciting new ways. We present two floor and cease growth, or alternatively applications of detrital thermochronology to preserve irregularities in their columnar explore the evolution of this unique New growth structure; (2) disruption of the cave’s Zealand landscape. hydrological system and water flow/chemistry. Dating of the tips of broken or Our first application exploits a predictable irregularly grown speleothems and abrupt relationship between apatite fission-track geochemical anomalies in them may be able cooling age and southeastward distance to greatly refine and extend NZ paleo-seismic across the Southern Alps to trace sediment records, over timescales up to hundreds of provenance in six east-draining river thousands of years. We will ground-truth this catchments. In all six rivers, apatite fission- methodology by documenting the effects track cooling ages do not reflect a provenance caused by the 2016 Mw 7.8 Kaikoura consistent with long-term (~106 yr) patterns of earthquake on nearby caves, and search for rock exhumation. Instead, cooling age similar “damage” in other cave sites distributions are better explained by storage throughout NZ that can be compared with and destruction of apatite grains within the older, conventional paleo-earthquake records river network. This observation contrasts with at those sites. Ultimately, this method may similar “tracer” thermochronology of late make it possible to greatly extend the paleo- Pleistocene offshore glacial deposits, seismic history of much of NZ and assess if and suggesting that intermontane sediment how often large earthquakes occur, for dynamics may vary with high frequency example, in the upper North Island. climate signals like Quaternary glacial cycles.

Our second example reconstructs the DETRITAL THERMOCHRONOLOGY IN THE exhumation history of the Southern Alps from SOUTHERN ALPS: NEW INTERPRETATIONS proximal basin deposits. We present new OF SEDIMENT DYNAMICS AND detrital fission-track results from Miocene- EXHUMATION HISTORY Pleistocene units in Mackenzie and Canterbury basins along with ~9-1 Ma samples K. A. Lang1,2, U. Ring1, P. Kamp2, T. Ehlers3 from Waiho-1 borehole cuttings. The absence 1Department of Geological Sciences, of reset detrital apatite fission-track cooling Stockholm University, 10691 Stockholm, SE ages in eastern exposures of the Pliocene 2Department of Earth Sciences, University of Kowai Formation constrain a maximum ~2-4 Waikato, 2001 Hamilton, NZ km pre-Quaternary exhumation east of the 3Department of Geosciences, University of drainage divide, suggesting that Quaternary Tübingen, 72074 Tübingen, DE glaciation may account for 50-85% of the total [email protected] exhumation of the eastern mountain flanks. Preliminary detrital zircon fission-track 57 analyses from the Waiho-1 borehole suggest and almost certainly link in a complex fashion. that exhumation of the zircon partial From SW to NE, i.e. following the propagation annealing zone occurred between ~9 and 4 of these ruptures, the Jordan Thrust (dextral- Ma, prior to the earliest observations of Haast normal in 2016) overlaps the dextral-reverse schist fragments. Ongoing analyses will slip Kekerengu Fault near George Stream. In continue to paint a more detailed picture of an this same area, surface slip on the reverse- evolving Southern Alps landscape. sinistral Papatea Fault approaches and almost intersects the Jordan Thrust at a high angle. To close the triangle, the reverse-sinistral THE ROLE OF SURFACE-RUPTURING FAULTS Waiautoa Fault links the Papatea with the IN THE ‘WAIAUTOA MICRO-BLOCK’, Kekerengu Fault. The Waiautoa Fault is CLARENCE VALLEY, DURING THE MW 7.8 2016 partially concealed as it is followed by the KAIKOURA EARTHQUAKE Clarence River. Assessment of piercing line markers indicates that co-seismic surface slip R.M. Langridge1, J. Rowland2, P. Villamor1, increases to the NE along the Jordan, and is W.F. Ries1, J. Kearse3, T. Little3, E. Nissen4, N. largely conserved north of George Stream Litchfield1, C. Gasston2, B. Hall2, A. Canva2, A. across the Waiautoa triangle as the Jordan, Hatem5, R. Zinke5 Kekerengu and Waiautoa faults share and 1Active Landscapes, GNS Science, PO Box 30- exchange 8-10 m of surface slip. Seismological 368, Lower Hutt, New Zealand data indicates that rupture of the Papatea 2Dept. of Earth Sciences, University of Fault lagged those of the Jordan-Kekerengu Auckland, New Zealand faults which provides some indication of the 3Dept. of Earth Sciences, Victoria University role of the Papatea Fault and Waiautoa of Wellington, New Zealand triangle in the Kaikōura Earthquake 4School of Earth and Ocean Sciences, Victoria University, British Columbia, Canada 5Dept. of Earth Sciences, University of ELEMENTAL VARIATIONS IDENTIFIED IN Southern California, Los Angeles, California WELL POHOKURA SOUTH-1, TARANAKI USA BASIN, USING A PORTABLE X-RAY FLUORESCENCE DEVICE (pXRF) Post-seismic geodetic models highlighted the intersection and roles of the transpressive M.J.F. Lawrence Jordan, Kekerengu and Papatea faults, which GNS Science, 1 Fairway Drive, Avalon, P O Box form a high angle fault intersection in 30368, Lower Hutt association with the largest fault slips in the [email protected] 2016 Mw 7.8 Kaikōura Earthquake. The ‘Waiautoa triangle’ refers to the intersection Chemostratigraphy is a technique that has area between these faults and is further been used relatively commonly overseas in defined by minor ruptures of the Fidget and petroleum wells to characterize monotonous Waiautoa faults. These faults define a cluster sandstone or mudstone successions that lack of micro-blocks that transfer >10 m slip across biostratigraphic or seismic markers. Normally, from the Seaward and Kekerengu blocks to the relatively time-consuming and potentially Papatea Block, over an area of 2.5 km2. expensive laboratory-based ICPMS or XRF Detailed field observations and post- analyses are used. This study is a preliminary earthquake LiDAR mapping indicate that these determination of the applicability of the five faults that ruptured to the ground surface comparatively quick and inexpensive pXRF for 58 chemostratigraphy. Well Pohokura South-1 Göttingen, 37077 Göttingen, Germany was chosen as a case study as it contains good 3School of Biological Sciences, The University quality wireline logs including borehole of Adelaide, Australia images, 94 m of core, and a full suite of 4GNS Science, PO Box 30368, Lower Hutt cuttings. All the washed cuttings were [email protected] analysed, and the conventional core was analysed at approximately 1 m intervals using Araucarian forest trees have a continuous pXRF. Repeat analysis of a selection of samples record in from the Late Cretaceous through and two NIST standards indicated good the Cenozoic to the living Agathis australis precision, with accuracy increasing for heavier forests of northern North Island Araucarian elements. Detection limits meant a number of wood with anatomical preservation is present potentially useful elements (e.g. Cr, Cd, Ta) at several localities of Paleocene, Eocene, were not detected. Initial results show good Oligocene and Miocene age. Araucarian agreement between cuttings and core foliage is known from several Late Cretaceous acquired over the same depth interval. sites, and leaves of Agathis with cuticl occur at Geochemical trends with depth for several some Oligocene-Miocene sites. The earliest elements (e.g. Si, Ti, Ca, Mg, Fe, K, V, Rb, Nb, sites with amber are Late Cretaceous and Y, Zr) matched some known stratigraphic droplets, layers and blocks of amber occur in boundaries, but also indicated heterogeneity lignite, sandstone and mudstone from within formations, probably reflecting factors Cenozoic sites throughout New Zealand. such as weathering, provenance and Commonly bubble-filled and opaque, the diagenesis. Identification of geochemical amber was considered devoid of fossils. variations indicates the possibility for However, methodical screening of several subdivision of some stratigraphic zones thousand samples, combined with new resulting in higher resolution correlations preparation techniques, has revealed many between wells. In addition, results could aid in three-dimensionally-preserved organisms and the characterization of heterogeneity in considerable biological and ecological reservoirs and seals. Results to date support complexity. Most inclusions represent new use of the pXRF for fast and relatively precise species and some represent the first global acquisition of geochemical data. Such data fossil records at genus and subfamily level. could be obtained shortly after core or There is an impressive diversity of arthropod cuttings acquisition, and be used as input for fossils, including species from the arachnid ongoing drilling operations. orders Acari, Araneae and Pseudoscorpiones and at least 14 families of Hexapoda in the orders Collembola, Hemiptera, Psocoptera, A 70 M.Y. LONG RECORD OF ARAUCARIAN Hymenoptera, Coleoptera, Lepidoptera, and FORESTS IN ZEALANDIA: WOOD, LEAVES, Diptera, together with nematodes (soft- POLLEN, AND INCLUSIONS bodied soil and litter metazoans) and a variety of mould fungi. Ecologically, the organisms Daphne E. Lee1, U. Kaulfuss1, A. Schmidt2, include predators such as spiders (including J.G. Conran3, J.M. Bannister1, J.K. Lindqvist1, web remains with prey), tiny carnivores such M.R. Vanner1, E.M. Kennedy4 & D.C. as pseudoscorpions, diverse soil-dwelling Mildenhall4 mites, detritivores such as springtails, biting 1Department of Geology, University of Otago, and gall midges, fungus gnats and PO Box 56, Dunedin chironomids, parasitoid and other wasps, 2Department of Geobiology, University of ants, carpet and other beetles, bark lice and 59 lepidopteran wing scales. This is the first major programme. These data shed new light on the amber deposit with an abundance of tempo, style and hazards of eruptions from biological inclusions from the Southern the four supereruptions (Ongatiti, Kidnappers, Hemisphere and the first of confirmed Whakamaru, Oruanui) and the smaller but araucarian origin. These fossils expand the more frequent magmatic (millennial) and global record and evolutionary history of hydrothermal (decadal) eruptions. many arthropod and fungal groups, providing new insights into antecedents of the modern We have identified periods of caldera-forming New Zealand terrestrial biota. flare-ups, most recently from ~350 ka for >70 kyrs. In addition, previously unrecognised eruptive units have been identified and dated THE LIFE AND TIMES OF CENTRAL TVZ: from geothermal fields, and fitted into the 15 YEARS OF MAPPING AND regional stratigraphic system. There appears GEOCHRONOLOGY ILLUMINATE to be both spatial and temporal clustering of EARTH’S MOST PRODUCTIVE SILICIC SYSTEM smaller explosive and effusive eruptions, both following and apparently unrelated to caldera G.S. Leonard1, A.T. Calvert2, C.J.N. Wilson3, events. There is a spatial link of some B.F. Houghton4, D.B. Townsend1, M.A. Holocene vents with current shallow (~5km Lanphere2, J.G. Begg1, D.M. Gravley5, D.T. depth) areas of possible magma accumulation Downs2, P. Villamor1, J.V. Rowland6, M.D. (e.g. Rotokawa), and yet other areas of similar Rosenberg7, B.L.A. Charlier3 low resistivity and high heat flow (e.g. 1GNS Science, P.O. Box 30-368, Lower Hutt, Kapenga) are apparently un-associated with New Zealand young eruptions. There is clear temporal 2U.S. Geological Survey, 345 Middlefield variability in faulting of the Taupo Rift, Road, Menlo Park, CA 94025, USA including episodic narrowing, and sudden 3Victoria University, P.O. Box 600, Wellington, step-overs linked to caldera flare-ups. The New Zealand rates of post-caldera volcanic and 4University of Hawai’i, 1680 East-West Road, sedimentary infilling are remarkably rapid Honolulu, Hawai’i 96822, USA (kilometres thickness in tens of thousands of 5University of Canterbury, Private Bag 4800, years) and the distal landscape responses to Christchurch, New Zealand convulsive volcanic-induced sedimentation 6University of Auckland, Private Bag 92019, have been equally dramatic. Auckland 1142, New Zealand 7GNS Science, Private Bag 2000, Wairakei, Substantial multi-agency planning of New Zealand responses and communication during future [email protected] eruptive activity is underway but preparedness is challenging because of the Central Taupo Volcanic Zone represents (in its extremely diverse behaviour shown within overall evolution) a single rhyolitic caldera this unique area. Future hazards are not complex of comparable longevity and scale to confined to past caldera locations, but the Yellowstone volcanic system. It also has the modern caldera volcanoes dominate largest time-averaged rhyolite eruption rate questions from both public and emergency on Earth over the last ~25 ka. We present an managers. overview of results and discoveries obtained from 120 new 40Ar/39Ar ages combined with a decade of regional mapping for the QMAP 60

UNCOVERING LONG-RUNOUT PYROCLASTIC at distances >20 km from the summit of the FLOWS USING PALAEOMAGNETISM AT MT volcano extends their known range at Mt TARANAKI Taranaki by at least 5 km. These findings could have a significant impact on hazard mapping G.A. Lerner1 S.J. Cronin1 & G.M. Turner2 and emergency planning for the Taranaki 1School of Environment, University of region. Auckland 2School of Chemical and Physical Sciences, Victoria University of Wellington 20 YEARS OF CAMPAIGN AND CONTINUOUS [email protected] GPS ACROSS THE CENTRAL SOUTHERN ALPS – TIME-SERIES AND MODELLING Knowing the spatial distribution of different hazards at stratovolcanoes is vital for D. Lindsay1, S. Hreinsdóttir2 & J. Townend1 understanding which hazards represent a 1SGEES, Victoria University of Wellington, PO threat to different areas surrounding the Box 600, Wellington 6012 volcano. An important part of this is 2GNS Science, Lower Hutt, New Zealand understanding the conditions under which [email protected] deposits from the volcano were emplaced. The coherence of paleomagnetic directions in Previously published profiles of velocity and different parts of the blocking temperature strain spanning the Alpine Fault have been spectrum between the clasts of mass flow used to examine the fault’s geometry and to deposits has proven to be a useful tool for model the kinematics of the plate boundary ascertaining emplacement temperatures. zone. As part of a BSc (Hons) study, we are These temperature estimates can help in analysing data from a profile extending from distinguishing between hot pyroclastic density Methven to Hokitika and crossing the Alpine currents (PDCs) and cold lahars, which cannot Fault just south of the Hope Fault intersect. always be done definitively by field This profile provides an opportunity to observation. In the case of more clast-poor compare along-strike changes in the fault’s distal deposits, however, it can be difficult to geometry and kinematics, and to examine obtain sufficient clast material for effective how the current distribution of geodetic paleomagnetic study. In this study, the stations constrains fault slip inversions: are we problem was remedied by using oriented and taking measurements in the right places? Data strengthened samples of matrix material from from three continuous GPS sites were used to mass flow deposits in the ~11,500 BP Warea constrain the displacement of ten campaign Formation from Mt. Taranaki, New Zealand. GPS sites measured between 1997 and 2017. Paleomagnetic data from matrix samples was GPS processing was completed using used to supplement the limited data obtained Gamit/Globk processing flows. Annual and from the traditional clast analysis in order to semi-annual signals were removed from the determine the emplacement temperature of data and corrections made for co-seismic and the deposits. Comparison of paleomagnetic post-seismic displacements. The fault-parallel directions obtained from clast and matrix (shear) and fault-normal (shortening) samples at several sites within the Warea components of the velocity field have been Formation revealed it as a PDC with matrix calculated in both absolute and relative temperatures over 200°C and clasts reaching reference frames. This study has produced temperatures of up to 410°C at their time of horizontal and vertical inter-seismic velocity deposition. This discovery of hot PDC deposits fields to be used to evaluate the fault’s 61 geometry and slip rate. A 2D elastic half-space assessment. Beyond the science itself, over dislocation model will be used to describe the the years DEVORA has supported tens of fault plane, locking depth where the profile postgraduate students and researchers in crosses the Alpine Fault. New Zealand, and has forged strong relationships, not only between scientists across disciplines, but across the scientist- TEN YEARS OF DETERMINING VOLCANIC stakeholder divide. In particular, its RISK IN AUCKLAND stakeholder-based governance structure ensures DEVORA research findings continue to J. Lindsay1, G. Leonard2, N. Deligne2, T. strengthen the foundation for key decision- Wilson3, R. Smith4, R. Roberts5, E. Smid1 making in any preparation for and response to 1School of Environment, University of a future AVF eruption or ash fall event from Auckland, Auckland distal volcanic eruptions. 2GNS Science, PO Box 30-368, Lower Hutt 3Department of Geological Sciences, University of Canterbury, Christchurch GLACIAL-INTERGLACIAL PRODUCTIVITY AT 4Earthquake Commission (EQC), Wellington THE POLAR FRONT, SOUTHWEST PACIFIC 5Auckland Council, Auckland SECTOR OF THE SOUTHERN OCEAN [email protected] M. Liston1, H. Bostock2, G. Dunbar3 & M. The Determining Volcanic Risk in Auckland Harper1 (DEVORA) research programme was launched 1SGEES, Victoria University of Wellington, PO in 2008 as a multi-agency, transdisciplinary Box 600, Wellington effort with a mandate to investigate the 2NIWA, PO Box 14-901, Wellington Auckland Volcanic Field (AVF), a (mostly) 3Antarctic Research Centre, Victoria monogenetic volcanic field that spatially University of Wellington, PO BOX 600, coincides with Auckland, New Zealand’s most Wellington populous city. With DEVORA approaching its [email protected] tenth anniversary, it is timely to reflect back on the impacts of its research, its challenges The Southern Ocean plays a major role in and lessons learned over the last decade. Here global climate through redistributing heat and we discuss how volcanic hazard and risk nutrients into all the major oceanic basins and research, specific to Auckland and also more regulating ocean-atmosphere CO2 exchange. generically, is used to evaluate volcanic risk for Previous research from the Southern Ocean Auckland, and how DEVORA findings are used has shown evidence of changes in biological by emergency managers and policy and productivity, the so called “biological pump”, decision makers to prepare the city for a over glacial-interglacial timescales. It has been future volcanic eruption. We describe how the suggested that this change in productivity, DEVORA team is developing and populating a along with changes in ocean circulation, has a suite of volcanic fragility functions quantifying significant influence on modulating damage, loss of functionality, and clean up atmospheric CO2 draw-down, and thus from basaltic eruptions expected in Auckland. represents a key component in facilitating We explain how these, along with hazard glacial-interglacial global climate change. intensity maps, are being used to evaluate impacts from a range of scenarios, and how Two marine sediment cores collected from the we are moving towards probabilistic risk Polar Front, south-west of New Zealand, have 62 provided a new high resolution elemental detection. Whole (unopened) lake sediment record measured by XRF. These are combined cores totalling 34.7 m in length from three with stable isotopes, radiocarbon dates, Waikato lakes (Kainui, Ngaroto, and carbonate and opal content, ice-rafted debris Rotokauri) formed c. 21,000−23,000 cal. years (IRD) counts and diatom assemblage analysis. ago were scanned in one afternoon using a Preliminary age modelling suggests these medical X-ray computed tomography (CT) marine records extend back to Marine Isotope scanner at Hamilton Radiology. Volume Stage 8 (~275ky). The data show a progression reconstructions and image analyses using the of abrupt elemental changes, which agree Fiji package of ImageJ software revealed with peaks in IRD and shifts in plankton. This numerous cryptotephra deposits, significantly data will be compared with previous work increasing the number of observable deposits from the Southern Ocean to understand compared with findings from descriptive logs reorganisations of biological productivity and and associated photographs of the same cores ocean circulation, and their relationship to when opened. The use of X-ray CT scanning glacial-interglacial climate change. and image analyses can be used to inform a more targeted approach to core sampling in cryptotephra studies, ultimately aiding the RECONNAISSANCE AND DETECTION OF construction of more detailed histories of CRYPTOTEPHRAS IN ~20,000-YR-OLD LAKE ashfall events. Together with spatial SEDIMENTS, WAIKATO REGION, USING CT information, these enhanced frequency SCANNING records enable probabilistic modelling for future events to be evaluated more R.C. Loame1, D.J. Lowe1, A. Pittari1, S.M. realistically, thereby supporting the Davies2, C.R. Magill3, M.J. Vandergoes5, development of appropriate management A.B.H. Rees6, A. Harpur1 & N. Ross7 strategies for ashfall hazards and potential impacts in the region. 1School of Science, University of Waikato, Private Bag 3105, Hamilton 2Dept. of Geography, Swansea University, CT AND MICRO-CT SCANNING OF LIQUEFIED Singleton Park, Swansea, Wales SA2 8PP TEPHRA DEPOSITS IN ~20,000-YR-OLD LAKE 3Dept. of Environmental Sciences, Macquarie SEDIMENTS, WAIKATO REGION University, St Leonards, NSW 2065 5GNS Science, P.O. Box 30368, Lower Hutt Remedy C. Loame1, D.J. Lowe1, R. Johnston2, 5040 E. Evans2, A. Pittari1, V.G. Moon1, S.M. 6School Geogr, Environ, Earth Sci., Victoria Davies3, C.R. Magill4, M.J. Vandergoes5, Univ. Wellington, Box 600, Wellington 6140 A.B.H. Rees6 & Nic Ross7 7Hamilton Radiology, Gate 1, Thackeray 1School of Science, University of Waikato, Street, Hamilton 3204 Private Bag 3105, Hamilton 3240 [email protected] 2College of Engineering, Swansea University, Swansea, Wales SA1 8EN The study of cryptotephras (volcanic glass 3Dept. of Geography, Swansea University, shard and/or crystal deposits insufficiently Singleton Park, Swansea, Wales SA2 8PP concentrated or numerous to be visible as a 4Dept. of Environmental Sciences, Macquarie layer to the naked eye) is complicated by University, St Leonards, NSW 2065 difficulties in finding time-efficient, cost- 5GNS Science, P.O. Box 30-368, Lower Hutt effective, non-destructive methods of 5040 63

6School Geogr, Environ, Earth Sci., Victoria millimetres thick, hence possible local seismic Univ. Wellington, Box 600, Wellington 6140 events have not been recorded in the form of 7Hamilton Radiology, Gate 1, Thackeray SDSS because these tephras lack the required Street, Hamilton 3204 physical properties. [email protected]

Soft-sediment deformation structures (SSDS) PRE- AND SYN-ERUPTIVE PROCESSES can record evidence of the liquefaction and VISUALIZED THROUGH SEMI-AUTOMATIC fluidisation of deposits. The use of X-ray CRYSTAL SIZE DISTRIBUTION ANALYSIS OF computed tomography (CT) and micro-CT to MICROLITES FROM TONGARIRO VOLCANIC scan unopened lake sediment cores offers a CENTRE TEPHRAS, NEW ZEALAND way to reconstruct the volume of the disrupted tephra deposits within, capturing C. Lormand1, G. F. Zellmer1, N. Sakamoto2, K. structural features which may not be readily Nemeth1, G. Kilgour3, A. S. Palmer4 observable in a cut core. Cores from three 1Volcanic Risk Solutions, Massey University, Waikato lakes (Ngaroto, Kainui, Rotokauri) PO Box 11222, Palmerston North formed ~21,000−23,000 cal. BP were scanned 2Isotope Imaging Laboratory, Hokkaido using medical CT at Hamilton Radiology, and a University, Sapporo 060-0810, Japan segment of core from Lake Rotokauri was 3GNS Science, Wairakei Research Centre, PO scanned using the micro-CT facility at Swansea Box 2000, Taupo University. 3D-volume reconstruction of the 4Department of Soil Science, Massey cores using Fiji/ImageJ revealed that multiple University, PO Box 11222, Palmerston North tephra deposits (not the enclosing organic lake [email protected] sediment) display SSDS, including injection structures, dish structures, voids, and Crystal Size Distributions (CSDs) of microlites disrupted internal bedding. Disrupted tephras in volcanic rocks have become a useful tool to (‘tephra seismites’) include Tuhua (7641 ± 102 assess and estimate timescales of pre- and cal. BP), Mamaku (7992 ± 58 cal. BP), Waiohau syn-eruptive processes such as nucleation, (14,018 ± 91 cal. BP), Rotorua (15,738 ± 263 growth and ascent at the onset of explosive cal. BP), and Rerewhakaaitu (17,209 ± 249 cal. eruptions. So far, a time-consuming manual BP). The presence of non-disrupted tephra method is used to outline crystals, and thus deposits in the same cores gives temporal generate CSDs, from back-scattered-electron constraints to the SDSS. The SDSS therefore (BSE) images. The Tongariro Volcanic Centre are probably the result of episodic seismic (TgVC), which includes Ruapehu, Ngauruhoe shaking on one or more hidden faults and Tongariro volcanoes, has produced identified near the lakes in the Hamilton Basin, historical explosive eruptions of different or on faults associated with the distant eruptive styles. A semi-automatic method for Kerepehi Fault system in the Hauraki Basin, or selecting microlites based on BSE images using both. CT analysis of the tephra seismites in the a tool combining machine learning and image lake cores provides a new tool for segmentation was employed on four tephra palaeoseismology. The CT results, together formations from TgVC. CSDs of plagioclase and with historical core records for a further 9 pyroxene microlites from individual glass lakes, suggest that at least five palaeoseismic shards of each tephra are computed, events have occurred in the Hamilton Basin compared, and combined to obtain total since c. 17,000 cal. BP. After ~7600 cal. BP, tephra CSDs. Manual and semi-automatic tephras occur in the lakes as layers only a few CSDs for the same grains overlap, and the 64 method used in this study acquires CSD Cambridge MA 02138, USA considerably faster than the classic one. A 6School GeoSciences, Grant Inst Earth Sci., hundred and seventy nine CSDs were Univ. of Edinburgh, Edinburgh EH9 3JW, UK generated, and CSDs from the same tephra [email protected] were combined. All combined CSDs exhibit concave-up shape, similar intercepts and Correlations between tephra or cryptotephra slopes at the smallest sizes and thus similar deposits are testable hypotheses, subject to growth durations: from 22±15 (2σ) to 68±48 continual revision with expanded datasets. (2σ) hours for plagioclase and from 13±9 (2σ) Consequently, the strongest correlations are to 29±20 (2σ) hours for pyroxenes. The semi- those that show concordance between automatic method used in this study provides multiple independent datasets, including for fast-computing of CSDs. Also, the short lithostratigraphic, palaeoenvironmental or timescales of microlite growth obtained archaeological data, chronological data, and appear to overlap for both plagioclase and mineralogical and geochemical evidence. In pyroxene regardless the eruptive style or effect, prior correlations proposed on the source. We conclude that volcanic eruption basis of age equivalence are tested by style within the TgVC is independent of examining potential correlatives suggested by magma ascent time in the conduit prior to mineralogical variations or by compositional eruption. If more explosive eruptions are due variation within the glass or to more rapidly ascending magmas, they are crystal/phenocryst phases of tephra deposits, sourced from greater depth in the plumbing or by dating materials associated with the system. Comparison with experimental tephras. Statistical methods provide a less petrological data may provide additional subjective means of dealing with data constraints on physical parameters such as pertaining to tephra components than decompression rate and depth of alternative methods. They enable a better crystallization. understanding of relationships among the data to be developed from multiple viewpoints, and help to quantify the degree of ARE NUMERICAL AND STATISTICAL uncertainty in establishing correlations. In METHODS THE PANACEA FOR CORRELATING applying statistical methods to establish TEPHRAS OR CRYPTOTEPHRAS USING sample equivalence or difference, however, all COMPOSITIONAL DATA? methods have some degree of limitation. Furthermore, using statistical analysis of D.J. Lowe1, N.J.G. Pearce2, M.A. Jorgensen3, compositional data, it is easier to prove a S.C. Kuehn4, C.A. Tryon5 & difference between two samples than it is to C.L. Hayward6 prove they are the same. A two-stage 1School of Science, University of Waikato, approach to statistical correlation has been Hamilton 3240 useful in recent times, the first stage being to 2Dept. Geog. & Earth Sciences, Aberystwyth identify the main data structure via simple but University, Aberystwyth SY23 3DB, UK useful scatterplot matrices (bivariate plots) 3Dept. of Math. Sci., Auckland Univ. of before undertaking statistical distance Technology, Private Bag 92006, Auckland measures, SCs, hierarchical cluster analysis, 1142 and PCA. Some of these methods are also 4Department of Physical Science, Concord called machine learning. The second stage University, Athens WV 24712, USA typically examines sample variance and the 5Dept. of Anthropology, Harvard University, degree of compositional similarity. This stage 65 may involve DFA, CVA, and analysis of variance and imprecise ages on Tuhua from ~7100 to (ANOVA) or MANOVA (or its two-sample ~6600 cal. BP. Here we use a new approach to special case, the Hotelling two-sample T2 test). dating it by applying a key principle of Various transformations and scalings may be tephrochronology to Bayesian modelling: applied to compositional data prior to tephras are erupted and deposited effectively subjecting them to multivariate statistical instantaneously forming isochrons so that a procedures such as the calculation of distance primary tephra has an identical age matrices, hierarchical cluster analysis, and everywhere it occurs. We modelled ~50 14C PCA. Such transformations may make the dates, together with ages on nine interbedded assumption of multivariate normality more tephras, in three peat cores from each of appropriate. Kopouatai and Moanatuatua bogs in Waikato to attain an age for Tuhua Tephra, which occurs in all six cores. In applying the Bayesian RE-DATING TUHUA TEPHRA, A KEY MID- P_sequence routine of OxCal, the Tuhua HOLOCENE MARKER BED IN NORTHERN Tephra was cross-referenced (set as being the NEW ZEALAND, USING AN ISOCHRON- same event) in each of the cores, thus INFORMED BAYESIAN AGE MODELLING modelling was ‘isochron informed’. Using APPROACH SHCal13, the isochron-informed modelling yielded a new age for Tuhua Tephra of 7641 ± D.J. Lowe1, A.B.H. Rees2, R.M. Newnham2, 100 cal. BP (2-sigma), older and more precise Z.J. Hazell3, M.J. Gehrels4, than previous estimates. A similar age (~7630 D.J. Charman5 & M.J. Amesbury5 cal. BP) was obtained using P_sequence 1School of Science, University of Waikato, modelling whereby independent ages on Private Bag 3105, Hamilton 3240 Tuhua were estimated for each core without 2School Geogr, Environ, Earth Sci., Victoria cross-referencing and then amalgamated Univ. Wellington, Box 600, Wellington 6140 using Combine. Finally, using the 3Historic England, Fort Cumberland, Fort independently-modelled age distributions, we Cumberland Road, Portsmouth, PO4 9LD, UK defined Tuhua deposition as a ‘Phase’ set 4Environment Department, University of between start and end ‘Boundaries’, and then York, York YO10 5DD, UK used OxCal’s Difference function to estimate 5Physical Geography, College Life & Environ. the ‘Phase’ duration across cores (it should be Sci., Univ. of Exeter, Exeter, EX4 4SB, UK zero years based on tephrochronology): it [email protected] ranged from 0‒730 years (95.4% confidence- interval), mean 277 years, but reassuringly Tuhua Tephra, a distinctive peralkaline was markedly skewed towards zero eruptive from Mayor Island, forms a unique (instantaneous). chronostratigraphic marker bed for the Holocene of North Island and offshore. Its deposition coincided with the Holocene relative sea-level highstand ~8000‒7000 cal. BP when present sea-level was first attained. Deriving an accurate age for Tuhua Tephra is therefore a priority for palaeoenvironmental applications and volcanology. Bayesian age- modelling of the Kaipo bog sequence in eastern North Island generated contradictory 66

TEREBRATULIDE BRACHIOPODS FROM THE cosmopolitan and widely distributed. EARLY JURASSIC OF ZEALANDIA Loboidothyris is also cosmopolitan, but has a Tethyan aspect. Tegulithyris and Rugithyris are D.A.B. MacFarlan Tethyan, but less widely distributed. MacFarlan Geological Services Ltd, 13 Fairfax Linguithyris is also known from southern Terrace, New Plymouth 4310 Europe, North Africa and western Asia. [email protected] The fauna in general is cosmopolitan or weakly New Zealand and New Caledonian Early Tethyan. It follows the distinctive endemic Jurassic terebratulides have received little faunas that preceded the end- attention from palaeontologists, with only two extinctions, and is replaced after the Toarcian species described to date. In this study, a total event by a more strongly Tethyan fauna. of seven genera and ten species are recognised. TECTONIC EVOLUTION OF THE LATE Most of the material belongs to four genera. CRETACEOUS TO EARLY PALAEOCENE Lobothyris is present throughout the GREYMOUTH BASIN, WEST COAST Aratauran and Ururoan. Loboidothyris is common in the late Aratauran and early M. Maitra and K.N. Bassett Ururoan of the Hokonui Hills. Zeilleria first Department of Geological Sciences, appears with Zeilleria spiculata in the narrow University of Canterbury, Private Bag 4800, zone along the Otapirian-Aratauran boundary Christchurch in the Hokonui Hills. A further species is found [email protected] throughout the later Aratauran and Ururoan, and two more species have restricted The Greymouth Basin, in which the thick stratigraphic and geographic ranges. The sequence of Paparoa Coal Measures (PCM) sulcate Aulacothyris is represented by one was deposited, is part of the same Late Aratauran form, known from Ben Bolt in the Cretaceous to Early Palaeocene rift-tectonics Hokonui Hills and the coast north of along the West Coast that produced the Marokopa. Loboidothyris, Zeilleria and Taranaki Basin. The goal of this paper is to Aulacothyris are also found in the Middle and understand the subsidence history and basin Late Jurassic. evolution through time as recorded in the facies in the PCM. Isopach maps, a basal PCM The other three genera are known from a few unit map and a fence diagram of detailed localities in New Zealand and New Caledonia. facies correlations have been used in this Linguithyris agerorum was described from a research. single specimen from near Port Waikato. Three further specimens from New Caledonia The fence diagram indicates the half graben have now been found. Two genera are geometry of the Greymouth Basin and recorded for the first time in Zealandia. The illustrates three alternating fluvio-lacustrine Tethyan Tegulithyris is known from the late sequences from Late Cretaceous to Early Aratauran and Ururoan of Kawhia, and Paleocene. Braided river conglomerates are Rugithyris from two Ururoan localities in the restricted to the north-west. The deposition of Awakino area. meandering fluvial systems with scattered abandoned channel coals indicates a slow to Lobothyris, Aulacothyris and Zeilleria are moderate subsidence rate across the basin. 67

These are overlain by raised mire coals and hundred and sixteen sites were sampled at then by lacustrine mudstones in a three depths: O-depth (0-2 cm), A-depth (2-20 transgressive sequence suggesting an increase cm) and B-depth (50-70 cm). A modified aqua in subsidence rate rather than an increase in regia digest on the sub-180 µm fraction was rainfall since palaeontology studies indicate analysed by inductively coupled mass no climate change during that time. Lacustrine spectrometry (ICPMS), X-ray fluorescence and mudstones onlap braided river conglomerates LECO Analyser methods. Two additional, infill as well as thicken and widen upsection. surveys were conducted. One targeted West Isopach maps of the lacustrine units show that Dome and the other the Shotover area. The older units comprise several isolated smaller former took samples from an additional 83 lakes which later connect and become wider sites on a 2 km spaced grid from the north of through time expanding toward the west. The Mossburn to the Mararoa River. It targeted basal PCM unit map shows that the ultramafic, mafic igneous and sedimentary conglomerates step westward through time rocks of the Dun Mountain-Maitai Terrane with ever younger PCM members sitting which are perspective for platinum group directly on basement. metals. The Shotover survey took samples from 63 additional sites on a 4 km spaced grid The results suggest that the Greymouth basin covering the area between Glenorchy in the evolved from small sub-basins that widened west through the Cardrona valley in the east and deepened through time via small- including large parts of the Shotover, displacement normal fault segments which Motutapu and Arrow river catchments and the became progressively more connected until Richardson and Harris Mountains. The survey they formed a major border fault. This fault area is underlain by Otago Schist, particularly gave rise to the large half graben basin and by the Aspiring Lithologic Association of the was responsible for the lateral and vertical Rakaia Terrane and is prospective for Au, Sb facies changes across the basin. and W mineralisation. Together with the Southland-southern Otago survey (completed 2015), this constitutes the single largest, A GEOCHEMICAL BASELINE SOIL SURVEY systematic soil survey in New Zealand and OVER OTAGO-NORTHERN SOUTHLAND forms the template for completing other, regional surveys (e.g. Westland) and the A.P. Martin1, M.S. Rattenbury2, D.T Strong2 template for a survey of national coverage. & R.E. Turnbull1 1 GNS Science, Private Bag 1930, Dunedin NZ 2 GNS Science, PO Box 30-368, Lower Hutt NZ A SPATTER-RICH PYROCLASTIC DENISTY [email protected] CURRENT DEPOSIT FROM A NEOGENE VOLCANO, MASON SPUR, ANTARCTICA, A regional, 8-km spaced soil geochemistry SUGGESTS SIMULTANEOUS MULTI-VENT survey covering c. 20,000 km2 was undertaken ERUPTION over Otago and northern Southland. It uses include environmental assessment, mineral A.P. Martin1, L.J. Smellie2, Cooper A.F.3, & exploration, groundwater quality and regional D.B. Townsend4 geological interpretation. The survey extends 1 GNS Science, Private Bag 1930, Dunedin, north of Mossburn to Lake Hawea and from New Zealand the east coast near Hampden to Lake 2 University of Leicester, Department of Wakatipu/Mavora Lakes in the west. Three Geology, Leicester LE1 7RH, UK 68

3 Department of Geology, University of Otago, ANCIENT OF NEW ZEALAND: P.O. Box 56, Dunedin, New Zealand HOW MANY SPECIES OF PLATYDYPTES? 1 GNS Science, PO Box 30-368, Lower Hutt, New Zealand K. Matts1 & R.E. Fordyce1 [email protected] 1Department of Geology, University of Otago, PO Box 56, Dunedin Well exposed caldera interiors are uncommon [email protected] but a remarkable section through the heart of a volcanic island, Mason Spur, in the south- Penguins are uniquely adapted to aquatic life. western Ross Sea, Antarctica, is helping help Their dense, ballasting, bones predispose to elucidate interpretations of other, less well penguins to fossilise readily, contributing to exposed pyroclastic density current deposits New Zealand’s excellent fossil record. The elsewhere in Antarctica and globally. Near- Oligocene Platydyptes, first described by B.J. continuous exposure, 10 km laterally and >1 Marples, is one of the most crownward of the km vertically, at Mason Spur cuts through stem (basal) penguins and one of few Cenozoic alkalic volcanic rocks of the Erebus described Late Oligocene genera. Currently volcanic province (McMurdo Volcanic Group). there are three described species, P. The caldera filling sequence includes an novazealandiae, P. amesi and P. marplesi. unusual trachytic spatter-rich lapilli tuff Platydyptes penguins are robust; there is (ignimbrite) facies that is particularly striking some variation in size, but generally because of the presence of abundant fluidal, Platydyptes can be considered a medium sized juvenile spatter clasts of trachytic obsidian up ancient (the smallest described to 2m long supported in a pumiceous lapilli species closer in size to a than to tuff matrix. New field mapping indicates that a crested). Due to its position in penguin the deposit is an ignimbrite and, together with phylogeny, the genus needs redescription; petrological considerations, it is suggested there is also scope for functional and that mixing of spatter and lapilli tuff in the ecological studies. New Platydyptes penguins investigated deposit occurred during from Hakataramea will be used in reviewing emplacement, not necessarily in the same the genus. vent, with the mixed fragmental material emplaced as a pyroclastic density current. A key new specimen, OU 22804, is a semi- Liquid water was not initially present but a articulated partial skeleton from the Otekaike steam phase was probably generated during Limestone (Waitakian, latest Oligocene). The transport and may represent water ingested fossil also includes several rarer elements such during passage of the current as it passed over as the quadrate, mandible, and a semi- either wet ground (possibly puddled), a complete sternum. The bone preservation is stream or a shallow lake. Mapping at Mason good; for example, both coracoids are present Spur permits the study of an ancient volcanic with much of the extremities preserved. The succession that is rarely available due to taxonomically diagnostic humerus shows subsequent burial or erosion and is helping characteristics typical of Platydyptes, understand eruption dynamics associated including a small dorsal tubercle with clear with a complex large island volcano. separation from the articular surface of the humerus head. The new humerus is more robust and slightly broader than in other Platydyptes species, with a midshaft length/width ratio of 0.25 (all three named 69 species share a ratio of 0.24). Study of OU Western Dome Belt, Southwest Domes and 22804 will elucidate the structure, systematics North East Dome Complex. An additional and lifestyle of New Zealand's Platydyptes aspect will focus on identification and analysis penguins. of pyroclastic deposits within an initial time slice starting from Oruanui at 26.5 ka to the Rotoehu/Rotoiti eruptions of ~61 ka, building MAGMA INCEPTION AND THE BIRTH OF A on the existing tephrastratigraphic SUPERVOLCANO framework. To provide a more comprehensive picture of magmatic processes and evolution, Kate Mauriohooho1 & Colin Wilson1 this time slice may extend further back in time 1School of Geography, Environment and Earth to ~305 ka and correlate with existing studies Science, Victoria University of Wellington on formations from drillholes in the [email protected] geothermal fields of the northern Taupo area (e.g. Wairakei-Tauhara). Many aspects of the post-350 ka magma systems (including those at Maroa) that This study has implications for understanding erupted within the Whakamaru Caldera, prior the very earliest phases of assembling magma to the Oruanui 25.4ka eruption from Taupo for the Oruanui eruption of the Taupo super have previously been examined in detail. volcano and the tempo of these caldera However, to resolve questions on magma producing rhyolitic magma systems. evolution post-Whakamaru, including development of the Oruanui super volcano system, there is a need for glass and mineral SUBMARINE ERUPTIVE PROCESSES IN THE chemistry as well as precise ages on rhyolite BROOK STREET TERRANE lavas and pyroclastic deposits. J.F. Mawson1, J.D.L. White1 & J.M. Palin1 The study outlined here will use this data to 1Dept. of Geology, University of Otago, PO discriminate between grouped or individual Box 56, Dunedin, New Zealand magma batches and reconstruct the [email protected] configuration both temporally and spatially of the magma system or systems responsible for A sequence of volcanic and volcaniclastic rocks the chemically and isotopically distinct domes of the Brook Street terrane crops out along the and pyroclastic deposits that outcrop on the Southland coast from Howells Point, Riverton, Northern, West and Southwest margins of into Colac Bay. This sequence includes pillow Lake Taupo. This study will also establish the lavas, dikes, hydroclastic breccias, tuffs and relationship of the magmatic systems lapilli tuffs. It is well-exposed for 8 km along between Whakamaru and Maroa to strike in a section 220 m thick that reveals understand how they behave and have lateral variations in deposits of an oceanic evolved over time. island arc; such sequences are rarely studied, and provide different constraints on arc We aim to achieve this by focusing on three volcanism than the more common vertical aspects. The major aspect builds on existing sequences. Ar40/Ar39 data and existing geochemistry by providing new age data, new glass and mineral Detailed mapping, lithofacies analysis, and chemistry and new Sr isotope analyses of geochemical analysis were undertaken in dome complexes including Whakaroa, order to ascertain the eruptive processes of 70 the succession, the environment of deposition on-farm infrastructure (e.g. irrigation systems, and emplacement, the magmatic conditions, dairy sheds and woolsheds) and essential and the sequence of events. Tuffs and lapilli services provided by distributed infrastructure tuffs exhibit sedimentary structures that networks (e.g. road, electrical power, etc.) suggest subaqueous deposition by mass flows, were severely impacted. As a result, farms and bear angular pillow clasts suggesting throughout the Hurunui District have fragmentation of pillow lavas. Pillow lava piles experienced substantial on-going land use are small (4-20 m high and up to 600 m across) impacts since the initial earthquake. and closely spaced (50-600 m) with the Earthquake disaster impact studies on rural exception of one large pile (up to 120 m in areas, in particular on farms, are less common height and 2.5 km across), indicating one main compared to studies on urban areas. eruptive centre extending fingers of lava, and ‘Cascading hazards’ are often mistakenly possibly several smaller vents. Pillow lavas are included under ‘multi-hazards’ in current less common toward the western end of the literature. This interpretation over-simplifies section, and tuff grain size decreases in the the complexity of the interdependent same direction, supporting this hypothesis. networks involved. This project defines cascading hazards as a series of hazard events The whole sequence is hydrothermally altered that interlink through various triggering and metamorphosed to prehnite-pumpellyite mechanisms. The concept currently lacks a facies, so major and trace element analyses standardised definition, data collection were conducted on the freshest augite approach and impact assessment phenocrysts wherein the magmatic signal is methodology. Using examples from the likely to be preserved. These data indicate Hurunui District, the effects of cascading variable primitive island arc to MORB-like hazards on land use are explored, highlighting magma sources. The latter suggest the ongoing geohazard issues faced by rural involvement of decompression melting under communities both during and following major regions of thin lithosphere possibly earthquakes. attributable to back-arc spreading.

UNDERSTANDING THE PHYSICAL THE IMPACT OF CASCADING HAZARDS ON SEDIMENTOLOGY OF THE MADDEN RURAL LAND USE- A HURUNUI-KAIKŌURA CONTINENTAL SLOPE DISTRIBUTARY SYSTEM EARTHQUAKE SEQUENCE CASE STUDY M. Mckeown1, L. Strachan2, & A. Orpin3 J. McHale, C. Fenton & T. Wilson 1,2School of Environment, University of Dept. of Geology, University of Canterbury, Auckland, Private Bag 92019, Auckland 1142 Private Bag 4800, Christchurch 3NIWA, Private Bag 14901, Wellington [email protected] [email protected]

On November 14th, 2016, a M7.8 earthquake The Hikurangi Subduction Margin (HSM) is occurred near Waiau, Hurunui District. This arguably New Zealand’s largest earthquake earthquake, its aftershocks and related and tsunami hazard, though the uncertainty seismicity triggered cascading co-seismic around these hazards is great. To increase hazards. These cascading hazards caused a understanding around the potential hazards range of direct and indirect impacts to farms of the HSM it is vital to gain a greater throughout the affected region. In particular, understanding of the earthquake history. In 71 order to gain a better understanding of the of the North Island. Volcanic activity spanned history of the area, it is essential to investigate from the late Pliocene to early Pleistocene and analyse the sedimentology of the area, (2.74 – 1.60 Ma) over which time a regionally this will give a basis for further studies significant basaltic to andesitic volcano was required in order to create more accurate constructed from numerous vents. This study hazard analysis models. documents the spatial distribution of volcanic deposits associated with the Pirongia volcanic Focussing on the Madden Complex, on the succession, in order to understand how the east coast of New Zealand, paleoseismic volcanic edifice was constructed over time. An sediments are going to be investigated using extensive field campaign across ~240 km2 was six piston cores. Sediment characteristics and conducted to map and sample volcanics flow dynamics will be analysed and used to deposits, and this was incorporated with GIS understand the Madden continental slope data (aerial photographs, digital elevation distributary system. Some of the aims of this models at 15 m and 1 m resolution) and study are to determine whether there are any petrographic correlation to define the volcanic drastic changes across the Madden system, succession. The lowermost parts of the edifice and whether any of the turbidites can be are constructed from thinly layered lava flows correlated to a specific event. Triggers for of basalt and basaltic-andesite (0.5-2 m turbidity currents will also be investigated thickness), including large volumes of augite along with sediment provenance, and megacryst-rich (ankaramitic) basalt. The sediment accumulation rates. upper edifice is dominated by thick, localised extrusions of hornblende-andesite (up to 70 m Data which will be used to carry out this thick) interspersed with basaltic sub-aerial research includes CT scans, high quality deposits. Pyroclastic successions are rare and imagery, p-wave velocity, gamma and, occur mostly around vent areas, where they multibeam bathymetry. Further analysis to be record evidence of strombolian basaltic carried out includes grain size, carbonate eruptions and block and ash flows. content, microscopic and possibly Volcaniclastic heterolithological breccias are foraminifera analysis, and dating using tephra widespread on the southern flanks and data and C14 if further information is required. originate from vigorous pyroclastic and laharic activity that deposited material up to 15 km away from the summit. Prominent flank vents STRATIGRAPHIC ARCHITECTURE AND occur on the southwestern and eastern sides VOLCANIC PROCESSES OF THE PLIO- of Pirongia and are associated with extensive PLEISTOCENE PIRONGIA VOLCANIC lava fields up to 3 km long. Intense fluvial SUCCESSION, WAIKATO. erosion and mass wasting over the last 2 Ma has produced inversed topography across the O.E. McLeod, A. Pittari & R.M Briggs mountain, whereby valley filling lavas now School of Science, University of Waikato, form resistant ridges. Material deposited by Private Bag 3105, Hamilton 3240. lahars and flank collapse has formed a thin [email protected] ringplain that overlies the gently-dipping, distal basaltic lavas of Pirongia. Mt Pirongia (959 m above sea level) is a prominent composite-shield volcano situated within the Alexandra Volcanic Group, Waikato – the most voluminous (55 km3) basaltic field 72

INSIGHTS FROM PROXIMAL DEPOSITS OF main phases of bubble nucleation. The pumice THE 1995-1996 SUBPLINIAN ERUPTIONS OF has 60-85% bulk porosity, with a population of MT. RUAPEHU large coalesced bubbles (0.06-2.5 mm2), along with a modal population of small isolated S.A. Mills & S.J. Cronin vesicles (0.02 mm2). These data show that School of Environment, University of magma rose to shallow levels to slow, Auckland, 23 Symonds Street, Auckland vesiculate and bubbles coalesced. Once Central magma rose into the vent hydrothermal [email protected] system, explosive magma-water interaction led to top-down magma excavation and Subplinan eruptions during 1995-1996 activity decompression, triggering a second phase of at Ruapehu deposited tephra falls and lahars bubble nucleation and sub-plinian eruption. on the North-Eastern flanks of the volcano. Proximal deposits sampled 20 years after the eruptions were compared to the observed MICROSTRUCTURE AND STRENGTH dynamics of the largest eruptive phases on the CHARACTERISTICS OF HALLOYSITE-RICH 11th and 14th of October 1995. Textural SENSITIVE SOILS FROM THE BAY OF PLENTY properties of the deposits provide new insights into the gas-expansion, V.G. Moon1, P.R. Mills1,2, M.O Kluger3, D.J. environmental influences and conduit Lowe1, W.P. de Lange1 processes during the eruption. These deposits, 1School of Science, University of Waikato, from a relatively small eruption, were Private Bag 3105, Hamilton 3240 compared and contrasted to well-studied 2Coffey Geotechnics, Tauranga, New Zealand deposits from the largest subplinan eruptions 3MARUM, University of Bremen, Germany known from this volcano. The results of this [email protected] study show that external water influenced various stages of this eruption, contributing to Weathered rhyolitic pyroclastic materials are phreatomagmatic fragmentation, alongside associated with many landslides in the Bay of that driven by gas-expansion/bubble growth. Plenty, including a large number (> 20) of new The most sustained eruptions led to “dry” and reactivated landslides that occurred phases once water had been expelled from during and following the passage of ex- the Crater Lake basin and a clear conduit Tropical Cyclones Cook and Debbie in April established through the upper hydrothermal 2017. Both translational landslides and flow system. There were sufficient pauses in slides occur, but the ones causing significant between the main eruption phases (11 to 14 damage to infrastructure are the flow slides October) to allow re-accumulation of meteoric that exhibit very long runout and several water in the crater and re-saturation of the phases of landsliding that cause slow conduit from the lateral margins of the vent- retrogression of the headscarp. These are hosted hydrothermal system. This allowed for characteristics of sensitive soil behaviour. the generation of further small phreatomagmatic eruptions as well as Undrained, consolidated static triaxial tests of phreatomagmatic phases at the start of the 14 a sensitive soil layer at the base of one such October event. Along with the water influence landslide at Bramley Drive, Omokoroa, show on fragmentation and particle-size contractive p’-q’ plots, shear band distribution, the internal texture of lapilli localization, and strain-softening behaviour clasts of the main eruption phases show two coupled with rising pore water pressures post- 73 failure. Cyclic triaxial tests confirm brittle complexes and carbonatites, and although we failure and extensive softening of the soil. have occurrences of these rock types in the Pore pressure gradients developed during South Island of New Zealand, no REE deposits shearing are inferred to initiate collapse of have yet been found here. We 1) propose an clay microstructures into shear zones; further intrusion-related REE mineral systems model excess pore pressure generation following to help us understand the transport and collapse of structure in the shear zone leads to concentration of REEs in igneous fluids; 2) progressive fracture development. identify the mappable components of that system to aid exploration for and protection of Halloysite, a low-activity clay mineral, is potential REE resources; and 3) use the Petlab, associated with sensitive layers within these REGCHEM, GERM and QMAP databases to pyroclastic sequences. Mushroom cap– map the distribution of these components on shaped spheroidal halloysite is a newly a regional scale. The minerals system described morphology for halloysite. We approach identifies the source of energy, postulate that the surface charge distribution metals and ligands, the migration of REE-rich on the mushroom-caps results in weak short- fluids into mineral and structural traps, and range interactions between exposed clay the modern surface expression of REE surfaces. This weak bonding allows mineralisation. Our mapping of these disassociation of clay aggregates during slope components of the mineral system includes failure, leading to strain softening and a very geochemical maps such as alumina saturation low remoulded strength. Hence, long runout index, igneous fractionation, Nd isotopes and debris flows are characteristic. REE distribution, that characterise the intrusive suites of the South Island. By identifying areas where the mineral system USING A MINERAL SYSTEMS APPROACH TO components overlap and results are MAP RARE EARTH ELEMENT DISTRIBUTION favourable for mineralisation, or alternatively, IN IGNEOUS INTRUSIONS OF THE SOUTH where sample coverage is poor, REE ISLAND, NEW ZEALAND concentrations can be explored for in more detail or further sampling and mapping R. Morgenstern1, M. Hill1, R.E. Turnbull2, D.T. acquisition programmes planned. Strong1 and R. Smillie2 1GNS Science, PO Box 30-368, Lower Hutt 5010, New Zealand CHATHAM RISE, CHATHAM SCHIST 2GNS Science, Private Bag 1930, Dunedin 9054, New Zealand N. Mortimer1 & H.J. Campbell2 [email protected] 1GNS Science, Private Bag 1930, Dunedin 2GNS Science, PO Box 30368, Lower Hutt Global demand for rare earth elements (REEs) [email protected] is on the rise due to unprecedented technological advances and a shift in societal The Chatham Rise is a broad, straight, east- attitudes towards cleaner and more efficient west trending, 1500 km-long bathymetric renewable energy. A key component of these feature of southern Zealandia. Schist innovative technologies are the REEs, whose basement on the Chatham Islands has been many applications include magnets in wind described by Haast (1868), Hay et al. (1970) turbines and batteries in hybrid cars. Primary and Adams and Robinson (1977). Chatham sources of REEs are from alkaline igneous Schist protolith is Permian and Triassic 74

Torlesse Rakaia Terrane, based on U-Pb ages propagation modelling for use in tsunami of zircons (Adams et al. 2008). forecasting and warning. Forecasting and warning systems for distant sources, defined In 2013 we re-examined Chatham Schist by travel times well over one hour, are existing structure on well-exposed shore platforms. now and forecasts are refined by tsunami Earlier work is largely confirmed. However, we source inversion based on DART buoy clarify that Robinson's 4750 m thick information. These systems are also used for stratigraphy is a structural (flattened) section, regional tsunami forecasting and warning Matarakau Greywacke is a semischist, and purposes. However, there is typically a period Kaingaroa Volcanics are 99% psammitic and of about 30 minutes or sometimes longer pelitic schist. The maximum textural grade of before enough information can be gathered to Chatham Schist is TZ3 chlorite zone refine tsunami source information sufficiently. greenschist facies. Thin sections show that If the area under tsunami threat falls within schists previously dated at 198-180 Ma by Rb- this travel time boundary, uncertainties Sr and K-Ar methods contain relict detrital remain until the tsunami arrives. micas, so true metamorphic K-Ar ages lie in the range 171-157 Ma. Chatham Schist was We propose to include uncertainties into the exhumed at 108 +/- 11 Ma, based on He ages forecast in such circumstances, by using of zircons (Mortimer et al. 2016). ensemble simulations which vary tsunami propagation and source parameters. To be Structurally and lithologically, Chatham Schist useful, such forecasts require the calculation on Chatham Island resembles TZ2A to 3 Otago of ensemble scenarios in faster than real-time Schist around Lindis Pass and Danseys Pass. within the early development stages of the TZ4 garnet-biotite-albite schist has been tsunami. This requirement can typically not be sampled in a xenolith on Mangere Island 60 achieved by using pre-calculated scenario km SE, and amphibolite facies schist in a databases. dredge 300 km SE from the Chathams, thus indicating a broad southward increase in This study investigates the sensitivity of metamorphic grade. Chatham Rise and forecasting products to uncertainties in the Chatham Schist provide excellent long tsunami source process, by using examples baseline, linear markers with which to track like threat level maps and near shore tsunami oroclinal bending across Zealandia. wave height forecasts. The study focuses on the effect of uncertainty in the distribution of earthquake slip considering sources on the UNCERTAINTIES IN REGIONAL TSUNAMI Tonga- and effects on New FORECASTING Zealand coastal areas. Uncertainty due to non- DUE TO UNKNOWN DISTRIBUTION OF uniform slip follows tsunami ray paths, is a EARTHQUAKE SLIP complex function of distance and bathymetry, does not decay with distance, and has C. Mueller1 considerable effect on shoreline forecasts. 1GNS Science, 1 Fairway Drive, Avalon, Lower Hutt 5010, New Zealand [email protected]

Since the 2004 Indian Ocean tsunami, there has been a major increase globally in tsunami 75

UNUSUAL FLUID BEHAVIOR OF A SILICIC and brittle fracture of the Havre melt during MELT DURING FRAGMENTATION IN A DEEP eruption. Syn- or post-fragmentation viscous SUBAQUEOUS ERUPTION, HAVRE deformation of the magma, is therefore, SEAMOUNT 2012 extremely unusual, and implies high eruption temperatures. A.P. Murch1 J.D.L. White1 & R.J. Carey2 1 Dept. of Geology, University of Otago, PO Here we discuss possible mechanisms to Box 56, Dunedin account for increased magmatic 2 Room 327, Geography-Geology Building, temperatures, including volcanic lightning, Sandy Bay Campus, Hobart, 7001, Australia viscous dissipation, and a hot source magma. [email protected] The formation mechanisms of the fluidal particles and their implications for submarine Magma can respond to applied stresses in eruption processes at Havre will also be either a viscous or elastic manner, dependent examined. The presence of fluidal grains on the system chemistry, temperature, and alongside brittlely produced ash suggests a deformation rate. The rheological response of duality in fragmentation mechanisms at magma to stress is of importance in Havre, indicating strong, local gradients in determining eruption processes. The higher eruption temperature. silica content and lower temperature of silicic magmas vs mafic magmas leads to elastic deformation during eruption. This generates EARLY MASS FLOW SEDIMENTATION high bubble overpressures and stores more PROCESSES IN THREE MAAR CRATERS, energy in the melt, leading to brittle HINDON MAAR COMPLEX, OTAGO fragmentation and highly explosive eruptions. Caitlin Murphy1, Beth Fox1 & Adrian Pittari1 In 2012, a submarine rhyodacitic eruption 1School of Science, University of Waikato, occurred at Havre Seamount from a depth of Private Bag 3105, Hamilton 700-900 mbsl, producing four primary seafloor [email protected] ash deposits. Subunit 1 (S1), the basal layer of these, is composed of glassy vesicular ash with The Hindon Maar Complex, located near <5% crystal content. Particle shape analyses, Hindon, 25.0 km NW of Dunedin, consists of shows that up to 30% of grains in S1 display four volcanic craters infilled by lake sediments features implicate of viscous deformation syn- and mass flow deposits. The maars form part or post-fragmentation. These ‘fluidal grains’ of the Waipiata volcanic group, which was exhibit evidence of surface tension rounding, active from 25-9 Ma. Drilling of Maar 1, Maar particle-particle welding, post fragmentation 3 and a sediment-filled depression between vesicle inflation and Pele’s Tear like particles. Maar 2 and Maar 3 revealed up to 10 m of laminated biogenic lake sediments underlain The glass of S1 ash shows 72-75 wt% SiO2 and by siliciclastic mass flow deposits. This project water contents of 0.5-0.8 wt%. Using the GRD describes the siliciclastic deposits from these model this gives a calculated melt viscosity of drill-cores and from limited outcrops of Maar 107-108 Pa s. 2. Physical properties, stratigraphic logs, X-ray fluorescence spectrometry and optical The high calculated viscosity and the high petrography are used to create a facies strain rates generated during ash analysis and infer the processes of initial fragmentation suggests elastic deformation sedimentation into the maar craters following 76 the maar-forming eruptions. range from basalt to rhyolite, major eruptive Initial results have indicated that the mass magma is silicic. Many tephra layers from flow deposits from Maar 1, Maar 2 and the these volcanoes are widely distributed sediment-filled depression consist mostly of eastward. Tephrastratigraphy and unconsolidated well-sorted fine to medium tephrochronology at proximal to distal region sand. The sand is sub-angular to sub-rounded, of these volcanoes could reveal not only the bluish grey, and highly micaceous, being eruptive history of each volcano but also the composed primarily of quartz and schist sequence of each larger eruptive episode. To fragments. Structures include laminations, identify the source volcano for these tephra soft sediment deformation and massive layers, chemical analysis of volcanic glasses intervals. Intervals of semi-consolidated was quite useful. We clarify that three matrix-supported breccia occur in several volcanoes started their activity at nearly the cores. These breccia intervals are of similar same time after long quite period in composition to the sandy intervals, but with southwestern Hokkaido for ca. 400 ky. At first, the addition of volcanic glass and 0.5 mm-2 cm Toya and Yotei volcanoes, located at the voids with clay linings. These voids appear western region, started the activity 130 ka and with varying frequency throughout the breccia occurred largest caldera-forming eruption intervals. Maar 3 is infilled with (VEI=7) forming Toya caldera 110 ka. After the unconsolidated, well-sorted fine sand with eruption, Kuttara and Shikotsu volcanoes extensive iron staining. Based on the started their eruptive activity ca.95 and 85 ka, mineralogy, we infer a basaltic source rock. respectively, suggesting that the activity had Here we present more detailed mineralogical developed eastward and toward the arc-arc and geochemical data from these sedimentary junction. The activity of the STVF had been and volcaniclastic deposits, along with vigorous during the period from 60 to 40 ka. preliminary interpretations of their origins. Large eruptions with VEI=5 – 7 had repeated at Kuttara and Shikotsu volcanoes. The largest caldera-forming eruption occurred at Shikotsu TEPHRASTRATIGRAPHY AND volcano 42 ka. After the eruption, post-caldera TEPHROCHRONOLOGY OF THE SHIKOTSU- volcanoes of the three calderas and Yotei TOYA VOLCANIC FIELD, HOKKAIDO JAPAN: volcano have been active until now. It should BEGINNING AND DEVELOPMENT OF SILICIC be noted that episodic and strong silicic VOLCANISM AT AN ARC-ARC JUNCTION eruptive activity at the STVF since 130 ka could be possibly affected by the change of tectonic M. Nakagawa & M. Amma-Miyasaka stress at the arc-arc junction. Dept. Earth & Planetary System Sci., Hokkaido University, Sapporo, Japan [email protected]

The Shikotsu-Toya volcanic field (STVF) is located at an arc-arc junction of Kuril and NE Japan arcs, and consists of three caldera volcanoes, Toya, Kuttara and Shikotsu, and a large stratovolcano, Yotei. These volcanoes had sequentially started their eruptive activity since late Pleistocene, and have continued the activity until now. Although eruptive rocks 77

QUANTITATIVE PALEOENVIRONMENTS cave is required to calibrate the geochemical FROM SPELEOTHEMS (QUEST): CAVE information. We have been monitoring four MONITORING AS A KEY TO strategic drip sites inside Waipuna Cave over RECONSTRUCTING PAST ENVIRONMENT the last year to gather information about drip FROM WAITOMO SPELEOTHEMS rate; the pH, alkalinity and stable isotopes (δD and δ18O) of drip water; air temperature; 1 3 3 C. Nava , A. Hartland , B.R.S. Fox , O. humidity; and pCO2. Temperature and 1 2 1 Kwiecien , F. Gázquez , S.F.M. Breitenbach precipitation information has also been 1Department of Sediment & Isotope Geology, collected from a meteorological station Ruhr-Universität Bochum, Germany outside the cave. 2School of Earth & Environmental Sciences, University of St. Andrews, UK Here we present preliminary results of 3School of Science, University of Waikato, NZ. monitoring of both external climate and [email protected] internal cave conditions. Waipuna Cave reacts very quickly to precipitation events, and Waipuna cave is located in Waitomo Region, therefore we expect the speleothems to North Island, NZ, which in turn is situated at represent very highly (sub- to multi-annually) the southwestern fringe of the Pacific Ocean, resolved climate archives, which will provide an area highly sensitive to El Niño-Southern valuable information about local and regional Oscillation (ENSO) and the southern climate dynamics, such as the frequency of westerlies. This work is part of the strong El Niño events. multidisciplinary project Quantitative PalaeoEnvironments from SpeleoThems (QUEST), which employs speleothems as VOLCANIC GEOSITE SELECTION AND THEIR paleoclimatic archives to investigate ENSO GEOHERITAGE VALUE ASSESSMENT: dynamics and associated teleconnections METHODOLOGY REVIEW across the Pacific during the Holocene. In order to understand the processes that B. Nemeth, K. Nemeth, J. Procter, T. Farrelly control calcite precipitation during the last 10 Volcanic Risk Solutions, IAE, Massey ka, cave monitoring is an essential University, PO Box 11 222, Palmerston North component. Knowledge of the present-day [email protected] surface environment and the microclimatic parameters inside the cave will allow us to The protection of cultural and natural heritage construct robust proxies of past climate. is institutionalised and in New Zealand become the domain of a few Government Drip discharge rates are one key parameter agencies. In New Zealand, conservation values controlling speleothem growth, affecting the have generally focused on biodiversity tending delivery of calcium and CO2 degassing rates. to ignore other values such as geology and Drip response to rainfall provides information landscape conservation. There is very limited about flow path, storage, mixing and public awareness of any need to protect ultimately, signal transfer time into the cave. geological sites let alone recognising concepts Measurements of on-site water chemistry such as geoheritage or geoconservation. such as electrical conductivity, pH, and total alkalinity are necessary to estimate the A geoconservation strategy is based on several equilibrium pCO2 and calcite saturation. An successive steps: inventory, quantitative or understanding of the meteorology around the qualitative assessment, interpretation, 78 visualisation, promotion and monitoring. This THE UNDERUTILIZED VOLCANIC study proposes to provide an overview of GEOHERITAGE VALUES OF UPOLU, WESTERN methods available to identify, select, evaluate SAMOA - CHALLENGES TO DEVELOP and classify the geoheritage sites and find an SUSTAINABLE GEOTOURISM PROGRAMS appropriate method that can be easily INCORPORATING POLYNESIAN HERITAGE adapted to any geological site. Different methodologies have been K. Németh1 & A. Fepuleai2 developed in geoconservation. Their 1Massey University, CS-IAE, Volcanic Risk characteristics depend on the choice of Solutions, Turitea Campus, Palmerston North methods and techniques associated with 2The University of the South Pacific, School of evaluation using qualitative and/or Geography, Earth Science and Environment, quantitative systems of classification. These Suva, Fiji methods however are also not consistent as [email protected] the main purpose for conservation (e.g. economical, educational, tourism) can differ. The two largest islands of Samoa (Savai’i & These objectives need to be considered when Upolu) contain ~400 young volcanic cones. In establishing the right assessment criteria as Savai’i, the most recent eruption (Matavanu: they are the key to answer the broad range of 1905-11) covered the N-E sector of the island challenges associated to geoconservation. with pahoehoe lava flows and littoral cones. In Statistical approaches available for the Savai’i, volcanic eruptions took place few estimation of geoconservation/geoheritage times since the Polynesian migration ~3500 values vary from the preliminary geosite years ago. An inventory of these volcanic assessment model (GAM) to loglinear, geosites is under development to promote component analysis models. The complexity geotourism (Samoa Geopark Project). Upolu of the methods available could be overcome received far less attention in spite that recent by combining them with spatial analysis in GIS researches indicate the presence of young to produce indicators such as the volcanic features along the dorsal ridge of the geomorphodiversity index. island. Fissure aligned vents are common with crater lakes in SE Upolu and large scoria cone As a first attempt to define geoheritage we will complexes including Tafua Upolu in West examine the Auckland Volcanic Field which Upolu among those volcanic landforms carry displays a unique combination of young high geoheritage values that could be used monogenetic volcanic landforms and more effectively for geotouristic purposes as archaeological remains of an indigenous well as geoeducational sites for local culture through to European colonisation communities to understand volcanism in through to present day. It is envisaged that Samoa. As Upolu is the main gateway for through further analysis, we will provide an visitors (most of them stays only in Upolu), and opportunity for developing the first geopark in many of its prime resort sites are nearby those New Zealand that is part of the UNESCO Global volcanic geosites, promoting them could Geopark Network. develop sustainable tourism to the region. To develop a truly sustainable programs the local communities could also benefit from, volcanic geoheritage research needs to involve Samoan village communities through informal and formal participatory approaches to 1) assess their knowledge they have about 79 volcanism, 2) gather information from their discovery and stratigraphic position below cultural heritage associated with volcanism two Rangitoto-derived tephras enables a and 3) identify the best dissemination method clearer picture of environmental change to be of Western science that is conform with the drawn. The new pollen record shows an early Polynesian world view and everyday practices. phase (step 1) of minor, localised forest clearance around the time of Kaharoa tephra (c. 1314 AD) followed by a later, more TWO-STEP HUMAN-ENVIRONMENTAL extensive deforestation phase (step 2) IMPACT PREHISTORY FOR AUCKLAND, commencing at around the time of deposition LINKED TO LATE HOLOCENE CLIMATE of the Rangitoto tephras (c. 1400‒1450 AD). CHANGE This pattern, which needs to be corroborated from other well-resolved records from R.M. Newnham1, D.J.Lowe2, M.J. Gehrels3, northern New Zealand, concurs with an P.C. Augustinus4 emerging hypothesis that the Little Ice Age 1 Victoria University of Wellington had a significant impact on pre-European 2 University of Waikato Māori with the onset of harsher conditions 3.University of York, UK causing a consolidation of populations and 4. University of Auckland later environmental impact in northern New [email protected] Zealand.

Following resolution of a long-standing debate over the timing of the initial settlement of ORGANIC CARBON TRANSFER TO THE DEEP New Zealand from Polynesia (late 13th OCEAN BY A CO-SEISMIC TURBIDITY century), a prevailing paradigm has developed CURRENT EVENT DURING THE KAIKŌURA that invokes rapid transformation of the EARTHQUAKE landscape, principally by fire, within a few decades of the first arrivals. This model has S. Nodder1, A. Orpin1, J. Howarth2, J. been constructed from evidence mostly from Mountjoy1, P. Barnes1, A. Rowden1, D. southern and eastern regions of New Zealand Leduc1 & D. Bowden1 but a more complicated pattern may apply in 1NIWA, Private Bag 14-901, Kilbirnie, the more humid western and northern regions Wellington where forests are more resilient to burning. 2School of Geography, Environment & Earth We present a new pollen record from Lake Sciences, Victoria University of Wellington Pupuke, Auckland, northern New Zealand, [email protected] that charts the changing vegetation cover over the last thousand years, before and after the Significant ground-shaking events have the arrival of people. Previous results from this potential to transfer substantial organic site concurred with the rapid transformation carbon and other geological materials into model, although sampling resolution, deep-water environments via submarine mass chronology and sediment disturbance make transport processes along the continental that interpretation equivocal. Our new record margin. This carbon is effectively sequestered is dated principally by tephrochronology and restricted from further interaction with together with radiocarbon dating, and near-surface processes, thereby acting as a includes a cryptotephra deposit identified as geological “sink” in the marine carbon cycle. Kaharoa tephra, a key marker for first settlement in northern New Zealand. Its The November 2016 Kaikōura earthquake 80 sequence caused significant local and regional SEISMIC TOMOGRAPHY IN THE NORTHERN ground-shaking that resulted in submarine SOUTH ISLAND AND THE 2016 KAIKOURA mass failure in the Kaikōura Canyon and the EARTHQUAKE devastation of one of the world’s most productive benthic ecosystems. This event T. Okada1, Y. Iio2, S. Matsumoto3, S. also led to the initiation of a co-seismic Bannister4, S. Ohmi3, S. Horiuchi1, T. Sato1, T. turbidity current and the deposition of deep- Miura3, J. Pettinga5, F. Ghisetti6, R. H. ocean turbidite deposits, up to ~700 km from Sibson7 source. As part of the scientific response to the 1Tohoku University, Sendai 980-8578, Japan earthquake, a series of sediment cores were 2Kyoto University, Uji 611-0011, Japan collected subsequently in Kaikōura Canyon 3Kyushu University, 2-5643-29 Shin'yama, itself, along the path of the turbidity current Shimabara, Nagasaki, 855-0843, Japan (Hikurangi Channel) and from adjacent 4GNS Science, PO Box 30-368, Lower Hutt submarine canyons along the Hikurangi 5040 subduction margin. Organic carbon 5University of Canterbury, PB 4800, measurements in these sediment cores and Christchurch 8140 from previous samples in Kaikōura Canyon 6TerraGeologica, 60 Brabant Drive, Ruby Bay were undertaken and allowed a comparison to 7005 be made of the sedimentary composition of 7University of Otago, PO Box 56, Dunedin pre- and post-Kaikōura deposits, where these 9054. specific units could be determined. These data [email protected] indicate that the inferred Kaikōura deep-sea turbidite contains higher average amounts of The Mw 7.8 Kaikoura earthquake occurred on carbon (and nitrogen) than pre-turbidite the 14th November 2016, in NE South Island. In sediments, suggesting greater carbon order to investigate the cause of this sequestration potential during such episodic earthquake we have undertaken seismic events. Comparable δ13C and molar C:N ratios tomography in the region surrounding the between these units indicate that similar focus of the Kaikoura earthquake. A key geological materials have been mobilised finding from this study is that fluids, inferred during the co-seismic event as were being to have promoted the occurrence of the deposited on the pre-turbidite “modern” earthquake, could be detected as a seismic seafloor. velocity anomaly.

Since the Canterbury earthquake sequence (2011) we have deployed a dense seismic array in the central and northern South Island. Data from both the temporary stations (51 stations) and GEONET stations (22 stations) were used. Data collection was from March 2011 to April 2015, with 4939 earthquakes located and identified by GEONET. The minimum magnitude of catalogued earthquakes in this study is about 1.0. Subsequently, we have added aftershocks from the 2016 Kaikoura earthquake and their arrival times from the GEONET catalogue. The 81 total number of located earthquakes pockmarks related to past fluid escape (including the aftershocks) is 5389. We used releases. These are interpreted to be caused the double-difference tomography method by the sudden release of overpressured gas [Zhang and Thurber, 2003 and 2006] to generated by gas hydrate dissociation during determine hypocenter locations and three- glacial sea-level lowering. We simulate the dimensional velocity structure evolution of the gas hydrate system through simultaneously. Grid intervals are 20 km in the Plio-Pleistocene sea-level changes in the study horizontal plane. The Initial velocity structure area using thermodynamic modelling. Our adopted is from Eberhart-Phillips et al. [2010]. models were constrained by stable isotopic data gathered from piston cores collected As a result, we located a region of low-Vp, low- along the crest of the Chatham Rise (water Vs and high Vp/Vs surrounding the mainshock ~550-1000m). The Chatham Rise provides a and aftershocks of the Kaikoura earthquake. unique opportunity for the study of the effects We also have detected low-Vp, low-Vs and of depressurization from sea-level lowering to high Vp/Vs zones beneath other major faults gas hydrate systems because it is a in northern South Island. These low-Vp, low- bathymetric barrier preventing the Sub- Vs and high Vp/Vs zones are coincident with tropical Front separating sub-tropical and sub- low electrical resistivity areas detected by MT Antarctic waters from migrating during glacial- soundings [Wannamaker et al., 2009] and can interglacial cycles. This bathymetric barrier be interpreted as zones with overpressured enabled us to assume constant bottom-water fluids. These observations indicate that temperatures are constant. Our results show overpressured fluids, which are inferred to more gas is released at shallower water depth, originate from slab dehydration, have acted to which relates to the position of the large promote the occurrence of the Kaikoura pockmarks in the Chatham Rise. However, the earthquake. results from paleo-oceanographic studies indicate that in reality bottom-temperatures may have varied locally. These temperature NUMERICAL MODELLING OF GAS HYDRATE changes may have a more significant effect on DISSIOCATION DURING THE GLACIAL-INTER- the shallow gas hydrate system in the study GLACIAL CYCLES, CASE STUDY THE area than the relatively gradual decrease of CHATHAM RISE, NEW ZEALAND. pressure associated with sea-level lowering.

P.A. Oluwunmi1, I. Pecher1, R. Archer1, M. Reagan2, G. Moridis2, Helen Neil3 1 The University of Auckland, New Zealand 2 Lawrence Berkeley National Laboratory, Berkeley, California, USA 3National Institute of Water and Atmospheric Research [email protected]

The Chatham Rise has been observed to have seafloor depressions, each 150m -11km in diameter, also covering an area >20,000 km2, south east of New Zealand. These seafloor depressions have been interpreted as 82

CO-SEISMIC TURBIDITES TRIGGERED BY THE tomography, extracellular polymeric KAIKOURA EARTHQUAKE substance (EPS), organic carbon and meiofaunal analysis. Provisional data show Alan Orpin1, Jamie Howarth2, Scott Nodder1, that a number of slope-basin distributary Laura Wallace3 systems along the southern Hikurangi margin 1National Institute of Water and Atmospheric have preserved a co-seismic event, Research (NIWA), Private bag 14-901, characterised by a fluidised mud unit that is Kilbirnie, Wellington 6241, unbioturbated, faintly laminated and weakly [email protected] graded. It immediately overlies a bioturbated 2School of Geography, Environment and Earth and oxidised mud, interpreted to be the pre- Sciences, Victoria University of Wellington, earthquake seafloor. Some locations show PO Box 600, Wellington coarse-grained material entrained in the GNS Science, PO Box 30368, Lower Hutt 5040 turbidite base, with one example from Cook Strait having a very porous shell hash. Recent Long turbidite records of pre-historic emplacement of the turbidite and burial of earthquakes underpin our improved pre-earthquake seafloor are confirmed on the understanding of the pre-historic seismic levee of the Hikurangi channel by the very- behaviour and hazard represented by the short lived radioisotope 234Th in concert with Hikurangi subduction margin; New Zealand’s CT data. A compelling story that constrains the largest yet most poorly constrained source of character and spatial extent of the co-seismic seismic hazard. Sediment cores allow the deposit is emerging. In addition, re-coring at along-strike correlation of deep water critical sites is showing the progressive turbidite deposits formed in response to evolution of the event deposit and will inform earthquake strong ground motions. The large our understanding of the preservation 2016 Mw7.8 Kaikōura Earthquake triggered a potential in the geologic record. collapse in the outer-shelf rim of the Kaikōura canyon (Mountjoy, January 2017), and a co- seismic turbidite that traversed Hikurangi ENGINEERING GEOLOGICAL PROPERTIES channel at least 300 km of the southern AND SLOPE INSTABILITY OF TAURANGA margin (Barnes et al., November 2016). This GROUP SEDIMENTS IN THE BEACHLANDS event provided an unprecedented LANDSLIDE ZONE (BLZ), AUCKLAND opportunity to examine a modern analogue and calibrate the along-strike variability of A. Palma, M. Brook & J. Tunnicliffe deep water turbidite deposits formed in School of Environment, University of response to measured ground motions. This Auckland, 23 Symonds Street, Auckland presentation will provide an overview of the Central range of co-seismic turbidites observed and [email protected] images collected from the recently completed benthic survey of Kaikōura canyon. This study analyses a recent landslide initiated in the Beachlands Landslide Zone (BLZ), east Three voyages since the Kaikōura Earthquake Auckland. The BLZ is a region of coastal slope have collected precision short cores from failures, occurring in suburban areas, creating within the Kaikōura canyon head to as far substantial hazards for homeowners. We north as the Poverty Bay margin 600 km to the focus on the most recent slope failure in the north. Samples were taken for 210Pb area at Sunkist Bay, triggered on 5 April 2017. radioisotope analysis, sedimentology, CT The landslide is characterized as rotational 83 slumping in the clay/silt cliffs, with TIMING OF SEDIMENTATION AND retrogressive failure propagating an arcuate DEFORMATION IN PLIO-PLEISTOCENE headscarp to within a few metres of the rear WHANGANUI BASIN, NEW ZEALAND of houses on First View Avenue. Tension cracks extended laterally into neighbouring Julie Palmer*, Callum Rees, Alan Palmer properties. The landslide was investigated Institute of Agriculture and Environment, using a combination of in situ testing and Massey University, Private Bag 11 222, remote sensing techniques. Shear strength, Palmerston North penetration resistance and soil index [email protected] properties were measured at various heights in the exposed headscarp, formed in Tauranga Pliocene to Recent sedimentary succession of Group sediments. Structure-from-Motion Whanganui Basin is one of the most complete photogrammetry of drone-acquired imagery Quaternary stratigraphic records in the world. allowed a detailed engineering The thickest succession, which lies offshore, geomorphological map to be constructed. has not been drilled. Onshore, four Observations of the headscarp exposures exploration wells drilled in Whanganui – suggest that perched water tables developed Manawatu region between 1942 and 1964, on impermeable tephra layers, increasing encountered basement at 2400m or less. Each porewater pressure in overlying soils, and well was located on one of a number of leading to rotational failure. Downslope, the growing folds in the area. Farther east faulting slumping transitioned to an earthflow, which and associated folding occur along the North overtopped the seawall at the toe of the cliff, Island dextral fault zone and blind active faults depositing a lobate fan of material on the to the west. These are uplifting the axial beach below. The slope failure on 5 April ranges forming piercement structures as followed ex-Tropical Cyclone Debbie deformed Mesozoic basement is elevated and delivering Auckland its normal April rainfall stripped of its late Neogene coverbeds. This (84.6 mm) in 14 hours on 4/5 April. Preceding tectonism is part of the deformation this, the ‘Tasman Tempest’ delivered a 1 in a associated with crustal shortening along the 100-year rainfall event at nearby Hunua on 7 present day North Island subduction margin. March (225 mm of rain in 12 hours). Hence, prior to failure, high antecedent porewater Pumice units present in the coverbeds provide pressures had prevailed for some time. basinwide chronostratigraphic horizons that constrain the timing of uplift in the main axial range and formation of actively deforming anticlinal structures, such as Pohangina Anticline. Rhyolitic pumice (primary airfall (tephra) and reworked pumice) provide a high resolution chronostratigraphic framework for sedimentary and bio- facies preserved in the coverbeds. Thus constraining the timing of syn- and post-depositional deformation in the Whanganui Basin.

A study by Melhuish et al. (1996) suggested folding associated with the active anticlines had been going on for at least 3My. However, 84 tephrostratigraphy of southern Ruahine becoming widely applied to the rapid and non- Range indicates the area was experiencing destructive chemical analysis of sediment estuarine and shallow marine conditions 1My cores. ago and that piercement of the greywacke has occurred largely since this time. Prior to the Although µ-XRF core scanning techniques are uplift of the ranges the Whanganui Basin increasingly used to locate crypto-tephra in extended east of the present Ruahine Range. sediment cores, no attempt to fingerprint and The uplift of the ranges is gradually dissecting identify tephra layers using µ-XRF core the basin cutting the central part of the basin scanning techniques has been published to off from its eastern counterpart. date. We test the ability of this approach on numerous thick, easy to see rhyolitic tephra in Reference: continuous, organic-rich and well-laminated Melhuish, A., van Dissen, R., Berrryman, K., lake sediment cores from maar craters in 1996. Mount Stewart-Halcombe Anticline: a Auckland spanning the period ca. 7 to 46 ka. look inside a growing fold in the Manawatu region, New Zealand. New Zealand Journal of µ-XRF derived elemental ratios and magnetic Geology and Geophysics, 39(1): 123-133. susceptibility scans, quickly and non- destructively obtained with the Itrax® core scanner, yield the highest information value FINGERPRINTING RHYOLITIC TEPHRA LAYERS for identifying and fingerprinting tephra WITH NON-DESTRUCTIVE RAPID µ-XRF CORE layers. Calibration of the µ-XRF scan data with SCANNING conventional XRF and comparison to EMPA glass shard allowed: (1) characterization of L. Peti1 & P. Augustinus1 discrete tephras, (2) a test of the ability of 1 School of Environment, The University of Itrax® scans to rapidly and reliably fingerprint Auckland, Private Bag 92019, Auckland 1142 tephra from macroscopic to crypto-scale, and [email protected] (3) the proposal of optimal µ-XRF scanning conditions for tephra fingerprinting. Tephra layers are the backbone of chronology development in New Zealand due to their (near) simultaneous deposition in the COMPOSITE STRATIGRAPHY AND sedimentary archive over a wide area. Their PRELIMINARY AGE-MODEL OF 80 m MAAR identification is crucial for the robust LAKE SEDIMENT FROM ORAKEI BASIN chronological control of climate change events (AUCKLAND CITY) discerned in Auckland maar lake sediment cores, as well as for determination of the L. Peti1, P. Augustinus1, L. Hope-Wilson1 frequency and magnitude of the volcanic 1 School of Environment, The University of eruptions they are the product of. Auckland, Private Bag 92019, Auckland 1142 [email protected] Tephra layers are identified based on their mineralogy and fingerprint of major and trace The Orakei Maar Crater Lake (Auckland elements since each volcanic centre, and most Volcanic Field) provides a well preserved, eruptions, contain a unique geochemical finely laminated, high-resolution record of signature. However, traditional fingerprinting palaeoenvironmental change over the last of tephras is a slow, expensive and destructive glacial cycle. One core of ca. 80 m length was process unlike µ-XRF core scanning that is drilled in 2006 followed by two cores to depths 85 of ca. 100 m below sediment surface with GEODETIC RESULTS FROM THE HAURAKI nearly 100% recovery. The two longer cores RIFT: SLOW CONTINENTAL RIFTING OBLIQUE reach into volcanic ejecta interpreted to be TO SUBDUCTION, NORTH ISLAND the primary deposit of the maar forming eruption and further into the Waitemata R.C. Pickle1, J.D. Eccles1, S. Hreinsdottir2, J.V. sandstone basement. Here we describe the Rowland1, N. Palmer2 Orakei Maar Crater Lake composite 1 University of Auckland, School of stratigraphy established based on these three Environment, Private Bag 92019, Auckland cores. Large intervals of the record show fine 1142 sub-mm laminations which allow visual 2 GNS Science, 1 Fairway Dr., Avalon, Lower correlation between the overlapping cores. In Hutt 5010 other intervals where correlation is not as [email protected] straightforward statistically more robust methods based on magnetic susceptibility The Hauraki Rift, an active but slow-deforming measurements, µ-XRF core scanning (Itrax) (<1mm/yr) narrow intra-continental rift in results and X-ray density have been employed northern New Zealand paradoxically strikes to obtain a composite stratigraphy. The nearly normal to the Pacific-Australian oblique accuracy and strength of applied methods subduction boundary 300+ km to the could be tested in the overlapping finely southeast. Both the driving mechanism and laminated intervals of the core. The entire quantitative details of the rift's current activity sedimentary record of Orakei Maar Crater are unknown. A three year, ~40 station GNSS Lake below the marine/freshwater transition geodetic campaign beginning in 2015 has now caused by the crater rim breach due to the completed, producing new velocity solutions post-glacial sea-level rise at ca. 9 ka comprises throughout northern North Island. Preliminary ca. 80 m. vectors show that the Hauraki Rift may be discontinuous and accommodated not only by A preliminary age-model could be established the active Kerepehi fault serving as its based on the composite stratigraphy and the presumed median axis, but also by the active preliminary identification of known and dated Wairoa North fault striking parallel 20 km to volcanic ash (tephra) layers. The average the west. The northern continuation of the sedimentation rate for this crater lake below Wairoa North fault may continue further than the Rotoehu tephra (ca. 45 ka) is previously supposed, possibly extending into approximately 0.4-0.5 m/ka and by Auckland harbour. Additionally, an eastern extrapolation of the latter an Orakei eruption extension of the presumed-inactive, rift age of approx. 135 ka is estimated. perpendicular Waikato fault delineates a visible velocity discontinuity between geodetic stations and may serve as an active transform fault/transfer zone between these. We also determine lateral offsets resulting from the November 2016 Kaikoura Earthquake at continuous GPS reference stations (KTIA, CHTI, MAC1) over 800 km away from source.

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THE CENOMANIAN–TURONIAN δ13C RECORD removal of adhering carbon contaminants OF THE CHATHAM ISLANDS: IMPLICATIONS with hydrochloric acid, the fossilised material FOR TERRESTRIAL STABLE CARBON was dried and δ13C levels were analysed using CHEMOSTRATIGRAPHY elemental analysis isotope ratio mass spectrometry (EA-IRMS). The values obtained S.B. Piva1, C.M. Mays1 & J.D. Stilwell1 range between -23‰ and -28‰, which are 1School of EAE, Monash University, VIC, 3800, typical of those acquired for extinct and extant Australia C3 plants. Statistical analyses of these data [email protected] were performed to assess the inter- and intra- species variation in 13C values obtained for Global hothouse climatic conditions prevailed this first taxonomically controlled profile of during the Cretaceous (Cenomanian- terrestrial carbon, facilitating comparisons Turonian) amidst the tectonic separation of with global type sections. Subsequently, this southeastern Gondwana and poleward study established the benefits and limitations radiation of angiosperms. The fossilised of taxonomically-controlled terrestrial carbon remnants of the highest southern chemostratigraphy. palaeolatitude (~70–80˚S) forest studied to date from this important time interval are preserved within the Tupuangi Formation ANALYSIS OF FLUID FLOW SYSTEMS AND located on Pitt Island, Chatham Islands, New LINKS TO POTENTIAL GAS HYDRATE Zealand. Analysis of the preserved spore- DEPOSITS IN THE NORTHERN TARANAKI pollen record of this fluvio-deltaic succession BASIN has enabled correlation to the Ngaterian, Arowhanan and Mangaotanean stages of the G. Pradel1, I. Pecher1, L. Strachan1, G. New Zealand chronostratigraphic scheme. In Crutchley2 & K. Kroeger2 the absence of absolute dating, this study 1School of Environment, The University of applied a new method of chemostratigraphic Auckland, Private Bag 92019, Auckland correlation in order to constrain these 2GNS Science, Institute for Geological and biostratigraphic stage boundaries, primarily Nuclear Sciences. PO Box 30368, Lower Hutt the Arowhanan-Mangaotanean boundary [email protected] which has previously been correlated with the Cenomanian-Turonian boundary (CTB). Global In this study we provide evidence for gas type sections of the CTB (93.9 Ma) preserve a hydrates in the Taranaki Basin occurring off distinct signature within the ratio of stable the continental margin. Modelling of the gas carbon isotopes (δ13C), specifically an increase hydrate stability zone (GHSZ) suggest that in C13:C12, attributed to Cretaceous Oceanic pressure and temperature conditions for Anoxic Event 2 (OAE-2). This study aimed to hydrate formations exist at water depths of identify this characteristic δ13C signal by 500 m and greater. Interpretation of high- analysing the stable carbon ratios preserved resolution 2D and 3D seismic data reveal the by coalified leaf compressions of two of the presence of large deep seated faulting, dominant taxa collected at semi-regular polygonal faulting, seismic chimneys/pipes, stratigraphic intervals (3–8m) across an mounds, pockmarks and high amplitude approximately 400m thick section of the anomalies here interpreted as free gas. These Tupuangi Formation. These leaves were features are linked to evidence suggesting isolated via manual preparation techniques upward migrating fluids (liquids and gas) from and sieving from bulk samples. Following the Late Cretaceous deposits into the shallow 87 sediments where hydrate deposits may be TERRESTRIAL CLIMATE EVOLUTION IN THE expected. Subsequently, the observation of SOUTHWEST PACIFIC OVER THE PAST 30 patchy, polarity-reversed, high amplitude MILLION YEARS reflections (HARs) at the base and in the regional GHSZ are interpreted as bottom Joseph G. Prebble1, Tammo Reichgelt2, simulating reflectors (BSRs) indicating the Dallas C. Mildenhall1, David R. Greenwood3, presence of free gas below a layer of hydrates, J. Ian Raine1, Elizabeth M. Kennedy1, Hannu which exist at the base of gas hydrate stability C. Seebeck1 (BGHS). These reflections appear 1 GNS Science, Lower Hutt, New Zealand predominantly on the down-dip side of 2 Lamont-Doherty Earth Observatory of canyon incisions that are commonly located Columbia University, Palisades NY, USA on the continental slope. It is proposed here 3 Department of Biology, Brandon University, that these lower the extent of the BGHS and Brandon, Canada consequently trap up dip migrating, which [email protected] may then facilitate the formation of gas hydrates in these regions. The patchy nature A reconstruction of terrestrial temperature of these reflections is believed to be and precipitation for the New Zealand characterised by areas of focussed fluid flow landmass over the past ~30 million years is into heterogeneous deposits in the shallow produced using pollen data from >2000 sediments. This suggests that sources of gas samples lodged in the New Zealand Fossil may be derived from thermogenic origins Record Electronic Database and modern associated with the Late Cretaceous source climate data of nearest living relatives. The rocks in the basin. The lack of any strong HARs reconstruction reveals a warming trend observed in the deeper regions of the basin through the late Oligocene to early Miocene, suggests that upward fluid migration in these peak warmth in the middle Miocene, and areas may be trapped well below the BGHS stepwise cooling through the late Neogene. and subsequently migrate laterally into the Whereas the regional signal in our continental slope regions. However, a number reconstruction includes a ~5-10° northward of moderate amplitude reflections in the GHSZ tectonic drift, as well as an increase in high are observed, suggest that more diffuse gas altitude biomes due to late Neogene and emissions here may be at play, resulting in Pliocene uplift of the Southern Alps, the possibly weak BSR reflections. pattern mimics inferred changes in global ice extent, which suggests that global drivers played a major role in shaping local vegetation. Importantly seasonal temperature estimates indicate low seasonality during the middle Miocene, and that subsequent Neogene cooling was largely due to cooler winters. We suggest that this may reflect increased Sub-Antarctic influence on New Zealand vegetation as the climate cooled.

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VOLCANISM AT MAUNGATAUTARI geochemical and strontium and neodymium COMPOSITE CONE VOLCANO, CENTRAL isotope analyses demonstrate these lavas WAIKATO were derived from at least three distinct mantle-melt sources: subduction-related, M. L. Prentice & A. Pittari deep, garnet-bearing, depleted mantle (most School of Science, University of Waikato, andesites and dacites); a shallower, garnet- Private Bag 3105, Hamilton free, upper mantle (low SiO2 hornblende [email protected] andesites) and an area of deeper enriched mantle (Kairangi olivine basalt). Activity at Maungatautari is an extinct andesitic-dacitic Maungatautari is interpreted to reflect composite cone volcano, situated 35 km andesitic volcanism occurring along the edge southeast of Hamilton that rises prominently of the continental tip of the Colville volcanic in the Waikato region. A single radiometric age arc c. 2 Ma. The olivine basalt at Kairangi is of 1.8 Ma indicates volcanic activity here was more reflective of intraplate over subduction- contemporaneous with subduction-related related melts and is unrelated to magmatism volcanism of the nearby Alexandra Volcanics at Maungatautari. and the early Taupo Volcanic Zone. The volcanic history of Maungatautari has been reassessed using field and desktop GEOCHEMISTRY AND STRUCTURE OF BACK- geomorphic analysis, volcanic stratigraphy ARC BASINS IN THE HAVRE TROUGH, and facies analysis, petrographic and SOUTHWEST PACIFIC mineralogical studies, and elemental and isotopic geochemical analysis, which has V. Pullan1,2 R.J. Wysoczanski1 M.R. Handler2 provided new insights into how & C. Timm3 Maungatautari relates to volcanism elsewhere 1National Institute of Water & Atmospheric in the Waikato Region around 2 Ma. Research, Greta Point, Wellington 2School of Geography, Environment & Earth This study is the first to document a record of Sciences, Victoria University of Wellington explosive volcanism at Maungatautari. Track 3GNS Science, Avalon, Lower Hutt development by Maungatautari Ecological [email protected] Island Trust (MEIT) exposed two pyroclastic successions located near the summit and on Magmatism at subduction zone systems the southern flank. Activity at the now-eroded represents one of the principal forms of summit vent included complex, multiple volcanic activity on earth, and is the main foci phase eruptions with cycles of dome growth for significant mass and chemical transfer and collapse, whereas deposits on the flank between the crust, mantle, hydrosphere and show repeated production of eruption atmosphere. The Havre Trough back-arc columns from associated vulcanian to sub- system located behind the Kermadec arc, in plinian style activity which created numerous the southwest Pacific Ocean, is associated pyroclastic density currents. with the subduction of the Pacific plate beneath the Australian plate and is a classic Lavas at Maungatautari consist of non- example of an intra-oceanic back-arc system. vesicular labradorite, pyroxene and hornblende andesites and hornblende dacites. The location of back-arc basins can provide a Olivine basalt is found at the small Kairangi wealth of information in understanding key cone ∼7 km to the northwest. Whole rock structural and geochemical dynamics of 89 subduction systems. Previous Kermadec arc TIME-COMPOSITION TRENDS IN A research has focussed on active arc front COMPREHENSIVE SUITE OF LAVAS FROM volcanoes yet the back-arc basins in the Havre TONGARIRO VOLCANO Trough remain poorly understood. Therefore, significant gaps exist in our understanding of L.R. Pure1, G.S. Leonard2, A.T. Calvert3, C.J.N. the nature of magmatism, and onset of rifting Wilson1, D.B. Townsend2 & J.A. Gamble1 in the Havre Trough. 1SGEES, Victoria University, PO Box 600, Wellington 6140 Extensive seafloor sampling and high 2GNS Science, 1 Fairway Drive, Avalon, Lower resolution acoustic surveying of back-arc Hutt 6315 basins in the Havre Trough was undertaken 3US Geological Survey, 345 Middlefield Road, during several marine voyages of the RV MS-937, Menlo Park, CA 94025, USA Tangaroa between 2012 and 2015 to [email protected] investigate the formation of the back-arc basins. Dredge sampling recovered fresh back At stratovolcanoes, time-resolved eruptive arc basin basalts (BABB) from depths up to stratigraphies provide the essential ~4000 mbsl, and 30 kHz multibeam framework for reconstructing the evolution of echosounder (MBES) data reveal a range of magmatic systems. For systems that produce different morphological features such as infrequent and low volume explosive elongated ridges oriented at 45° and small eruptions, records of sequential magma volcanic cones. evolution are best preserved in lava flows for timescales exceeding tens of millennia We present MBES and whole rock (because small volume unconsolidated tephra geochemical data of BABB from these layers are highly susceptible to erosion or previously unexplored basins. The samples are bioturbation where thin). Tongariro volcano in from the southern sector of the Havre Trough New Zealand has an edifice constructed between 33.7° S and 36.6° S (with one dominantly by andesitic lavas that date from northern location at -30.3° S) and span the ~270 ka to present. This edifice history breadth of the Havre Trough. The results show provides a framework for examining time- variable modification of ambient back-arc composition relationships of Tongariro’s past mantle by subducting plate derived and present magmatic systems. components across the Havre Trough, and combined with digital terrain models give new We here present 25 new 40Ar/39Ar age insights into the tectono-magmatic evolution determinations on lavas, principally from of the Havre Trough. undersampled sectors of Tongariro’s edifice (NW, NE, E) and peripheral vents, to augment existing K/Ar ages. These combined age data are coupled with new and existing whole rock geochemical analyses to interrogate time- composition relationships. The data show that consistent incompatible element concentrations (e.g., 0.9-1.5 wt% K2O; 90-120 ppm Zr) persist from ~270-120 ka and 80 ka- present, interrupted by a series of incompatible element-enriched lavas (1.6-2.1 wt% K2O; 120-160 ppm Zr) from 120-80 ka. We 90 interpret Tongariro’s higher incompatible presently communicated and to what effect? element concentrations at 120-80 ka to reflect The paper presents a review of current increased country-rock assimilation of literature and discusses the need for bridging incompatible-element fertile phases in the between the various scientific communities mid- to upper-crust (e.g., biotite in greywacke and the public, and posits need for more metasediments). This assimilation period was responsive and representative possibly triggered by increased mid-upper communication models using a New Zealand crustal temperatures from continued magma context. injection over Tongariro’s lifespan that were incapable of triggering voluminous melting prior to 120 ka. From 80 ka-present, ENGINEERING GEOMORPHOLOGICAL AND incompatible element concentrations GEOTECHNICAL CHARACTERIZATION OF returned to pre-120 ka levels, reflecting the TROPICAL CYCLONE WINSTON INDUCED exhaustion of accessible fertile material. SLOPE FAILURES IN VITI LEVU, FIJI Similar explanations have been proposed for an incompatible element spike at Ruapehu A.R. Ram1, M.S. Brook1 & S.J. Cronin1 volcano, 20 km south of Tongariro, at ~45 ka. 1 School of Environment, The University of The separated timing of similar time- Auckland, Auckland, New Zealand composition events at Tongariro and Ruapehu [email protected] suggest that the petrogenetic processes in the southern TVZ arc are decoupled. Battering Fiji for nearly 24 hours from 2 am 20 February 2016, with wind gusts of up to 306 km/hr, Severe Tropical Cyclone (STC) Winston ADAPTIVE COMMUNICATION FOR A was the first category five cyclone to make a DYNAMIC LANDSCAPE landfall in Fiji and one of the strongest cyclones to traverse the southern hemisphere. J. Rae Affecting at least 80% of the country’s Lincoln University, PO Box 85084, population, STC Winton caused 44 fatalities Christchurch, New Zealand and cost the Fijian economy US$1.3 billion [email protected] with at least 10% relating to road infrastructure. Slope failures resulting from New Zealand is a relatively young country tropical cyclones have caused a high number situated astride an active margin. Change is of fatalities and infrastructure damage in the certain; resilience a byword of our modern past, particularly along the King’s Road, one of times. There is an upward trend in research the two major highway’s spanning Fiji’s largest aimed at building more resilient cities and island, Viti Levu. Despite the severe economic developing more engaged and prepared impacts and damage to road infrastructure communities. Drawing upon disaster risk experienced in Fiji by landslides triggered by research and hazard mitigation studies, this tropical cyclones, they are rarely documented. paper explores the divide between science Here, we report on engineering research and local public response and geomorphometric and geotechnical character questions whether there are other ways that of slope failures triggered by the STC Winston scientific knowledge might be more effectively along the 35 km stretch of King’s Road in communicated. What are the ways perception northern Viti Levu, Fiji. At least 61 distinctive and value systems influence awareness of risk failures were identified all of which were small and uncertainty? How is future change (min. 12 m2, max. 1125 m2, mean 81 m2) and 91 shallow in nature (<5 m in depth), occurring on core from geotechnical drilling associated with gentle to steep slopes (min. 5°, max. 50°, mean Auckland CBD site investigations and 23°), and low to intermediate relief (min. 4 m, excavations. Laboratory hardness tests were max. 89 m, mean 86 m). Most of failures were conducted using a model C-2 Shore earth and debris-slides (rotational and Scleroscope. A total of 51 cylindrical translational) with minor flow components. specimens with an average volume of 56.55 Geotechnical analysis of the soils sampled cm³ were tested for a total of 5364 Shore from the erosive scarps of the slope failures Scleroscope Rebound Hardness (SSRH) values. revealed most the soils to be cohesive, stiff, Statistical analysis of the data show that the plastic, sensitive silts. XRD analysis further hardness varies with lithology. In particular, confirmed the presence of Smectite and/or the mudstone showed the highest man Halloysite contributed to the sensitive nature hardness values, while the coarse sandstone of the slope materials. The trigger for the slope showed the lowest mean SSRH values. The failures was the ~258 mm of rainfall in 24 Parnell Grit had the highest range of values, hours after 30-day antecedent rainfall of 482 indicative of the it’s lithological variability mm which caused rapid increases in pore often seen over short distances in outcrop. water pressures which together groundwater The microstructure of the samples were pathways caused loss in shear strength of the analysed using scanning electron microscope sensitive surficial soils within the highly (SEM) to identify pre-existing defects and weathered soil profiles. examine resulting fracture patterns as a result of the SSRH test, which may be scaled up to understand fracture propagation and SURFACE HARDNESS AND LITHOLOGICAL permeability when undertaking civil PROPERTIES OF WAITEMATA GROUP EAST engineering excavations. COAST BAYS FORMATION, AUCKLAND

Z. Rana, M. Brook THE AEROMAGNETIC EXPRESSION OF THE School of Environment, University of ALPINE FAULT: REGIONAL DISPLACEMENT Auckland, Auckland 1010, New Zealand AND ENTRAINMENT OF IGNEOUS ROCK [email protected] M.S. Rattenbury1 & P. Vidanovich2 The hardness of a rock can be defined as the 1GNS Science, PO Box 30368, Lower Hutt elastic resistance to local compression. It is an 2PVC Ltd, 5/3 Parliament St, Auckland important geomechanical property, which is [email protected] often overlooked when characterizing the geotechnical properties of Miocene East Coast The Alpine Fault is very well delineated by Bays Formation of the Auckland region. recent high resolution aeromagnetic datasets Hardness testing was undertaken on rock over much of its length in New Zealand’s South samples in order to characterize the rocks Island. Aeromagnetic data acquired over the based on surface hardness, while the West Coast, Buller, Nelson and Marlborough influence of microstructures on rock hardness regions for the New Zealand Government was also examined. Five rock types (siltstone, reveal many total magnetic intensity mudstone, Parnell Grit, fine-grained anomalies that truncate at the Alpine Fault sandstone, and coarse sandstone) of the East surface trace or are truncated where the fault Coast Bays Formation were analysed in this is interpreted to be at depth. Strongly positive study. The samples were acquired from drill anomalies occurring in the Alpine Fault zone 92 are generally associated with igneous rocks; stratigraphic subdivision. Contemporary notably Mesozoic mafic metavolcanic and counterparts persisting around modern day ultramafic rocks, Late Cretaceous basalt and New Zealand waters provide some Early Cretaceous intrusions. Greenschist palaeoenvironmental analogues. The bands within the Alpine Schist are well succession contains a Plio-Pleistocene volcanic expressed magnetically and the Dun Mountain record derived from early eruptive products of Ultramafic Group serpentinised peridotite the Taupo Volcanic Zone (TVZ). The rocks and dikes have a very strong magnetic development and application of geochemical expression. Isolated anomalies parallel and ‘fingerprinting’ techniques to primary tephra within the Alpine Fault zone are attributed in and reworked volcaniciclastic deposits in the part to ultramafic rocks incorporated into the Whanganui Basin has led to a revolution in fault zone. The strong anomalies associated mapping, allowing for identification of with the Hohonu Range and some other chronostratigraphic horizons and basin wide foothills are caused by magnetic granitoids correlation. New research presented here and dikes that are interpreted to persist at continues the ongoing stratigraphic depth to the southeast in the footwall to the subdivision of early work by New Zealand’s dipping Alpine Fault plane. The broad anomaly pioneering geologists, presenting one sheet of under the Mataketake Range in South a 1:25 000 geological map series Westland is attributed to numerous dipping encompassing the Central Rangitikei area. This metavolcanic layers in the Alpine Schist work draws from over 50 years of research hanging wall to the fault. The very broad within the Whanganui Basin and Rangitikei positive anomaly underneath Blenheim District. Tephrochronology, biostratigraphy reflects a very deep source, potentially related and lithostratigraphy are implemented to to the subducting Pacific Plate. define sedimentary units and map them across the landscape. The aim of this project is to inform territorial authorities, landowners, PLIO-PLEISTOCENE GEOLOGY OF CENTRAL developers and industry by providing RANGITIKEI, WHANGANUI BASIN, NEW information on the geology of the district. ZEALAND Particular emphasis is placed on the water bearing properties of sedimentary units, with Callum Rees, Julie Palmer, and Alan Palmer the goal of investigating chemical and physical Department of Earth Sciences, Massey properties, which are relevant to University, Palmerston North, New Zealand environmental issues being faced in central [email protected] Rangitikei today.

Central Rangitikei provides a cross section through the Plio-Pleistocene succession of eastern Whanganui Basin (WB), Lower North Island, New Zealand. Sedimentary units exposed in the cliffs and valley sides of the Rangitikei by ongoing regional uplift and erosion provide part of one of the most comprehensive onland Quaternary stratigraphic records in the world. Geologically young faunal assemblages and their associated lithofacies form the basis for 93

THE ALPINE FAULT – A TECTONOPHYSICS ruptures, in agreement with recent geological PERSPECTIVE studies.

Martin Reyners GNS Science, PO Box 30368, Lower Hutt A JUMBLE OF HOBBITS AND GIANTS: [email protected] PENGUINS AND OTHER VERTEBRATES FROM THE LATE OLIGOCENE ROCKY SHORELINE AT The Alpine Fault has traditionally been COSY DELL, SOUTHLAND, NEW ZEALAND interpreted as a plate boundary through continental lithosphere, with attendant M.D. Richards1, D.E. Lee1, H.J.L. Gard1,2 & widespread deformation. But recent 3-D R.E. Fordyce1 imaging of deep crustal structure has shown 1Dept. of Geology, University of Otago, PO that the habitat of the fault is dominated by Box 56, Dunedin strong, large igneous province (Hikurangi 2GNS Science, PO Box 30368, Lower Hutt Plateau) lithosphere, producing a much [email protected] narrower deformation zone. The fault formed at ca. 23 Ma as a subduction-transform edge The Cosy Dell rocky shore deposit near Gore, propagator (STEP fault), when the subduction Southland (Late Oligocene, Duntroonian - zone to the north rolled back by ripping lower Waitakian) reveals much about the oceanic crust seaward of the trench from the biota of Zealandia during a period of marine western edge of the strong Hikurangi Plateau. transgression and minimal emergent STEP fault propagation stopped at ca. 15 Ma, landmass. The vertebrate assemblage includes when the edge of the plateau became parallel penguins, rays, sharks, bony fish, probable to the strike of the subduction zone. Strike-slip cetaceans (whales, dolphins), and a presumed motion on the fault renewed at ca. 7 Ma, when sea and sea turtle. Specimens are isolated the fault linked with the Marlborough fault and generally fragmentary bones, worn due to system. If the 480 km offset of geological the active wave-dominated depositional terranes across the fault occurred only during setting. these two episodes, this implies an average strike-slip rate of 32 mm/a, close to the Bones from different-sized penguin species relatively constant Late Quaternary strike-slip are present, but none are complete enough to rate of 27 ± 5 mm/a. The current pattern of be named to genus. No bones exhibit juvenile convergence along the fault is dominated by features. Some hindlimb elements are larger the 16⁰ mismatch between the strike of the than emperor penguin (Aptenodytes). STEP fault and the strike of the converging Fragmentary tibiotarsi and a radius are similar plateau, which leads to the highest uplift and in size to the yellow-eyed penguin and exhumation rates occurring in the Aorangi/Mt medium-sized crested penguins (Megadyptes, Cook region. The fault is weak on a Eudyptes). An ulna and coracoid are from tiny lithospheric scale. Bending of geological penguins comparable in size to little blue terranes into the fault, previously ascribed to penguin (Eudyptula) and the smallest banded fault drag, can be explained by impact of the penguins (Spheniscus). Elsewhere, small Hikurangi Plateau with subduction margins in Eudyptula-sized fossil penguins are rare; two the Cretaceous and Cenozoic, prior to STEP Late Oligocene South Canterbury localities are fault initiation. The current low level of the only New Zealand sites yielding associated seismicity near the fault is consistent with a bones from tiny specimens. Lone bones are characteristic model of large earthquake known from Canterbury-Otago mid-Cenozoic 94 localities. Small Paleogene penguins are engineered geothermal reservoir. Here, we reported only from New Zealand and Seymour challenge this assumption. We consider the Island, Antarctica. case of the Paralana-2 EGS stimulation, undertaken in South Australia in 2011, where Cosy Dell has the richest Chatton Formation 4172 micro-earthquakes were detected and vertebrate biota, and one of the greatest size- located. Injectivity, the ratio of injection rate ranges recorded for a fossil penguin to wellhead pressure, increased assemblage. The Cosy Dell penguins probably approximately linearly during the stimulation, nested in colonies along Southland’s implying permeability enhancement, and thus subtropical coastlines of sandy beaches, rocky reservoir creation. To test whether shores and estuaries, festooned with permeability enhancement and seismicity rainforest and mangroves. Small ancient triggering occurred concurrently, we develop penguins, like their modern counterparts, an inversion procedure designed to obtain probably had restricted foraging ranges, and permeability spatio-temporal evolution, a likely exploited local marginal shallow seas. process independent from assumptions on the Larger penguins probably foraged in deeper mechanisms responsible for its increase. In continental shelf and slope waters further order to do so, we use hypocentre density afield. computed from the induced seismicity cloud as a proxy measure of pore pressure increase, a correlation established from a previous EGS KINEMATIC PERMEABILITY INVERSION experiment. The results indicate that USING INDUCED SEISMICITY APPLIED TO THE permeability enhancement is limited to PARALANA EGS STIMULATION volumes close to the wellbore, and largely uncoupled from seismicity triggering occurring J. Riffault1, D.E. Dempsey1, R. Archer1, S. further away. The reservoir created at Karra2 Paralana is thus much smaller than assumed 1 Department of Engineering Science, the by looking just at the seismicity cloud. University of Auckland, Auckland Furthermore, it indicates that hydroshearing is 2 Los Alamos National Laboratory, Los not the mechanism primarily responsible for Alamos, New Mexico, USA permeability enhancement in this case. Our [email protected] study suggests that the success of hydraulic stimulations may be overestimated in other In Enhanced Geothermal Systems (EGS) EGS settings. projects, in-situ permeability is artificially enhanced through high pressure injection of cold water. These stimulation operations typically induce large seismicity cloud. Earthquake triggering is assumed to be mainly a consequence of pore pressure increase through an existing fracture network, a mechanism called hydroshearing. It can potentially develop the overall permeability of the reservoir through mismatch of the rough surfaces of the shearing fractures. Thus, seismically active volume is commonly inferred to reflect the extent of the 95

DATING ALPINE SCHIST MYLONITISATION 40Ar/39Ar illite/mica age of 11.46±0.47 Ma AND THE ROLE OF THE MID-CRUSTAL from Harold Creek. Our ages of ~11 Ma are DECOLLEMENT similar to the age for the onset of transpression by Cande and Stock (2006). We U. Ring1, J. Glodny2, S. Angiboust3, T. Little4 propose that the onset of transpression and & I.T. Uysal5 associated thrusting/metamorphism started 1Department of Geological Sciences, by ~11 Ma. Stockholm University, Stockholm, Sweden [email protected] If current convergence rates were used to 2Deutsches Geoforschungszentrum Potsdam, move the mylonite eastward back along the Germany mid-crustal decollement to its 11 Ma position, 3Institut de Physique du Globe, Paris, France the mylonite would end up outside the 4School of Earth Sciences, Victoria University, orogen. Furthermore, a decollement at 15-25 Wellington, New Zealand km is unlikely to sample rocks that formed at 5CSIRO, Perth, Australia 35-40 km. We suggest that the Alpine Schist mylonite formed in the orogenic root and was We constrain the pressure-temperature (PT) slowly exhumed until the Southern Alps conditions and the timing of mylonitisation of rainshadow developed and the current Alpine Schist directly above the central Alpine tectonic regime with the decollement was Fault for discussing the timing of established. transpressional crustal thickening and the role of the mid-crustal decollement in the Southern Alps. Crustal-thickening related ASSESSMENT OF DEBRIS FLOW/FLOOD thrusting reflects the direct response of the HAZARD AT TE PURU TOWNSHIP, rocks to initiation of oblique plate COROMANDEL, USING TITAN-2D AND convergence. A common concept is that the RAMMS MODELLING lithosphere of the incoming Pacific Plate delaminates along a mid-crustal decollement Tom Rishworth, Martin S. Brook and lower crustal material is either added to 1School of Environment, University of the orogenic root or subducted with the Auckland, Private Bag 92019, Auckland 1142, Pacific lithospheric mantle. The fact that no New Zealand rocks higher than amphibolite-facies grade are exhumed despite huge dip slip movement is Debris-flows can have peak discharges of c.40 compelling evidence for the mid-crustal times greater than that of anticipated flood decollement. Kinematic modelling suggests a flows due to the entrainment of sediment ramping decollement between 15-25 km from stream beds and banks. Due to their depth (Herman et al., 2009). velocity, and rapidity of development, they can have deadly consequences. The Melton Three Rb-Sr multi-mineral isochrons yielded Ratio, R (ratio of basin relief to the square toot ages of 10.4±0.5 and 8.9±3.2 Ma for of basin area) is typically used to determine amphibolite-facies mylonitisation at Gaunt debris flow and debris flood hazard. The Creek and Harold Creek. PT conditions for important threshold is R=0.3, below which mylonitisation were ~1 GPa and ~565°C. The conventional fluvial processes are assumed to Rb-Sr age of 10.4±0.5 Ma from Harold Creek is be the dominant fan-forming processes. While a maximum age for the end of ductile many of the catchments around the deformation and almost identical to an Coromandel Peninsula on which townships 96 are built have Melton R<0.3, geomorphic and important site in the limited scale of quarries historic evidence show that such townships producing good quality aggregate to the may be vulnerable to debris flows and floods. Auckland area. Transport costs associated For a recent comparison, the Matata event in with aggregates are substantial as they double 2005 developed from catchments with a with every 30 kilometres transported away Melton R=0.17 and 0.25. We focus on the Te from the source. Therefore, maximising the Puru Stream fan-delta on the western side of safe production from quarries like Matakana is the Coromandel Peninsula, on which Te Puru critical to economic development in the Township is located. Te Puru Stream now region, particularly with the new roading plans follows an engineered course on exiting the for north of Puhoi. Numerous factors impact mountain front, diverted north within levees on the safe production of aggregates, these around the fan apex into the Firth of Thames. include the scale of the excavation and the Landslide susceptibility mapping upstream of machinery/equipment being used. In the Te Puru fan, both in-field and using GIS particular, slope design is critical maximising in indicates the catchment is vulnerable to both aggregate production, while ensuring hazard shallow soil landslides, leading to debris flows. risks are minimised and yet still maintaining An assessment of debris flow hazard using the economically viability. An understanding of flow simulation programs Titan2D and host rock stratigraphy and structure is integral RAMMS modelled the impacts of a series of to the decision making when designing slopes. discharge estimates from extratropical rainfall This study used a combination of the events. This modelling indicates that while the conventional scanline surveying and discharge reaching the fan apex is somewhat computational digital photogrammetry constrained by the channel bend as the river mapping techniques to define the different exits the mountain front, debris flows are geological and structural characteristics within likely to super-elevate prior to reaching the the quarry. Both kinematic and limit fan apex. This would lead to avulsion of the Te equilibrium analysis geotechnical Puru Stream down the centre of the fan-delta programmes were used to classify the through the township. different structural zones within the quarry and quantify their stability, which allowed for an interpretation of aggregate production at THE GEOLOGICAL AND STRUCTURAL the Matakana quarry. CONSTRAINTS ON THE PRODUCTION OF AGGREGATE, AT MATAKANA QUARRY, RODNEY POTENTIAL STABILISATION OF HALLOYSITE- RICH SENSITIVE SOILS OF THE BAY OF Tom Rishworth, Julie V. Rowland PLENTY BY CATION MANIPULATION 1School of Environment, University of Auckland, Private Bag 92019, Auckland 1142, T. Robertson, V. G. Moon, D. J. Lowe New Zealand School of Science, University of Waikato, Private Bag 3105, Hamilton, NZ Aggregate demand for infrastructure and [email protected] building in Auckland is predicted to increase substantially as a result of increasing growth in The aim of this study is to determine whether population and wealth. In 2012 alone, the salt treatment of sensitive soils formed in total value of industrial minerals mined was halloysite rich soils of the Bay of Plenty over $388 million. The Matakana quarry is an provides a viable means of improving soil 97 behaviour. Soil collected from the base of the DEVELOPING SEDIMENT FINGERPRINTING landslide at Bramley Drive, Omokoroa, was TECHNIQUES FOR THE WHANGANUI treated with 3 differing potassium based salts CATCHMENT, NEW ZEALAND (KCl, KOH and K2CO3). Intact soil cores were 1 1 1 1 soaked in K2CO3 solution for a period of three J. Robinson , J. Proctor , G. Lube , I. Fuller , weeks before being subjected to static tri-axial J. Dymond2, G. Harmsworth2 & S. Vale2 testing; untreated soil cores were tested at the 1Institute of Agriculture & Environment, same stress conditions. Tri-axial testing Massey University, Palmerston North showed a significant increase in the peak 2Landcare Research, Palmerston North, New deviator stress measured when comparing the Zealand untreated and treated soils at its point of [email protected] failure, with increases in peak deviator stress measured for the treated soils in the order of Suspended sediment is an important 124 - 227%. Strain softening for treated soil component of the fluvial system, affecting was also measured to be less than that of the water quality, chemistry, channel morphology untreated soil at all confining pressures, a trait and ecological character of streams and rivers. reflected in pore pressures measured at point Due to the inherent geological and of failure also. Stress path plots indicated that geomorphological character of the untreated samples underwent contraction Whanganui catchment, anthropogenic rapidly as deviator stress increased, with no influences such as land use change have clear failure point observed as would be greatly exacerbated rates of erosion leading to expected from an over consolidated clay. In increased suspended sediment entering contrast, stress paths for the treated samples waterways. Understanding the spatial origin showed the soils dilating before reaching and movement of suspended sediment is an point of failure and undergoing contraction important step in guiding sustainable following failure. Differences in friction angle management of the natural resources within and cohesion were also measured between the Whanganui catchment. treated and untreated samples, with untreated soil indicating friction angle and Sediment fingerprinting is a tool for evaluating cohesion of Φ’=19.3o, C’=26.6 kPa. Both sediment provenance, capable of directly friction angle and cohesion values increased in quantifying sediment supply through treated soils (Φ’=28.2 and C’=58.4). These differentiating sediment sources based on results indicate a real potential for slope inherent geochemical signatures. The remediation by cation manipulation in the Bay preliminary approach for this research is to of Plenty. conduct a catchment-wide time-integrated sampling programme. Geochemical fingerprints will be established for major tributaries using statistical analysis and un- mixing models will be employed on samples collected lower in the catchment to elucidate sediment provenance. Further aims of this research are to develop techniques to analyse a wider spectrum of grain sizes and to provide insight into historical sediment flux regimes using flood deposits.

98

Māori have a long-standing relationship with date petroleum source rocks. Re-Os isotopic the Whanganui Catchment and its waterways. dating has also been extended to crude oils, More than a millennium of occupation has potentially providing the timing of oil embedded this environment deep into the generation and/or expulsion from the source collective consciousness of Whanganui iwi. A rocks. Further, it has been established that the substantial environmental knowledge base Os isotopic composition of oils and bitumen has accrued during this time and is contained faithfully reflects that of their main source in the forms of recitation of whakapapa, units. The isotopic system can thus provide a stories, proverbs, sayings, songs, cultural potential means for tracing oils to their source activities and tribal expressions. Incorporating rocks, showing particular promise for these philosophies into this research presents biodegraded oils where conventional an opportunity to study the catchment with a biomarkers based on lighter oil components unique Maori perspective using methods that have been compromised. But while the Re-Os adhere to mātauranga ā-iwi principles and isotopic system shows excellent promise in values. This indigenous knowledge base can dating and tracing source rocks and oils, there provide holistic traditional and contemporary remain some fundamental questions. In insights into the processes operating within particular, most published work has focused the Whanganui catchment and will be a key on sediments and oils of marine origin. How component in developing effective research applicable is the Re-Os isotope system to tools and management strategies. terrestrial, coaly sourced systems such as typify most of New Zealand’s petroleum basins? We aim to evaluate the behaviour of APPLICATION OF THE RHENIUM-OSMIUM the Re-Os isotopic system in well ISOTOPIC SYSTEM TO NEW ZEALAND characterised terrestrial source-oil systems SOURCE ROCKS AND OILS from the Taranaki Basin, and assess its ability to trace and date such systems. We will E. Rotich1, M.R. Handler1, S. Naeher2, D. present results from our preliminary analyses Selby3 and R. Sykes2 and the methodologies used. 1Victoria University of Wellington, PO Box 600, Wellington 2GNS Science, PO Box 30-368, Lower Hutt CHARACTERIZING AMORPHOUS MATERIALS 3The University of Durham, UK BY X-RAY DIFFRACTION: APPLICATIONS ON [email protected] EARTH AND MARS

The application of the Rhenium-Osmium (Re- M.C. Rowe1 and B. J. Brewer2 Os) isotope system in understanding the 1School of Environment, Auckland University, processes and elements of a petroleum PB 92019, Auckland 1142 system is a developing area of research with 2Department of Statistics, Auckland great potential. Re and Os are organophilic University, PB 92019, Auckland 1142 trace metals that become enriched in organic- [email protected] rich sedimentary rocks. The resulting combination of high and variable Re and Os Although classically used for determining concentrations with variations in Os isotopic mineral componentry in geologic samples, X- composition produced by the radioactive ray diffraction (XRD) also records important decay of 187Re to 187Os, means that these information on amorphous materials, such as metals can be used to directly and precisely volcanic glass, amorphous silica, and other 99 partially-amorphous materials. Recent studies HIGH RESOLUTION SIMS ANALYSIS OF have utilized XRD to determine crystallinity in 87SR/86SR IN PLAGIOCLASE: METHOD volcanic materials related to a range of DEVELOPMENT AND INITIAL APPLICATION different processes including ignimbrite devitrification, volcanic dome emplacement, M. Sas1, N. Kawasaki2, P. Shane1, N. and determining basaltic eruption styles. In Sakamoto3, H. Yurimoto3 & G. Zellmer4 order to standardize the methodology, we 1School of Environment, University of present a new approach to processing XRD Auckland, Private Bag 92019, Auckland 1142 patterns, using Bayesian statistics. This in new 2JAXA Institute of Space and Astronautical approach, in the program AMORPH, not only Science, Sagamihara 252-5210, Japan quantifies the crystallinity of geologic 3Isotope Imaging Laboratory, CRI, Hokkaido materials but it characterizes the shape of the University, Sapporo 001-0021, Japan amorphous component in terms of skewness, 4IAE, Massey University, Private Bag 11222, nongaussianity, centre of mass, and width. Palmerston North 4442 [email protected] We see a significant improvement in reproducibility of crystallinity results using the Plagioclase, a ubiquitous igneous mineral, statistical approach and AMORPH software, responds readily to fluctuations in regardless of user, and the composition of the crystallization conditions and records material. The methodology is best-suited for variations in host magma composition. These crystallinities between 10-90%. In addition, qualities make plagioclase ideal for testing on compositionally diverse volcanic deciphering magma evolution and pre- glasses (basalt and rhyolite) clearly indicates eruptive changes, which are determined that we can independently assess changes in through combination of mineral textures, the XRD patterns associated with structural compositional zoning and isotopic ratios. The changes in the silicate glass. Compared to temporal scale at which we can determine basaltic glass, the tested rhyolite has an changes in magmatic conditions is dependent increased positive skewness and a shift to on the spatial resolution of techniques used to lower two-theta values. Processing of XRD obtain mineral compositions. Therefore by results of inferred basaltic and silicic Martian improving the resolution at which isotopic sediment samples produces similar changes in compositions can be determined, specifically amorphous characteristics, particularly with a Sr in plagioclase, we can improve our distinctive 4x increase in skewness in the silicic understanding of rates of magmatic change. material. Overall, we see that regardless of Methods presently used are laser ablation instrumentation, characterization of multi-collector inductively-coupled plasma amorphous materials produces systematic mass spectrometry (LA-MC-ICPMS) and results with regard to glass composition and thermal ionization mass spectrometry (TIMS). our new AMORPH program more accurately TIMS is the most precise, but necessary reproduces crystallinity results in a range of microdrilling and chemical separation make it compositions and rock types. a time-consuming technique. Although LA- MC-ICPMS offers in-situ analysis, the diameter of ablation spots (commonly 100 µm) limits the number of crystal domains that can be analysed. Additional issues for both methods include diffusion and averaging of Sr isotopes across the analysed region, and size limitation 100 on the crystals that can be analysed. Here we calculated the spatio-temporal variation of the investigate the potential for MC-secondary ion crustal stress field by stress tensor inversion mass spectrometry (SIMS) as a new method using focal mechanisms of the micro- to for obtaining 87Sr/86Sr ratios in plagioclase. moderate-sized earthquakes in the area. This was done using a CAMECA IMS 1280-HR at Hokkaido University. Run conditions include In the period before the Kaikoura earthquake, 16O– primary ion beam (~12 µm diameter, 6 we analyzed seismic data acquired by a dense nA, 23 keV), mass resolving power (M/∆M) of seismic array, which has been recording over 7,000, 400 s total count time per spot, and 2 years, from 2013 to 2015. We determined average external precision of ±0.0005 (2σ). focal mechanisms using the HASH program 85 40 Rb and Ca2 were measured to determine (Hardebeck, 2002; 2003) and estimated the contribution of interferences of 87Rb and Ca crustal stress field using the SATSI algorithm dimers to 86Sr+ and 87Sr+. Crystals from three (Hardebeck and Michael, 2006). In the period rhyolite Okataina volcano deposits were after the Kaikoura earthquake we analyzed examined initially. Future work includes the data acquired by a dense seismic array improving analytical precision, analysing which recorded, from 13 November 2016 to plagioclase with variable An contents, and 30 November 2016, to estimate the post- locating natural plagioclase with seismic stress field. We also used GeoNet 87 86 homogeneous Sr/ Sr and An70-30 as CMTs calculated over the 7 month period from additional analytical standards. 14 November 2016 to 30 June 2017.

We compared the stress tensor solutions from SPATIO-TEMPORAL REGIONAL STRESS FIELD before and after the Kaikoura earthquake. ASSOCIATED WITH THE MW 7.8 KAIKOURA Using a 1° × 1° regular grid inversion, we EARTHQUAKE BY STRESS TENSOR determined the orientation of the axes as INVERSION IN THE NORTHERN SOUTH SE-NW, both before and after the earthquake. 1 ISLAND The orientations of and 𝜎𝜎 axes interchanged after the Kaikoura earthquake. 1 1 2 3 2 3 T. Sato , T. Okada , Y. Iio , S. Matsumoto , S. Before the earthquake the𝜎𝜎 axis was𝜎𝜎 vertical 4 4 3 3 Bannister , J. Ristau , S. Ohmi , T. Miura , J. and the stress regime was one of strike-slip 5 6 7 2 Pettinga , F. Ghisetti , R. H. Sibson faulting, while after the earthquake𝜎𝜎 the axis 1 Tohoku University, Japan is vertical and the stress regime is that of 2 3 Kyoto University, Japan reverse faulting. 𝜎𝜎 3 Kyushu University, Japan 4 GNS Science, New Zealand To consider the effect of irregularity of the 5 University of Canterbury, New Zealand aftershock distribution, we also group 157 6 TerraGeoLogica, New Zealand focal mechanisms spatially into 6 clusters 7 Dept. of Geology, University of Otago, New using k-means algorithm. The result from the Zealand 3D clustering inversion using the k-means [email protected] method shows a similar result utilizing the regular gridding. We conclude that the The Mw 7.8 earthquake occurred in the observed temporal variation is robust using Kaikoura region of northern South Island on 14 the different groupings. November 2016 (UT), with rupturing of a complex network of right-lateral, left-lateral and oblique-reverse faults. We have 101

SEISMIC ANISOTROPY CHANGES times increase after the foreshock and ASSOCIATED WITH THE 2016 KUMAMOTO decrease with time afterwards, suggesting EARTHQUAKE, JAPAN that cracks form with the rupture and then heal. Further work is under way to determine M. K. Savage1 & Y. Aoki2 whether the changes in orientation are more 1SGEES, Victoria University of Wellington, PO likely due to changes in stress during the Box 600, Wellington observation time, or due to spatial changes in 2Earthquake Res. Inst., Univ. of Tokyo, 1-1 anisotropy combined with changes in Yayoi 1, Bunkyo-ku, Tokyo 113-0032 earthquake locations. [email protected]

Seismic anisotropy, measured by shear-wave GEOCHEMISTRY AND PARAGENESIS OF splitting, may be an indicator of stress in the SCHEELITE AT GLENORCHY, OTAGO, NEW crust due to the effects of stress on aligned ZEALAND cracks. However, the effects of mineral or structural alignment, and the difficulty of E.J. Scanlan & J.M. Scott distinguishing between changes in anisotropy Department of Geology, University of Otago, along an earthquake-station path from PO Box 56, Dunedin distinguishing changes in the path itself, have [email protected] made such findings controversial. Scheelite (CaWO4) is an important tungsten The sequence of earthquakes related to the ore mineral and has uses in both industrial and M=7.2 Japanese Kumamoto earthquake of 14 commercial settings. Scheelite-bearing quartz April 2016 includes both foreshocks, veins in the Glenorchy region have been mainshocks and aftershocks. The sequence mined intermittently since the 1880’s but was recorded by the NIED permanent have had little investigation. We report a study network, which already contributed of samples from the Glenorchy and Bonnie background seismic anisotropy Jean lodes on Mt Judah that we have measurements in a previous study of geochemically and isotopically characterised. anisotropy and stress in Kyushu. This provides Electron backscatter imaging shows the large a unique dataset to test the use of shear wave scheelite masses in the veins are made up of splitting for measuring variations in stress numerous small grains with different because clusters of closely-spaced crystallographic orientations. earthquakes occurred both before and after a Cathodoluminescence (CL) imaging reveals mainshock. We use the automatic, objective that the grains within the scheelite masses to splitting analysis code MFAST to speed process have slightly different responses, but all are and minimize unwitting observer bias when Mo-poor and fluoresce bright blue under short determining time variations. wave UV light. Scheelite is a major host of REE, and REE variations within samples correspond Earthquakes in the region that occurred in to CL response. The scheelite grains show 2016 yielded over 100,000 shear-wave MREE variations that form three types, which splitting measurements. Results at some we interpret to represent precipitation from a stations clearly differ from those of our earlier fluid that had undergone variable fractional of study. They also change between earthquakes MREE. In-situ scheelite 87Sr/86Sr by LA-ICP-MS recorded before and after the mainshock. For averages ~0.7070. Since host rock samples stations near the fault rupture, median delay have less radiogenic age-corrected whole rock 102

87Sr/86Sr values of 0.7046-0.7050 at 135 Ma, comprising the outlet dam were sampled and there must be a more radiogenic lithology at analysed using rock and soil physical and depth that has imparted its Sr isotopic mechanical laboratory tests. These properties signature on the mineralising fluid. This source were used as input in finite element and limit is suggested to be the Aspiring Terrane. equilibrium method-based groundwater and Paterson and Rankin (1979) showed that stability models. Groundwater models wallrock adjacent to mineralised veins is indicate that a layer of laminated ash depleted in Sr, and so our results mean that deposited on the inside of the crater during the volume of fluid flowing through this past eruptions likely serves as a low- hydrothermal system must have been large permeability barrier preventing water from enough to overprint the Sr signature of the seeping through a matrix-rich breccia unit of host rock. Carbonate is present in the veins, the outlet dam. The degradation or removal of but it replaces scheelite and is therefore a this impermeable unit could result in later mineral. It takes on the scheelite isotopic undercutting and collapse of the outlet. composition where it replaces it but otherwise Stability models suggest that the continued is more radiogenic. The geochemical and incision of a lava cap on top of the breccia unit, isotopic compositions of minerals in the which is activity eroding due to the flow of Glenorchy W systems therefore require large water over time, could also result in water scale redistribution of hydrothermal fluids seepage into the breccia unit and subsequent from depth. failure. Ground acceleration from local and regional earthquake events sourced from nearby stations were additionally used in a Newmark stability analysis to determine STABILITY ASSESSMENT OF THE CRATER critical slip surfaces and displacements for LAKE OUTLET DAM AT MT. RUAPEHU different sized earthquake events. These VOLCANO results indicate that major volcano-tectonic earthquakes could induce failure of the outlet L. Schaefer1, B. Kennedy1, M. Villeneuve1, S. dam, leading to drainage that could lower the Cook1, H. Keys2, G. Leonard3, A. Jolly3 crater lake up to 4 m. Engineering-focused 1Dept. of Geological Sciences, University of studies such as these can reveal the influential Canterbury, Christchurch variables in volcanic stability, useful for long- 2Dept. of Conservation, Turangi term hazard planning at Mt. Ruapehu. 3GNS Science, Lower Hutt [email protected] STRUCTURAL EVOLUTION OF SOLANDER Mt. Ruapehu volcano hosts a 106 m3 lake in the BASIN active summit crater, making it prone to lahars due to the abundance of water stored at high R. Schuurmans1, A. Nicol1 & M. Arnot2 elevation. Apart from eruptive periods, large 1Dept. of Geology, University of Canterbury, lahar events can occur when portions of the Private Bag 4800, Christchurch crater rim fail and partially drain the lake; such 2GNS Science, PO Box 30-368, Lower Hutt lahars occurred in 1953 and 2007. Here, we [email protected] investigate the potential of future dam-break lahars at the current outlet dam using detailed The Solander Basin is nestled between the geotechnical assessments and numerical Alpine Fault and Stewart Island at the foot of modeling. Prehistoric lavas and breccias New Zealand. Since its inception in the mid- 103

Cretaceous, the basin has been translated 450 ARE GARNET PYROXENITES IN KAKANUI km south-westwards along the Alpine Fault MINERAL BRECCIA PART OF HIKURANGI from a location near the southern Taranaki PLATEAU? Basin. Given its location, deformation in the Solander Basin provides a unique record of J.M. Scott & J. Sun evidence for the timing and kinematics of Department of Geology, University of Otago, tectonic events in southern Zealandia; PO Box 56, Dunedin including the Fiordland block and Emerald [email protected] Basin. The subducted extent of the Hikurangi Plateau The aim of this research is to determine the beneath southern Zealandia remains debated. structural evolution of the Solander Basin by It has been suggested from seismic data that describing the geological structures and the southernmost limit of the Hikurangi sedimentary sequences that can be identified Plateau is located somewhere between on 2D seismic reflection lines. The data Dunedin and Timaru. We test this theory from available for the analysis consists of 147 a petrological view point by looking at garnet seismic reflection lines collected from 1971 to pyroxenite xenoliths in the Kakanui Mineral 2006. The Late Eocene to Recent sedimentary Breccia, since these could be metamorphosed stratigraphy and age of seismic horizons in the components of the plateau. Petrographical basin have been mainly constrained by the and geochemical analysis has been applied to Solander-1 and Parara-1 wells. six garnet pyroxenite samples. Temperatures given by garnet-clinopyroxene thermometer Preliminary seismic interpretation reveals range between 1081-1260oC and imply that mid- Cretaceous to early Cenozoic normal last equilibration of the xenoliths occurred faults associated with half-grabens and Late within the lithospheric mantle, which is Miocene to Recent reverse faults and appropriate for the plateau. Whole rock trace associated folds. Most of the early normal element and REE data show that Kakanui faults are reactivated to produce inversion garnet pyroxenites have MORB-like structures. Each of the two phases of faulting chemistries, which are similar to the plateau. are followed by periods of uplift and erosion Whole rock Sr-Nd isotope data show which produced regional angular significant differences between the garnet unconformities of possible Late Eocene and pyroxenites and the MORB-like Hikurangi Pliocene ages. Thus the tectonic history of the Plateau, with the garnet pyroxenites being less Solander Basin appears to be comparable to radiogenic in Sr and more radiogenic in Nd. the Taranaki Basin. Based on interpretations The garnet pyroxenites are instead chemically of the Solander Basin to date we can neither and isotopically similar to the intraplate conclusively demonstrate significant (e.g., kms basalts that have erupted throughout to hundreds of kms) strike-slip movement on Zealandia, and we suggest that these rocks the Moonlight Fault nor see evidence for represent stalled basaltic melts in the lower extension associated with Emerald Basin lithosphere that were subsequently entrained opening. by the nephelinite magma that formed the Kakanui Mineral Breccia. There remains an absence of petrological data that indicates the presence of the Hikurangi Plateau beneath Otago.

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configuration, the establishment of the CRETACEOUS TO RECENT PLATE TECTONIC modern plate boundary through Zealandia, RECONSTRUCTIONS OF ZEALANDIA and internal deformation of North and South islands during the Neogene. H. Seebeck1, D. Strogen1, P. King1, A. Nicol2, G. O’Brien1 Using GPlates, we use a simple double-hinge 1GNS Science, PO Box 30368, Lower Hutt slat model to describe Neogene deformation 2Geological Sciences, University of within the New Zealand plate boundary zone, Canterbury, Private Bag 4800, Christchurch while the geometry of north and south [email protected] Zealandia during the Eocene is modified from recently published models based on geologic Reconstructions of the past relative positions considerations. This study ultimately of north (Lord Howe Rise and Challenger highlights the need for integrated studies of Plateau) and south Zealandia (Campbell the Zealandia plate circuit. Plateau and Chatham Rise) provide important constraints on the orientation and amount of strain accumulated between rigid plates MICROSTRUCTURES AND ANISOTROPIES OF separated by divergent, convergent and HARZBURGITE AND LHERZOLITE XENOLITHS transform boundaries within the Australia- FROM EAST OTAGO Pacific plate tectonic circuit. This configuration of plates ultimately determines how, where, Y. Shao, D.J. Prior, J.M. Scott and when sedimentary basins formed during Dept. of Geology, University of Otago, PO Box and since continental breakup along the 56, Dunedin eastern margin of Gondwana. [email protected]

While the first-order geometry of Zealandia is Mantle xenoliths, entrained in volcanic rocks, well established, uncertainty still remains provide constraints on mantle geodynamics. regarding plate motions through the latest We have examined spinel-facies peridotites, Cretaceous to Eocene. Recent reconstructions from Trig L, East Otago, that occur as xenoliths are, in some cases, inconsistent with in alkaline basalt volcanics, erupted during the geological observations at key time intervals, late Oligocene-Miocene (24-9 Ma). Ten highlighting uncertainties inherent in plate xenoliths were selected for quantitative reconstructions for the SW Pacific. microstructural analysis using Electron Backscattered Diffraction (EBSD). The samples Building on previous tectonic reconstructions comprise harzburgites and lherzolites. Mineral and incorporating published seafloor chemistry constrains the harzburgites to have magnetic interpretations, paleomagnetic equilibrated at lower temperatures (748-849 observations and geological constraints (e.g. ℃) than the lherzolites (827-960 ℃). Terrane geometry and distribution), we have Crystallographic preferred orientations (CPO) developed a first-iteration tectonic framework of olivine in all samples are characterised by to reconstruct Zealandia back through to the mutually perpendicular single maxima clusters latest Cretaceous. of [100] and [010] with [001] less strongly aligned. Olivine CPOs are stronger in We have developed a consistent and harzburgite than lherzolite. The shape of accessible model with which to test harzburgite and lherzolite olivine CPOs hypotheses relating to the pre-breakup overlap but the tendency is for [010] 105 alignment to be better developed in fault rocks. harzburgite and [100] in lherzolite. In the harzburgites, the orthopyroxene [001] aligns M > 5.5 fault ruptures ‘sample’ substantial in a cluster parallel or sub parallel to olivine portions of the seismogenic upper crust. [100], with orthopyroxene [100] and [010] less Global dip compilations have been made for strongly aligned with olivine [100], [010]. In near-pure dip-slip ruptures in continental lherzolites the orthopyroxene CPOs do not crust where the rupture plane is positively correspond so well with the olivine CPOs, but discriminated. 2-D reactivation analysis shows clinopyroxene (100) is broadly aligned in a that for faults containing σ2 and oriented at θr cluster parallel to olivine [100]. The CPO data to σ1, optimal reactivation occurs when θr* = -1 suggest that the operating deformation ½tan (1/µs), and frictional lock-up occurs -1 mechanisms and potentially the mantle when θ 2θr* = tan (1/µs). Assuming rheology of the harzburgites and lherzolites ‘Andersonian’ horizontal σ1 trajectories for were different. Calculated elastic properties pure reverse-slip faulting, θr corresponds to for average harzburgite and lherzolite samples the fault dip, δ, but for normal faulting with would give rise to shear wave splitting in vertical σ1, θr = (90° - δ). In the case of reverse- steeply inclined teleseismic data if the olivine slip faulting, a well-defined peak in the dip [100] were orientated horizontally. 80km histogram at 30 ± 5° is flanked by two thickness of harzburgites or 150km thickness subordinate peaks at 50 ± 5° and 10 ± 5° with of lherzolites, or some combination in a no dips above 60°. For normal fault ruptures, layered mantle structure, can explain the ~1s the dip range extends from 65° down to 30°. of shear wave splitting in data related to the Thus θr = 60° to inferred σ1 (twice the optimal present day mantle. angle, θr = 30°, for reshear of reverse faults) appears to represent the angle of frictional ‘lock-up’. This is consistent with µs ≈ 0.6, at the FAULT FRICTION IN THE SEISMOGENIC base of Byerlee’s (1978) range for hard-rock UPPER CRUST friction.

R.H. Sibson Fault weakening by fluid overpressuring, Department of Geology, University of Otago, especially in the lower seismogenic zone, P.O. Box 56, Dunedin 9054 remains a possibility. [email protected]

Seismic activity is largely restricted to the upper 15 ± 5 km of deforming continental crust where T < 350°C. Within this seismogenic zone, frictional shear strength of faults is governed by: τf = Cf + µs(σn – Pf), where σn is normal stress across the fault, Pf is pore-fluid pressure, Cf is residual cohesion, and µs is the friction coefficient. Laboratory determinations generally show 0.6 < µs < 0.85 (Byerlee, 1978), but application to natural faults has been questioned because of small displacements and specimen size in laboratory experiments, and possible clay mineral alteration in natural 106

MULTI-PARAMETER STUDIES OF A November 2016. Results are used to identify PERSISTENTLY ACTIVE VOLCANO, YASUR, magmatic, as well as external (e.g. VANUATU environmental) processes that affect eruption behaviour and consequent hazard. A multi- B. Simons1, S. Cronin1, J. Eccles1 & E. component dataset has been produced using Garaebiti2 a variety of instrumentation and analytical 1School of Environment, University of methods, including seismometers, infrared Auckland, Private Bag 92019, Auckland thermal cameras, UV gas spectrometers, 2Vanuatu Meteorology and Geohazards visual observations and statistical records, Department, PMB 9054, Port Vila, Vanuatu meteorological observations, as well as ash [email protected] and plume-rain-fallout sampling. These combined data sets comprise a particularly Yasur is a globally rare persistently active powerful group of tools for parameterizing volcano that has been in eruption for at least and understanding volcanic activity over both 800 years. It produces sustained, small long and short time-scales. Strombolian explosions from several summit vents. The processes that sustain such consistent activity over such long timescales EXPLORING THE SUBDUCTED PACIFIC PLATE are currently poorly understood, as are the WITH LEAKY MODES mechanisms that drive changes in eruptive style, vigour and power. Whilst small on a J. Simpson & K. van Wijk global scale, the spectacular explosions can 1Department of Physics, The University of change suddenly to endanger lives of tourists Auckland and guides that visit its crater rim on a daily [email protected] basis. Furthermore, the regularity of eruptions can cause a false degree of safety for visitors. Observations of earthquakes originating from Sudden changes, even minor ones, may send the Kermadec subduction zone contain low explosive ballistics at low angles or farther amplitude, high frequency (2-6 Hz) P-wave than their normal range. It is these small-scale phases arriving before the main P-wave phase variations from the regular eruption processes at seismometers in New Zealand. Previous that are deadly, and understanding the studies suggest a continuous thin high velocity processes that precede them is a major focus eclogite layer within the subducting Pacific of our research. plate is the structure responsible for 'trapping' fast waves called leaky modes. This research An effective approach to gaining a holistic has identified leaky modes arriving at understanding of the dynamics of explosive seismometers across New Zealand, and the volcanoes is through synergy of multiple data seismograms have been analysed for sets. Each data set provides different pieces of frequency content and dispersion. We are information about the physical processes that exploring to extract inter-station information drive the activity. In bringing together these about the subducting plate that hosts the diverse sets of data, it is possible to build a leaky mode via seismic interferometry. unified model of the factors that control explosive vigour and consequent hazard.

Observations were carried out during an extended field campaign from September to 107

NORTHERN HEMISPHERE INFLUENCE ON THE diagonality of the SPCZ. SPCZ POSITION DURING MIS3: A HIGH RESOLUTION GLACIAL RAINFALL RECORD Our record also captures a response to strong FROM A NIUEAN SPELEOTHEM northern Hemisphere cooling. The 25-45 ka record is bounded by large hiatuses (inferred Dan Sinclair1, Robert Sherrell2, Darrel dry conditions) coincident with cold Heinrich Tremaine3, James Sweeney2, Harry Rowe4, Stadials (HS) 2 and 5, while HS3 and HS4 are James Wright2, Richard Mortlock2, John captured as distinct reductions in speleothem Hellstrom5, Hai Cheng6,7, Angela Min6,7, R. growth rate and proxy evidence for declining Lawrence Edwards6 rainfall. This is consistent with a counter- 1Victoria University of Wellington clockwise rotation of the SPCZ during 2Rutgers University Northern cooling, supporting our proposed 3Oberlin College mechanism. Interestingly, our record also 4Bureau of Economic Geology, UT Austin captures several other (non-Heinrich) cooling 5University of Melbourne events, including a strong 500-year dry 6University of Minnesota interval at ~26ka that is captured in Chinese 7Xi’an Jaiotong University and Brazilian speleothems and coincides with [email protected] a strong cooling over Asia (inferred from Greenland dust records). We note the Here we present a high-resolution glacial (possibly coincidental) timing between this paleorainfall record from the heart of the event and the Oruanui super-eruption at 25.6 South Pacific Convergence Zone (SPCZ) ka. extracted from a stalagmite from the remote island of Niue (19°03′S 169°52′W). The record spans much of MIS3 (25-45 ka) and captures MIXED THOLEIITIC AND CALC-ALKALINE rapid rainfall changes associated with shifts in PALEOVOLCANOLOGY OF THE MERCURY the SPCZ. BASALTS, COROMANDEL VOLCANIC ZONE (CVZ) It is clear that rapid climate shifts in the Northern Hemisphere have a strong influence David Skinner on the SPCZ. All of the warm Dansgaard- GNS Science, PO Box 30-368, Lower Hutt Oeschger (‘D-O’) interstadials across this 5040 period are represented by rainfall increases, [email protected] with D-O Events 9-11 particularly strongly represented. Since Niue lies south of the core The “Mercury Basalts”, erupted within, but of the SPCZ, this implies that rather than aligned mostly perpendicular to, the NNW- shifting northwards (as the ITCZ does), the trending, andesitic-dacitic-rhyolitic, Neogene SPCZ instead rotates clockwise in response to CVZ of northern New Zealand. K/Ar dating northern Hemisphere warming (analogous to defines two broad periods of activity at c. 9 to a shift between modern El Nino and La Nina 8 Ma and c. 6 to 3.8 Ma, each corresponding states). We propose that changes to surface to major eruptions of caldera-associated ocean temperature gradients in the Eastern rhyolites and ignimbrites. Pacific modulate the strength of the Wind Evaporation SST feedback, changing the size The older group erupted on northern Great and westward penetration of the eastern Mercury Island and along the ENE-trending Pacific dry zone, resulting in changes to the Kuaotunu Peninsula as stacked lava flows with 108 interlayered breccias and tuffs, some of which include sanidine-bearing rhyolitic material. SEARCHING FOR SUBDUCTION: INFLUENCES Other features are relict scoria spatter ON MAGMA CHEMISTRY IN THE AUCKLAND mounds, agglomerate-filled rifts, dike swarms, VOLCANIC FIELD, NEW ZEALAND a composite lava dome, rarely pillow lavas, and plugs with doleritic to microgabbroic E. R. Smid1, M. C. Rowe1, & J. M. Lindsay1 textures. The rocks consist of ol-hy, hy-ol and 1University of Auckland, School of Q-hy normative basalts and Q-hy normative Environment, Private Bag 92019, Auckland basaltic andesites, within a range of 50-55% [email protected] SiO2. Small-scale volcanism, where a single batch of The younger group occurs east of the magma ascends from the mantle and erupts Kuaotunu Peninsular on the Mercury Islands, once, is the most common type of subaerial but is also associated onshore with the volcanism on Earth. However, the cause for rhyolites and ignimbrites of the Kapowai this type of volcanism, particularly in Caldera in the eastern CVZ (Woody Hill). The intraplate settings, is not as well-understood two largest occurrences (Red Mercury Island- as it is for volcanism at mid-ocean ridges, rift Whakau and Stanley Island-Atiu) are remnants zones, subduction-related arcs, or above of small shield volcanoes that consist of deep-seated mantle plumes. stacked and ponded lava flows, with intercalated breccias and tuff breccias that The 53 volcanic centres in the dormant, include sanidine-bearing rhyolitic pumice and intraplate, basaltic Auckland Volcanic Field crystal tuffs. There are also scoria cone and (AVF), New Zealand, were formed from this lava neck volcano residuals, scoriaceous kind of small-scale activity. The Auckland tephra layers, welded agglomerate and region has had a complex tectonic history, spatter-filled vent residuals, sills, dikes and including active subduction off of the coast of doleritic to microgabbroic plugs, and rarely the North Island c. 20 Mya, which will have pillow lavas. The rocks consist of hy-ol contributed metasomatising fluids to the normative picritic basalt and basalt, and Q-hy lithosphere. Current major North Island basalt, basaltic andesite and low SiO2 tectonic activity includes extension at the andesite, within a range of 48-58% SiO2. Hauraki Rift (located ~75 km to the southeast), and subduction at the Hikurangi Trench Tholeiitic attributes are shown by zoned (located ~400 km southeast of the field). olivine and augite with reaction coronas of Fe- Ti oxides, pigeonitic augite, pigeonite, Our ongoing study is using olivine-hosted melt inverted pigeonite, and hypersthene, and inclusion compositions from key centres in the phenocrystic and poikilitic to ophitic AVF to identify possible tectonic influences on hypersthene. Spidergrams normalised to magma chemistry. We will present new AVF NMORB show typical LILE-HFS elemental data in comparison to typical arc, mid-ocean patterns of arc lavas of continental affinity, ridge basalt (MORB), and ocean island basalt with low Nb and elevated Pb. (OIB) chemistry. Results thus far reveal that AVF magmas are consistently most similar to OIBs, although a subset of samples have higher H2O/Ce ratios than would be expected (up to 600; above ~300 usually indicates a subduction influence). 109

MANTLE FLOW AND THE LATE CENOZOIC Mantle flow beneath this junction led to small- BASALT FIELDS OF NORTHERN NEW scale decompression melting in stratified and ZEALAND heterogeneous mantle sources producing the magmas that rose to produce the volcanism of Ian E.M. Smith the northern New Zealand fields. An as yet School of Environment, The University of unresolved question is why the location of Auckland, Private Bag 92019, Auckland intraplate volcanism has been stationary in [email protected] Northland over the past 10 my but has migrated systematically northward during the As convergent tectonics and associated last 3 my in the Auckland province. subduction-related magmatism in northern New Zealand migrated southward during the late Cenozoic, fields of basalt volcanoes on PROVENANCE OF LATE CRETACEOUS AND small spatial and short to medium but variable PALEOCENE SEDIMENTS IN THE SOUTHERN temporal scales and with characteristic intra- TARANAKI BASIN, NORTHWEST NELSON plate chemical compositions developed behind the active arcs; these are the Auckland S.L. Smithies1, K.N. Bassett1, G.H. Browne2, & province (Ngatutura, South Auckland and A.R.L. Nichols1 Auckland) and the Northland province 1Dept. of Geological Sciences, University of (Kaikohe-Bay of Islands and Whangarei) Canterbury, Christchurch volcano fields. Differences between these 2GNS Science, 1 Fairway Drive, Lower Hutt volcanic systems are in longevity and, in detail, [email protected] their chemistry, indicating subtly differing conditions of magma generation and of The northwest Nelson region has excellent mantle source regions. The Northland fields outcrop of the Late Cretaceous Rakopi and have characteristic trace element and isotopic North Cape formations and the Paleocene signatures that are clearly different from Farewell Formation, which extend north those of the Auckland fields. Interpretation of through much of the Taranaki Basin. During selected trace element ratios indicates that their deposition, uplift of sediment source their source area is within the spinel lherzolite rocks and sediment transport was controlled facies of the upper mantle whereas the by the northeast striking Wakamarama and Auckland fields originated in the Kahurangi faults. These bound the Pakawau asthenosphere at greater depth. Further, sub-basin. Potential sediment sources include some Northland basalts show compositional intraformational clasts, the Buller and Takaka features indicating a subduction modified terranes, and Tuhua Intrusives (Separation source. Point Suite and Karamea Suite). The aim of this research is to examine the changes in A possible explanation for the intraplate sediment provenance through these three volcano fields in northern New Zealand is edge formations using conglomerate clast counts, driven convection where the boundary sandstone point counts and geochemical between thick and thin lithosphere focuses analysis of siltstones. This will contribute to a upwelling that brings hot material from under better understanding of the paleogeography thicker lithosphere to shallower levels. The of the southern Taranaki Basin. asymmetry and the discontinuity in the thickness of the lithosphere is provided by the The conglomerates in the North Cape and juxtaposition of Paleozoic and Mesozoic crust. Farewell formations are dominated by fine- 110 grained metasedimentary clasts, likely complex fault zones striking approximately sourced from the Buller Terrane. Granitoid SW-NE through and near Hamilton City. clasts are another significant component, and Geomorphological signatures including become increasingly weathered up-section. rectangular drainage patterns, stream The petrography of these clasts suggest a knickpoints, and linear ridge and drainage Separation Point Suite source, although XRF systems which all point to structural control analyses are inconclusive. Volcanic clasts are a on the path of the Waikato River and its minor constituent, most likely derived from tributary gullies. Several fault traces are the Takaka Terrane. Other minor clasts are accessible, including one very complex fault vein quartz, schist, and siltstone. Rakopi, zone at Kay Rd in northern Hamilton which North Cape, and Farewell formation was exposed during earthworks for the sandstones are dominantly lithic Hamilton Section of the Waikato Expressway. feldsarenites. Lithic types include siltstones, These exposed fault traces indicate significant plutonic rock fragments, volcanics, schist, and splintering of fault planes on encountering the chert. Towards the top of the Farewell soft sediments and tephras infilling the basin; Formation in the northeast, the sandstones hence fault zones are wide and characterised become more quartzose, and the lithics by multiple traces forming a complex ridge dominated by quartz siltstone. geomorphology. Steeply dipping normal faults are typical, with relative uplift to the north, The increasing quartz content and weathering indicating a north-south extensional of clasts through the Farewell Formation likely environment. While several geomorphic lines indicates increased transport time and of evidence suggest fault movement has reworking. The prevalence of Buller and displaced the < 20 ka Hinuera Surface, no Takaka Terrane clasts suggests there was a definitive evidence for movement more significant component of axial drainage along recent than 350 ka has yet been identified. the Pakawau sub-basin. The Separation Point Suite clasts show sediment was also supplied from uplifted granitoids to the southeast of PROVENANCE AND POROSITY ANALYSIS OF the Wakamarama Fault, continuing into THE LATE CRETACEOUS GREYMOUTH BASIN, Farewell Formation time. NEW ZEALAND

R. Steadman & K. Bassett PROGRESS ON UNDERSTANDING FAULT Department of Geological Sciences, STRUCTURE IN THE HAMILTON BASIN University of Canterbury [email protected] F. Spinardi, B. R. Campbell, V. G. Moon, A. Pittari, B. R. S. Fox, W. P. de Lange The coal and lacustrine deposits of the School of Science, University of Waikato, Greymouth Basin have been explored for their Private Bag 3105, Hamilton 3240 economic potential. However, the associated [email protected] coarse clastic sediments have not been as thoroughly investigated. Thus there is The Hamilton Basin is considered an area of continuing uncertainty about the provenance low seismic risk, partly due to the lack of any of the sediments and tectonic setting of the mapped active fault traces within the basin. basin. This study uses conglomerate clast Recent geological and geomorphological counts, sandstone point counts and mapping provides evidence for at least three geochemical analyses of clasts to examine the 111 provenance of the Paparoa Group. SPELEOTHEM RECORDS OF VOLCANIC ERUPTIONS Results show a dramatic eastern vs western lithological difference with conglomerates S. Suresh1, J. Lang1, S.J Barker1, P. Williams1, primarily on the west side of the basin, O. Buchanan1, K. Sutton1, N. Gampell1, C.J.N sandstones on the east, and mudstones inter- Willson2, B.L.A. Charlier2, T. Cross3, J. fingering both. Most of the clasts encountered Hellstrom4, D. Hikuroa1, A. Hartland5, J.A. were granite, hornfels, and metasedimentary Baker1 with rare unusual volcanic clasts. Aplite was 1University of Auckland, PB92019, Auckland recorded in the lowermost conglomerates and 2Victoria University of Wellington, P.O. Box faded out with the introduction of granitic 600 clasts in the middle Paparoa Group. Trace 3Waitomo Gloworm Caves, Waitomo element geochemistry on basaltic clasts in a 4University of Melbourne conglomerate associated with a fault on the 5University of Waikato, PB3105 eastern side of the basin shows typical rift [email protected] signature. Geochemistry analysis of the granites was consistent with the Karamea Explosive (super)volcanic eruptions can have a Suite. The sandstone porosity was variable profound effect on climate. For example, at with grain size, location and stratigraphic the Permian–Triassic boundary almost 95% of position in the basin. The degree of life became extinct at the same time as the weathering in the sandstones was also Siberian Traps flood basalt eruptions took variable from minor to major feldspar place. Volcanic eruptions have repeatedly alteration to clays. altered conditions on Earth in recent history and have been proposed to account for many Provenance and geochemistry analysis show of the coldest periods over the past 2500 that the sediment sources of the basin years. However, our understanding of the changed throughout time with results actual volcanic impacts on our environmental showing two main sources, the eastern system remain poorly understood, partly due granitic Karamea suite and the western to challenges in linking different geological Greenland Group metasedimentary sources. records of volcanic eruptions with archives of This contradicts some previous paleo-environmental data. Research to-date interpretations. Clast counts also show has focused on polar ice cores to identify the evidence for the un-roofing of a granitic chemical signatures of volcanic eruptions. source with the presence of aplite clasts lower Typically, the environmental effects of these in the basin conglomerates replaced by eruptions are examined using granite clasts stratigraphically higher. The dendrochronology (tree ring widths). volcanic clasts are evidence of active However, it is challenging to directly correlate volcanism in the area which could be between the ice core and tree ring attributed to the rift setting. Porosity in the chronologies. This study aims to identify sandstones was variable spatially and different elements peaks and geochemical stratigraphically making them a poor option fingerprint for different type of volcanic for hydrocarbon reservoirs. eruption using speleothems. Having identified volcanic spikes we will then, in the same archive, geochemically quantify the magnitude and longevity of regional and global post-eruptive environmental changes. 112

This research will yield fundamental advances chemistries. Minor volumes of mafic in identifying and quantifying environmental compositions also occur (Wilson et al., poster). changes from local and global volcanic Renewal of activity for member C after some eruptions of varying sizes and magma decades evacuated regenerated and newly compositions. formed melt-dominant bodies. The low Ba (<230 ppm) rhyolite suite reappears, chemically similar to those in member A but A MAGMA CARTA: HOW THE HUCKLEBERRY with markedly different physical RIDGE TUFF (YELLOWSTONE) REWRITES THE characteristics. In addition, juvenile materials POSSIBILITIES FOR LARGE SILICIC MAGMATIC defining a dacitic trend (66-71 wt% SiO2, 670- SYSTEMS 1200 ppm Ba) and a high-silica rhyolite trend (76-78 wt% SiO2, 2300-400 ppm Ba) were also E.J. Swallow1, C.J.N. Wilson1, B.L.A. Charlier1 erupted. These wholly new suites, despite & J.A. Gamble1 their diverse elemental chemical 1SGEES, Victoria University, PO Box 600, characteristics, have overlapping, highly 87 86 Wellington 6140 radiogenic isotopic signatures ( Sr/ Sri = [email protected] 0.72463-0.72962), indicative of a high degree of crustal assimilation. The Huckleberry Ridge Large silicic caldera-forming eruptions are Tuff is unique in its complexity and diversity of conventionally viewed as representing the magmatic compositions, all of which are linked runaway evacuation of a single, unitary, melt- within a single geological event. dominant body. Here we summarise compositional data from the 2.08 Ma, 2,500 km3 Huckleberry Ridge Tuff, the first and NEW INSIGHTS INTO GLACIO-LACUSTRINE largest caldera-forming eruption from SEDIMENTATION IN SOUTH WESTLAND Yellowstone. The tuff comprises an initial fall deposit, three ignimbrite members (A, B and A. Thomas1, S. C. Cox2, C. B. Atkins1, J. C), with another fall deposit separating Howarth1 and the DFDP-2 Science members B and C. Pumice/fiamme, mineral Team and matrix glass elemental and isotopic data 1Victoria University of Wellington, P.O. Box reveal an extraordinary degree of intra- and 600, Wellington inter-member diversities and hence 2GNS Science, Private Bag 1930, Dunedin complexities in the magmatic system. [email protected] Pyroclasts from ignimbrite members A and B are dominated by a rhyodacitic to high-silica Recent work has revealed the presence of rhyolite suite (69-77 wt% SiO2, 3500-45 ppm numerous, previously unmapped glacio- Ba) that is mirrored in glass chemistries. A lacustrine sedimentary sequences exposed in subordinate rhyolitic compositional suite in South Westland. Outcrops in the the initial fall deposits and member A (but Waitangitaona and Arahura rivers provide missing in member B) is characterised by low new opportunities to understand landscape Ba concentrations in pumice and glass (<250 response to deglaciation at these locations. ppm). Moderately radiogenic isotopic Outcrop exposures were described in detail 87 86 compositions ( Sr/ Sri = 0.70958-0.71146) in using field mapping, sampling and structure pyroclasts and their constancy with indices of from motion photography. These descriptions geochemical evolution indicate a dominant are then utilised to understand the unique fractional crystallisation control on the felsic depositional setting of each outcrop, as well as 113 the lateral and vertical variance observed. GEOTRIPS WEBSITE – AN UPDATE Collectively, the outcrop exposures are used to develop a facies model for glacio-lacustrine J. Thomson, D. White, D. D’Cruz, C. Timm, sedimentation in high erosion-high H.J. Campbell, N. Mortimer precipitation environments. GNS Science, P O Box 30-368, Lower Hutt, 5040 This model is then applied to interpret the [email protected] glacio-lacustrine sedimentary sequence recovered by Deep Fault Drilling Project 2 GeoTrips (www.geotrips.org.nz) is the website (DFDP-2). Drilled in the Whataroa Valley in late that informs non-specialists in New Zealand 2014, initial findings suggest the formation of about where to go to investigate interesting a large pro-glacial lake in response to geological outcrops and landforms. deglaciation, extending across the Westland piedmont. Radiocarbon dating has shown the The website has been live since March 2017, ~180m post-glacial sequence accumulated in and we are continuing to add content and to 655 ± 200 years, suggesting the extremely improve usability. The aim for the end of 2017 rapid sedimentation rate of ~27 cm/yr. has been to achieve more widespread coverage of locations around NZ, with a focus Comparison between the DFDP-2 sedimentary on population centres and tourist hot spots, record with outcrop exposures and modern prior to a more targeted and widespread analogues suggests a transition from an ice- promotional campaign in the early summer. contact to ice-distal depositional setting at the drill site. This is related to rapid glacial retreat This presentation will include an update on and high post-glacial sediment flux promoting progress of the website design, content rapid lake infill and delta progradation. The creation by participating scientists, and user developed facies model also allows the analytics. It will also include a look at dominant modes of deposition into the pro- possibilities for further development of glacial lake to be examined in detail, and GeoTrips so that it can become a popular and linked to processes controlling sedimentation comprehensive platform that enables the at the drill site. public to explore New Zealand’s dynamic history and rich geological environment. Future work will aim to develop a chronology for the Arahura and Waitangitaona outcrop sequences, to relate them temporally with the SUBMARINE GEOMORPHOLOGY IN THE SUB- DFDP-2 sequence. ANTARCTIC AUCKLAND ISLANDS

E.J. Tidey & C.L. Hulbe School of Surveying, University of Otago, 310 Castle Street, Dunedin, New Zealand [email protected]

At about 50.7S, the sub-Antarctic Auckland Islands/Maungahuka are located near the northern limit of the subantarctic front, a boundary across which southern high- and mid-latitude atmospheres influence each 114 other. Understanding the paleoclimate of THE EPISODIC EXPLOSIVE PHASE OF THE AD these islands may therefore improve 1314 KAHAROA ERUPTION (TARAWERA understanding of climate processes and VOLCANO, NEW ZEALAND): NEW INSIGHTS climate change in the southern hemisphere FROM TEPHRA DEPOSITS more broadly. While these low-elevation islands are not currently glaciated, terrestrial A. Todde1, K. Nemeth1, J. Procter1, P. Shane2 morphological features including cirques and 1Volcanic Risk Solutions, IAE, Massey steep-sided fjords, indicate that they were University, PO Box 11 222, Palmerston North glaciated during past, colder, conditions. 2School of Environment, University of Marine bathymetric observations can extend Auckland, PO Box 92019, Auckland the record beyond the shoreline by providing [email protected] evidence of glacier terminus extent and characteristics. This supports additional Mid- to large-intensity explosive eruptions are details regarding glacial history, in particular commonly fed by intermediate- to-silicic the conditions associated with retreat from magmas, and they are characterized by the the most recent glacial advance. Here, we generation of sustained and quasi-steady report on submarine features observed using eruptive plumes, dispersing large volumes of high-resolution multibeam swath bathymetry, tephra fallout in the areas nearby. Such and the events they imply. eruptions may include a sustained phase of constant activity but they typically consist of a The new bathymetric model of the sea floor complex succession of volcanic pulses with used for this work was created using data quasi-steady, convective plumes that collected on recent hydrographic charting and alternate and overlap with explosions of research voyages (LINZ, University of Otago). different styles and intensities. This makes the Modern multibeam swath technology collects time-variant evolution of eruptive behaviour spatially dense and highly accurate data hard to constrain. Detailed field studies of allowing analysis of previously unknown tephra deposits, together with submarine geomorphic features. Depth of sea sedimentological and textural floor can also be analysed to highlight aspect, characterization of the erupted, deposited rugosity and other morphometric material can provide a dataset to understand characteristics, while intensity of the acoustic complex eruptive sequences associated with return to indicate sediment type and biotic these eruptions. In this context we investigate environments. Glacial morphology is of the AD 1314 Kaharoa eruption, the youngest, particular interest here, and we combine this rhyolite-dominated eruption of Tarawera with estimates of past sea level change to infer volcano. The eruption developed from conditions at glacial termini (sub-aerial, multiple vents along an 8 km linear zone and submarine) prior to retreat. exhibited a complex succession of different eruptive events, including initial sub-Plinian to Plinian explosions with associated pyroclastic density currents (PDCs), and extrusions of lava domes with associated block-and-ash flows (Nairn et al. 2001, Sahetapy-Engel et al. 2014). This study focuses on the explosive phase recorded in the tephra deposits dispersed toward the SE. Preliminary results from field observations, grain-size and componentry 115 analyses indicate that the Kaharoa eruption with exponents of ~1 that are similar to those was an episodic (occurrence of time breaks) of seismicity occurring in much larger crustal and unsteady (fluctuations in mass discharge volumes and with a range of focal rate) eruption. At least seven lapilli-bearing, mechanisms. Using examples from fallout-dominated units record the deposition seismotectonically distinct parts of New from convective columns, each associated to Zealand (Taupo Volcanic Zone, central Alpine an individual eruptive episode throughout the Fault, Southern Lakes) and magnitudes eruption. The sedimentological features of the calculated using singular value decomposition, tephra units suggest a slightly different we consider the extent to which Gutenberg- evolution for each eruptive episode, Richter (power-law) scaling characterises characterized by changes in eruption intensity. individual faults. We suggest that the Ash layers at the top of lapilli-bearing units magnitude-frequency scaling of earthquakes mark the cessation of each episode. In detected with specific templates pertains to proximal areas, the fallout-dominated both a geographically (x, y, z) and a sequence is capped by PDC and block-and-ash geometrically (φ, δ, λ) restricted set of flow deposits. sources, providing a means of studying low- magnitude seismogenesis on a fault-by-fault basis. WHAT DO THE MAGNITUDE-FREQUENCY CHARACTERISTICS OF EARTHQUAKES DETECTED BY CROSS-CORRELATION TELL US CAN ALONG STRIKE VARIATIONS IN THE ABOUT FAULT SOURCE SCALING? ALPINE FAULT GEOTHERMAL GRADIENT AFFECT DEFORMATION MECHANISMS AND John Townend1, Calum J. Chamberlain1, FAULT STRENGTH AT THE BRITTLE-CREEP Carolin M. Boese1,2, Emily Warren-Smith3, TRANSITION? Laura-May Baratin1, Martha K. Savage1, Chet Hopp1, Konstantinos Michailos1, and Katrina V.G. Toy Jacobs3 Dept. of Geology, University of Otago, PO Box 1SGEES, Victoria University of Wellington 56, Dunedin 2Johann-Wolfgang Goethe University, [email protected] Frankfurt/Main, Germany 3GNS Science, Lower Hutt A characteristic feature of Alpine Fault (AF) [email protected] mylonites with dislocation creep microstructures is a coarse recrystallized Methods of earthquake detection based on quartz grain size (40-70 µm). This suggests cross-correlation are now in widespread use maximum creep stresses of 35 MPa at and provide a means of greatly expanding minimum temperatures of 500°C, which could earthquake catalogues and mitigating the be explained by a stepped exhumation effects of noise and low-magnitudes. As the temperature trajectory related to extremely earthquakes detected with such approaches rapid cooling when meteoric fluids are able to have similar waveforms to the template with penetrate into the mylonites at the base of the which they correlate, they have (by design) seismogenic zone. similar hypocentres and focal mechanisms. Intriguingly, the magnitudes of earthquakes Ultramylonites with finer grain sizes (<10 µm) detected by such methods exhibit Gutenberg- are also locally preserved as clasts within Richter magnitude-frequency characteristics cataclastic rocks. These are of two types: (i) 116 lacking crystallographic preferred orientations bounding-fault. Nature 546, 137-140. (CPOs) and in aggregates with greenschist facies minerals; (ii) with single girdle CPOs, in monomineralic layers with GSI creep A RECORD OF HOLOCENE PALEOCLIMATE microstructures. Type (i) probably deformed EVOLUTION FROM ROBERTSON BAY, by solution-accommodated GSS creep at fairly VICTORIA LAND, ANTARCTICA low stress or fast strain rate, while type (ii) reflect GSI creep at high stresses (>100 MPa). Olivia Truax1,2, Christina Riesselman1,2, Gary This suggests that in places rocks at the brittle- Wilson1,2, Rebecca Parker3, Kyu-Cheul Yoo4, creep transition are strong and dry, and Jae Il Lee4, Richard Levy5, Rob McKay6 elsewhere they are damp and weak. The 1University of Otago, Department of Geology former may represent asperities that are likely 2University of Otago, Department of Marine sources for earthquake nucleation. Science 3University of Exeter, Department of Geology Similar variation in microstructures observed 4Korea Polar Research Institute in the Hatagawa Fault Zone, Japan, occurs on 4GNS Science a 5-10km length scale (Shigematsu et al., 5Victoria University of Wellington, 2009). A surprisingly high geothermal gradient Department of Geology measured in DFDP-2B has been attributed to Email: [email protected] advection of heat in meteoric-derived fluids circulating between high ridges and deep Regionally representative records of how Quaternary sediment-filled valleys that strike Antarctica responded to the transition from perpendicular to the fault (Sutherland et al., the Last Glacial Maximum into the Holocene 2017), yielding along-strike variation in the are an essential component of understanding thermal gradient and the fluid pressure at the the processes by which the Antarctic 5-20km length scale. Valley vs. ridge cryosphere responds to a changing climate. geotherms of 120°C km-1 and 40°C km-1 yield Here, we present a high-resolution record of brittle-creep transitions at 4km vs. 8km, and Holocene Antarctic paleoclimate evolution shear stresses of 50MPa vs. 140MPa; solution- from a previously unstudied section of the accommodated creep further reduces the Victoria Land margin. In 2015 the Korea Polar maximum supported stresses. Research Institute collected a 571 cm sediment core, GC57, from Robertson Bay, a It seems likely that topographically-driven protected embayment west of Cape Adare variations in thermal structure and fluid and adjacent to the outlet glaciers of the availability persist to sufficient depths to Transantarctic Mountains. Using diatom affect the deformation mechanisms at the assemblages, bulk sediment geochemistry, base of the AF seismogenic zone. and the magnetic properties of GC57, we reconstruct the response of the East Antarctic References: Ice Sheet to warming associated with Shigematsu, N. et al. 2009. Localisation of deglaciation at the interface between the Ross plastic flow in the mid-crust along a crustal- Sea and the Southern Ocean. Our multiproxy scale fault: Insight from the Hatagawa Fault approach allows us to study sea ice extent, Zone, Japan. Journal of Structural Geology 31, terrigenous input, seasonality, ocean 608-614. stratification and circulation, and primary Sutherland, R., et al. 2017. Extreme productivity from the mid-Holocene (7,400 14C hydrothermal conditions at an active plate year BP) to the present. 117

unaffected. However, lava flow crises (e.g. A sea-ice associated diatom assemblage Pāhoa, Hawaii 2014-2015) have demonstrated indicative of summer sea surface lava flow impacts to critical infrastructure temperatures below 0˚C and a high networks can have non-binary consequences. concentration of magnetic minerals When lava flows have threatened buried demarcate a lower unit in GC57. A rapid infrastructure networks, engineers transition at 4600 14C yr BP is identified by a responsible for these networks have still steep increase in wt% BSi (average 9% to implemented, and potentially benefited from, average 13%), a decrease in magnetic lava flow mitigation measures: lava flows are minerals, and a subtle assemblage change estimated to heat anywhere between 2 cm towards sea-ice associated diatoms with and 3 m of the substrate beneath them. This is warmer temperature tolerances. a particularly relevant issue for Auckland, where the vast majority of buried The novel ramped pyrolosis 14C dating infrastructure is less than 3 m from the methodology allows us to date the carbon surface. fixed concurrent with deposition and generate a robust age model for GC57 with an accuracy We present results from a series of lava pour previously difficult to achieve given the experiments measuring thermal profiles in uncertainties associated with dating bulk acid substrates beneath basaltic lava flows. The insoluble organic matter in Antarctic experiments involved pouring molten lava sediments. When complete, this study will onto a surface in a controlled environment contribute to the larger project of identifying and were designed to simulate a’a and drivers of Antarctic climate dynamics during pāhoehoe lava flows. The first set of lava pours intervals of rapid change. focused on developing a depth-temperature- time relationship in a dry soil substrate. The second set of lava pours used the same set-up, THERMAL GRADIENTS IN SUBSTRATES but the substrate was saturated with water. BENEATH LAVA FLOWS: A LABORATORY These first two sets of experiments use molten APPROACH basalt to simulate pāhoehoe lava flows; the third set of lava pours focused on S. Tsang1, J. Lindsay1, R. Wysocki2, T. differentiating temperature-depth-time Wilson3, N. Deligne4, B. Kennedy3, & J. relationships of pāhoehoe flows from a’a Karson2 flows. To simulate the rubbly base of a’a-type 1School of Environment, University of lava flows, we heated volcanic scoria and then Auckland, 23 Symonds St, Auckland poured the molten basalt over it. Finally, we 2Department of Earth Sciences, Syracuse poured lava onto concrete and asphalt, University, NY, USA representing footpaths and roads 3Dept. of Geological Sciences, University of respectively. Together, the results of these Canterbury, 20 Kirkwood Ave, Christchurch experiments create a temperature intensity 4GNS Science, 1 Fairway Dr, Avalon, Lower model to assess the vulnerability of buried Hutt infrastructure to lava flows. This will enable [email protected] engineers at infrastructure companies to make informed decisions about lava flow Lava flows are generally considered a hazard protection measures when their systems are with binary impacts: anything not in direct threatened by lava flows. contact with a lava flow is assumed to be 118

structures, and the coincidence with Late THE CAMPBELL MAFIC COMPLEX OF SOUTH Cretaceous Chatham Island lavas, we interpret ZEALANDIA that the CMAS is not caused by terranes or batholiths. Instead, we conclude that the Andy Tulloch, Nick Mortimer CMAS represents alkalic, predominantly GNS Science, Private Bag 1930, Dunedin 9054 mafic, magmatism associated with a failed rift, [email protected] some of it at least, only slightly older than final 84 Ma breakup along the Campbell margin. South Zealandia (1.5M km2) offers only five islands/groups, five drill holes, four dredge sites and one volcano to directly determine DETRITAL ZIRCON EVIDENCE FOR THE the nature of its basement crust. A major PROVENANCE OF CRETACEOUS–PALEOGENE feature with no exposed source on the SANDSTONES IN THE is the Campbell Magnetic 1 2 Anomaly System (CMAS). First reported by Andy J. Tulloch , Matthew W. Sagar & J. Davey and Christoffel (1978), they and others Michael Palin3 explained it as being caused by the same 1GNS Science, Private Bag 1930, Dunedin basement terranes and batholiths that caused 9054 the onland Stokes Magnetic Anomaly System 2GNS Science, PO Box 30-368, Lower Hutt (SMAS). The CMAS=SMAS interpretation 5040 required a putative Campbell Fault or 330km 3Dept. of Geology, University of Otago, PO dextral displacement. Others including Beggs Box 56, Dunedin 9054 et al. (1990) have pointed out various [email protected] problems with this interpretation. The Great South Basin (GSB) lies mostly We have thresholded recent magnetic maps offshore southeast of South Island and of South Zealandia and find that the main straddles several Paleozoic–Mesozoic Campbell anomaly has a predominant WSW- basement terranes and batholiths. The GSB ENE trend that is accompanied by a NNW-SSE initially formed as a series of fault-bound grain, producing an orthogonal pattern. The terrestrial depocenters during mid-Cretaceous orthogonal ENE and NNW striking pattern (~105 Ma) extension that preceded parallels Southern Ocean mid-ocean ridge Zealandia–Gondwana separation. Basin-wide spreading magnetic anomalies and transform subsidence began during the Late Cretaceous fracture zones, respectively, to the SE. To the (~80 Ma) with opening of the Tasman Sea, NW of the CMAS the low angle Sisters leading to progressive marine incursion from detachment fault of southern Stewart Island the east. By Eocene time, the entire basin was strikes ENE and is offset by at least three NNW submerged. km-scale transfer faults. Rapid extensional exhumation of footwall mid crust occurred To investigate the provenance of Cretaceous– from 89-82 Ma. Three smaller orthogonal Eocene sandstones within the GSB, U–Pb anomalies also occur SE of Chatham Is where dates were acquired for detrital zircons from one of them can be associated with 86 Ma 12 samples in six petroleum wells (Tara-1, alkali basalts and trachytes, the only location Rakiura-1, Toroa-1, Pukaki-1, Kawau-1A and where the orthogonal magnetic anomalies are Hoiho-1C). The majority of zircon grains (80%) exposed onshore. On the basis of orthogonal are <400 Ma and define a broadly bi-modal alignments with known extensional age spectrum with peaks in (1) the Early 119

Cretaceous (~132–105 Ma) and (2) mid- zone. The abandoned margin extends along Paleozoic (~370–350) Ma. This indicates two the north Chatham Rise and through the main sediment sources: (1) the Early Raukumara Basin. Between these two regions, Cretaceous Separation Point Suite (~132–105 the East Coast of North Island has been so Ma), and (2) the mid-Paleozoic Ridge (~350 overprinted by modern subduction along the Ma) and Karamea (~370 Ma) suites. Western Hikurangi Trough that no indications of the Province metasedimentary rocks (>400 Ma), older margin can be seen on seismic data. Brook Street Terrane (~300–270 Ma) and However, outcrops of the Torlesse Supergroup Darran–Longwood suites (~270–133 Ma) were are widespread along the East Coast and subordinate. However, the proportion of document development just inboard of the Western Province zircons (~20%) is abandoned margin. significantly greater than age-equivalent Taranaki Basin sandstones. Rift volcanism Subduction ceased along the New Zealand associated with extension is represented by Gondwana margin about 105 Ma after the ~102–84 Ma zircons. Hikurangi Plateau collided. Seismic data reveal some of the internal structure of the Plateau In general, the proportions of zircons from the and guide speculation about its geology. The Karamea, Ridge and Darran suites, and advent of modern seismic data has answered Western Province rocks increase from the some geological questions and has given rise Cretaceous to Eocene, while those from the to more. Now we can see the Gondwana rift volcanics and Separation Point Suite margin preserved offshore and we have decrease over the same period. We infer that information about the structure of the the dominance of Separation Point Suite Hikurangi Plateau, we can start to ask further sources in the Cretaceous was due to tectonic questions, such as: where is the Gondwana exhumation of proximal source areas, margin beyond the Raukumara Peninsula? whereas N–S longshore drift and emergent How far does the Hikurangi Plateau extend? land to the west provided more distal and Why is it subducting under the East Coast now, varied local (e.g., Darran Suite) sediment when it stopped subduction along the sources during the Eocene. Gondwana margin? Did the collision of the Plateau cause obduction of the Dun Mountain ophiolite and folding of the Murihiku Basin? NEW ZEALAND’S GONDWANA MARGIN AND While this paper cannot offer answers to all ITS NEMESIS these questions, it does suggest some future discoveries that marine researchers may Chris Uruski make. 3390, Western Lake Road, RD3 Featherston

New Zealand’s basement developed as part of the Gondwana margin over a considerable period. Rocks ranging from Paleozoic to late Mesozoic ages form the substrate within, and on which, later units were deposited. In recent years, seismic reflection data, mostly acquired for petroleum exploration, have imaged the latest stages of the development of this margin and its abandonment as a subduction 120

CENOZOIC FOSSIL WOOD FROM SOUTHERN (Lepidothamnus and Podocarpus), Newvale ZEALANDIA and Gold Sandpit (Phyllocladus). Cupressaceae (Libocedrus) were identified at Idaburn, M.R. Vanner1, J.G. Conran2, J.M. Bannister1, Mataura and Newvale. A number of sites (Cosy D.E. Lee1 Dell Lime Pit, Bennett’s Pit and Mataura) had 1 Dept. of Geology, University of Otago, PO samples that could represent either Box 56, Dunedin Libocedrus or Podocarpus. Lake Aviemore has 2 School of Biological Sciences, The University angiospermous wood that resembles of Adelaide, SA 5005, Australia Casuarinaceae, Myrtaceae or [email protected] Picrodendraceae, while Idaburn and Landslip Hill produced Casuarinaceae wood Cenozoic fossil wood (branches, logs and in (Allocasuarina and Gymnostoma, situ tree stumps) preserved in lignite, respectively). Angiosperms recovered from conglomerate, sandstone, mudstone and Pikopiko included Ixerba and Elaeocarpaceae. silcrete at 14 sites from the southern South Nestegis was found at Orepuki. Identification Island is investigated. Both angiosperms and of samples of fossil wood provides new data gymnosperms are present, but gymnosperm that can be used to reconstruct the forest wood is more abundant. Specimens were vegetation that grew in southern Zealandia collected from south Canterbury (Lake during the Cenozoic. Aviemore and Waihao River), Central Otago (Idaburn, Roxburgh and upper Manuherikia River) and Southland (Bennett’s Pit, Cosy Dell SEISMIC IMAGING AND GEODYNAMIC Coal Pit, Cosy Dell Lime Pit, Gold Sandpit, MODELING OF THE AUCKLAND VOLCANIC Landslip Hill, Mataura Coal Mine, Newvale FIELD Coal Mine, Orepuki and Pikopiko). Except for the Eocene-aged Waihao River and Pikopiko Kasper van Wijk1, Josiah Ensing1, Gugi Fossil Forest and Pliocene-aged Gold Sandpit Gianefianto1, Nick Rawlinson2, and Rhodri and Orepuki locations, all sites are Late Davies3 Oligocene to Early Miocene in age. Less 1Department of Physics, University of compressed and silicified samples were Auckland, New Zealand selected for rock thin-sectioning and SEM 2Cambridge University, Cambridge, United imaging, while softer lignified material was Kingdom charcoalified. SEM imaging did not produce 3Australian National University, Canberra, good results, but sectioning of wood using Australia traditional orientations for wood anatomy, [email protected] combined with cellular structure keys was used to determine modern affinities for the The city of Auckland, New Zealand, sits atop a fossilised wood samples. young and active volcanic field, whose earlier eruptions stem from a series of small yet Araucariaceae were identified at three sites: violent volcanic episodes. Despite the obvious Waihao River, Roxburgh and Newvale. hazard beneath Aucklanders' feet, the origin Podocarpaceae were present at Pikopiko and mechanisms of the Auckland Volcanic (Podocarpus), Idaburn (Podocarpus and Field (AVF) remain largely unknown. Prumnopitys), Roxburgh (Dacrycarpus/Dacrydium), Cosy Dell Coal Pit While plate tectonic theory successfully (Lagarostrobos and Podocarpus), Mataura explains many of Earth's geological features, 121 an important class of volcanism occurs within plates. The AVF is a prime example of such One of the most common methods to study intra-plate -- and active -- volcanism, and it is volcanic eruptions is to analyse their deposits. widely accepted that the AVF is not an Modern subaqueous deposits are, however, expression of a mantle plume. expensive to study and typically lack cross- sectional exposures, whereas older uplifted The AVF is monitored with a network of ones have commonly suffered alteration seismometers, as part of New Zealand's and/or tectonic deformation. Here we report national GeoNet project. Here, we report our results from two relatively young (∼15 ka), latest 3D subsurface model of the AVF, based partly dissected, Surtseyan volcanoes, Black on seismic ambient noise tomography (ANT) Point, California and Pahvant Butte, Utah. of the crust and seismic P-wave tomography These volcanoes formed in now-drained that extends well into the mantle. Pleistocene lakes and are ideal examples of well-preserved shallow to emergent explosive Initial ANT differentiates areas of the AVF basaltic volcanoes. crust with continental and oceanic features, which extend deep into the AVF crust. To infer Some past works have confined the the origin and dynamics of the AVF, we are “Surtseyan style” of such eruptions to activity optimizing ANT models and adding P-wave visible at the surface, but we aim to infer the tomography to constrain structural eruption dynamics of Surtseyan eruptions information of the lithosphere and from their onset, including both subaqueous asthenosphere. These models then serve as and subaerial deposits, correlated through inputs for geodynamic modeling efforts, geochemical variations and textural ones. For aiming to understand the how and why of the Black Point and Pahvant Butte, we assess AVF. whether the subaqueous parts of the eruptions are represented in distal lake- deposited ash, or whether that ash was ERUPTION DYNAMICS OF SURTSEYAN initially distributed only during subaerial VOLCANOES: STUDY CASES FROM BLACK phases of eruption. POINT AND PAHVANT BUTTE, WESTERN USA Energy-dispersive X-ray spectroscopy has A. Verolino & J.D.L. White been carried out on samples from different Geology Department, University of Otago, PO stratigraphic sequences for Black Point and Box 56, Dunedin 9054, New Zealand. Pahvant Butte to analyse sideromelane glass [email protected] for samples from proximal, medial and relatively distal deposits. We find that the Surtseyan eruptions are shallow underwater geochemistry differs for subaqueous proximal to emergent explosive eruptions that involve versus subaqueous distal deposits for Black contact between magma and surface water Point and Pahvant Butte. This suggests that (e.g. lakes or oceans). They have potential to the distal ash was not formed during the same threaten shoreline communities and affect the part of the eruption as was the main local fauna, both at the onset of the eruption subaqueous-to-emergent deposits forming (i.e. subaqueous eruption) and/or as the the volcanic edifices. eruption proceeds and reaches the water surface (subaerial eruptive material transported by winds or remobilised). 122

DETAILED TEPHROSTRATIGRAPHY AS A TOOL than previously thought. Earlier defined TO DEVELOP A MULTI-HAZARD MODEL FOR nineteen tephra fall members represent multi- MT. RUAPEHU, NEW ZEALAND stage eruption episodes rather than previously assumed single events. At least ten M. Voloschina, G. Lube, J. Procter & A. additional multi-stage eruption episodes have Moebis been identified, increasing the existing Volcanic Risk Solutions, Massey University, eruption frequency by nearly an order of Private Bag 11222, Palmerston North magnitude. These multi-stage eruptions [email protected] involve a broad range of phreatomagmatic to dry magmatic eruption styles and slightly Volcanic hazards are among the most lethal different groundmass glass compositions. natural hazards in the world and can These patterns form the basis for on-going potentially pose enormous threat to life and analyses that aim at better constraining the economy. Traditionally, volcanic hazards and dynamics of Ruapehu’s source-conduit-vent their underlying physical processes are system. studied in isolation. However, recently observed eruptive episodes have shown that a wide range of eruption scales and styles can CAUSAL LINKS BETWEEN GEOLOGY AND THE occur throughout a multi-stage multi-hazard SUBSURFACE GEOMETRY OF A eruption. Frequently active andesitic GEOTHERMAL RESERVOIR composite volcanoes such as Mt. Ruapehu in New Zealand are particularly notorious for Irene C Wallis1, Julie V Rowland1, William sudden changes in eruptive behaviour and Cumming2 & David Dempsey3 dynamics. This leads to a broad spectrum of 1 School of Environment, University of related hazards and may result in a high Auckland, 23 Symonds Street, Auckland degree of unpreparedness. Despite extensive Central studies on Ruapehu’s eruptive history, the 2 Cumming Geoscience, 4728 Shade Tree dynamic evolution within an eruption episode Lane, Santa Rosa, CA 95405, USA and thus the relationships between hazards 3 Engineering Science, University of Auckland, are not entirely understood yet. 70 Symonds Street, Auckland Central

This research aims at providing a high- The geometry of a geothermal reservoir resolution multi-hazard record for the late dictates the exploitable resource volume and Holocene eruptive record of Ruapehu. This therefore influences the scale of sustainable will be achieved by creating a framework of power development. That geometry is proximal-medial tephra sequences which can typically illustrated by a conceptual model and be related to other concurrent deposits, both is primarily defined using a pattern of natural explosive and effusive in origin. Here, we will state isotherms. Prior to drilling, surface show how a detailed characterisation of exploration sets out to constrain the reservoir depositional units can be used to distinguish geometry even though the shape is highly between single eruptive events and multi- uncertain. Subsequently, it is useful to develop stage eruptions and how to define sequence, a range of alternative models that fit the number, magnitude and style of eruptions available data and to use well-defined within an episode. Our preliminary results reservoirs as analogues. The uncertainty suggest that the eruptive history of the past associated with reservoir geometry will, few thousand years is much more complex however, remain significant until it is 123 extensively drilled, so considering alternative we utilize >20 ocean-bottom seismometers geometries is also an aspect of ongoing and pressure sensors deployed as part of the resource capacity assessment and makeup Hikurangi Ocean Bottom Investigation of well targeting. Tremor and Slow Slip (HOBITSS) experiment (May 2014 – June 2015), to offer improved We present initial results of research that uses constraints on focal mechanisms of case histories to define the geometry of earthquakes during the deployment. This reservoir permeability in relationship to the network recorded a shallow MW6.8 SSE in geologic architecture. The results are September-October 2014, and hence allows presented as a continuum that may be used as analysis of both microseismicity and a practical tool for developing alternative earthquakes M>4 pertaining to the onset, conceptual models. This work highlights development and shutdown of slow slip. causal links between the geologic architecture and geothermal reservoir permeability, and Specifically, we focus on 14 well-constrained we discuss two examples in detail: structures events of magnitude >3 to demonstrate the (faults & fractures) and intrusive rocks. These improved coverage provided by OBS stations, links highlight the value of investing in quality and to optimise a non-linear location local and regional geologic mapping during procedure using a 3D velocity model. We then exploration, as well as clearly communicating implement a Bayesian method to constrain geologic model uncertainty during all focal mechanisms using improved take off development stages. angles, and compare our results with other approaches. We extend the workflow to re- locate many more microearthquakes, and IMPROVED FOCAL MECHANISMS OF estimate focal mechanisms for events as small SEISMICITY PERTAINING TO SHALLOW SLOW as ~M1.5 occurring within the network. SLIP IN THE NORTHERN HIKURANGI Earthquakes exhibit a range of mechanism types, dominated by dip-slip events in the E. Warren-Smith1, E. Chon2, B. Fry1, A. subducting Pacific plate, with strike-slip events Sheehan2, L. Wallace1,3, K. Mochizuki4, D. occurring in both the Australian and Pacific Haijima4, S. Schwartz5 plates. Preliminary coarse stress inversions of 1GNS Science, Avalon, Lower Hutt, NZ focal mechanisms indicate large-scale margin- 2University of Colorado at Boulder, Boulder, parallel contraction consistent with previous CO, USA Hikurangi and global subduction zone studies. 3University of Texas Institute for Geophysics, Austin, TX, USA 4ERI, University of Tokyo, Japan VARIABLE PARTIAL MELTING AS A CONTROL 5University of California Santa Cruz, Santa ON THE FORMATION OF ANOMALOUS Cruz, CA, USA BASALTIC ACHONDRITES [email protected] B.W. Waterson & J.A. Baker Slow slip events (SSEs) on the northern School of Environment, University of Hikurangi are commonly associated with Auckland, 23 Symonds Street, Auckland increased seismicity rates, yet limited network Central azimuthal coverage for offshore earthquakes [email protected] means source properties, such as focal mechanisms, are difficult to constrain. Here, Meteorites are an invaluable archive of 124 geochemical information. Generated in Solar Fault zones comprise clay-rich fault rock and System forming environments, meteorites associated minor faults. The widths of fault preserve a direct record of planetary accretion zones and fault rock generally increase with and differentiation. 4 Vesta is a rocky displacement, but often display significant protoplanet and the second largest body in variation. Here we quantify variations in fault- our Solar System’s asteroid belt. Vesta zone geometry and examine the controlling generates a vast number of meteorite factors in a well-bedded turbidite sequence. fragments – the Howardite-Eucrite-Diogenite The research was conducted on normal faults (HED) suite – through which its formation has with displacements of 0.001 – 70 m that been extensively studied. In this study, disrupt Miocene (~7.5-11 Ma) interbedded analysis of five eucritic meteorite samples has sandstones and mudstones of the Mount revealed the role of partial melting as a control Messenger Formation in Taranaki, New on their formation. Of particular interest was Zealand. These rocks are poorly lithified, with an anomalous eucrite-like sample, the genesis a maximum burial of ~1500m, and sand-sized of which and relationship to the HED parent particles dominated by ~55-80% lithic grains. body has remained inconclusive. The trace element composition of the five basaltic Fault analysis was conducted using a achondrites samples was investigated using combination of outcrop-scale measurements LA-ICP-MS. Trace element data was used to along faults at spacings as small as 5 cm, thin aid in interpretations of asteroidal sections, SEM images and laser sizer analysis. magmatism. Preliminary results suggest that These data provide information on fault the genesis of the full suite of meteorites processes from individual grains (~0.1-350 analysed within this study can be explained by µm) to cliff scale (10-20 m). Fault-rock and variable degrees of partial melting on the HED fault-zone thicknesses vary by up to three parent body Vesta. These results have orders of magnitude for a given displacement implications for current differentiation models and at short distances (2-10 m). These that have been proposed for the asteroid. variations partly reflect the role of Previous works have suggested that the stratigraphy on the generation of fault rock presence of the anomalous samples can only and minor faulting adjacent to the primary slip be explained by the involvement of another surface. Cataclasis of sandstones and smear of parent body. These results challenge that mudstones are the primary mechanisms for assumption. fault rock generation, with the dominant mechanism being dependent on bed grain- size and displacement. Faults zones are widest VARIATIONS IN FAULT-ZONE ARCHITECTURE and have the highest densities at fault IN A WELL-BEDDED SEQUENCE intersections, bends and segment boundaries, the location of which may be influenced by G. Watson1, H. Winter1, A. Nicol1 & C. Childs2 mechanical heterogeneities. With increasing 1Department of Geological Sciences, displacement these asperities are University of Canterbury, Christchurch 8020, continuously removed resulting in increases in New Zealand fault rock thickness, the densities of minor 2Fault Analysis Group, School of Geological faults and strain localisation. Sciences, University College Dublin, Belfield, Dublin 4, Ireland [email protected]

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EVOLUTION OF MAGMATIC VOLATILES diffusion profiles developed, and if so how DURING DRILLING INTO A MAGMA BODY, they responded with time. KRAFLA ICELAND Preliminary results show that average H2O T. Watson1, A.R.L. Nichols1, B. Kennedy1, E. contents in the glass samples increase with Saubin1, I. Schipper2, H. Tuffen3 & F. W. von- time from 1.58 to 2.57 wt%. This suggests Aulock4 variable degassing in response to the 1Dept. of Geological Sciences, University of interception of the magma body by drilling Canterbury, Christchurch and/or subsequent rise of magma up the 2School of Geography, Environment and Earth drillhole. Detailed examination of the textures Sciences, Victoria University of Wellington, and volatile contents and their distribution in Wellington conjunction with pressure data recorded 3Lancaster Environment Centre, Lancaster during drilling will be used to constrain this University, Lancaster, United Kingdom further. 4School of Environmental sciences, University of Liverpool, Liverpool, United Kingdom [email protected] BEDROCK EROSION BY HYDRAULIC PLUCKING: EXPERIMENTS AND In 2009, the Iceland Deep Drilling Project IMPLICATIONS (IDDP-1) borehole unexpectedly intercepted a 1,2 2 3 silicic (76.5% SiO2) magma body at a depth of C. Wilkinson , D.J. Harbor , S.D. Levy & J.P. approximately 2.1 km. Glass samples Kuehner4 quenched in the drilling mud were directly 1Dept of Geological Sciences, University of sampled at regular (~15 minute) intervals Canterbury, Private Bag 4800, Christchurch, throughout the time the magma was NZ intercepted, providing a unique opportunity 2Geology Dept, Washington & Lee University, to investigate the behaviour of magmatic 204 W Washington St., Lexington, VA, USA volatiles and bubbles during rapid 3Comp Sci Dept, Washington & Lee decompression and freezing of a magma body. University, 204 W Washington St., Lexington, During decompression, volatiles diffuse VA, USA through the magma and exsolve into growing 4Phys & Eng Dept, Washington & Lee bubbles. Conversely, pressure increases or University, 204 W Washington St., Lexington, temperature decreases can cause volatile VA, USA species to diffuse back from bubbles into the [email protected] surrounding melt. These processes should create distinct diffusion gradients in magmatic Bedrock channel erosion by plucking—the glass surrounding the bubbles. Synchrotron wholesale removal of bedrock blocks from a radiation Fourier transform infrared channel bed—is likely the dominant non- spectroscopy (SR-FTIR) was used to generate glacial driver of incision into topography over maps of H2O and CO2 absorbance in each both short and long timescales. However, the sample. Using these maps average H2O and process is poorly understood because it is CO2 concentrations were obtained allowing difficult and often dangerous to observe and the evolution of H2O and CO2 after the magma measure in the field. As such, plucking is had been intercepted to be examined. In mostly understood through engineering or addition, transects around bubbles will be physical/numerical modelling studies. extracted to examine whether H2O and/or CO2 126

Results are presented from a study conducted in an experimental flume using Plaster of Paris High resolution ITRAX elemental data has model bedrock tiles, and from a field study in previously been used in conjunction with which a bedrock block was instrumented with other proxies (e.g. sedimentary, pressure and motion sensors. The flume study, palaeontological, contextual) in tsunami inspired by existing modelling studies, sediment studies to identify potential investigates the roles of block geometry, palaeotsunami deposits in the geologic protrusion factor, and pressure fluctuations in record. Raw ITRAX data has inherent the plucking process. The field study examines uncertainties associated with organic dilution the influence of pressure pulse transmission and matrix effects (e.g. grain size, moisture through the joint network in fractured content, surface roughness). For sediments bedrock; engineering studies inform the with large fluctuations in organic content, it is influence of pressure pulse transmission necessary to normalize the raw element data through joint networks of concrete blocks against a conservative element to account for from impinging jets, and it is likely that the organic dilution as well as assess changes in same phenomenon contributes to plucking in elemental inputs to the lithogenic fraction of natural channels with jointed bedrock. the sediment. Previously presented ITRAX results in the tsunami deposit literature have Our flume experiments reveal that blocks can not adequately accounted for organic dilution, be plucked in the absence of protrusion, and resulting in potentially non-representative that plucking of blocks is most likely to occur results. Here we use sediment cores near the upstream end of a hydraulic jump. containing high organic content variability as We propose that the mechanism driving block well as deposits of the 2016 Kaikōura Tsunami uplift is a pressure gradient in the sub-bed at Little Pigeon Bay, Banks Peninsula, to crack network generated by a hydraulic jump, demonstrate that normalization of ITRAX and that transient pressure fluctuations from element data against aluminium (Al) provides turbulence trigger plucking. This suggests that an effective filter for organic dilution in the the presence of bedrock steps and step-pool dataset. This yields results that are more systems, which cause hydraulic jumps at high representative of the lithogenic component of flow rates, may increase the ability of the the sediment and which are more reliable for stream to incise bedrock when the entry tsunami interpretation compared with Froude number is high enough that the jump normalization against other elements. We lies above bedrock. show that the 2016 Kaikōura Tsunami deposit has a distinct elevated elemental pulse relative to pre-tsunami-inundation soil at this USING ITRAX ELEMENTAL DATA TO DETECT site. This provides a benchmark for identifying TSUNAMI PULSES IN THE LANDSCAPE: A similar pulses in the geologic record which CASE STUDY AT LITTLE PIGEON BAY, NEW could be associated with older tsunami and/or ZEALAND other extreme coastal inundation events (e.g. storms). We discuss the implications of these S. Williams1, I. Qasim2 findings as well as provide directions for 1 NIWA, PO Box 8602, Riccarton, Christchurch further research. 2 School of Environment, Faculty of Science, The University of Auckland, PB 92019, Auckland [email protected] 127

MAFIC INPUTS INTO THE RHYOLITIC that the HRT mafic suite, despite being MAGMATIC SYSTEM OF THE erupted in close spatial and/or temporal 2.08 Ma HUCKLEBERRY RIDGE TUFF, proximity to olivine tholeiites, is sourced from YELLOWSTONE contrasting, heterogeneously enriched portions of the sub-continental lithospheric C.J.N. Wilson1, E.J. Swallow1, B.L.A. Charlier1 mantle. The enrichment was by solute-rich & J.A. Gamble1 fluids/partial melts derived from the 1SGEES, Victoria University, PO Box 600, underlying Farallon slab in a Cretaceous high Wellington 6140 temperature, high pressure regime. Our data [email protected] highlight the magmatic complexities of the mafic roots beneath the voluminous The Yellowstone Plateau volcanic field (YPVF) Huckleberry Ridge rhyolitic magma system is the modern focus of the Yellowstone-Snake during the initiation of the YPVF. River Plain (YSRP) province. The bimodal YSRP has mantle-derived olivine tholeiites providing the thermal and volatile fluxes to generate the HYDRO-ACOUSTIC AND SHALLOW SEISMIC voluminous rhyolites. However, and in REFLECTION DATA FROM THE contrast, volumetrically minor trachybasalts CANTERBURY SHELF – THE MARCAN and trachyandesites represent a contrasting PROJECT Craters of the Moon (COM) suite. COM eruptives generally occur at the YSRP margins S. Woelz1, A. Micallef2, J. Mountjoy1, D. and are interpreted to represent small-volume Spatola2 & C. Mueller3 magmas derived by mid-crustal extreme 1 NIWA, Private Bag 14901, Kilbirnie, fractionation of a tholeiitic parent. Wellington, 6241 2 Marine Geology & Seafloor Surveying, The 2,500 km3 caldera-forming Huckleberry Department of Geosciences, University of Ridge Tuff (HRT), the earliest voluminous Malta, Msida, Malta rhyolitic∼ YPVF product, consists of initial fall 3 GNS, PO Box 30-368, Lower Hutt 5040 deposits, then three ignimbrite members (A, [email protected] B, C), with fall deposits between B and C. The HRT was temporally bracketed by eruption of The MARCAN project is a 5-year project YSRP olivine tholeiites from an area spanning funded by the European Research Council that the subsequent caldera. Previously identified addresses the hypothesis that scoria in ignimbrite B, and newly identified topographically-driven meteoric groundwater juvenile mafic material in ignimbrite A are plays a key role in the geomorphic compositionally overlapping, with 49.3-63.3 development of passive continental margins. wt% SiO2, Ba to 3500 ppm and Zr to 1850 ppm. The objectives of the project are a) to define These HRT materials define a third mafic suite, the characteristics and dynamics of parallel to but offset to higher Ba from that topographically-driven meteoric groundwater defined by the younger surficial COM lavas systems in passive continental margins and b) west of the HRT caldera. We present major, to test the hypothesis that topographically- trace and isotopic data from all three mafic driven meteoric groundwater is an important suites, which temporally bracket the HRT geomorphic agent in passive continental eruption. We compare our data with those margin. from other COM lavas and evaluate published models for their petrogenesis. We propose One of the project’s two study areas is the 128

Canterbury margin, offshore the eastern MINERAL CHEMISTRY OF PRE-CALDERA South Island of New Zealand. This site has MAGMA SYSTEMS IN JEMEZ MOUNTAINS been selected because it is representative of VOLCANIC FIELD, NEW MEXICO, USA siliclastic margins (the most prevalent type of passive continental margins worldwide) and J. Wu1, S.J. Cronin1, M.C. Rowe1, J.A. Wolff2 because it is thought to host the shallowest & S.J. Barker1 offshore freshwater reservoir. 1School of Environment, University of Auckland, Auckland 1142, New Zealand On R.V. Tangaroa’s voyage TAN1703 in April 2School of the Environment, Washington 2017, a vast amount of data was collected in State University, Pullman, WA 99164, USA the shallow part of the Canterbury Bight. The [email protected] data set comprises of multi-channel seismic reflection data (MCS), sub-bottom chirp data Caldera-forming eruptions are the largest (SBP), multibeam echosounder bathymetry types of volcanism known. This study (MB), backscatter data (BS) and water column concentrates on understanding how such data (WCL), controlled-source electro- large volumes of magma accumulate to cause magnetic data (CSEM), CTD profiles, seafloor such events. We use the example of the Jemez imagery from CoastCam (CC), and sediment Mountains volcanic field in the USA, which cores. These data will be used to investigate produced two enormous eruptions resulting in potential offshore aquifers on the Canterbury ~780 km3 of deposits at 1.6 Ma and 1.2 Ma. Shelf. In particular, we will characterise the Prior to these caldera-forming eruptions, the geometry and distribution of the offshore volcanic field experienced a long period of groundwater reservoir using the CSEM data smaller eruptions in two phases from >13-7 and generate a 3D model of the shelf million years and 5-2.7 million years. Mineral stratigraphy and structure using MCS and SBP chemistry is used to estimate the physical data. Sites of groundwater seepage will be conditions and processes of magma identified from MB, BS, WCL, CTD data, accumulation in the crust in build up to the imagery, and pore water chemistry. major eruptions. Sedimentological, geotechnical and hydraulic properties of seabed sediment will be Electron microprobe analysis was used to determined using the sediment cores. investigate the in-situ chemistry of plagioclase and amphibole mineral grains. Amphibole Here we will present data and first results thermobarometry (Ridolfi and Renzulli, 2012) from the hydro-acoustic and shallow seismic indicates that there were three major magma reflection data acquired during TAN1703. reservoirs at different crustal depths in the 5- 2.7 million year system (i.e., Reservoir 1 at 16- 18 km, Reservoir 2 at 7-14 km, and Reservoir 3 at 3-5 km). Mixing of amphiboles crystallized in Reservoir 2 and 3 is commonly observed, suggesting that Reservoir 2 was feeding the shallower Reservoir 3. Reservoir 1 and 2 hosted magma mixing as additionally revealed by compositional variation (mafic enclaves within dacitic hosts). The older 13-7 million year system extended up to a depth of 8 km and was subsequently overlapped by 129

Reservoir 1 and 2 of the younger phase. arc structure. This knowledge gap also applies Diversity in plagioclase textures further to any potential volcanic hazard that this reflects a range of complex magma processes region may pose to continental New Zealand. occurring in reservoirs of both magma systems. Disequilibrium textures may To ascertain the extent and style of volcanism represent a range of processes including in the OTVZ (which accounts for nearly half the mineral migration between reservoirs and areal extent of the TVZ) an extensive sampling potentially magma recharge episodes. and acoustic survey of the OTVZ was conducted in October 2015 during a research The first results of this work are already voyage (SAMSARA) of the RV Tangaroa. The showing how the development of magmas to survey was focussed on knolls and depressions feed very large caldera-forming eruptions may northwest of White Island, and included involve the amalgamation and rejuvenation of seismic and magnetic surveys along the length older diverse and spatially separated magma of the Motiti Graben and the Tauranga systems. Trough.

Dredge sampling recovered a diverse range of VOLCANISM IN THE OFFSHORE TAUPO volcanic samples, from mafic to silicic. The VOLCANIC ZONE region centred on Matatara Knoll, between 700 and 2000 mbsl, is characterized by dense R.J. Wysoczanski1 G. Lamarche1,2 F.J. Davey3 rhyodacite/rhyolitic material and pumice, a M.R. Handler4 F. Caratori Tontini3 J.A. large dome (Matatara) composed of dome- Gamble4 C.J.N. Wilson4 R.J. Carey5 & A.R.L. building dacite overlain by pumice deposits up Nichols6 to 100 m thick, three mafic cones up to 500 m 1National Institute of Water & Atmospheric high and a potentially extensive hydrothermal Research, Greta Point, Wellington deposit. To the southeast lies a 2-km-wide 2School of Environment, University of caldera-related structure (Mahina knoll) Auckland composed of porphyritic felsic lava and 3GNS Science, Avalon, Lower Hutt altered pumice, and a number of volcanic 4School of Geography, Environment & Earth domes, composed mostly of silicic material, Sciences, Victoria University of Wellington although at least one is mafic. 5CODES and School of Physical Sciences, University of Tasmania, Hobart, Australia We present geochemical, seismic and 6Geological Sciences, University of magnetic data of this previously little- Canterbury, Christchurch surveyed region. Together the data show the [email protected] OTVZ to consist of dominantly silicic volcanic products, but with minor mafic and The Taupo Volcanic Zone (TVZ) is one of the hydrothermal material, that collectively most active silicic volcanic systems on Earth, highlight the extensive recent volcanic activity yet the geology and volcanic history of its that this region has seen. offshore continuation (OTVZ), remains virtually unknown. This lack of knowledge is a fundamental gap in our understanding of the origins and architecture of the TVZ, its northern continuation into the Kermadec arc, and its evolution from the Miocene-Pliocene 130

THE PIGROOT DUALITY: AN EXPERIMENTAL MONITORING TEMPORAL VELOCITY ANALYSIS OF THE PIGROOT PHONOLITE CHANGES AT WHITE ISLAND VOLCANO USING SEISMIC AMBIENT NOISE Y. Yagolnitzer1 & M. Brenna1 1Dept. of Geology, University of Otago, PO A.S. Yates1 & M.K. Savage1 & A.D. Jolly2 Box 56, Dunedin 1 Victoria University of Wellington, P O Box [email protected] 600, Wellington 2 GNS Science, P O Box 30-368, Lower Hutt Phonolite is a type of alkaline magma [email protected] occurring in intraplate volcanic settings. Despite its SiO2 and alkalis (Na + K) rich nature, Forecasting volcanic eruptions is a which implies some degree of chemical fundamental aim of volcanology. Crucial to evolution, some occurrences host mantle this is the ability to detect rising magma or the xenoliths. This is contrary to genetic models disturbance of a pre-existing shallow that assume phonolite evolution at shallow chamber. Over the past decade, significant crustal depths. This project aims to improvements have been made towards characterise the dynamic conditions of detecting small velocity changes around magma evolution of the peridotite xenolith- volcanoes by cross-correlating ambient hosting Pigroot phonolite within the Miocene seismic noise. This involves measuring Waipiata Volcanic Field, New Zealand. This fluctuations in the travel time of repeatedly- volcanic centre consists of a basal tuff layer, generated seismic energy along a path pillow lava and overlying lava flows. The between two receivers. Such temporal eruption products range compositionally from variations carry information about the tephrite to sensu stricto phonolite, with stresses and fluids present within peridotite xenoliths being present in all rocks. hydrothermal and magmatic systems. Analysed samples find that mineralogy Additionally, the approach benefits from the consists of a variety of K-feldspars including production of continuous data, offering microcline and anorthoclase, as well as olivine application towards real-time monitoring. In and volcanic glass. this study, we further test the technique at White Island, using noise recorded between A piston cylinder experimental apparatus will 2007 – 2017. The volcano represents an be utilised to simulate the pre-eruptive excellent case study, where a new stage of magma storage conditions that generated the eruptive activity began in 2012 following a chemical variation in the Pigroot phonolite. decade of inactivity. Thus we are able to The project aims to determine the sequence investigate velocity changes during quiescent, of crystallisation at a variety of pressures and inter-eruptive and eruptive periods. Ten temperatures to investigate phase relations in station-pairs are used, consisting of five the host magma. These will be compared to onshore broadband stations around the Bay of those in the natural samples to gain greater Plenty region and two located on White Island. understanding of mechanisms controlling This provided an opportunity to assess the alkaline magma evolution to phonolite capability of resolving coherent noise composition and magma genesis in intraplate between onshore and offshore stations, with settings. implications for global monitoring of volcanic islands. Preliminary results show clear decreases in velocity of 0.1 – 0.2 % during the two–to-three weeks prior to three eruptions, 131 recorded by the majority of station-pairs. In 2004), followed by freely slipping in a different addition, long-term velocity trends are part of fault segment. The latest interseismic identified in the four-to-five months leading velocity suggests that both segments ruptured up to and following two eruptions in 2016. during the 2005 and 2007 earthquakes are Further work will therefore focus on now partially coupled to freely slipping. identifying why not all eruptions exhibit the However, the best fitting model shows that same precursory signals and investigating the the Siberut segment of the megathrust (0.5– characteristic differences between active and 2.0°S) remains fully coupled throughout three inactive periods at White Island. interseismic periods. Hence, the results of this study support the present-day understanding of the interseismic coupling of the subduction THE STRAIN SEGMENTATION AT THE zone where it varies with time. SUMATRA SUBDUCTION ZONE BASED ON GPS-DERIVED INTERSEISMIC COUPLING TEMPORAL VARIATIONS IN SEISMIC C.Z. Yong, P.H. Denys & C.F. Pearson ANISOTROPY DURING THE 2014 GISBORNE National School of Surveying, University of SSE, NEW ZEALAND Otago, 9016 Dunedin, New Zealand [email protected] Hubert Zal1, Katrina Jacobs2, Martha Savage1, Stefan Mroczek1, Jefferson Yarce3, A total of 164 continuous GPS position time Erin Todd4, Heather Shaddox5, Jenny Nakai3, series from 142 unique GPS locations in six Yuriko Iwasaki6, Anne Sheehan3, Kimihiro different countries were combined to examine Mochizuki6, Susan Schwartz5, Laura Wallace2 changes to fault segmentation during a series 1Victoria University of Wellington, P. O. Box of earthquakes that occurred on the Sumatra 600, Wellington, New Zealand trench between 2004 and 2012. These events 2GNS Science, Lower Hutt, New Zealand 3 include the 2004 Mw 9.0 Aceh, the 2005 Mw 8.6 CIRES, University of Colorado, Boulder, USA 4 Nias, the 2007 Mw 8.5 Bengkulu and the 2012 University of Otago, Otago, New Zealand 5 Mw 8.6 Wharton Basin earthquakes. For the University of California, Santa Cruz, USA first time, the far-field GPS sites (more than 6Earthquake Research Institute, Tokyo, Japan 500 km) are used to examine the elastic strain [email protected] from stress build up on the thrust-type subduction zone. The inversion of GPS velocity In October 2014, a 2-week long slow slip event along the western margin of the Sundaland (SSE) occurred near Gisborne at the northern plate is used to estimate the interseismic Hikurangi Margin, New Zealand. It was coupling distribution on the subduction zone recorded by offshore instruments, deployed interface underneath the Sunda trench, as by the Hikurangi Ocean Bottom Investigation well as the kinematics of the tectonic block of Tremor and Slow Slip (HOBITSS) project. rotations. The analysis agrees with previous This study uses data compiled from May 2014 studies that the Sunda megathrust is to July 2015, recorded on 15 HOBITSS ocean segmented, whereby this characteristic will bottom seismometers as well as 12 Geonet lead to the potential of multiple earthquake stations around the time of this uniquely cycles. The comparison of three sets of recorded SSE. We use the S-wave splitting velocity fields: prior-2004, between 2005.2- technique to detect stress and fluid changes 2012.2, and after 2012.2; indicates a change of associated with slow slip. The shear wave state from partially to fully coupled (prior- splitting fast polarization direction is often 132 inferred to represent the maximum horizontal [email protected] stress directions (SHmax) in crustal studies and has been shown to vary temporally at The Taupo Volcanic Zone (TVZ) is a back-arc volcanoes and in association with large continental rift zone within the North Island of earthquakes. Using Multiple Filter Automatic New Zealand, and extends from White Island Splitting Technique (MFAST) we analyse more in the Bay of Plenty southwards to the than 3000 local earthquakes to look for Tongariro Volcanic Centre. Extension rates temporal changes in S-wave fast polarization vary from >12 mm yr-1 in the North to < 7 mm directions and delay times during the Gisborne yr-1 within the Tongariro graben in the south. 2014 SSE. Because S-wave splitting results are The central TVZ is characterized by high sensitive to variations in earthquake locations, magma production rates (> 10,000 km3 since we also analyse results from individual spatial c. 2 Ma), with 95% erupted as rhyolites and earthquake clusters to test the robustness of less than 1% as basalts. However, mafic temporal changes and to better indicate magmas are thought to be the heat source for where the measured anisotropy originates. the extensive crustal melting that produces The mean fast directions in the area show a felsic eruptives, and thus the rates and NE-SW trending fast polarization direction processes of mafic magma production are similar to local SHmax directions mapped by critical in our understanding of all magmatism previous studies and to local fault trends. within the TVZ. We have sampled 7 Late Preliminary SWS results at LOBS stations show Pleistocene to Holocene basaltic eruption approximately 5-10 degrees of change in fast products from Rotokawau in the North to polarization direction from before to after the Waimarino in the South, and have separated SSE. We also observe increased delay times (~ groundmass, olivine, pyroxene, and 0.5 seconds) occurring around the time of the plagioclase, for U-series (238U-234U-232Th-230Th) SSE with a slow decrease in delay time in the isotope work, targeting the timescales of following months. We hypothesize an initial crystallisation and how these may or may not movement of fluids in cracks due to changes in vary with extension rates within the TVZ. stress during the SSE, followed by a relaxation Preliminary U-series data provides some period where cracks slowly return to their insights into the complex petrogenetic previous state. processes operating in the genesis of these basaltic magmas, indicating the uptake of hydrothermally altered crystal cargo in 234U- INSIGHTS INTO THE PETROGENESIS OF 238U disequilibrium into ascending basaltic arc TAUPO VOLCANIC ZONE BASALTS FROM U- melts prior to their eruption. Ultimately, our SERIES ISOTOPE ANALYSIS OF WHOLE work will provide important insights into the ROCKS, GROUNDMASSES, AND MINERALS timescales of mafic melt ascent from mantle source to surface within the TVZ. G. F. Zellmer1, C. H. Stirling2, M. C. Arpa1, G. Lube1 & P. A. Shane3 1Volcanic Risk Solutions, IAE, Massey University, Palmerston North 4410, New Zealand 2Department of Chemistry, University of Otago, Dunedin 9054, New Zealand 3School of Environment, University of Auckland, Auckland 1142, New Zealand 133

EXPLORING THE GEOCHEMICAL SIGNATURES cm in size) indicating eruptive material that OF GROWTH AND COLLAPSE OF TARANAKI has been rapidly remobilised after a significant VOLCANO eruptive phase.

A. Zemeny, J. Procter, K. Nemeth, G. Zellmer, After investigating the stratigraphy of the A. Zernack lahars of Opunake Formation, we intend to 1Volcanic Risk Solutions, IAE, Massey correlate tephras with these lahars in the area. University, PO Box 11 222, Palmerston North Examining the petrology and chemistry of the [email protected] pyroxene and plagioclases, that are abundant in these pumicaeous clasts from the layers of New Zealand’s long-lived stratovolcanoes lahars, may provide suitable candidates to such as Taranaki, Tongariro and Ruapehu, determine crystal residence times between exhibit some of the best long-term record of that may provide insights into the magma growth and destruction. This research progression and eruptive phases of this attempts to find answers for one of the growth phase. interesting questions of volcanic hazards by finding the relationship between magmatic behaviour prior and after volcano destruction and growth phases. Geochemical techniques could lead us to understand more the magmatic response to the pressure releases and changes pre- and post-debris avalanche events. Residence times can be determined by modelling and examining the diffusive equilibrium of major, minor and trace elements using several geochemical measurements, such as ICP-MS, Ion Probe and Sr - Mg diffusion patterns across selected crystals.

The ring plain deposits of Taranaki/Egmont Volcano contains volcaniclastic deposits representing a continuous record of the evolution of the volcano’s fourteen collapse and growth phases. Initial field investigations have focused on deposits in-between the Te Namu (29 ka) and Rama (>35 ka) debris avalanche deposits. This time range partially represents volcaniclastics associated with the Opunake Fm. The Opunake Fm provides a well preserved sequence of lahars (hyperconcentrated flows – debris flows) that represent a substantial growth phase of Taranaki. The hyperconcentrated flow deposits are unique in that they contain relatively well preserved pumice rich clasts (<5 134