New Zealand Journal of Geology and Geophysics ISSN: 0028-8306 (Print) 1175-8791 (Online) Journal homepage: http://www.tandfonline.com/loi/tnzg20 Late Quaternary geology of the Wairau Plain, Marlborough, New Zealand L. J. Brown To cite this article: L. J. Brown (1981) Late Quaternary geology of the Wairau Plain, Marlborough, New Zealand, New Zealand Journal of Geology and Geophysics, 24:4, 477-489, DOI: 10.1080/00288306.1981.10422739 To link to this article: http://dx.doi.org/10.1080/00288306.1981.10422739 Published online: 07 Aug 2012. Submit your article to this journal Article views: 227 View related articles Citing articles: 14 View citing articles Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=tnzg20 Download by: [125.239.173.16] Date: 30 August 2017, At: 05:23 New Zealand Journal of Geology and' Geophysics, 1981, Vol. 24: 477-490 477 Late Quaternary geology of the Wairau Plain, Marlborough, New Zealand L. J, BROWN Macrofaunas from Dillons Point Formation New Zealand Geological Survey, DSIR (mainly drillhole samples) are detailed in an P.O. Box 30368 appendix and the paleoecology is discussed. Lower Hutt Keywords Quaternary; stratigraphy; postglacial environment; tectonics; water well data; paleoecol­ ogy; Wairau River; Wairau Plain; Marlborough; with an Appendix Dillons Point Formation; Rapaura Formation; new stratigraphic names Faunas and paleoecology of Dillons Point Formation INTRODUCTION A. G. BEU New Zealand Geological Survey, DSIR Marlborough consists of a series of northwest-tilted P.O. Box 30368 blocks forming mountain ranges, hills, and drowned Lower Hutt valleys (Marlborough Sounds) separated by major transcurrent faults along which are developed fault­ angle depressions. Wairau River lies in the fault­ Abstract The late Quaternary deposits of angle depression formed along Wairau Fault, a Wairau Plain are subdivided on the basis of c.ontinuation of the Alpine Fault (Fig. 1). The valley mapping, test drilling, radiocarbon dating, and and plain of ¥!airau River separate upper Paleozoic macropaleontology (paleoecology). Otira (last) schist and greywacke in the north, from Mesozoic Glaciation fluvial gravel, sand, and clay deposits greywacke in the south. Tectonic activity is a major (cOlTelated with the Speargras1.i Formation of the influence on the geology of the Wairau Plain. upper Buller River valley) are capped by a surface Northwest tilting of the block (Awatere Block) which extended at least to the present-day coast and between the Wairau and Awatere Faults (Fig. 1) has possibly into Cloudy Bay. Postglacial deposits resulted in the main tributaries of Wairau River overlying Speargrass Formation are grouped into 2 being on the southern side of the Wairau valley. contemporaneous formations described in this In the lower reaches of the Wairau valley, alluvial paper. deposits laid down by Wairau River and its DiUons Point Formation (new name) consists of tributaries during periods of glacial advance in the marine embayment and estuarine sediment and inland mountain ranges have been eroded and Downloaded by [125.239.173.16] at 05:23 30 August 2017 fauna, deposited over the land surface during the redeposited during warmer interglacial periods. postglacial marine transgression and the subsequent Higher level and dissected alluvial deposits on the regression. The maximum inland transgression southern margin of the Wairau valley and plain are occurred about 6000 to 7000 years ago before a remnants of former glacial outwash deposits. barrier spit (Boulder Bank) was formed part of the Postglacial aggradation by the Wairau River has way across Cloudy Bay. Progradation of the coast partially dammed the tributaries joining it from the occurred outside the northern end of the Boulder north. These southward flowing tributaries have Bank simultaneously with the infilling of the lagoons also been affected by northwest tilting of the block and estuaries behind the Boulder Bank. (Marlborough Sounds Block) north of Wairau Rapaura Formation (new name), a postglacial Fault. As a result, Tuamarina River has an extensive fluvial gravel, sand, silt, and clay deposit, is derived swamp (Para Swamp) at the southern end of the mainly from erosion of the Speargrass Formation as Tuamarina valley; the Areare Creek (Okaramio a result of alternating aggradation and degradation valley) and Pukaka Stream disappear into swamps by the Wairau River. Rapaura Formation lenses out which drain into the Wairau River, and Waikakaho against, and interfingers with, Dillons Point River has established a meandering course at the Formation. mouth of its valley. Over the greater part of the lower Wairau valley Received 12 March 1981, accepted 9 April 1981 and plain, postglacial aggradation has formed fluvial 478 New Zealand Journal of Geology and Geophysics, 1981, Vol. 24 w w deposits on top of glacial outwash deposits. Near the . modem coast, postglacial swamp, lagoonal, .... ....... '" estuarine, and beach deposits overlie fluvial and glacial outwash deposits. The Wairau Plain is the surface developed on the postglacial and last glaciation deposits of the lower Wairau valley from "The Narrows" (just upstream of the Waihopai River junction) to Cloudy Bay (Fig. 2). PREVIOUS WORK The geology of the Wairau valley was summarised by Lensen (1962) and Beck (1964). Quaternary tectonics have been considered by Cotton (1954), Eiby (1973), and Lensen (1976). Various workers have discussed the evolution of the coastal part of the Wairau Plain. Cotton (1913) and Jobberns (1928) supposed that the lower plain formed as a delta of the Wairau River, whereas Wild (1915), Jobberns (1935), and Pickrill (1976) suggested that the plain formed as a result of infilling with sand, silt, and clay (by the Wairau River) of a lagoonal system, a remnant of which survives to the present day as the Wairau Lagoons, partially enclosed by a w 50 100 150 barrier spit (Boulder Bank). km. '".... Fig. 1 Northern South Island, New Zealand, showing the study area in relation to the Wairau and Awatere Faults. Downland, hill and ~ mountain topography a 5 km ! I ~ Sand dunes Boundaries of surface deposits related to a common derivation Downloaded by [125.239.173.16] at 05:23 30 August 2017 -_/ source CLOUDY N BAY Fig. 2 Deposits of the Wairau Plain related to their parent rivers or origin. Brown-L. Quat. geology, Wairau Plain 479 N o 5 km I 1 I I j I CLOUDY BAY 'p LITHOLOGY FORMATION STAGE Fig.3 Geological map of Wairau Plain. tt:~=;=4 Lagoon deposits r-. ...:-.::.,.<.<::.,:i1 Beach ndgesand swales DILLONS POINT ilIIIIIJJJ Boulder bank w iE u _sanddunes ARANUIAN o <5 I~-:k.~ Swamp :I: STRATIGRAPHY I r===:J 1=-=;...1 OralnedswampsandalluVlal Silt RAPAURA Figure 3 is a map of the surface geology of the O Modern and recently abandoned [O o O"Od Wairau Plain, and Fig. 4 illustrates the subsurface o 000 floodplains sequence. The late Quaternary stratigraphy of the lS~':~'J Fluviatilegravel,silndarldsilt Wairau Plain can be summarised thus: ~lGI","IOO<W"" Formation Derivation ~somesanda"dsllt.Typ'CaIIV,,,,,,Iw,," SPEARGRASS OTIRAN w the olde' gravels are more iE U ~ weatheJi!'d,yeUow brown and Dillons Point* Coastal and lagoon Contemporary ~haveathlckerloesscoverthan TOPHQUSE WAIMEAN ~ <Jl the younger gravel deposits postglacial ~The5urtaceofthe~lderdeposits W MANUKA WAIMAUNGAN a: Rapaura* Fluviatile and swamp Contemporary ~aremoredlsseeted deposits postglacial Loess covered deeply weathered Downloaded by [125.239.173.16] at 05:23 30 August 2017 ~ yellow brown gravel,sand and silt MIOCENE Speargrass Glacial outwash Otira gravel Glaciation ~ Greywacke/Sch;st Tophouse Glacial outwash Waimea Fault gravel Glaciation Manuka Glacial outwash Waimaunga gravel Glaciation *New formation names MANUKA AND TOPHOUSE FORMATIONS tions, Suggate 1965) of the Wairau and Buller (Suggate 1965) valleys. In Fig. 3 the separation of Tophouse and Fan deposits laid down by the rivers flowing to the Manuka Formations at the surface is based on the Wairau Plain from the south are dissected and Manuka Formation having a thicker loess cover and mantled with loess to produce a "rolling" being more dissected with more weathered topography. These are correlated with glacial (brown/yellow) gravel, sand, and clay content than outwash deposits (Tophouse and Manuka Forma- the younger Tophouse Formation. Sig.3 480 New Zealand Journal of Geology and Geophysics, 1981, Vol. 24 WEST EAST Metres ALATE POSTGLACIAL B 20 FLUVIATILE DEPOSITS Creek Marshlands BEACH DEPOSITS S8'i Level CLOUDY BAY ~ Gravel ~ Clay o Sand ~ Shells _ 8 Peat or Timber - GLACIAL OUTWASH DEPOSITS 65 Well Number -40 I- NZ 4019A NZ Radiocarbon Number Metres 1-=-------------------------------------------------=1 C LATE POSTGLACIAL D 20 f- FLUVIATILE DEPOSITS BLENHEIM Riverlands _ - Dillons POint 950 723 402 472 739 Boulder Bank ~ \ NZ 3140A NZ 1619A;z.... 643 518 680 603 708 w:. L - Sea Level 9~(j jAAPAURA 00 FORMATlON)~~ :.:"':""~~'. ..". ::::::.-::. ,. ,_ ~ r-- '"-'-" a/tau agoons~7 .,"- 0 ~ l~oi!J f~$ POSTGLACIALZ~ :".S .....,.... I- P"''P' OV' fA,,~. p,~. ,yt ~...;.2' :t§:. I DILLaNS - °0° / 0°'" (RAPAURA ~~ q:.~. L ... -.r-......- . ~ MARINE DEPOSITS:-"_ v_v ~ ::$=i I"'oq, .0:2 Q..O·I --;:;-:::; F-_~"'::: -20 NZ3'141A NZ 0 Q~ il:u .~ POINT - o:o!.':q:cj 1620A ,.!i-.I FOAMATiON)-~ r3u =_.~ ~.:o. EARLY POSTGLACIAL 0, ~p: .Cf"& ~~ FLUVIATilE DEPOSITS .Q:)i ~ ~;~9: FORMATION} -40 '- [0'- 9"'0. 1'b~:--~>'lT-______- 0.2 G~CIAL OUTVV"c:.H DEPOSITS (SPEARGRASS FORMATION) 6:·:· 0 ~ _0 o 1 2 3 km - I I I I Fig. 4 Stratigraphic columns from well data, Wairau Plain. Positions of section lines A-B and C-D are shown in Fig. 5. SPEARGRASS FORMATION (Suggate 1965) deposition in an environment dominated by net Speargrass Formation, representing Otira (last) aggradation by the Wairau River. Glaciation deposition, has been described in the The surface boundary between Speargrass Forma­ upper Buller valley; its surface is correlated with a tion and postglacial fluvial deposits is marked by a low-level aggradation surface of the Wairau valley degradational terrace with a maximum height of 6 m (Suggate 1965).