Antepenultimate glacial to last glacial deposits in southern Wairarapa, New Zealand

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<ul><li><p>This article was downloaded by: [Washington State University Libraries ]On: 16 October 2014, At: 00:53Publisher: Taylor &amp; FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK</p><p>Journal of the Royal Society of NewZealandPublication details, including instructions for authors andsubscription information:http://www.tandfonline.com/loi/tnzr20</p><p>Antepenultimate glacial to last glacialdeposits in southern Wairarapa, NewZealandC. G. Vucetich a b , P. Vella a c &amp; P. N. Warnes a da Geology Dept. , Victoria University of Wellingtonb 17 Ruru Street, Waikanaec 1 Vella Street, Titahi Bayd Institute of Geological and Nuclear Sciences , Lower HuttPublished online: 30 Mar 2010.</p><p>To cite this article: C. G. Vucetich , P. Vella &amp; P. N. Warnes (1996) Antepenultimate glacial to lastglacial deposits in southern Wairarapa, New Zealand, Journal of the Royal Society of New Zealand,26:4, 469-482, DOI: 10.1080/03014223.1996.9517521</p><p>To link to this article: http://dx.doi.org/10.1080/03014223.1996.9517521</p><p>PLEASE SCROLL DOWN FOR ARTICLE</p><p>Taylor &amp; Francis makes every effort to ensure the accuracy of all the information (theContent) contained in the publications on our platform. However, Taylor &amp; Francis,our agents, and our licensors make no representations or warranties whatsoever as tothe accuracy, completeness, or suitability for any purpose of the Content. Any opinionsand views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor &amp; Francis. The accuracy of the Contentshould not be relied upon and should be independently verified with primary sourcesof information. 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Terms &amp;</p><p>http://www.tandfonline.com/loi/tnzr20http://www.tandfonline.com/action/showCitFormats?doi=10.1080/03014223.1996.9517521http://dx.doi.org/10.1080/03014223.1996.9517521</p></li><li><p>Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Was</p><p>hing</p><p>ton </p><p>Stat</p><p>e U</p><p>nive</p><p>rsity</p><p> Lib</p><p>rari</p><p>es ]</p><p> at 0</p><p>0:53</p><p> 16 </p><p>Oct</p><p>ober</p><p> 201</p><p>4 </p><p>http://www.tandfonline.com/page/terms-and-conditionshttp://www.tandfonline.com/page/terms-and-conditions</p></li><li><p> Journal of The Royal Society of New Zealand,Volume 26, Number 4, December 1996, pp 469482</p><p>Antepenultimate glacial to last glacial deposits in southernWairarapa, New Zealand</p><p>C. G. Vucetich, P. Vella and P. N. Warnes*</p><p>In southern Wairarapa valley, north of the marine terraces adjacent to Palliser Bay,three fluvial aggradation gravel terraces with small vertical separation, at successivelylower levels, represent the Porewa, Rata and Ohakea stadials of the Last Glacial Stage.Their correlative loess deposits and interbedded Kawakawa and Middle TongariroTephras mantle much of the lower part of the valley and higher areas to the east,providing stratigraphic control on underlying surfaces of pre-Ohakean, pre-Ratan andPre-Porewan ages. A slightly higher terrace represents the Last Interglacial Stage. It hasa cover of Francis Line Formation, predominantly fine-grained fluvial overbank depositsc.5-7 m thick, locally thicker lacustrine deposits, with overlying Porewa, Rata andOhakea Loess with their interbedded tephras. The eastern limit of Francis Line Formationis defined approximately, and farther east the Last Interglacial Stage is represented bya paleosol, usually strong red in colour, and at places developed in thin wind-blownsand. Ahiaruhe Formation underlies Last Interglacial deposits unconformably, consistsmainly of alluvial gravel, but includes relatively thin loess and fresh-water silt and sandlayers, Mount Curl Tephra and a strong brown paleosol above the tephra. It is consideredto represent the Penultimate Glaciation, Penultimate Interglacial, and AntepenultimateGlaciation, and was deposited in a regime of tectonic subsidence.</p><p>Keywords: river terraces; loesses; tephras; paleosols; eustatic sea-levels; tectonic deformation</p><p>INTRODUCTIONVella (1963) mapped three fluvial aggradation terraces in Wairarapa Valley and correlatedthem from highest to lowest with the first, second and third stadials of the Last Glacial Stage.Palmer and Vucetich (1989) described cover-bed sequences comprising Porewa (First Stadial),Rata (Second Stadial) and Ohakea (Third Stadial) loesses overlying Last Interglacial Stagedeposits. Each loess layer is presumed to be derived from dust that was blown mainly by theprevalent north-westerly wind off the surface represented by its corresponding terrace whenthe terrace was forming as a broad aggrading fluvial flood-plain with little vegetation cover.</p><p>Between Carterton and the Ruamahanga River, Warnes (1989, 1992) recognised fourterraces. The younger three terraces correlate with the three described by Vella (1963). Theoriginal tread of the oldest (fourth) terrace is the top of Francis Line Formation (Warnes1992), consisting of mainly fine-grained fresh-water deposits with some lenses of sand andfine gravel. It now has a mantle ranging up to five metres thick containing the three loessunits derived from the Porewa, Rata and Ohakea flood-plains, and is correlated with the LastInterglacial Stage. New observations (Appendix Table 2; Fig. 1) define the approximateeastern margin of the Francis Line Formation.</p><p>* All formerly at Geology Dept., Victoria University of Wellington. C.G.V. now 17 Ruru Street,Waikanae; P.V. 1 Vella Street, Titahi Bay; P.N.W. Institute of Geological and Nuclear Sciences, LowerHutt.</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Was</p><p>hing</p><p>ton </p><p>Stat</p><p>e U</p><p>nive</p><p>rsity</p><p> Lib</p><p>rari</p><p>es ]</p><p> at 0</p><p>0:53</p><p> 16 </p><p>Oct</p><p>ober</p><p> 201</p><p>4 </p></li><li><p>470 Journal of The Royal Society of New Zealand, Volume 26, 1996</p><p>wmw/</p><p>Fig. 1 Map of southern Wairarapa Valley showing sampling sites listed in Appendix Tables 1 and 2.Heavy dash-dotted line shows approximate eastern edge of Last Interglacial fine-grained fluvial andlacustrine deposits (Francis Line Formation) and estuarine sandy mudstone (site J). Remnants of the6,500 y (BP). eastern shoreline of Lake Wairarapa are shown for comparison.</p><p>Mount Curl Tephra*, loess, and a prominent paleosol here correlated with the PenultimateInterglacial Stage are aeolian deposits buried within fluvial aggradation gravels of theAhiaruhe Formation. The aeolian origin was not recognised in the original description of theformation (Collen &amp; Vella 1984). The tectonic environment of deposition and status of theAhiaruhe Formation are discussed below.</p><p>*Mount Curl Tephra is sometimes referred to as Rangitawa Tephra. The holostratotype of RangitawaPumice described by Te Punga (1952, 1959) is a 6 m thick bed that is certainly mostly reworked tephricmaterial and has never had any primary airfall tephra described within it by Te Punga or anybody else.We examined it and could find no primary airfall tephra. What has been called Rangitawa "Tephra" ismore correctly referred to as Mount Curl Tephra, with its plainly primary airfall holostratotype atMount Curl Road (Milne 1973).</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Was</p><p>hing</p><p>ton </p><p>Stat</p><p>e U</p><p>nive</p><p>rsity</p><p> Lib</p><p>rari</p><p>es ]</p><p> at 0</p><p>0:53</p><p> 16 </p><p>Oct</p><p>ober</p><p> 201</p><p>4 </p></li><li><p>Vucetich Glacial deposits in southern Wairarapa 471</p><p>LAST GLACIAL STAGE DEPOSITSThe three names Ohakea, Rata and Porewa were first applied to fluvial aggradation gravelformations, each well preserved in terrace treads ascending in order of increasing age atRangitikei Valley (Te Punga 1952; Milne 1973). Each tread had its origin as a flood-plainfrom which channel silts were blown by wind to be deposited on higher surfaces as a loessmantle. The phases of alluvial aggradation and accompanying loess accumulation date to theLast Glaciation cold climate phases (stadials) when forest was sparse. Phases of riverdowncutting date to the intervening warmer climate phases, with narrow flood-plains, morevegetation cover, and little loess generation. Because of continuous uplift of the Rangitikeidrainage basin, the relation of alluvial aggradation to rapid loess deposition was easy torecognise; e.g. Ohakea Gravel is the stratigraphic equivalent of Ohakea Loess which formsthe top of the mantle on higher terrace gravels. The terrace gravels, derived from RuahineRange Mesozoic (Torlesse) greywacke, were partially protected from weathering by theloess mantle. Each loess unit itself was subject to soil weathering both whilst it was rapidlyaccumulating and during its following interval of negligible accumulation. Differing weatheringmodes resulting from local factors, chiefly differences of climate and of the freedom ofsubsurface drainage, are reflected by five loess facies recognised in New Zealand: aerieloams, aerie earths, aerie dense silts, aquic dense silts and clay silts (Milne 1988).</p><p>The three Last Glacial Stage fluvial aggradation terraces between Carterton and theRuamahanga River show the same genetic relationship to loess deposits as that demonstratedat Rangitikei by Milne (1973) and in northern Wairarapa by Vella et al. (1988). The mostthorough descriptions of southern Wairarapa Last Glacial Stage loess sequences are those ofPalmer &amp; Vucetich (1989), based on continuous cores taken using a truck-mounted drill.Three of the cored sites, H and I (Fig. 1), and another to the south near Lake Ferry on thePalliser Bay coast, are discussed below. All three overlie deposits of Last Interglacial age andcontain three distinct loess units separated by paleosols and correlated from core to core bylithological and soil weathering characters and by two tephric horizons. Other loess sequences,reported by Warnes (1989, 1992) and in this article (fig. 1; Appendix Tables 1, 2 &amp; 3), havebeen determined by Jarrett augering.</p><p>Almost invariably uppermost in the cover-beds is Ohakea Loess positively identifiedbecause it contains Kawakawa Tephra (Aokautere Ash of Cowie 1964), carbon14 dated as22 600 y old (Wilson et al. 1988). Kawakawa Tephra is rarely found as a macroscopic layerin southern Wairarapa. It is exposed as a 510 mm layer in a cutting on the Martinborough-Greytown Road adjacent to core site H, and Palmer and Vucetich identified it in the core1.5 m below the ground surface, two-thirds of the way down the thickness of Ohakea Loess.Warnes (1989) detected it microscopically as concentrations of glass shards in loess sandfractions from many sites, identifying it by glass chemistry using electron microprobeanalyses. The depth of the tephra below the top of the Ohakea Loess varies from place toplace. At Riverside, 4.5 km north of Martinborough at the top of a cliff on the east side of theRuamahanga River, the Ohakea Loess is 7 m thick and the Kawakawa pumiceous deposit isa prominent layer at half that depth. The extraordinary thicknesses of the loess and pumicethere are attributed to strong updrafts from the Ruamahanga flood-plain during north-westerly gales. In contrast the tephra is only 0.5 m deep or shallower in the area betweenCarterton and the the Ruamahanga River, (e.g. at site D, Appendix Table 3). The differencesin depth of the Kawakawa Tephra reflect differences in the amount of loess received at thedifferent sites. Each of the three loess units tends to vary in thickness from site to site (seeAppendix Table 3 for examples).</p><p>The drilled cores (Palmer &amp; Vucetich 1989) define lateral facies difference in the loesswithin southern Wairarapa, which need to be appreciated when correlating stadial units fromsite to site. The Lake Ferry core sampled a mantle of loess overlying freely draining gravel ofa Last Interglacial marine terrace mapped by Ghani (1978). The mantle contains three loessunits which by superposition are correlated with the Ohakea, Rata and Porewa Loesses of theLast Glaciation. A prominent reddish brown layer in the sequence, the Lake Ferry Paleosol,</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Was</p><p>hing</p><p>ton </p><p>Stat</p><p>e U</p><p>nive</p><p>rsity</p><p> Lib</p><p>rari</p><p>es ]</p><p> at 0</p><p>0:53</p><p> 16 </p><p>Oct</p><p>ober</p><p> 201</p><p>4 </p></li><li><p>472 Journal of The Royal Society of New Zealand, Volume 26, 1996</p><p>exposed near the core site, is a key marker bed between Rata Loess above and Porewa Loessbelow. The reddish brown colour has arisen from dominantly oxidising soil weathering of aniron-rich andesitic ash accretion (Middle Tongariro Ashes, Milne 1973) and contrasts withthe yellow-brown colours of the low iron quartz-feldspar dominant loess units derived fromTorlesse greywacke. Polygonal columnar cracks form a conspicuous veined pattern in allthree loess units. The cracks record former seasonal wet-dry cycles in Rata and Porewaloesses and ongoing cycles in the present ground soil and Ohakea Loess. The cracks in theRata and Porewa Loesses might be still active but more probably are entirely sub-fossil.</p><p>The Bidwill core (site H, Fig. 1) contains the three loess units overlying Last Interglacialpeat and impermeable grey and bluish-grey water-laid clay which impede drainage andremain wet the year round. In the adjacent road cutting polygonal columns are conspicuous inOhakea Loess but weakly developed in Rata Loess. Palmer and Vucetich (1989) describeRata Loess in the core as firm silty clay loam, very plastic when wet, with a dull yellowishorange base colour and profuse orange and light grey mottles. It is distinguished from theOhakea Loess above by its texture, stronger orange colour and blocky structure. The LakeFerry Paleosol separating Rata from Porewa Loess is not distinguished by the strong colourseen at Lake Ferry. The Porewa Loess is massive and totally mottled grey and orange, incontrast to its blocky structure and yellow brown colour at Lake Ferry.</p><p>Porewa and Rata Loess reported by Warnes (1989) and at several new sites listed here(Appendix Table 2) also overlie Last Interglacial clayey fresh-water deposits (Francis LineFormation, Fig. 2) which impede subsurface drainage, and resemble the facies at the Bidwillcore site.</p><p>LAST INTERGLACIAL DEPOSITSThe Porewa Loess is here taken to represent the First Stadial of the Last Glaciation, as it wasby Milne (1973) correlated with oxygen isotope Stage 4, with its base slightly younger thanthe marine bench on which it rests at Lake Ferry, inferred to be 80 000 y old by Ghani (1978).Berger et al. (1992), using the thermoluminescence method, estimated an age of 85 000 +15 000 y for a sample from the Lake Ferry core 40 cm above the top of the gravel. All of thesites where Porewa Loess has been recognised in southern Wairarapa inland from the LastInterglacial marine terraces adjacent to Palliser bay (Ghani 1978) are marked on Fig. 1.Lettered sites were reported by previous authors (Appendix Table 1) and numbered sites arereported here for the first...</p></li></ul>