Rewi Newnham

Dating initial colonisation and environmental impacts by Polynesians in New Zealand is controversial. A key horizon is provided by the Kaharoa Tephra, deposited from an eruption of Mt Tarawera, because just underneath this layer are the first signs of forest clearance which imply human settlement. The authors used a log of celery pine from within Kaharoa deposits to derive a new precise date for the eruption via "wiggle-matching" - matching the radiocarbon dates of a sequence of samples from the log with the Southern Hemisphere calibration curve. The date obtained was 1314 ± 12 AD (2σ error), and the first environmental impacts and human occupation are argued to have occurred in the previous 50 years, i.e. in the late 13th - early 14th centuries AD. This date is contemporary with earliest settlement dates determined from archaeological sites in the New Zealand archipelago.

The coastal plain of South Westland, New Zealand, is characterised by a complex pattern of Late Quaternary moraines and outwash surfaces formed form the advance and retreat of successive piedmont glaciers originating from the adjacent Southern Alps ice centre. Associated with the glacial landforms are numerous bogs and lakes, whose accumulated sedimentary sequences serve as rich natural archives for subsequent climate change. At one such site, Okarito Pakihi, 15 cores have been taken to depths of up to 10 m, without reaching bottom. The generalised stratigraphy from the top consists of a 2-4 m peat layer extending back to 12.0 14C ka, overlying 2-3 m of massive blue-grey silt, often with a zone of greater organic content in its midst. Towards the top of this unit is a layer of glass shards from the Kawakawa Tephra (22.5 14C ka), whilst optically stimulated luminescence (OSL) dating indicates the age of this unit ranges from 28 ka near the top to 75 ka near the base. At its base, the...

An IRSL age of 17.0 ± 2.2 ka (and a “mean age” of ca. 19 ka) reported by Grapes et al. [Grapes, R., Rieser, U., Wang, N. Optical luminescence dating of a loess section containing a critical tephra marker horizon, SW North Island of New Zealand. Quaternary Geochronology 5(2-3), 164–169.] for the Kawakawa/Oruanui tephra, and other ages associated with a loess section in New Zealand are untenable: age data presented are inconsistent, no formal statistical treatments or error determinations were undertaken in age analysis, and the ages proposed are seriously at odds with multiple radiocarbon age determinations on tephra sequences bracketing the Kawakawa/Oruanui tephra and with palaeoenvironmental evidence elsewhere for the time period concerned. We suggest that the bulk polymineral IRSL ages on the tephra and encapsulating loess deposits were underestimated in part because of contamination of the loess by the integration of younger materials during slow deposition and continuous modific...

ABSTRACT Pollen assemblages from Howard Valley, South Island, New Zealand, were used to reconstruct the palaeovegetation and infer past climate during the period ca 38-21 cal. ka, which encompasses the Marine Isotope Stage (MIS) 3/2 transition and Last Glacial Cold Period (LGCP). A glacier occupied the upper Howard Valley during the Last Glacial, whilst extensive glaciofluvial outwash surfaces were constructed in the lower valley. Episodic periods of fluvial aggradation and incision have produced a complex sequence of terraces flanking the main Howard River and its tributaries. Sedimentary sequences from three exposed valley fills, sampled for palynological analysis and radiocarbon dating, consist of a complex vertical and lateral arrangement of coarse textured cobbly sandy gravels interbedded with organic-rich silt deposits. Palynology of these organic-rich horizons was directly compared to an existing beetle record from these same horizons. During late MIS 3 the site was dominated by marshy shrubland vegetation interspersed with mixed beech forest, indicating temperatures ˜2-3 °C cooler than present. Climate cooling began as early as 35.7 cal. ka and coincides with evidence of cooling from other sites in New Zealand, South America and with an Antarctic cooling signature. A three phase vegetation and inferred climate pattern occurs at the site during the LGCP beginning with a transition to an alpine/sub-alpine grassland comparable to communities growing near treeline today marking the change to glacial conditions before 31 cal. ka. A small increase in tree abundance between ca 25.8 and 22.7 cal. ka suggests minor climate amelioration during the mid-LGCP. During this phase, a possible volcanically induced vegetation disruption caused by the deposition of the Kawakawa Tephra at 25 cal. ka is evident in the pollen record. This is followed by a further decline in tree pollen and increase in alpine grassland and herb pollen indicating further deterioration of conditions and a period of maximum cooling (˜4.5 °C) ca 22.5-20.9 cal. ka. This corresponds with the timing of greatest ice advance based on the geomorphic evidence in the region. Contrary to previous studies in New Zealand, the pollen and beetle records are in close agreement. Both indicate the site was forested during late MIS 3, with progressive reduction of trees during the LGCP. The consistent presence of beech pollen nevertheless confirms small refugia of trees persisted in the region.

... a Department of Geological Sciences, University of Canterbury, New Zealand. ... Optically stimulated luminescence dating of the phreatomagmatic succession together with palaeoecological evidence for interglacial climate suggests deposition in late Marine Isotope Stage (MIS) 7 ...

... Anna Sandiford E-mail The Corresponding Author , a , Rewi Newnham Corresponding Author Contact Information , E-mail The Corresponding Author , b , Brent Alloway E-mail The Corresponding ... Mean high sea level is 3.67 m below the current crater floor ( [Coomber, 1998]). ...

Abstract Coastal sections in the Auckland region reveal highly carbonaceous and/or highly weathered clay???dominated cover???bed successions with numerous discrete distal volcanic ash (tephra) layers, fluvially reworked siliciclastic (tephric) deposits, and two widely ...

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... Across the broad Tara-naki ring plain that surrounds Mount Egmont, many peat deposits have been buried and preserved beneath subsequent laharic detritus. ... l H 2O n Kawak aw a Tep hra AT-481 a,1 Airedale Reef, Tara naki 77.74 0.14 12.56 1.20 0.12 1.14 4.08 2.92 0.19 ...

Abstract: The City of Auckland (population c. 1 million), built on a basaltic volcanic field active as recently as c. AD 1400, faces an additional volcanic threat: that from several large and productive rhyolitic and andesitic eruptive centres of the central North Island, 140-280 km to the ...

... TERESA M. GILES, 1 REWI M. NEWNHAM, 1 DAVID J. LOWE 2 & ADAM J. MUNRO 2 1 Department of Geographical ... have shown evidence for the occurrence of forest fires following distal tephra fallout through increases in charcoal fragments and bracken spores immediately ...

ABSTRACT We present pollen records from three sites in south Westland, New Zealand, that document past vegetation and inferred climate change between approximately 30,000 and 15,000 cal. yr BP. Detailed radiocarbon dating of the enclosing sediments at one of those sites, Galway tarn, provides a more robust chronology for the structure and timing of climate-induced vegetation change than has previously been possible in this region. The Kawakawa/Oruanui tephra, a key isochronous marker, affords a precise stratigraphic link across all three pollen records, while other tie points are provided by key pollen-stratigraphic changes which appear to be synchronous across all three sites. Collectively, the records show three episodes in which grassland, interpreted as indicating mostly cold subalpine to alpine conditions, was prevalent in lowland south Westland, separated by phases dominated by subalpine shrubs and montane-lowland trees, indicating milder interstadial conditions. Dating, expressed as a Bayesian-estimated single 'best' age followed in parentheses by younger/older bounds of the 95% confidence modelled age range, indicates that a cold stadial episode, whose onset was marked by replacement of woodland by grassland, occurred between 28,730 (29,390-28,500) and 25,470 (26,090-25,270) cal. yr BP (years before AD, 1950), prior to the deposition of the Kawakawa/Oruanui tephra. Milder interstadial conditions prevailed between 25,470 (26,090-25,270) and 24,400 (24,840-24,120) cal. yr BP and between 22,630 (22,930-22,340) and 21,980 (22,210-21,580) cal. yr BP, separated by a return to cold stadial conditions between 24,400 and 22,630 cal. yr BP. A final episode of grass-dominated vegetation, indicating cold stadial conditions, occurred from 21,980 (22,210-21,580) to 18,490 (18,670-17,950) cal. yr BP. The decline in grass pollen, indicating progressive climate amelioration, was well advanced by 17,370 (17,730-17,110) cal. yr BP, indicating that the onset of the termination in south Westland occurred sometime between ca 18,490 and ca 17,370 cal. yr BP. A similar general pattern of stadials and interstadials is seen, to varying degrees of resolution but generally with lesser chronological control, in many other paleoclimate proxy records from the New Zealand region. This highly resolved chronology of vegetation changes from southwestern New Zealand contributes to the examination of past climate variations in the southwest Pacific region. The stadial and interstadial episodes defined by south Westland pollen records represent notable climate variability during the latter part of the Last Glaciation. Similar climatic patterns recorded farther afield, for example from Antarctica and the Southern Ocean, imply that climate variations during the latter part of the Last Glaciation and the transition to the Holocene interglacial were inter-regionally extensive in the Southern Hemisphere and thus important to understand in detail and to place into a global context.