Late Pleistocene palynology of terrestrial cover beds at the type section of the Rapanui Terrace, Wanganui, New Zealand

Abstract

This study investigates the vegetational and climatic history recorded by fossil pollen preserved in terrestrial cover beds at the type section of the Rapanui Marine Terrace, Wanganui, New Zealand. At this section, laterally extensive Rapanui Lignite and Rapanui Dunesand overlie marine sands of the Rapanui Formation, which were deposited after the cutting of the Rapanui marine platform during the last interglacial sensu stricto.The lowermost sample, below Rapanui Lignite proper, contains a pollen assemblage derived from podocarp-hardwood forest, indicating a palaeoenvironment similar to, or cooler and drier than, the present. The Rapanui Lignite contains pollen assemblages derived from a low forestlshrubland with prominent Myrtaceae, and including a nowextinct Acacia-type. These assemblages are derived from vegetation lacking a modern analogue in New Zealand, and they are considered to indicate a palaeoclimate which was also cooler and possibly drier and windier than at present. The presence of Libocedrus and Acacia-type on the Wanganui lowlands during the period of deposition of Rapanui Lignite indicates important late Pleistocene biogeographic differences for these taxa, compared with the present. Since the Rapanui Formation marine sands are estimated to be c. 120,000 years old, and the overlying terrestrial sediment appears to be more or less conformable, the lowermost pollen sample probably represents the end of the last interglacial (oxygen isotope substage 5e) or the transition period to the following stadial. The Rapanui Lignite is correlated with stadial oxygen isotope substage 5d, and is estimated to date to c. 110,000 years ago.

A terrestrial record of Last Interglacial climate preserved by voluminous debris avalanche inundation in Taranaki, New Zealand

“…It extends the record of environmental variability for MISS 5d, by revealing a subalpine-like shrubland vegetation at what is now the north Taranaki coast (cf. Bussell, 1992;Bussell and Pillans, 1992) and provides further evidence for the role of volcanism in vegetation development in the region. The similarities with the record at Inaha Terrace are noteworthy, especially for the near full forested conditions evident in MISS 5a and for the subsequent period of fire-ravaged vegetation, probably associated with volcanic activity, wind, lower rainfall and drought (McGlone et al, 1984a).…”

The last interglacial sea-level record of New Zealand (Aotearoa)

“…Most type sections are kilometers seaward of the inland terrace riser and indicate only minimum sea-level 285 estimates for their respective highstands. The shore platform of the Rapunui Terrace (MIS 5e) is found within a cliff section at Castlecliff at 29 ± 0.3 m amsl and is directly overlain by ~5.5 m of marine cover beds (Bussell et al, 1992;Figure 3 WID 38). An additional 7.5 m of terrestrial cover bed includes dune sand correlated to MIS 5c.…”

Late Quaternary vegetation and climate history reconstructed from palynology of marine cores off southwestern New Zealand

“…Surface ocean temperatures surrounding New Zealand during past interglacials appear to have been ~2-3°C warmer during MIS 5e and MIS 11c than the early Holocene (Hayward et al, 2012;Cortese et al, 2013;Prebble et al, 2016). While there is evidence for warm and moist conditions in reconstructions in vegetation change over MIS 5e from New Zealand (Bussell, 1990(Bussell, , 1992Heusser and van de Geer, 1994;Mildenhall, 1995;Shulmeister et al, 1999;Carter and Lian, 2000;Carter, 2002;Marra, 2003;Newnham and Alloway, 2004;Ryan et al, 2012;Williams et al, 2015), reconstructions of temperature change have remained largely qualitative in nature. While not independently constrained, sites along Westland previously correlated with the last interglacial (MIS 5e) on the basis that the palynomorph assemblage appear to be similar to that of the present interglacial palynomorph assemblage (Fig.…”