VEGETATIONAL AND CLIMATIC HISTORY DURING OXYGEN-ISOTOPE STAGE-7 AND EARLY-STAGE-6, TARANAKI, NEW-ZEALAND

A detailed palynological record from terrestrial cover beds of the Bru nswick Marine Terrace (c. 310 000 yr) is described from the Ararata Gu lly Site near Hawera, south Taranaki, New Zealand. Lignite 3 m thick c ontains compressed wood, thin andesitic and rhyolitic tephra, and abun dant fossil pollen. Following cutting of the marine terrace during int erglacial oxygen isotope stage 9, podocarp-hardwood forest with abunda nt Prumnopitys taxifolia grew in the area during interstadial substage 7c. This was succeeded by podocarp-beech forest and grass-shrubland d uring stadial substage 7b. Podocarp-hardwood forest, characterised by pollen assemblages similar to those of the early-mid Holocene for this area, then grew regionally during interglacial substage 7a. Dacrydium cupressinum and Ascarina lucida were prominent during the interglacia l peak. Later, during the cooling period leading into glacial stage 6, Metrosideros, Leptospermum-type, and Acacia-type expanded in vegetati on surrounding the site. These Myrtaceae-dominated assemblages have no modern analogue in New Zealand, but appear to have more affinity with Australian sclerophyll vegetation. Grass-shrubland and Nothofagus for est expanded regionally as temperatures continued to fall in early gla cial stage 6. The Ararata Gully pollen sequence is interpreted to repr esent almost all of oxygen isotope stage 7 and early stage 6 - a perio d from c. 240 000 to c. 180 000 years ago. This is the most complete r ecord of vegetation and climate covering this period so far obtained i n New Zealand. The results are compared with those from other sites in central-western North Island. Oxygen isotope substages 7a and 7c are shown to have been of substantially different climatic character. Only substage 7a was a fully interglacial period with vegetation and clima te which was, for a time, equivalent to that of the early-mid Holocene climate optimum. Substage 7c should be considered an interstadial per iod. Interglacial vegetation communities of apparently similar composi tion have been able to repeatedly re-occupy the south Taranaki lowland s during the warmest, wettest, and mildest periods of the late Quatern ary. Many taxa making up these communities were restricted in distribu tion to protective inland environments during the long glacial, stadia l, and interstadial periods, but were able to expand in response to cl imatic amelioration that culminated in relatively brief interglacials, such as the present. Other species may have been filtered out by this cyclical process if they were unable to respond to such rapid climati c changes. This plasticity of the New Zealand vegetation has resulted in a lack of distinctive vegetation types that might distinguish any o ne interglacial period from another in the middle and late Quaternary, at least in south Taranaki. A rhyolitic tephra bed, informally named Ararata Gully tephra, is described and correlated with the oxygen isot ope sub-stage 7c and 7b boundary (c. 235 000 yr).