Quaternary environmental change in New Zealand: a review

The discovery that orbital variations are the driving force behind Quaterna ry climate change provides an impetus to set local and regional records of environmental change into the global context, a principle that has been str ongly embraced by Quaternary scientists working in New Zealand. Their major achievements and significant current initiatives are reviewed here. The im portance of the New Zealand Quaternary stems from its geographical context: a climatically sensitive, remote oceanic, southern location spanning 17 de grees of the mid-latitudes; an obliquely convergent plate boundary setting resulting in a high mountain range athwart the prevailing westerlies, activ e volcanism, a youthful and dynamic landscape, and mountains high enough to maintain glaciers today; and a remarkably short prehistory. The resultant records show marked environmental changes due not only to climatic oscillat ions but also to vigorous, active tectonism and volcanism. The Taupo Volcan ic Zone, containing the world's strongest concentration of youthful rhyolit ic volcanoes, has produced at least 10 000 km(3) of magma in the last 2 Ma. Climatic interpretations of records from marine sediments in the New Zeala nd region, together with several long sequences of alternating marine and t errestrial sediments, indicate broad synchrony with Northern Hemisphere eve nts (within limitations of dating), although there are differences in detai l for shorter-term climatic events. It is not yet certain that glacial adva nces coincided precisely with those in the Northern Hemisphere or were of s imilar duration. Late Cainozoic glaciation commenced c. 2.6-2.4 Ma but the record of glacial deposits is fragmentary and poorly dated except for the m ost recent events. The Last (Otira) Glaciation, from c. 100-10 ka, was char acterized by at least five glacial advances including during the Last Glaci al Maximum from 25 to 15 ka, when snowlines fell by 600-800 m. New Zealand evidence for cooling during the Younger Dryas stade is equivocal whilst iso topic records from speleothems, and other data, indicate warmer and wetter conditions from 10-7 ka, broadly conforming with records from mid-latitude Northern Hemisphere locations. Future advances will require sampling at sho rter timescales, improvements in the accuracy and precision of exisiting da ting methods and the development of new ones, extension of palaeoecological techniques to cover the full potential of Nem Zealand's diverse biota, and a stronger emphasis on quantification of palaeoclimatic parameters.