Contributions to the Quaternary history of the New Zealand flora 8. Interglacial and glacial vegetation in the Westport District, South Island

Abstract

Pollen analysis of organic layers exposed in quarries and road cuttings provides the framework for an understanding of vegetation and climate history during and since the last (Oturi) interglacial in the Westport district. The early and late Oturi are separated by a stadial of unknown duration when forest was replaced by grassland-shrubland. During the early Oturi Nothofagus forest was dominant, but during the late Oturi Dacrydium cupressinum was dominant until it was replaced by Nothofagus. The Otiran record, like the Oturian, is incomplete, but an interstadial characterised by shrubland and by minor spread of Nothofagus began earlier than 31 000 yr B.P. and ended c. 26 000 yr B.P. Subsequently vegetation of grassland or grassland-shrubland remained dominant until the post-glacial spread of forest. The transition from grassland to forest was abrupt and not preceded by the shrubland phase common to the early post-glacial in most areas investigated in New Zealand; there is no evidence of a break in deposition at the sites concerned. The pollen diagrams are compared with pollen data from other sites on the west coast of the South Island and an attempt to correlate them in terms of glacial/interglacial chronology is presented.