LATEGLACIAL LANDSCAPE AND VEGETATION CHANGE AND THE YOUNGER DRYAS CLIMATIC OSCILLATION IN NEW-ZEALAND

Lateglacial sequences in New Zealand show progressive afforestation an d landscape stabilization reflecting a warming climate. Between 14,500 BP and 11,500 BP, afforestation and landscape stability was achieved throughout most of the North Island and the northwest sector of the So uth Island. In the South Island, scrub and tree ferns were replacing p revious grasslands in the east by 11,000 BP, and broadleaved forest wa s spreading in the west. No significant reversals of these trends occu rred and afforestation was complete by 9500 BP. Glaciers of the high c entral part of the Southern Alps made a series of advances between 14, 000 and 9000 BP. Most of these advances are poorly dated but two morai nes are of Younger Dryas age. Glacial advances in the face of the gene ral Lateglacial warming trend may have been driven by stronger westerl y winds increasing snowfall on high altitude neves, and by reduced abl ation as a consequence of moist, cloudy, low insolation summers. The c ause of the northern hemisphere Younger Dryas cooling is still uncerta in, and expected Southern Hemisphere responses may differ according to the mechanism proposed for the cooling. Poor chronological resolution and apparent conflict between the various types of evidence for clima tic change make detection of an unambiguous Younger Dryas in New Zeala nd problematical.