The Australasian region experienced extremely cold conditions that coincided with a significant sea level (SL) drop commencing at ~71.8 ka, but was followed by a much more rapid decline just before 71 ka and that lasted just over twelve millennia. Around 64.5 ka, SL dropped close to 100 m. Conventionally, this phase is referred to as Marine Isotope Stage 4 (MIS4) but so far it was poorly documented, even worldwide. Offshore southern Australia, the start of MIS4, sea-surface temperatures (SST) rapidly decreased by 3°C in less than 1000 years, and this coincided with the disappearance of the warm water Leeuwin Current that originates from the tropics and arid conditions in southern Australia ensued. Glacial conditions culminated at 65.1±2.7 ka in New Zealand when SSTs were the lowest offshore southern Australia. This glaciation was clearly more significant than at the Last Glacial Maximum (LGM) as well as in SE Australia and Papua New Guinea.
In my talk, I will define the time span of MIS4, and the conditions that occurred both at sea and on land in the Australasian region and these are compared with Antarctic ice cores and also sea-ice extent.