Initiation of the Australian summer monsoon 14,000 years ago

Definitive evidence for the onset of monsoon moisture in northern Australia following the and phase of the Last Glacial Maximum has been elusive, in large part due to the lack of long, continuous sediment records. Here we report new evidence from two separate drainage basins in the Kimberley region of monsoonal northwestern Australia. At both sites, radiocarbon ages on (basal) biogenic materials in flood deposits indicate stream flow, as high or higher than maximum historic levels, began about 14 cal ka BP. These results suggest that the Australian summer monsoon was fully active several millennia earlier than previously expected. The early onset of the monsoon and the widespread evidence for diminished monsoon activity in the late Holocene cannot be reconciled with primary forcing of the Australian monsoon by changes in low-latitude summer insolation over Australia. (C) 2001 Elsevier Science Ltd and INQUA. All rights reserved.