A 30,000 year record of extreme floods in tropical Australia from relict plunge-pool deposits: Implications for future climate change

Relict plunge-pool sedimentary sequences provide much longer paleoflood records than normally provided by slackwater deposits and other previously reported paleoflood sedimentary signatures. The only two relict plunge-pool sedimentary sequences so far reported lie 300 km apart in tropical northern Australia and provide a record of extreme floods for the last 30,000 years. Each of these sequences identify the early to mid-Holocene and the period immediately prior to the Last Glacial Maximum as the two periods of greatest flood magnitudes of the late Quaternary. Flood discharges at these times were up to five times greater than any floods experienced over the last 4,000 years. Most climate models predict that the magnitude and frequency of storms and rainfall events will increase under a warmer 'greenhouse' climate. The plunge-pool sedimentary sequences, however, show that periods of greatly enhanced discharge compared to present can be associated with both warm, wet and cool, wet phases of climate.