Geophysical Mapping of Coastal Landscape During the Last Glacial Cycle, NW Shelf Australia

Summary The last glacial cycle covers ~128kaBP to present. On the NW Australian shelf extensive seismic coverage has allowed geomorphological interpretation of an evolving coastal and fluvial landscape for an area encompassing the Bonaparte Gulf. It is possible to infer coastal positions and landscapes over the last glacial period denoted by Marine Isotope Stages (MIS) 5e-1. A key focus for the present study is MIS 4 where a lowstand relative sea level minimum of approximately 77-80m below present day developed ~63kaBP based on SE Australia measurements. This time range is consistent with some of the earliest recorded archaeology in Australia supporting human occupation of northern Australia by 65kaBP. In order for human occupation of Australia to have occurred by this time a sea crossing would have been required. The interpretation of geomorphological features from the seismic database has allowed prediction of most likely coastal position and possible tidal ranges during the MIS 4 lowstand in addition to contemporaneous depositional environments associated with reef, beach, estuarine, lagoonal and fluvial facies in an emergent landscape. The predicted palaeocoastline models are now being used to run simulations of tidal and ocean currents to inform possible maritime transit routes from Sunda to Sahul.