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Abstract
During the Late Pleistocene, the large and shallow Lake Carpentaria occupied part of the continental shelf linking northern Australia and New Guinea. The former lake lay within the modern Gulf of Carpentaria, between the —53 m isobath and the deepest part of the embayment at — 67 m, and may have been as much as 500 km long, 250 km wide and 15 m deep. The basinal feature is separated from the outer margin of the continental shelf in the northwest by an area of shallower sea floor with a maximum water depth of about — 53 m and referred to as the Arafura Sill. We have investigated the sedimentary record of the shallow substrate, both within and beyond the basin perimeter, by using surficial sediment samples, piston cores, and continuous seismic reflection profiling. Sediments interpreted to be of lacustrine origin occur only within the enclosed basin, and have been covered by a blanketing marine sandy mud deposit approximately 1 m thick. Beneath the lacustrine mud and sandy mud is a cohesive clay and sandy clay unit, subaerially weathered, saline and possibly of estuarine/marine origin. In shallower areas beyond the basin perimeter, the surficial marine sediment blanket directly overlies the subaerially weathered unit. Radiocarbon dates have been obtained from the surficial unit, and from the lacustrine deposits, to obtain a time frame for the Late Quaternary geological history. The existence of Lake Carpentaria has been linked to cycles of channel erosion and back‐filling on the Arafura Sill. Over several cycles of sea‐level change, this has led to a gradual shallowing of the sill, and closure of a previously open basin. In the enclosed depression, Lake Carpentaria was able to exist throughout the period of the last glacial maximum, sustained by fluvial inflow from its large drainage basin.