New discoveries on the continental shelf of NW Australia

New underwater sites have recently been discovered on the continental shelf offshore of the Dampier Archipelago in NW Australia. Details are reported in the latest issue of PLOS One and The Conversation.

Underwater targets for closer investigation were identified through the application of a predictive model of site location and mapping of the underwater landscape using a combination of of airborne LiDAR and marine geophysical survey. Promising targets were investigated by divers and two have yielded in situ stone artefacts, one at a depth of 2.4 m , the other at a depth of 14 m in association with an underwater freshwater spring. Minimum ages, based on the latest date when the sites were inundated by sea-level rise, are 7500 and 8500 cal BP.

The publication provides a detailed analysis of the cultural material, its geomorphological context, its taphonomic and depositional history, and the question of whether the artefacts could have been eroded from onshore sites and displaced to their present position by wave action or storm surges during cyclone activity.

The results are the first of their kind in Australia, a clear indication that cultural landscapes extended out onto the continental shelf at lower sea level, and evidence that the shelf region, amounting to 2 million square kilometres of drowned land, likely hides an important missing part of the the continent's history, including regions of earliest landfall and dispersal by the first human colonists to reach Australia and New Guinea by seaborne crossings from SE Asia 60,000 years ago.

The study is a model of a purposeful survey strategy designed to find underwater sites and concludes with an assessment of the likely targets for the discovery of sites on the deeper areas of the continental shelf and the modified strategies that will be required to find them.

The work is one of the results of the Deep History of Sea Country (DHSC) Project, funded by the Australian Research Council, and led by Jonathan Benjamin of Flinders University, with colleagues from the University of Western Australia, James Cook University, The ARC Centre of Excellence for Australian Biodiversity and Heritage, the University of York, UK and Moesgaard Museum, Denmark