Marine mapping survey reveals broad-scale seabed environments of remote offshore basins in Western Australia

Abstract

Between October 2008 and January 2009, Geoscience Australia conducted a marine mapping survey to document the seabed environments and subsurface geology of the Zeewyck, Houtman, Exmouth sub-basins and the deep-water Wallaby (Cuvier) Plateau, Western Australia. The seabed mapping survey, the second and largest mapping survey of the Federal Government’s Offshore Energy Security Program, documented seabed environments and biota from multibeam sonar and sub-bottom profiler data, towed video footage and physical samples. Preliminary analysis of the data indicates that for all of the sub-basins the seabed is comprised of carbonate mud that supports relatively sparse infaunal populations. Rocky substrates, principally in the numerous submarine canyons, supported sparse communities of sessile organisms. Interestingly, some of these hard-grounds were associated with volcanic (basaltic) peaks on the upper slope that attain 200 metres above the surrounding seabed. Data collected from the survey are being analysed in conjunction with existing environmental data to establish a series of environmental summaries that describe the key seabed habitats and biota for the offshore basins. The environmental summaries are being made available to support future acreage release in the sub-basins. The marine mapping survey was run in combination with a regional 2D seismic survey of the same offshore basins, also completed as part of the Offshore Energy Security Program.