Australian northwest margin, meteorite impact and seismic velocities: is there a connection?

Abstract

The Bedout High in the Roebuck (formerly offshore Canning) Basin at the NW Australian Margin (NWAM) has recently been re-interpreted as a massive impact structure that appears to be associated with the global Permian/Triassic extinction event. This impact may have significantly modified the crustal structure in the region. Depth conversion of reflection seismic data indicates that depth to basement at the top of the Bedout High is ~ 3.9 km, and that the High stands more than 4 km above the surrounding sedimentary basins. The basement and crust in the Roebuck Basin have a number of features that distinguish it from other basins at the NWAM. Rapid crustal thinning outboard of the Bedout High and the presence of a thick layer of magmatic underplating in the lower crust are among these features. The meteorite impact may have been one of the possible causes to have triggered upper mantle melting and generation of a voluminous layer of underplated material. On a finer scale, OBS-derived seismic velocity variation along the basement is speculatively interpreted to be consistent with impact-related effects. However, existing seismic and potential field data do not allow accurate estimates of the extent of the crust affected by the meteorite impact, and effects that it may have had on the subsequent rifting, thermal, sedimentation and hydrocarbon maturation regimes in the area. Further multidisciplinary research is necessary to answer these questions.