Seismic Velocity Insights into the Wallaby Plateau

Abstract

Analysis of interval seismic velocities from Geoscience Australia?s 2008/09 seismic survey 310 in conjunction with seismic reflection interpretation provides new insights into the geology of the Wallaby Plateau. Seismically distinctive basement core packages and divergent dipping reflector (DDR) packages have been identified. The seismic character of the DDR packages is similar to seaward dipping reflector (SDR) packages of inferred volcanic composition. Initial analysis of seismic velocity profiles indicated affinities between the DDR packages and known sedimentary strata in the Houtman Sub-basin. However, subsequent water depth adjustment of seismic velocities reduces this distinction between SDR, DDR and sedimentary strata such that discrimination between volcanic and sedimentary strata in DDR or SDR packages is equivocal. Despite ambiguities, velocity analysis provides important insights into the seismic characteristics of the Wallaby Plateau basement. The well constrained decrease in interval velocity from a DDR package into an underlying stratified basement is interpreted to indicate localised continental blocks within the Plateau. Although seismically derived velocities may be equivocal for certain lithologic interpretation, they still provide useful insights into understanding the geology of a rank frontier area such as the Wallaby Plateau.