Structural Architecture of Australia's Southwest Continental Margin and Implications for Early Cretaceous Basin Evolution

Abstract

The southwest margin of Australia is a complex andrelatively poorly studied offshore continental region thatincludes the Perth and Mentelle basins. Plate reconstructionmodels, in conjunction with regional seismic and potentialfield data, demonstrate that the margin comprises three majorsegments: the normal to oblique Mentelle and southernPerth margins and the Wallaby-Zenith Transform Margin.Margin architecture and overlying basin geometries changemarkedly across segment boundaries and the patterns ofstructural reactivation during basin development indicate astrong basement control on margin evolution. Linking platereconstructions and seismic studies provides new insightsinto Early Cretaceous basin evolution, including the relativetiming of breakup within each sub-basin, the timing ofaccommodation generation and the distribution of breakuprelated igneous activity. Active development of the Wallaby-Zenith Transform Margin lasted from the Valanginianto the Aptian and controlled structural activity and thepatterns of sediment fill across the northern Perth Basin.Immediately prior to Early Cretaceous breakup, the majorityof accommodation-space generation and igneous activitywas focused within the Zeewyck and Western Mentelle subbasins.