Tectonic Evolution of Bass Strait–Origins of Tertiary Inversion

Abstract

The sedimentary basins of Bass Strait display a marked asymmetry of structure. This is particularly evident in the Gippsland Basin and Torquay Sub-basin where Tertiary structures are better developed along their northern margins. The origins of this asymmetry are reviewed and a structural model for the evolution of Bass Strait basins set out. Mapping of the regional structures developed at three stages of the region's evolution demonstrates that dextral strike slip movement was important throughout. During the Cretaceous the regional stress regime was dextral transtensive, changing to transpressive by the mid-Eocene. Despite early similarities in these basins' formation, their Tertiary histories diverged, contributing to the wide variations in hydrocarbon potential seen today. It is suggested that the present day structural asymmetry is a consequence of partial inversion of initial half-graben basin geometries.