Tectonic activity initiated in the Early Jurassic led to extensional faulting and block rotation resulting in significant erosion and the emergence of a structural NNE–SSW horst and graben trend. Subsequent sea level rises and subsidence following the cessation of rifting along Australia’s northwestern margin led to the deposition of the Cretaceous Muderong Shale which drapes the Mungaroo Formation horsts and grabens. The Muderong Shale consists of regionally thick marine shales with excellent sealing capabilities. In this study area the Muderong Shale overlies the subcropping Mungaroo Formation at a major
unconformity surface.