Geology of Richmond-Sorell area

Permian mudstones and sandstones crop out over much of the Richmond area; Triassic sandstones, shales, and coal measures occur east of Richmond and in the Sorell area. Faulting of Permian and Triassic strata and injection of dolerite, possibly as sheets, broke up the area.
Lakes formed in fault-angle troughs produced by Tertiary faulting; deposits in them occur between Richmond and Sorell. Faults of Jurassic and Tertiary age trending north and west of north control topography and stream direction. The Richmond Graben is Jurassic, pre-dolerite in age: Tertiary movement occurred along earlier lines of weakness.