PETROLEUM GEOLOGY OF WESTERN NEW SOUTH WALES

Abstract

The only area of Western New South Wales considered to have petroleum potential is the intracratonic, fault-bounded Darling Basin, which evolved during Late Silurian to Early Carboniferous time and which contains up to 7000 m of sediments. Initially deposition was controlled by a shallow marine transgression from the east. Regression during the Middle Devonian was followed by basin-wide extension of alluvial sedimentation, which prevailed until the Early Carboniferous. Strike slip movements during Late Devonian time along old basement trends fragmented the basin into distinct troughs. Movements along the same trends during the Carboniferous modified the troughs' configuration. Permian, Mesozoic and Cenozoic sag-like downwarps in various parts of the region had negligible effect on bedding attitudes.

The only play of the Basin thought to have a chance for significant petroleum generation and entrapment lies in the Lower and (?) Middle Devonian, where marginal marine deposits flank highs created by strike slip movements. This play is regarded as one of high risk for modest returns, but its continued exploration seems warranted in view of proximity to markets and to the Moomba-Sydney pipeline.