The Sydney Basin is part of a major basin system that extends over from the Bowen Basin in Queensland through to the Basin in NSW. Onshore, the basin contains of Permo-Triassic clastic sediments, while the offshore basin contains of sediments. The basin overlies the Lachlan Fold Belt and Late Carboniferous volcanoclastic sediments. The basin formed during extension in the Early Permian, with half-graben infilled with the Dalwood and Talaterang Groups. Foreland loading followed with the compression of the Currarong Orogen in the Early Permian.