Australia and Gondwanaland

Along the western margin of the Australian continent there exist four major sedimentary basins, filled with predominantly marine rocks from Cambrian to Tertiary in age, and up to 40,000 feet thick. Seaward these basins continue into depressions recognizable in the continental shelf and even the continental slope. Their very presence, the nature of their sediments and the composition and relationships of their fossil faunas indicate the existence of an open ocean to the west of Australia since early Paleozoic time. Composition of the Australian fossil land vertebrate faunas suggests isolation of the Australian continent since at least Permian time.