The deeper central and western development of the Great Australian Artesian Basin is now considered to offer the most promising prospects for commercial oil on the Australian continent. Thicknesses of 5,000 to possibly 10,000 feet or more of Mesozoic sediments, including several thousand feet of marine Cretaceous shales, overlie great and variable thicknesses of unmetamorphosed marine Upper Devonian, Ordovician, and Cambrian sediments in the central and western basin areas. Metamorphism has effected these older sediments only in the eastern part of the basin in Queensland and New South Wales.

Numerous oil and gas showings have been authenticated in the Mesozoic basin sediments in the shallower marginal zones of the basin, but the deeper areas remain virtually untested. Over the most interesting deeper parts of the basin, no bore has penetrated even the full section of the marine Cretaceous in an area of more than 160,000 square miles.

A recent development which re-orients the Great Australian Artesian Basin as an oil prospect, has been the discovery of long lines of anticlines in the central basin area (Cordillo Downs, in northeastern South Australia extending into Queensland). Many of these exhibit complete domal closure at the surface, measured in hundreds of feet.