Description and Geology

The Southern Georgina Basin comprises a succession of Neoproterozoic, Cambrian, Ordovician and Devonian carbonate and clastic sediments up to 5,000 metres in thickness deposited in a broad northwest–southeast depression.  Several structural phases have shaped the basin, the most important of these events being the Petermann and the Alice Springs orogenies.  The Toko Syncline formed in the later part of the Alice Springs Orogeny by northerly thrusting of the Arunta Block. The basin was extensively eroded after uplift in the east.  The basin has two established Middle Cambrian source rocks, one developed at the base of the Lower Arthur Creek Formation, and the other within the Thorntonia Limestone.  These source rocks are responsible for ubiquitous oil and gas shows in some 30 wells drilled in the basin.  A sub-commercial gas flow of ~200 Mcfd from the Coolibah formation was recorded in the exploration well Ethabuka 1.