The selection and correlation of zones of characteristic gamma ray deflection in the Great Australian in NSW yielded two related systems of zones - one for the eastern part of the basin and for the west. The gamma ray logs alone cannot be easily interpreted in terms of lithology as the basin contains unusual clay mineral assemblages which greatly affect the gamma radiation emitted by a rock unit. A relationship between the known lithologies and the gamma ray correlation zones has however been established and the gamma ray correlation can be used to extrapolate lithological information from control boreholes to other boreholes for which only gamma ray logs are available. The cuttings lithological logs and geophysical logs from the Lightning Ridge Town Water Supply bore and exploratory petroleum wells do however provide additional control. The lack of data in the transition between the eastern and western areas prevents a good understanding of the E-W relationships. Some correlations can be inferred between the upper parts of the sequences in both areas. It should be noted that the areal distribution of available gamma ray logs is such that very detailed correlations could be attempted only in some localised parts of the basin.
Hawke J.M. and Cramsie J.N. 1984. Contributions to the Geology of the Great Australian Basin in New South Wales. Geological Survey of New South Wales - Bulletin 31.