Abstract Located in the northern part of Lachlan Fold Belt, in semi-arid north-western New South Wales, the Nyngan and Walgett 1:250000 map sheet areas consist largely of flat to gently sloping alluvial plains. Quaternary alluvium up to 100m thick covers 90% of the area. Five major meridional structural zones of buried Palaeozoic basement were interpreted from geophysical data and water bore logs. Basement youngs from Cambro-Ordovician in the west to Siluro-Devonian in the east. The overlying Jurassic to Cretaceous sequence of the Great Australian Basin represents a period of terrestrial to marine deposition. Major Cainozoic depocentres are located in the central northern Walgett sheet area and in the north-east of the Nyngan sheet area. Several sources of loam, sand, gravel and aggregate are exploited in the area. There is also potential for copper and platinum group metals (PGM) mineralisation in the Girilambone Structural Zone, porphyry style copper-gold in the Parkes Structural Zone, and opal within the Cretaceous sequence.
Reference Watkins J.K. and Meakin N.S. 1996. Nyngan and Walgett 1:250 000 Geological Sheets SH/55-15 & SH/55-11: Explanatory Notes, viii + 112 pp. Geological Survey of New South Wales, Sydney.