The area covers the Narromine 1:250000 map sheet, with mostly very low relief and is more than half covered by surficial deposits. Most rock units are deeply weathered and good exposures are generally limited to quarries, road and railway cuttings. The area is of significant economic importance as it contains the North Parkes copper and gold mine as well as other gold, base metal and platinum group metals occurrences. The western third of the area has the multiply deformed Girilamborne Group, consisting mostly of quartzite, phyllite and schist as basement. The eastern two thirds of the map area comprises the Early Ordovician Nelungaloo Volcanics and Late Ordovician trachyandesitic Goonumbla Volcanics and silicious sediments of the Cotton Formation. Granites are predominantly of the I type, intruded in the Early to Late Devonian. Canozoic volcanism is restricted to the north east, while alluvial plains have an ill defined basal Tertiary age and extent into the Recent.
Sherwin I., 1996. Naromine 1 :250 000 Geological Sheet SI/55-3: Explanatory Notes, viii + 104 pp. Geological Survey of New South Wales, Sydney