The Cargelligo 1:250 000 map sheet area is located in central New South Wales, approximately 550 km west of Sydney. The map area contains a poorly exposed sequence of the central Lachlan Orogen, consisting of Ordovician to Devonian volcanic, sedimentary and plutonic rocks. Tertiary to Quaternary deposits of the eastern Murray Basin onlap the Palaeozoic sequences in the west of the map area and minor Tertiary volcanic units are present in the east of the map area. Widespread unconsolidated Quaternary deposits cover much of the older sequences. Remapping of the Cargelligo 1:250 000 map sheet area, aided by airborne geophysical data, has enhanced understanding of the stratigraphy, structure, mineral potential and evolution of the central Lachlan Orogen. High-quality aeromagnetic, radiometric and gravity data has enabled further investigation of the generally poorly -outcropping rocks in the area. The early Palaeozoic bedrock is divided into two major structural zones east and west of the Bootheragandra Fault: the Wagga-Omeo Zone to the east and the Howqua Zone to the west. Younger Siluro-Devonian volcanic rocks and sedimentary rocks combine to form the southern part of the Darling Zone - including the Mount Hope Trough, Rast Trough, the Walters Range Shelf and Melrose Trough. Structures in Late Devonian fluvial basins are superimposed on the previously deformed basement and are included in the Cocoparra, Narriah and Lachlan Range Synclines.
Colquhoun G.P., Meakin N.S. & Cameron R.G. (compilers) 2005. Cargelligo 1:250 000 Geological Sheet SI/556, 3rd edition, Explanatory Notes. Geological Survey of New South Wales, Maitland, NSW, 291 pp.