Australia: The Land Where Time Began

A biography of the Australian continent 

The Darling Basin covers the Cobar and Nymagee regions in western New South Wales. Significant mineralisation occurs in the area, the Cobar Supergroup containing deposits of copper and gold (Gilligan et al., 1994).

The formation of the Darling Basin began in the Earliest Devonian with major crustal extension through fault reactivation. Where extension was at its greatest, major troughs and basins formed, Cobar Basin, Mt Hope Trough, Rast Trough and Melrose Trough. Shelves were formed in areas of lesser extension, such as the Kopyje Shelf, the Mouramba Shelf, Winduck Shelf and the Walters Range Shelf. The Cobar Supergroup is comprised of these troughs and shelves that were filled by volcanic and sedimentary materials (Suppel & Gilligan, 1993).

In the basins and troughs, deposition of deep-water turbiditic sedimentary deposition occurred. In the Mt Hope and Rast Troughs, to the south, deep-water felsic volcanism accompanied turbiditic sedimentation. In the eastern part of the Kopyje Shelf there are thick deposits of felsic volcanics associated with the Florida volcanics, Babinda volcanics, Majuba volcanics and Mineral Hill Volcanics. The remaining shelf and trough features of the Cobar Supergroup are characterised by quartz-rich clastics, and contain very few volcanic intercalations. There are 2-phase evolution occurs in each of the depocentres of the Darling Basin, with a period of synrift sediment deposition that was followed by a period of sag phase sedimentary deposition (Gilligan et al., 1994).

In the late Early Devonian the Cobar Supergroup was deformed, resulting in the formation of different structural zones. Basin inversion and deposition of the fluvial Mulga Downs Group of the Barka Basin.

Sources & Further reading

1. Geology of the Murray-Darling Basin - Simplified Lithostratigraphic Groupings