Australia: The Land Where Time Began

A biography of the Australian continent 

The eastern part of the Tasman orogenic system is formed by the New England Fold Belt, extending from north of Sydney, across the Hunter Thrust, to the coast of central Queensland. The orogen is of late Palaeozoic age, developing close to the continental margin of Gondwana (Coney, 1988). Within the Murray-Darling Basin the New England Fold Belt is in 2 parts for the pre-Permian rocks. West of the Peel River fault system is the Tamworth Belt, the Tablelands Complex being on the eastern side of the Peel River Fault System (Korsch & Harrington, 1981), which is comprised of several structural subdivisions.

Sedimentary rocks, of Cambrian to Permian age, deposited in fore arc basins are found in the Tamworth Belt. During at least 4 regional deformations in the late Palaeozoic, the rocks of the Tablelands Complex were subjected to low to medium grade metamorphism. These sedimentary rocks, that are all of a similar age, are believed to be an accretionary subduction complex (Leitch et al., 1988).

In the Early Permian, the boundaries of the above subdivisions were commonly transgressed by depositional environments. During the Permian and Triassic, granite plutons were intruded into the Tablelands Complex. The extensive Emmaville Volcanics of the Late Permian partly covered the Tablelands Complex, as did, though to a lesser extent, the extensive volcanics of the Tertiary (Gilligan & Brownlow, 1987).

The Tablelands Complex has been divided into 4 main sedimentary associations (Korsch & Harrington, 1981). These are the Woolomin Association of the ?Devonian, the Sandon and Beenleigh Associations of the Late Devonian-Carboniferous, the Nambucca association, Silverwood association and Coffs Harbour association, all of the Late Carboniferous-Early Permian, and the Dummy Creek association from the Late Permian.

In the Tamworth belt there are a number of outcroppings of major geological units, such as the Tamworth Group and Baldwin Formation from the Devonian, the Keepit Conglomerate, Mandowa Mudstone, Tangaratta Formation, Tulcumba Sandstone, Namoi Mudstone and Merlewood Formation, all from the Early Carboniferous. The Currabubula Formation from the Carboniferous and the Temi Formation and Werri Basalt from the Permian.

Sources & Further reading

1. Geology of the Murray-Darling Basin - Simplified Lithostratigraphic Groupings
2. Sydney Basin - Geological Overview