Australia: The Land Where Time Began

A biography of the Australian continent 

Three structural entities comprise the eastern third of the Australian continent, the most westerly is the Australian Craton from the Proterozoic, together with associated fold belts and epicratonic basins. The second is the Tasman Fold Belt System, situated to the east of the Tasman Surface, between the Tasman Line and Toe-line, from the latest Neoproterozoic, Palaeozoic and Mesozoic. The Third component is the epicratonic cover of Phanerozoic sedimentary and igneous rocks. These rocks include those formed along the rifted continental margins on the south and east.

The outcrop of the inclined Tasman Surface, the main suture of eastern Australia, is the Tasman Line, that is the eastern outcrop of the Australian Proterozoic craton. It was along this line that the rifting and breakup of the Neoproterozoic, and the subsequent active-plate contraction of the Phanerozoic took place (Scheibner & Basden, 1998). This surface has been interpreted as having upper- and lower-plate margin geometry. The Tasman Surface dips east in the lower-plate setting. To the east of the Tasman Line, a wedge of Proterozoic crust extends to its intersection with the moho at the Tasman Toe-line. The Tasman Line dips west, and the Toe-line lies to the west in the upper-plate setting.

The Tasman Line (Murray et al., 1989) is modified in the area of the Burdekin River (Schreibner, 1993), in the area of Kangaroo Island-Adelaide (Flottmann & Cockshell, 1996). Material from the VIMP-12 drillhole, at 36.95 S, 141.5 E, in western Victoria, in a magnetic low west of the magnetic  welt that underlies the Murray Basin, marks the position of the toeline (Maher et al., 1997).

Sources & Further reading

1. Scheibner, E, in Veevers, J. J  (ed.), 2000, Billion-year earth history of Australia and neighbours in Gondwanaland, GEMOC Press Sydney.
2. Veevers, J.J., 2001, Atlas of Billion-year earth history of Australia and neighbours in Gondwanaland, GEMOC Press Sydney.