Australian Neoproterozoic palaeogeography, tectonics, and supercontinental connections

Increasingly precise stratigraphic resolution by biostratigraphy, isotope stratigraphy, and sequence analysis in the Neoproterozoic allows more convincing palaeogeographic reconstructions than hitherto possible, so that the original connections amongst structural basins can be demonstrated. The Neoproterozoic stratigraphy of Australia can now be analysed in terms of four supersequences, with finer subdivision possible in the Ediacarian or 'Terminal Proterozoic'. The palaeogeography of Australia during eight time intervals within the Neoproterozoic is assessed, with varying degrees of confidence. Our interpretation follows previous models of the Adelaide Rift Complex as a Neoproterozoic intracratonic rift between the Gawler and Curuamona cratons. The rift is at a high angle to the associated east-west elongated epicratonic sag of the Centralian Superbasin. In the earliest Cambrian the Flinders zone of the Adelaide Rift Complex was transformed to a failed arm or aulacogen by continental breakup along its southern part. Sedimentation ceased before the Late Cambrian-Early Ordovician (500 Ma) Delamerian Orogeny. The Rift Complex underwent two phases of onlap (= extension) accompanied by the deposition of (Sturtian and Marinoan) glacials. A third phase of onlap represented by the Billy Springs Formation occurred during right-lateral shearing (Petermann Ranges orogeny) that caused thrusting and the emergence of the east-west oriented Musgrave Block in the middle of the Superbasin. The Superbasin was finally dismembered by the rise of the southern Arunta Block between the Amadeus and Ngalia structural basins during the mid-Carboniferous Alice Springs Orogeny. According to the SWEAT hypothesis, Australia was joined in the Neoproterozoic with India, Antarctica, and Laurentia, so that the Tasman Line faced the Canadian-Wyoming cordilleran line. The configuration of the north-south trending Adelaide Rift Complex and the east-west trending Centralian Superbasin was mirrored by the basins in Laurentia to form a T, which split at the end of the Neoproterozoic by growth of a precursor of the Pacific Ocean.