The Neoproterozoic Throssell Range Group, Western Australia: A Peri‐Marginal Continental Basin in Rodinia and Its Implications for the Centralian Superbasin

ABSTRACT This paper presents a new interpretation of an early Neoproterozoic cratonic basin. Its depositional history is a record of fault reactivation and differential subsidence in a heterogeneous basement during Rodinia's breakup. Globally, the reactivation of deep structures in older Proterozoic lithosphere surrounding the Archaean cratonic cores probably controlled the development of Neoproterozoic cratonic basins. These structures may also have provided conduits for mineralizing fluids. The Throssell Range Group (TRG) is a 1–3.5 km thick siliciclastic succession, topped by a carbonate platform, in the Paterson Orogen of north‐western Australia. It hosts the c .2 Mt. Nifty Cu deposit. It is among several successions attributed to the large continental Centralian Superbasin, thought to have its origin in crustal sagging at c .840 Ma. However, the TRG includes deep water strata unusual for continental sag basins, and the ages of intrusions suggest that it is older than 840 Ma. Based on detailed logging of recent drillcore, two sedimentary sequences separated by a disconformity are recognised. This differs from previous work which interprets the TRG as a single conformable succession. Sequence 1 consists of three lithofacies associations, interpreted as the record of deposition in half‐graben sub‐basins, bounded by basement faults reactivated by extensional stresses related to Rodinia's breakup. Sequence 2 comprises four lithofacies associations, interpreted as recording a period of reduced clastic sediment supply in a peri‐marginal continental basin exposed to wind‐driven upwelling of nutrient‐rich oceanic water. The subsidence of thin, more juvenile Proterozoic lithosphere produced a flooded margin between the Pilbara and North Australian Cratons. As sea level rise slowed, a carbonate platform prograded over the basin. More generally, this suggests that the Centralian Superbasin, and other Neoproterozoic cratonic basins, may best be thought of as mosaics of roughly coeval sub‐basins, each with a specific history determined by local basement reactivation.