New U[sbnd]Pb, Hf and O isotope constraints on the provenance of sediments from the Adelaide Rift Complex Documenting the key Neoproterozoic to early Cambrian succession

Abstract

The Adelaide Rift Complex is arguably one of the most complete and best studied Neoproterozoic to early Cambrian successions worldwide, preserving evidence of the breakup of Rodinia, two Cryogenian glaciations and the interglacial phase, and one of the best documented Ediacaran to early Cambrian biotic transitions. However, the complex and protracted tectono-sedimentary history of this 0.8�0.5 Ga province is still being debated. We present new and published U\\Pb ages and Hf and O isotope data for detrital zircons from the Adelaide Rift Complex, representing the most complete assembly of such data for this succession. Deposition during initial mid-Tonia extension was largely sourced locally from rift shoulders. As the basin evolved from rift- to sag-phase following continental breakup in the Cryogenian the provenance regions extended to more distal late Mesoproterozoic terranes to west and northwest. New data from Sturtian Glacial Epoch deposits are consistent with termination of this event at 0.66 Ga, with most deposition during deglaciation. Uplift of the Musgrave region during the Ediacaran to early Cambrian Petermann Orogeny led to dominant sediment supply from that terrane at that time in the north. In the south, earliest Cambrian deposition followed local tectonism, initially revitalising local proximal basement sources. An abrupt change in provenance occurred at the base of the Cambrian Kanmantoo Group, the youngest sediment package in the south. Paleocurrent data indicates transports from the south, probably from formerly contiguous Antarctica, possibly reflecting the onset of convergent tectonics and deposition in a foreland basin, consistent with the near depositional age of the dominant detrital zircon population. Whilst several episodes of significant crustal reworking are identified in the Hf and O isotope data, many of the zircon TDM ages lie within 0.5 Ga of the U\\Pb ages indicating that new additions from the mantle were common in the provenance regions Show more