Jarred Cain Lloyd , Alan S. Collins , Morgan L. Blades , Sarah E Gilbert, Kathryn J Amos

Late Tonian sequences of the Adelaide Superbasin were witness to the birth of the proto-Pacific Ocean during the breakup of Rodinia. Understanding the sedimentology and provenance of these rocks from across the basin is key to understanding their deposition over c. 70 million years, the local palaeogeography, and leads to a better understanding of the early development of the proto-Pacific Ocean. While the sedimentology of the Burra Group is well studied in most areas, provenance studies on these sequences using detrital zircon have been limited in scope and lack both spatial and temporal diversity. We begin to address this knowledge gap. Samples were taken from across the Adelaide Superbasin to understand both spatial and temporal related changes in provenance. Our findings highlight the necessity of this approach by uncovering both subtle, and abrupt significant changes in detrital zircon spectra for coeval samples from across the basin, and up-sequence in local areas. Our results highlight significant changes in provenance c. 790 Ma in the north of the basin, and c. 740 Ma in the south of the basin. This suggests a southward advancement of the rift basin, gradually opening to southerly sediment supply. We posit the existence of an unrecognised source of c. 1000–900 Ma zircon to the north or northeast of the basin to account for latest Stenian to earliest Tonian detrital zircon in the Myrtle Springs Formation. Additionally, we explore the comparison of coeval Tasmanian and Laurentian sequences, suggesting a stronger Australia-Tasmania link than Tasmania-Laurentia as time progresses.