Detrital provenance and geochronology of the Burra, Umberatana and Wilpena Groups in the Mount Lofty Ranges

Abstract

The Adelaide Superbasin contains sedimentary rocks that preserve chemical and sedimentological evidence for major changes in the biosphere, atmosphere and climate that occurred during the Neoproterozoic. Yet many major questions about the age of the stratigraphy, the contemporaneity of lithostratigraphic changes across the length of the basin and source of sediment within it remain unknown. I present new detrital zircon and rutile U–Pb, Hf isotope, and REE data from the southern Mount Lofty Ranges region of the Adelaide Rift Complex within the Adelaide Superbasin. Additionally, the Belair Subgroup was also mapped to minimise gaps in geochronology throughout the Burra, Umberatana and Wilpena groups of the Adelaide Superbasin.

U-Pb ages along with Hf isotopes broadly indicate the Gawler Craton and Curnamona Province as important provenance regions for the Burra group, and a Musgrave and Albany Fraser provenance for sediments of the Umberatana and Wilpena groups. The source of the Belair Subgroup was found to diverge from that of older Burra Group formations and reflect a new siliciclastic source- perhaps at the onset of a basin sag phase. The stratigraphy of the Mount lofty Ranges does not directly match that of the northern Flinders Ranges and these results provide a means to test their temporal correlation. Comparisons are made against existing data to indicate that lithostratigraphy is not likely to be coeval over the length of the entire rift complex. These results contribute to both local and global efforts to gain a detailed understanding of the interaction between tectonics and significant changes to the earth system during this time.