Sedimentary geochemical record of the middle Mesoproterozoic―early Neoproterozoic tectonic geography of Northern Australia

The Beetaloo Sub-basin, northern Australia, is considered the main depocentre of the 1000 km-scale Mesoproterozoic Wilton package of the greater McArthur Basin. The ca. 1.40-1.31 Ga upper Roper Group and the latest Mesoproterozoic to early Neoproterozoic unnamed group of the Beetaloo Sub-basin, together, record ca. 500-million-years of depositional history within the North Australia Craton. Whole-rock shale Sm-Nd and Pb isotope data reveal a dynamic interaction between sedimentary provenance and ancient tectonic geography. The ca. 1.35-1.31 Ga Kyalla Formation of the upper Roper Group is composed of isotopically evolved sedimentary detritus, whereas the upper portions of this formation contain more isotopically juvenile compositions. The increase in juvenile compositions also coincides with elevated total organic carbon (TOC) and phosphorous (P) content of these sediments, which are thought to reflect an increase in nutrient supply associated with the weathering of basaltic sources. Possible, relatively juvenile, basaltic sources include the Wankanki Supersuite in the western Musgraves and the Derim Derim-Galiwinku large igneous province (LIP). The transition into juvenile, basaltic sources directly before a supersequence-bounding unconformity, is here interpreted to reflect uplift and erosion of the Derim Derim-Galiwinku LIP, rather than an influx of southern, Musgrave sources. A new baddeleyite crystallization age of 1312.9 ± 0.7 Ma provides both a tight constraint on the age of this LIP, along with its associated magmatic uplift, as well as providing a minimum age constraint for Roper Group deposition. The supra-Roper Group lower and upper Jamison sandstones were both sourced from the Musgrave Province, at least 300 million years after deposition of the Kyalla Formation. An up-section increase in isotopically juvenile compositions seen in these rocks, are interpreted to document the continuous exhumation of the western Musgrave Province. The overlying Hayfield mudstone received detritus from both the Musgrave and Arunta regions, and its isotopic geochemistry reveals affinities with other early Neoproterozoic basins (e.g. Amadeus, Victoria and Officer basins), indicating the potential for inter-basin correlations.