Re-assessing the Upper Permian Stratigraphic Succession of the Northern Sydney Basin, Australia, by CA-IDTIMS

Abstract

High precision Chemical abrasion-isotope dilution thermal ionisation mass spectrometry (CA-IDTIMS) U-Pb zircon results from tuff marker beds that are interstratified within the Upper Permian deposits of the northern Sydney Basin add constraints on the timing of sediment deposition, and afford a better understanding of the regional stratigraphy. The results indicate a magmatic influence during the deposition of the sediments, with episodic events spanning at least from 255.65 ± 0.08 to 255.08 ± 0.09 Ma. The zircon data suggest that the studied sedimentary rocks and tuffs have accumulated simultaneously over a short time interval, which contrasts with current stratigraphic models that suggest a much greater period of deposition and stratigraphic thickness. Therefore, an updated stratigraphic correlation of the basin is suggested, which combines the presently defined Lambton, Adamstown, and Boolaroo sub-groups into a single Lambton sub-group. This updated correlation framework is stratigraphically and geochronologically constrained and provides a more precise exploration model for the northern Sydney Basin. This case study highlights the valuable contribution of the CA-IDTIMS method in intrabasinal correlations of sedimentary successions, when integrated with a robust sedimentological framework, to minimize the stratigraphic uncertainties.