Structural analysis and facies distribution of Cryogenian glacial rocks and regional structures in the Willouran Ranges, SA.

Abstract

The Willouran Ranges lie at the far NW extremity of the Flinders Ranges, on a NW-SE fault-bound trend with the Peake and Denison Ranges along strike to the NW, and the Olympic Domain of the Gawler Craton on the footwall to the west. The range is formed from a near-continuous sequence of Adelaidean Neoproterozoic sedimentary and volcanic rocks and is cut by two major fault systems. The lower part of the Adelaidean succession is particularly well exposed in the region, including a Sturtian (ca. 720-660 Ma) aged glacial deposit, the Bolla Bollana Formation. This formation is a glacial deposit thought to be deposited from the oldest Cryogenian global glaciation event. The study will present new maps of Termination Valley, presented alongside cross-sections outlining major structures in the area and sedimentary logs characterising the glacial diamictite deposits. Detrital zircon dates obtained from the study outline radiometric U-Pb data corresponding to the maximum age of deposition of the Bolla Bollana Formation and overlying Tapley Hill Formation, with ages corresponding to 673 ± 19 Ma and 654 ± 13 Ma respectively. In addition to providing Australia’s first informative U-Pb radiometric age constraint on a Sturtian Tillite facies, the study will discuss the provenance of the sediments using multi-dimensional scaling techniques and provide evidence for extensive north and west extending continental ice sheets.