Structure, sedimentology, and detrital Zircon U-Pb analysis of Burra Group rocks in the southern Willouran Ranges

Abstract

Neoproterozoic geology of the Adelaide rift complex is comprised of extremely thick sedimentation of deep subsidence; with very few breaks in sedimentation. In this respect the Adelaide rift complex becomes an ideal place to study this passive margin type setting and to study arrangement of continents. This study will use field mapping to determine paleo-stresses by measuring strain through field mapping. Furthermore, analysing U/Pb geochronology on detrital zircons through LA-ICP-MS to determine provenance and perhaps narrow down age of deposition. The area hosts a broad syncline-anticline pair with maximum principle stresses of 60NE 240SW which matches up with shortening direction in the area for Delamarian orogeny. For the Copley Quartzite formation, the primary sediment input was 1690-1750Ma which correlated with the Gawler Craton’s Kimban Orogeny and secondary peak at 2250-2500Ma which matched the Gawler Craton’s Sleaford Orogeny. The Skillogallee Dolomite formation had its major peak at 1020Ma which didn’t correlate with any known local sources and warrants speculation on exotic source terrains such as the Ottowan Orogeny and the Sunsas Province of North and South American continents which were juxtaposed against Australia at the time. The Skillogallee Dolomite still has a major peak at 1660Ma which can be attributed to both the Upper Willyama Supergroup of the Curnamona Province and the Kimban Orogeny of the Gawler Craton. Structurally, the region likely experienced only one deformational event due to its simplistic strain history observed; although nearby areas such as the Peake and Denison Ranges have a more pronounced Alice Springs Orogeny strain history. The provenance of the Copley Quartzite formation is dominated by Gawler Craton sourced sediments. The primary peak of the Skillogallee Dolomite does seem to have a source that cannot be explained by currently known Australian sources and more likely is from the Ottawan Orogeny or Sunsas Province.