Wolfgang Preiss presents 'Adelaide Superbasin basementgeology & tectonic controls on sedimentation'

Wolfgang V. Preiss presents 'The Adelaide Superbasin – what we know and what we don’t know of its basement geology and tectonic controls on sedimentation' at the Adelaide Superbasin Mini-symposium.

Abstract
The basement beneath the Neoproterozoic to Cambrian Adelaide Superbasin is exposed only near its margins; in the depocentres the basement lies too deeply buried even to leave any imprint on aeromagnetic imagery. Clues to the nature of the basement are found in the marginal outcrops and basement inliers and their inferred extensions, as well as in gravity data, a very few drillholes, and rare inclusions in diapirs and kimberlite diatremes. This shows that, like many other orogens, the Delamerian Orogen in which large parts of the superbasin were deformed, partly overlaps an earlier orogen, in this case the ~1600 Ma Olarian. To what extent are the tectonics of the superbasin inherited from the older orogen? The notion that Neoproterozoic sediments of the Adelaide Superbasin relate to a passive continental margin dates back 70 years, predating plate tectonic theory. Today the superbasin is widely interpreted as progressing from early rift phases to phases of thermal subsidence and continental separation of Australia-Antarctica from Laurentia, but the details and timing remain controversial. Although the zone of rifting within the superbasin is broadly meridional, most individual controlling normal faults trend NW-SE or NNW-SSE, suggesting dominantly NE-SW extension, also consistent with the orientation of the ~830 Ma Gairdner dykes. The latest phase of NE-SW extension occurred during the 660 Ma Sturt glaciation, with the formation of not only the Baratta Trough in South Australia, but also the Yancowinna Trough in the Barrier Ranges, NSW, and a NW-trending syn-glacial trough in the Georgina Basin, NT. The post-glacial unconformity coincides with the first transgression of the platformal areas of the superbasin (Stuart ‘Shelf’ and Coombalarnie Platform). Early Cambrian normal faulting represents a completely different stress field, with NW-SE extension, commonly interpreted as due to back-arc extension. The resulting arcuate Kanmantoo Trough cuts across earlier rift structures and penetrates the southern Gawler Craton. Its bounding normal faults are deeply rooted in the basement and are the precursors of many Delamerian thrusts.

Biography
Wolfgang Preiss arrived in Australia from China as a child in 1949 and received all his education in Adelaide, majoring in geology at the University of Adelaide. In 1971 he was awarded a Ph.D. for his thesis ‘The biostratigraphy and palaeoecology of South Australian Precambrian stromatolites’ and joined the Geological Survey of South Australia. During his 46 years in the Survey he worked extensively on the Proterozoic rocks of South Australia with major mapping projects in the Flinders Ranges, Mid-North, Officer Basin, Mount Lofty Ranges and Curnamona Province. He has published more than 100 papers on many aspects of South Australian geology. In retirement he is an Honorary Research Fellow at the University of Adelaide and maintains a close association with the Geological Survey.