REASSESSMENT OF THE SEISMIC STRATIGRAPHY OF THE EARLY PALEOZOIC STANSBURY BASIN, GULF ST-VINCENT, SOUTH AUSTRALIA

Seismic reflection surveys suggest that the Gulf St Vincent area of th e Stansbury Basin, South Australia is filled with four pre-Permian sed imentary packages. The upper three packages (S0-S2) are interpreted as Early Palaeozoic rocks that are considered to be underlain by a Neopr oterozoic package. The Early Palaeozoic packages are up to 6000 m thic k in the east but less than 500 m thick in the west. In particular, th e middle package (S1) tapers distinctly westward and northwestward. Th e Early Polaeozoic successions show little internal deformation but ar e separated by faults from the highly deformed Delamerian Orogen to th e east and are also faulted against Early to Middle Cambrian strata th at crop out on Yorke Peninsula td the west. Early Palaeozoic reverse m ovement along faults that may have originated as growth faults during deposition of S0 outlasted deposition of package S1. Internal onlap re lationships suggest a westward migration of the depocentre of the midd le package S1 through time. Package S2 is not affected by Delamerian d eformation and only shows imprints of Cenozoic deformation, which also affects the overlying Permian and Cenozoic sedimentary rocks. We inte rpret the lowest Palaeozoic package as an equivalent to the Early Camb rian Normanville Group. The middle and upper packages are interpreted as deposits of a hitherto unrecognised foreland basin to the Delameria n Orogen and are interpreted to be of Cambrian to Ordovician age.