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 the Stansbury Basin, South Australia is filled with four pre-Permian sedimentary packages. The upper three packages (S0-S2) are interpreted as Early Palaeozoic rocks that are considered to be underlain by a Neoproterozoic package. The Early Palaeozoic packages are up to 6000 m thick in the east but less than 500 m thick in the west. In particular, the middle package (S1) tapers distinctly westward and northwestward. The Early Polaeozoic successions show little internal deformation but are separated by faults from the highly deformed Delamerian Orogen to the east and are also faulted against Early to Middle Cambrian strata that crop out on Yorke Peninsula td the west. Early Palaeozoic reverse movement along faults that may have originated as growth faults during deposition of S0 outlasted deposition of package S1. Internal onlap relationships suggest a westward migration of the depocentre of the middle package S1 through time. Package S2 is not affected by Delamerian deformation and only shows imprints of Cenozoic deformation, which also affects the overlying Permian and Cenozoic sedimentary rocks. We interpret the lowest Palaeozoic package as an equivalent to the Early Cambrian Normanville Group. The middle and upper packages are interpreted as deposits of a hitherto unrecognised foreland basin to the Delamerian Orogen and are interpreted to be of Cambrian to Ordovician age.