Morphology of the Late proterozoic to Early palaeozoic Officer Basin, South Australia

Abstract

Most of the Officer Basin in South Australia is covered either by Pleistocene sand dunes or by Cretaceous to Quaternary platform carbonates. Seismic coverage is poor and there are little well data available. For these reasons, potential field data are of particular importance in interpreting the morphology and understanding the development of the Officer Basin. Both the Bouguer gravity and total magnetic intensity (TMI) gridded-data sets give an excellent image of the overall morphology of the basin; however, unlike shield regions, these data are not as readily interpreted in terms of geological structure. We have applied filtering and edge enhancement techniques to these gridded data, in order to interpret the lower amplitude and longer spatial wavelength anomalies of the potential fields over the sedimentary basin. The edge-enhanced TMI data reveal a complicated pattern of anomalies within the basin. To interpret these, we have examined the seismic sections for features which correlate with the potential field anomalies. Most basement-involved faults mapped using the seismic data in the eastern Officer Basin correlate with anomalies in the enhanced potential field images. We also correlate an anomaly in the enhanced TMI image with the major diapiric wall in the eastern Officer Basin, and have used the TMI data to interpret the extent of this diapiric activity beyond the range of the current seismic network. There has been no serious hydrocarbon exploration in the central portion of the Officer Basin for around 25 years. We believe that integration of image-processed potential-field data with existing seismic networks and geological knowledge can assist in determining the structure of this basin and help target areas which warrant further exploration.