Ediacarian sequence and isotope stratigraphy of the Officer Basin, South Australia

The Ediacarian was a time of active tectonism over large areas of the Australian craton and sedimentary rocks of this age are relatively widespread. In spite of their wide distribution and the perception that they offer some of the most likely Neoproterozoic petroleum source rocks, their stratigraphy is not well understood and interbasinal correlation has proved difficult. Using available seismic and well-log data, 19 depositional sequences contained within two tectonically defined megasequences are recognised in the Ediacarian succession in the eastern Officer Basin. Systematic carbon and strontium isotope chemostratigraphy, combined with the sequence stratigraphy, has enabled correlation of the main sequence boundaries between the Officer Basin and the Adelaide Geosyncline and Amadeus Basin. A significant number of sequence boundaries recognised in the exceptionally complete Officer Basin succession are either missing or not expressed in the Amadeus Basin and Adelaide Geosyncline successions. This suggests that only the major tectonically enhanced sequence boundaries (megasequence boundaries) have been recognised in the adjacent basins. The megasequences bounded by these surfaces define major basin phases.