Permian palynostratigraphic correlations in south-western Australia and their geological implications

Abstract

South-western Australian Permian sequences are preserved in the Perth Basin, Officer Basin and three small intracratonic basins on the Yilgarn Block. The largest intractonic basin, the Collie Basin, has a Stage 2 periglacial unit at the base succeeded by the Collie Coal Measures, which range from Stage 2 to Lower Stage 5b/c. Successive first appearances of eight index species used for correlation within the basin define chronostratigraphic intervals across the basin and support palaeocurrent evidence that the sediments are a downfaulted remnant of a more extensive deposit. The Sue Coal Measures of the southern Perth Basin are considerably thicker than the Collie Coal Measures. Palynostratigraphic correlations indicate that chronostratigraphic intervals in the lower part of the Sue Coal Measures are analogous with those of the Collie Coal Measures and support the suggestion that coal measures were originally developed over much of the southern Yilgarn Block and adjacent areas. All Permian deposits known from the Officer Basin belong in Stage 2. This indicates that the Officer Basin has been tectonically stable since the earliest Permian.