A Review of the Correlation Potential of the Permian of Eastern Australia

The marine Permian of the Sydney-Gunnedah-Bowen Basin in eastern Australia was characterised by strong provincialism, high endemism and sparse conodont fauna. Consequently, for many years regional and global attempts at correlation were evaded. Positioned centrally in the Austrazean Province and tectonically separated from western Australian basins by the Tasman Line, the southern Sydney Basin developed a comparatively unique, highly abundant but low diversity, typically cool-water fauna dominated by brachiopods, molluscs, and bryozoans. Building on an earlier systematic and biostratigraphic study, there are now detailed brachiopod studies published on the Cisuralian Wasp Head Formation, Pebbley Beach Formation and Snapper Point Formation. Also, the brachiopod and molluscan fauna of the uppermost marine succession, the Broughton Formation, has been studied but remains unpublished. It contains fauna useful for provincial (e.g. Echinalosia) and global correlation (e.g. Terrakea). For many years these faunal studies implied a Wordian age for the Broughton Formation. Geochronological studies have further refined the age of the Broughton Formation. U-Pb single zircon CA-IDTIMS dating constrains the top of the formation to 263.51 ± 0.05 Ma, and using 40Ar/39Ar an older member (Bumbo Latite) was found to contain a 265.05 ± 0.46 Ma date. Critically, the Illawarra Reversal signature at 265 Ma is also located in the Broughton Formation and provides a valuable marker for global correlation. These studies more firmly placed the Broughton Formation in the mid Wordian to the early Capitanian. Additional high-resolution geochronological work is ongoing and aims to further constrain the age of this formation. The advances in the faunal and geochronological studies, reviewed herein, demonstrate that the Permian of eastern Australia can no longer be overlooked. In particular, the Broughton Formation offers unprecedented potential for provincial and global correlation and warrants wider integration into future mid-late Guadalupian studies.