INTEGRATION OF SEQUENCE STRATIGRAPHY AND STABLE ISOTOPE (δ13Ccarb AND δ18O) CHEMOSTRATIGRAPHY TO TEST AND IMPROVE CORRELATIONS IN GEOGRAPHICALLY SEPARATED SECTIONS IN THE DEVONIAN OF THE CANNING BASIN, NORTHWESTERN AUSTRALIA

Previous attempts to correlate coeval strata between physically disconnected locations within Middle and Upper Devonian strata exposed in the Canning Basin of northwestern Australia have been challenged by the presence of unconformities and depositional hiatuses of unknown lateral and temporal extent. The added difficulty of correlating shallow water facies devoid of biostratigraphically useful index fossils further highlights the need to explore other chronostratigraphic tools such as stable isotope geochemistry. Here we couple sequence stratigraphy and stable isotope (δ¹³C and δ¹⁸O) chemostratigraphy to construct cross-section correlations between two physically separated reef transects in the Pillara Formation at the Windjana Gorge section. Both sections exhibit a large negative excursion in δ¹³C values (7‰ negative excursion to -5‰ average values) that covary with a negative excursion of similar magnitude in the δ¹⁸O values and a low frequency sequence stratigraphic boundary. Above this tie point, the δ¹³C values generally trend, by 1 to 2 ‰ on average, towards more depleted values. This long term isotopic trend is characteristic of many Frasnian-aged sections from European and North African localities. Previous studies in south China and western Canada have also documented similar synchronous negative excursions in δ¹³C and δ¹⁸O, albeit at lower spatial and temporal resolution. In light of this previous work, this integrated study holds promise as a high resolution chronostratigraphic tool for both basinal and global scale correlations.