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Magnetostratigraphy of Frasnian-Fammenian (Devonian) Carbonates of the Canning Basin, Western Australia: Evaluating the Potential for Regional and Global Correlations


Correlation of carbonate sequences is bedevilled by heterogeneous facies that reflect a diversity of depositional, faunal, and isotopic settings. This diversity presents some challenges for detailed correlation, even at a regional scale. The Canning Basin of Western Australia presents world-class exposures of a carbonate-dominated shelf from Devonian times, where a highly irregular coastline created a variety of depositional environments: carbonate platforms and reefs, slope deposits, and hemipelagic basins, along with deposition around atoll-like blocks that were detached from the main coastline. Magnetostratigraphic correlation is based on the globally synchronous record of geomagnetic reversals, and can provide a temporal reference frame. In this contribution, we present the results of four magnetostratigraphic profiles from four different environments along the Lennard Shelf covering Givetian to end-Fammenian (middle to end-Devonian) times. Paleomagnetic results were obtained from thermal demagnetization of individual, oriented samples taken at the meter scale over approximately 2500 meter of composite section. Magnetite and hematite are inferred to be the principal magnetic carriers, and primary remanences are recovered from roughly 25% of all samples. A relatively high reversal rate is observed in all sections, consistent with previously obtained results from the Canning Basin (Hurley and Van der Voo, Geology, 1990). Comparison of the primary magnetic polarity record from these different environments will allow cross-checks on the correlation between different environments, as well as a providing a template for assessing other potential correlation schemes, including biostratigraphy, isotope chemostratigraphy, and magnetic susceptibility. The compiled results from this study will constitute the first systematic contribution to the construction of a Global Polarity Timescale for middle to late Devonian times.