CORRELATION AND SEQUENCE STRATIGRAPHIC INTERPRETATION OF UPPER DEVONIAN CARBONATE SLOPE FACIES USING CARBON ISOTOPE CHEMOSTRATIGRAPHY, LENNARD SHELF, CANNING BASIN, WESTERN AUSTRALIA
Kelly Hillbun, Ted E. Playton, David A. Katz, Eric Tohver, Kate Trinajstic, Peter W. Haines, Roger M. Hocking, Brett Roelofs, Paul Montgomery, 2017. "CORRELATION AND SEQUENCE STRATIGRAPHIC INTERPRETATION OF UPPER DEVONIAN CARBONATE SLOPE FACIES USING CARBON ISOTOPE CHEMOSTRATIGRAPHY, LENNARD SHELF, CANNING BASIN, WESTERN AUSTRALIA", NEWADVANCES IN DEVONIAN CARBONATES: OUTCROP ANALOGS, RESERVOIRS AND CHRONOSTRATIGRAPHY, Ted E. Playton, Charles Kerans, John A.W. Weissenberger
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Making reliable correlations and sequence stratigraphic interpretations can be challenging in depositionally complex settings due to depositional heterogeneity and data-set limitations. To address these issues, the Canning Basin Chronostratigraphy Project documented the development of a high-resolution, chronostratigraphic correlation framework across different depositional environments in the Upper Devonian (Frasnian–Famennian) of the Lennard Shelf, Canning Basin, by integrating stable isotope chemostratigraphy, biostratigraphy, magnetostratigraphy, and sequence stratigraphy. This integrated data set allows for a rare, detailed look at the carbon isotope record, and specifically its potential as a sequence stratigraphic interpretation tool and its application to improve correlation capabilities, both of which have implications for better understanding of the depositional history of the Lennard Shelf.
For platform-top settings, a sequence stratigraphic framework was constructed using stacking pattern analysis constrained by the paleomagnetic reversal record. In slope settings, where depositional variability and a lack of platform-top control have historically hindered our ability to recognize and correlate systems tracts, carbon isotope chemostratigraphy (in conjunction with conodont biostratigraphy and magnetostratigraphy) proved to be a useful chronostratigraphic tool because primary marine δ13C values were well preserved. Using the paleomagnetic reversal record, with additional age control from walkout correlations to key outcrop sections, we were able to confidently correlate from the platform-top into the slope. Evaluation of the slope isotope record, within the projected sequence stratigraphic framework from the platform-top, revealed that variations in δ13C values corresponded to changes in sea level. Using this relationship, isotopic trends were used as a proxy for delineating systems tracts in slope sections without direct platform-top control. In turn, this improved correlations through heterogeneous slope facies and also allowed for a refined sequence stratigraphic interpretation of Famennian strata in the Canning Basin. Results from this work also allowed us to develop a model that attempts to explain the observed relationships among global carbon cycling, sea-level fluctuations, and paleoceanographic conditions during the Late Devonian.