Application of Carbon Isotope Chemostratigraphy as a Chronostratigraphic Tool in Upper Devonian Carbonate Slopes: Lennard Shelf, Canning Basin, Western Australia

Hillbun, Kelly; Katz, David; Playton, Ted; Lewarch, Evan; Trinajstic, Kate; Tohver, Eric; Haines, Peter; Hansma, Jeroen; Hocking, Roger; Kirschvink, Joseph; Yan, Maodu; Ratcliffe, Ken; Pisarevsky, Sergei; Montgomery, Paul; Harris, Paul (Mitch); Ward, Peter

Chronostratigraphic correlations are integral for the development of sequence stratigraphic frameworks, understanding depositional variability, and distribution of reservoir properties in the subsurface. Subsurface correlations are challenged by dataset limitations coupled with complex depositional heterogeneity, and we document here a success case from an Upper Devonian (Frasnian and Famennian) outcrop analog along the Lennard Shelf, Canning Basin, Western Australia.

A preliminary correlation framework developed from the integration of carbon isotope chemostratigraphy, biostratigraphy, magnetostratigraphy, and sequence stratigraphy allows for an improved understanding of temporal and spatial distribution of depositional facies, when compared to the original framework constrained only by sequence stratigraphic concepts. For example, in slope settings where lateral and vertical depositional variability have historically hindered our ability to recognize and correlate systems tracts, stable isotope chemostratigraphy [in conjunction with conodont biostratigraphy and magnetostratigraphy] proved to be a useful chronostratigraphic tool as primary marine d13C values were well-preserved. In fact, stable isotopic trends observed in upper, middle, and lower slope depositional regions show a meaningful relationship with systems tracts, allowing us to not only identify transgressive and highstand systems tracts, but also to make high resolution correlations through heterogeneous slope sections with higher confidence. Use of the marine stable isotope values as a chronostratigraphic tool reached its limit in the platform-top setting due to the impacts of exposure, meteoric diagenesis, and frequent siliciclastics; as such, sequence stratigraphic concepts and magnetostratigraphy were heavily leveraged relative to stable isotopes to correlate with the slope.

Results from this integrated study have implications for developing better subsurface model frameworks and improving our reservoir characterization in complex depositional settings. Furthermore, we here present tools and workflows involving stable isotope chemostratigraphy that now enable correlation and the development of sequence stratigraphic frameworks in heterogeneous carbonate slope-to-basin systems. This approach can applied to carbonate slope and basin reservoirs that exhibit such complexity, like the Carboniferous fields of Kazakhstan and the Permian fields of west Texas, using core and cuttings.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013