Stable Isotope Profiles in from Isolated Carbonate Platform: Implications for Stratigraphic Correlations
Jean Hsieh1, David Katz1, Paul M. Harris1, Matt Buoniconti1, John Humphrey2, and Isabel Montanez3
1Energy Technology Company, Chevron, San Ramon, CA
2Department of Geology, Colorado School of Mines, Golden, CO
3Department of Geology, University of California, Davis, Davis, CA
The δ13Ccarb values of biotically and abiotically precipitated marine carbonates display significant temporal variation that is well documented through the geological record (e.g., Popp et al., 1997). These variations have been attributed to changes in carbon cycling through changes in productivity and organic carbon burial rates, variations in carbon sources to the atmosphere and ocean, and shifts in weathering patterns and rates. The potential of secular variation in marine carbonate δ13Ccarb records as a chronostratigraphic correlation tool and paleoenvironmental proxy has been well established over the past two decades (e.g., Vahrenkamp, 1996; Montanez et al, 2000; Saltzman, 2002). However, carbonates are susceptible to diagenetic modification, particularly those deposited in shallow-water epeiric seas subjected to sea-level fluctuations. Thus, potential diagenetic influences on the δ13Ccarb values must be considered when interpreting measured values.
This study presents the results of measurements of the carbon and oxygen isotopic values for an isolated carbonate platform that ranges from Devonian to Bashkirian (Carboniferous) in age. We are examining the implications of the bulk rock stable isotope profiles for stratigraphic correlation in a reservoir. The δ13C stratigraphy shows trends to positive and negative δ13C values that can be correlated with sequence boundaries picked using traditional facies variations based on core descriptions. Secular variability in the δ13C stratigraphy is also loosely correlated with changes in wireline log values. Several sequence boundaries could be modified and higher order cycle boundaries could be picked using the δ13C stratigraphy. These results suggest that stable isotope profiles can be used to help constrain the sequence stratigraphic framework of a carbonate reservoir.
AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery