Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Triassic Carbon Isotope Stratigraphy – Correlations Between Panthalassic and Tethyan Sections
(1) Earth & Environmental Sciences, Rensselaer Polytechnic Institute, Troy, NY.
(2) SINTEF Petroleum Research, Trondheim, Norway.
(3) Department of Geology and Mineral Resources Engineering, Norwegian University of Sciences and Technology, Trondheim, Norway.
(4) Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR.
Carbon isotopes were first shown to be effective for stratigraphic correlation in Neogene and Paleogene sections (e.g., Cramer et al., 2003; Dupuis et al., 2003; Woodruff and Savin, 1991). δ13C stratigraphy is now recognized as critical in older records, especially where biomagnetostratigraphy is insufficient to accurately correlate high-resolution datasets (e.g., Cramer and Saltzman, 2005; Grocke, 2006; Muttoni et al., 2004; Weissert et al., 1998). In this study, we present new carbon isotopic data from the Svalis Dome (Barents Sea) and focus on identifying δ13C events recorded in marine carbonates and organic carbon that can be used for correlation in Triassic sections.
High-resolution δ13C records of carbonates (δ13Ccarb)(Korte et al., 2005; Muttoni et al., 2004a; Payne et al., 2004) provide important glimpses of carbon cycle dynamics and potential for δ13C stratigraphic correlation during the Triassic, which began and ended with large δ13C excursions. Large δ13Ccarb fluctuations (up to 8‰) in the Tethys accompanied the Early Triassic reorganization of marine ecosystems over 4-8 myr (Payne et al., 2004), followed by more stable values punctuated by occasional smaller events through the rest of the Triassic (Korte et al., 2005; Muttoni et al., 2004). Although geographically restricted to the Tethys (Europe and China), these Triassic isotopic records demonstrate the potential to establish δ13C events that could be used in stratigraphic correlation.
We expand on these published Tethyan δ13Ccarb records both geographically and geochemically, with Early to Middle Triassic (Induan-Ladinian) δ13Ccarb and δ13Corg from the Panthalassic Ocean. We use 11 cores drilled by IKU/SINTEF along a depth transect on Svalis Dome (Barents Sea), recovering 315m of a 650m section of deep shelf to basinal siltstones and shales (Mørk and Elvebakk, 1999). Ammonoids and palynomorphs provide good age control (Vigran et al., 1998). The Svalis Dome succession contains an excellent hydrocarbon-rich source rock in the late Olenekian and Anisian with TOC values of 2 to 7%, with carbon isotope records that are independent of TOC increases. Our δ13Ccarb and δ13Corg data show large fluctuations, some of which are similar to coeval δ13Ccarb changes reported from China (Payne et al., 2004), supporting the utility of carbon isotopes for stratigraphic correlation in Triassic sections.