A HIGH RESOLUTION LATE PALEOZOIC 87SR/86SR SEAWATER CURVE

     The ⁸⁷Sr/⁸⁶Sr seawater curve is an important proxy record used both for stratigraphic correlation and to understand the interaction between the Earth's lithosphere, hydrosphere and climate. The Late Carboniferous-Early Permian hosts one of the most profound apparent changes in seawater ⁸⁷Sr/⁸⁶Sr.  However, a significant problem in using this isotope excursion for precise global correlation involves its accurate chronostratigraphic calibration. The current Carboniferous-Permian seawater Sr isotope curve is constructed from carbonate samples collected from a wide distribution of poorly correlated localities (the southern mid-continent U.S.A., Canada, Germany, Great Britain, and China), potentially compromising its use as a global correlation tool.

     Marine successions within the Southern Urals offer a unique opportunity to create a temporally accurate Sr isotope curve for the Late Carboniferous-Early Permian. The marine sections within the Southern Urals are geographically proximal, contain abundant and well-preserved fauna for precise biostratigraphic correlation, and are recognized as type sections and principal reference sections for the Late Carboniferous-Early Permian stages. These sections also contain common interstratified volcanic ash beds, allowing for precise absolute time (U-Pb zircon) calibration (Ramezani et a., 2003; Schmitz et al., 2005).  The combination of new U-Pb zircon age constraints and multi-taxa biostratigraphy in the sections of the Southern Urals are presently being used to develop the most accurate available age model for the Carboniferous-Permian transition. This study will report a new ⁸⁷Sr/⁸⁶Sr seawater curve constructed using interstratified marine carbonates and phosphates (conodonts) from these Uralian sections. This temporally refined Sr curve will provide a tool for precise correlation between Carboniferous-Permian marine sections worldwide.