EVALUATION OF DELTA-C-13 CHEMOSTRATIGRAPHY FOR INTRABASINAL CORRELATION - VENDIAN STRATA OF NORTHEAST SIBERIA

Integrated sedimentologic, stratigraphic, and geochemical (delta(13)C, delta(18)O, Fe, Mn, and Sr) data from Vendian-Cambrian carbonate-ramp deposits of the northeast Siberian platform (Olenek uplift and Kharau lakh Mountains region) are used to constrain primary, time-dependent o scillations in the carbon isotope record and to evaluate delta(13)C ch emostratigraphy for high-resolution intrabasinal correlation, The Vend ian delta(13)C record of northeast Siberia reflects global variations seen elsewhere by displaying (in ascending order) a strong positive is otopic shift to values near +6 parts per thousand (herein named the P- interval), an intermediate interval of relatively little isotopic chan ge (I-interval), which shows, in some sections, a monotonic decrease i n delta(13)C from +2 parts per thousand at the base to near 0 parts pe r thousand at the top, and a negative excursion to approximate to-4 pa rts per thousand (N-interval) just beneath the Vendian-Cambrian bounda ry, In addition to secular isotopic shifts, these strata exhibit local small-scale signals related to intrabasinal variations in subsidence, erosion, and diagenetic alteration (e.g., degradation of organic matt er, dolomitization, and hydrothermal and burial effects). These local, intrabasinal processes, in some cases, have modified both the magnitu de and form of the primary isotopic excursions, which are used as the basis for correlation in all studies. Carbon isotope profiles provide an important method to evaluate intrabasinal variations in subsidence, erosion, and stratigraphic completeness. These profiles reflect incre asing subsidence along the platform-to-basin transition, whereas progr essive truncation of isotopic profiles along this trend illustrate pro nounced uplift and erosion of ramp strata along unconformity surfaces.