C- AND Sr-ISOTOPE CHEMOSTRATIGRAPHY OF THE UPPER PROTEROZOIC – LOWER CAMBRIAN TRANSITIONAL DEPOSITS IN THE LENA-ANABAR TROUGH (NORTHEASTERN SIBERIAN PLATFORM)

Abstract

Studies have been made of the carbon and strontium isotope composition in carbonate sediments of the Khorbusuonka group and Kessyusa formation corresponding to the Upper Vendian in deep Khastakhskaya-930 and Burskaya-341-0 boreholes at the northeastern margin of the Siberian Platform. The maximum δ13С values in carbonates of the Turkut and Kessyusa formations in the Khastakhskaya-930 borehole are +7.0...+7.4 %, while the minimum 87Sr/86Sr ratios are as low as 0.7079. Such isotope-geochemical characteristics suggest that these formations are younger (Tommotian) or older (early Vendian) than it was supposed and allow for the possibility of alternatives to their regional correlation with the Burskaya-341-0 borehole and Olenek uplift sections. The deposition of sediments of the age considered, more intensive than in the adjacent regions, may be indicative of rift-related extension settings.

Keywords

• vendian
• ediacaran
• lower cambrian
• c- and sr-isotope chemostratigraphy
• siberian platform
• lena-anabar trough