U—Pb Age and Sr-Chemostratigraphy of Limestone from the Sorna Formation, Azyr—Tal Range, Kuznetsk Alatau

摘要

The U-Pb(Pb-Pb) age was determined for limestone from member III of the Sorna Formation outcropped on the Azyr-Tal Range, Kuznetsk Alatau. The weighted average value from three calculated values is 523 ± 5 Ma (MSWD = 0.02,2a). This age coincides with the Early Cambrian age interval determined with Sr iso-topic chemostratigraphy (~(87)Sr/~(86)Sr ratio is 0.70850-0.70852). The low value of μ_2 = ~(238)U/~(204)Pb for limestone is due to the evolution of diagenetic fluid containing lead from the mantle reservoir into the Sorna sediments.