Carbon and oxygen isotope geochemistry of Neoproterozoic limestones of the Shahabad Formation, Bhima basin, Karnataka, southern India

Petrography, major (including four trace elements), stable isotopes (carbon and oxygen), and 87 Sr/ 86 Sr geochemistry of limestones of the Shahabad Formation, Bhima basin, Karnataka, southern India are reported. These limestones show a narrow range of δ 13 C (~1.34−1.96‰) and δ 18 O (~ -6.04 to -7.61‰) values. The petrographic study reveals the presence of microsparite and micro- and macrostylolites. The δ 13 C and 87 Sr/ 86 Sr values indicate that these limestones were deposited during the late Neoproterozoic age and the δ 18 O values also are very similar to the average Proterozoic carbonate values. Mn and Sr concentrations and low Mn/Sr ratio (<1) together with the stable and radiogenic isotope data suggest that the studied samples are well-preserved or scarcely altered limestones and probably have retained their primary isotopic signatures.