Carbon and oxygen isotopic variations in stromatolitic dolomites of Palaeoproterozoic Vempalle Formation, Cuddapah Basin, India.

The marine stromatolitic dolomites of Palaeoproterozoic Vempalle Formation, of Cuddapah Basin, South India show significantly depleted δO (−8.19 to −18.25‰) and δC (−0.03 to −5.74) values and are consistent with the global Proterozoic data. A comparison of the stable isotope values from major localities of Proterozoic Basins of India has also been attempted in this study. Significantly depleted δO values of Vempalle carbonate samples could not be considered to be post-depositional modifications as there exists an inverse correlation relationship between C and O isotopic values. The Vempalle stromatolitic dolomite is likely to be precipitated in equilibrium with marine waters significantly depleted in oxygen isotopes (−10 to −15‰ SMOW) with respect to modern sea water. The negative δC values of the Vempalle carbonates are likely to be interpreted at the backdrop of global 'icehouse' as there is an indication of dropstone-like features in the lower part of the Vempalle Formation just 2 km, southwest of the study area. [ABSTRACT FROM AUTHOR]