CHEMOSTRATIGRAPHY OF CARBONATE SUCCESSION OF THE VEMPALLE FORMATION, CUDDAPAH BASIN, INDIA: A STRATIGRAPHIC RECORD OF TERMINAL PALAEOPROTEROZOIC OCEAN-ATMOSPHERE-BIOSPHERE SYSTEM

A shallowing-upward succession of intertidal to subtidal stromatolitic dolomites of the upper Palaeoproterozoic (Orosirian) Vempalle Formation of Cuddapah basin, Peninsular India, is preserved in the Bramhanapalle area (14 degrees 25'15 '' N, 78 degrees 12'19 '' E), near Pulivendla, south India. The delta C-13(carb) and delta O-18(V-PDB) values of some selected stromatolitic dolomite samples from this succession vary from +1.25 to -5.74 per mil and from -5.42 to -18.25, respectively. These values are consistent with the global data during the upper Palaeoproterozoic time. A positive to negative delta C-13 shift in the studied stratigraphic section is indicating (i) a gradual decrease in the biomass productivity during the deposition of Vempalle sediments (ii) the decline of stromatolite type carbonate rocks due to the volcanic activity during the deposition of the Vempalle sediments (iii) an advent of "snowball earth" - like condition in the Indian Peninsular region at the onset of Vempalle sedimentation.