Isotopic studies of beach rock carbonates from Konkan, central west coast of India

Abstract

The beach rock carbonates from the 200 km long stretch from Guhagar in the north to Deogad in the south along the Konkan coast (Maharashtra, India) are studied for sup(14)C dating and sup(13)C : sup(12)C and sup(18)O : sup(16)O ratio determination to understand their depositional processes and paleoenvironmental changes. sup(14)C ages of some of these rocks range from 1100 to 3130 Yrs B.P., suggesting their Recent to Sub Recent origin. delta sup(13)C signatures of beach rocks vary largely from -1.9 to -6.7% (PDB) and delta sup(18)O signatures lie in a narrow range of +27.5 to +28.6% (SMOW), respectively. Isotopic data obtained in this study show that cementation of beach rock carbonates might have taken place in a shallow vadose zone. The large variations delta sup(13)C signatures (-1.9 to -6.7%) can be attributed to changing influcnce of organically derived soil CO sub(2) in the formation of these carbonates. delta sup(18)O signatures of beach rock carbonates indicate the the paleotemperatures of waters precipitating these carbonates varied moderately.