Carbon,oxygen and strontium isotope geochemistry of Proterozoic carbonate rocks of the Vindhyan Basin,central India |
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| Institution: | 1. State Key Laboratory of Geobiology and Environmental Geology, China University of Geosciences (Beijing), Beijing 100083, China;2. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China;3. PetroChina Research Institute of Petroleum Exploration and Development, Beijing 100083, China;4. PetroChina Changqing Oil Field Branch Company, Xi''an 710018, China;5. Geological Geomatics Institute of Hebei, Langfang 065000, China;1. Department of Geoscience and NASA Astrobiology Institute, University of Wisconsin, Madison, WI 53706, USA;2. Department of Geology and Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20742, USA;3. Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA;4. Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China;5. Department of Geological Sciences, University of North Carolina, Chapel Hill, NC 27599, USA |
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| Abstract: | Carbon, oxygen and strontium isotope compositions of carbonate rocks of the Proterozoic Vindhyan Supergroup, central India suggest that they can be correlated with the isotope evolution curves of marine carbonates during the latter Proterozoic. The carbonate rocks of the Lower Vindhyan Supergroup from eastern Son Valley and central Vindhyan sections show δ13C values of ～0‰ (V-PDB) and those from Rajasthan section are enriched up to +2.8‰. In contrast, the carbonate rocks of the Upper Vindhyan succession record both positive and negative shifts in δ13C compositions. In the central Vindhyan section, the carbonates exhibit positive δ13C values up to +5.7‰ and those from Rajasthan show negative values down to –5.2‰. The δ18O values of most of the carbonate rocks from the Vindhyan Supergroup show a narrow range between –10 and –5‰ (V-PDB) and are similar to the ‘best preserved’ 18O compositions of the Proterozoic carbonate rocks. In the central Vindhyan and eastern Son Valley sections, carbonates from the Lower Vindhyan exhibit best-preserved 87Sr/86Sr compositions of 0.7059±6, which are lower compared to those from Rajasthan (0.7068±4). The carbonates with positive δ13C values from Upper Vindhyan are characterized by lower 87Sr/86Sr values (0.7068±2) than those with negative δ13C values (0.7082±6). A comparison of C and Sr isotope data of carbonate rocks of the Vindhyan Supergroup with isotope evolution curves of the latter Proterozoic along with available geochronological data suggest that the Lower Vindhyan sediments were deposited during the Mesoproterozoic Eon and those from the Upper Vindhyan represent a Neoproterozoic interval of deposition. |
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