Strontium and neodymium isotopic compositions in sediments from Godavari, Krishna and Pennar rivers

We report here strontium (Sr) and neodymium (Nd) isotopic compositions in bed sediments from the Godavari, Krishna and Pennar rivers, draining into the Bay of Bengal. The isotopic compositions of these sediments range from 0.7190 to 0.7610 for ⁷⁷Sr/⁷⁶Sr and –12.04 to –23.68 for εNd. This wide range in Sr and Nd isotopes is derived from variable proportions of sediments from different rock types in their drainage basins. All the three rivers have their characteristic isotopic signatures. The results display highest ⁷⁷Sr/⁷⁷Sr (0.7610) and most negative εNd values (–23.68) for the sediments of Pennar river. This is attributed to the chemical weathering of gneisses and granites in its drainage basin. The ⁷⁷Sr/⁷⁶Sr and εNd values for the Godavari river sediments range from 0.7196 to 0.7210 and –15.31 to –18.22 respectively. ⁷⁷Sr/⁷⁶Sr and εNd values in Krishna river sediments lie from 0.7217 to 0.7301 and –12.04 to –12.78 respectively. Our results show that the sedimentary load from the Godavari and Krishna rivers is primarily derived from the older rocks in their drainage basins. It is possible that the sediments transported through peninsular Indian rivers predominantly control Sr and Nd isotope sedimentary budget in the western Bay of Bengal.