REE geochemistry of core sediments of Cauvery delta, India for provenance studies

Abstract

The rare earth element (REE) geochemical composition of sediments from two cores were used to investigate the provenances of the Late Pleistocene to Holocene sediments of Cauvery delta, South India. The chondrite-normalized REE patterns and bi-variant plots of Th/Co vs. La/Sc and La/Th vs. Th/Yb indicated felsic source of sediments. Chondrite-normalized plots of REE in both cores are almost parallel and exhibit similar fractionation ratio (Ce/Yb)N of ~ 8.2. Furthermore, persistence in REEs patterns implies either uniform source rocks and/or efficient homogenization of sediments during transportation and deposition. Chondrite-normalized patterns of the samples show enrichment of light rare earth elements and flat pattern of heavy rare earth elements; such patterns imply dominance of felsic composition rocks in the provenance. Further, these samples show quite resemblance with Charnockites and Gneisses of Palani and Kodaikanal hill areas. Chondrite-normalized REE patterns of the Pleistocene sediments of Uttrangudi core show similar abundance, fractionation, and Eu anomaly values as of selected samples from Tertiary rocks near southwest part of the delta. We attribute the increased input from this region to the upliftment because of tectonic activity and lowering of sea level during the Pleistocene.