Rare Earth Elements as Indicators of Paleoclimate, Chemical Weathering and Redox Variability in Chodha Lake Core Sediments, Korba Region, Central India

Abstract

This study presents a rare earth element geochemical record using the 48cm long sediment core recovered from the Chodha Lake of the Korba district, Chhattisgarh. The rare earth elements were used to observe the fluctuating environmental conditions in and around the study area. The core was divided into four sections based on the variability in their concentration. The entire study is based on the down core characteristics such as ΣREEs, ΣLREEs, ΣHREEs, the ΣLREEs/ΣHREEs ratio, and Ce and Eu anomalies. At most of the depths δCe values remained predominantly positive, ΣREEs, ΣLREEs, ΣHREEs and the ΣLREEs/ΣHREEs ratio were persistently low. Together, these proxies indicate dominantly oxygenated bottom water conditions and warm, humid climate governed mainly by chemical weathering leading to deposition of coarser sediments. Two notable episodic events at the depths of 26 cm in the zone-B and 17cm in the zone-C, marked by a sharp drop in δCe, increased ΣREEs and the LREE/HREE ratio indicating a brief shift to anoxic, arid/cool conditions which also led to deposition of fine sediments in the catchment. These results demonstrate that REE geochemistry provides a sensitive, internally consistent multi proxy tool for reconstructing redox and climatic fluctuations in lacustrine sedimentary archives.