Climatic Impact on Major and Trace Elements in Deltaic Core Sediments: Evidence from Muthupet Lagoon, se Coast of India

Geochemistry of lagoon deposits provides a continuous record of climatic changes, and such core sediments at successive deeper and older layers have long been utilized for sedimentologic and organic geochemical studies. These ecosystems present a mechanism for trapping sediment and therefore record climatic changes in the form of geochemical imprints. The aim of the present study is to evaluate the climatic and depositional controls in the Muthupet lagoon, situated at the southern most end of the Cauvery delta, south east India. The variations of geochemical parameters with depth and their ratios were employed to reveal the characteristics of Holocene climate and associated paleoenvironmental implications of this region. Moderate values of the Chemical Index of Alteration (CIA) suggest intermediate chemical weathering of the source rock under tropical to subtropical climatic conditions. Index of Composition Variability (ICV) values indicate low proportion of non clay silicate minerals in these sediments. V/Cr ratio has been used as a paleo-oxygenation indicator and in the present study, the ratio V/Cr was found to be < 2 indicating oxic-depositional conditions prevailing in this lagoon. Fe/Ti and Fe/Al ratios reveal valuable information on the impact of climate changes on the sedimentation in the study area. Na and S, indicators of paleosalinity and marine flooding were evaluated. The increase in concentration of Na at various depths was identified and marine incursions characterized. Abrupt changes in the values at certain depths were directly related to major climatic events using the available rainfall and 210Pb data. Key words: Climate change, Weathering Pattern, Muthupet Mangroves, SE coast of India. Location map of the study area