Climate-induced denudation of the Eastern Ghat during the Holocene: A multi-proxy study from Chilika Lagoon (India)

Abstract

A Holocene sediment record from Chilika Lagoon, India, suggests that changes in climate control denudation and weathering rate change. We assessed climate variability in the region and through time using multiproxy data comprising biotic and abiotic proxies. Mangrove and its associate assemblages suggest a backwater estuarine environment between ∼7.8 and 6 ka B.P. Depleted δ13Corg values during ∼7.8 to 5.5 ka B.P. indicate dominance of C3 vegetation, suggesting a warmer climate and strengthened monsoon. Enhanced δ13Corg and absence of pollen/spores are observed in the sediment layers deposited after ∼5 ka B.P., indicating arid climatic conditions with a dominance of C4 photosynthesizing plants and a relative lowering of sea level. Paleodenudation rates estimated using 10Be(meteoric)/9Be ratios varied between 556 ± 35 to 242 ± 15 t.km−2.yr−1. Phases of intense denudation occurred during 7.8–6.7 and 2.2–1 ka B.P., corresponding to Holocene Climatic Optimum and Medieval Climatic Anomaly, respectively. The degree of chemical weathering appears to have gradually increased from the early to late Holocene and correlates well (negatively) with the denudation rate. A gradual increase in the degree of chemical weathering from the early to late Holocene suggests an increase in the residence time of minerals in the weathering zone as the monsoon weakened.