Abstract
The discharge of terrigenous clastics by seasonal peninsular rivers is known to reach the upper slope of the eastern margin of India, which is presently impinged by the monsoon-sensitive intense oxygen minimum zone (OMZ); however, their mutual behaviour in response to changes in the intensity of past Indian summer monsoons (ISM) is not clear. The δ 18 O G.sacculifer time-series of a sediment core from the upper slope off Chennai exhibits distinct enrichment (~0.4‰) during the last glacial period (30–18 kiloyears BP: ka), and depletion (~-2.2‰) during the Holocene, suggesting a significant shift in ISM intensity. The monotonously increased terrigenous elements (Al, Ti and Mg) content and depleted δ 18 O G.sacculifer during the Holocene suggest tight-coupling between ISM and terrigenous sediment input. Highly depleted redoxsensitive Mn (<0.04%) (lesser than the source sediment content of 0.07%) throughout the last 42 kyr suggests well-sustained intense OMZ irrespective of ISM variation.
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