Lithogenic fluxes to the northern Indian Ocean - An overview

Abstract

Lithogenic fluxes to the northern Indian Ocean, measurEd. by time-series sediment traps, exhibit a strong seasonality with the bulk of the material (40 to 80 %) being deposited during the southwest monsoon period. This seasonality is more pronounced in the Arabian Sea than in the Bay of Bengal. The western and central Arabian Sea receive predominantly eolian dust from the Somali-Arabian deserts while the eastern Arabian Sea and the Bay of Bengal receive mostly fluvial material from the rivers draining the Himalayas and the Indian Peninsula. Annual lithogenic fluxes in the Bay of Bengal (8.6 to 28.0 gm sup(-2)) are about five times that of the Arabian Sea (2.6 to 5.4 gm sup(-2)). Increase of lithogenic flux with depth is seen in areas where fluvial input is more due to scavenging of the standing stock of suspended matter by sinking biogenic aggregates. In areas where eolian sediments predominate there is no significant increase of lithogenic flux with depth. Trap fluxes are comparable to Holocene sedimentation rates only in the Arabian Sea and the offset between the two is less than a factor of 2. In the central and southern Bay of Bengal trap fluxes are higher by a factor of 5