Monsoon variability record from the Indian ocean

The benthic foraminiferal population from Recent sediments of the Indian Ocean can be divided into two faunal provinces – Province A and B, based on their relation with the water mass properties. Province A occupies northwestern Indian Ocean (northwestern Arabian Sea)and is dominated by foraminifera characteristic of low oxygen and high organic food flux. Province B covers southern, southeastern and eastern parts of the Indian Ocean and suggests well-oxygenated, cold deep water with low (oligotrophic) and pulsed food supply. Benthic foraminiferal diversity at Hole 716A is low during intervals of sustained flux of organic carbon with low oxygen levels (during intervals of intense SW monsoon) and vice versa. Higher populations of planktic foraminifer Globigerina bulloides (a well known SW monsoon proxy) are observed during intervals of intense SW monsoon. The surface and deep water conditions at Hole 716A are coupled probably due to the shallow water depth (533 m) of this hole. Spectral analysis show prominent peaks around 40, 30, 24, 20, 6, 1, 0.8 and 0.7 Kyr, thus signifying suborbital and orbital (precession-linked) forcing of the summer monsoon.