Planktonic foraminifera from core tops of western equatorial Indian Ocean

Abstract

A set of seven core tops from western equatorial Indian ocean were analysed for planktonic foraminifera, which has yielded 20 planktonic foraminiferal species. Among them Globorotalia menardii, Globigerinoides sacculifer and G. ruber constitute the majority of population. Distribution of foraminifera suggests that the tropical fauna gradually and progressively decreases from 6 degrees N latitude to 21 degrees S latitude from 98.92 to 58.2 per cent while, the sub-polar fauna shows inverse distributional pattern showing upward trend in its abundance from 38 per cent at 21 degrees S latitude to 0.8 per cent at 6 degrees N latitude. Sub-tropical fauna is sparsely distributed in the Equatorial Indian Ocean. Based on these studies it is interpreted that dissolution has been encountered at about 6 degrees S latitude owing to deeper depth. Occurrence of tropical fauna in abundance at about 20 degrees S latitude suggests either general warming of oceans or the prevailing warm water currents. Lastly, the presence of sub-polar fauna in the same latitude, in considerable proportion also indicates shift in polar/subpolar front during Holocene