Late Quaternary Monsoon and Productivity Variability in the Northwestern Arabian Sea

We studied the changes in planktic foraminiferal distribution along with some sedimentological and geochemical data at ODP Site 722B in the northwestern Arabian Sea to reconstruct monsoon upwelling and productivity variations during the last ~550 kyr. The higher relative abundance of Globigerinita glutinata and southwest (SW) monsoon assemblage along with increased Ba/Al ratio during most of the interglacial intervals, suggests lateral transport of eutrophic water due to strong upwelling causing enhanced productivity. A relatively higher test fragmentation and increased relative abundance of Globorotalia menardii during interglacial intervals indicate increased carbonate dissolution. The glacial–interglacial transitions are characterized by abrupt increase in the SW monsoon upwelling assemblage and Ba/Al ratio, suggesting more intensified upwelling and productivity due to accelerated SW monsoon and weak northeast monsoon conditions. Spectral analysis of the abundance data of SW monsoon upwelling assemblage and Ba/Al ratio demonstrates the 100-kyr cycle showing glacial– interglacial frequency and 23-kyr cycle indicating precession-driven insolation variability.