Millennial Scale Variations in Productivity and OMZ Intensity in the Eastern Arabian Sea

We studied high -resolution microfaunal (absolute abundances of planktic foraminifera and pteropods and relative abundance of G bulloides) and geochemical(C_org wt %) proxy records in a well-dated core (SK-17) from the present day Oxygen Minimurn Zone (OMZ)) In the Indian margin off Goa, to infer the varabi1tty of productivitya nd OMZ intensity in the last 30 ka The microfaunal and geochernical proxy records indicate three distinct regimes of monsoon-related varablility, viz, thelate glacial, the deglacial and the Holocene The late glacial records exhbit millennial scale changes, for e g , low productivity duribg the cold Heinrich Events, which can be llnked with a weaker SW monsoon Our record demonstrates a generally low productivlty during the deglacia1 period from Termination IA to the beginning of the Holocene The biological productivity was higher in the Late Holocene as evidenced by the well larninated sediments with high contents of C_org and planktic foraminifera The record of preservation and loss of aragontic pteropod shells In core SK 17 1s linked with vanations in the OMZ intenstty and Aragonite Compensation Depth (ACD) The core site appears to have remained below the ACD since 7 ka The pteropod abundance maxima of the Heinrich periods and the Younger Dryas (YD) suggest a weaker OMZ and deeper ACD during these periods The chronology of these millennial scale cycles indicates that they are synchronous with nsuch events recorded in the western Arabian Sea.