The Arabian Sea is unique in its seasonal reversal of monsoon driven winds and associated oceanographic changes and it is one of the most bio productive areas in the world. Previous high-resolution studies on Arabian sea sedimentary records using multiple proxies indicate high frequency variations in monsoonal climate and associated oceanographic conditions, and most of them were made from the northwestern and northeastern Arabian Sea. Such high-resolution studies from the southern sector of the Indian margin, is not much investigated. The present study aims to reconstruct the high-resolution late deglaciation- Holocene monsoon history in the southeastern Arabian sea at sub centennial – millennial time scale based on multi proxy approach of a well dated sedimentary core from the southern sector of Indian margin.
We selected a good quality sedimentary core off Cochin, SK-06 (9° 20′N Latitude, 75° 33′E Longitude water depth 890 m), for the present study. The age depth model of the core SK-06 is based on fifteen C¹⁴ AMS dates. High- resolution planktic foraminiferal record based on faunal counts > 300 specimens in >125 µm size fraction of nearly 162 samples at regular interval of 1 cm has been generated. Relative  and absolute abundance of significant species is also estimated. Temporal variations of mixed layer planktic foraminiferal abundances (eutrophic and oligotrophic species) and G. bulloides/Gs. ruber ratio are used to reconstruct surface hydrographic structure and productivity in response to the changes in intensity of seasonal monsoon winds. Our results show that, a small but net increase in productivity during Younger Dryas chronozone. We observed a short phase of low productivity during early Holocene followed by a phase of consistently increasing productivity until the mid-Holocene. No major change in surface productivity during the last 5.8 Kyr has been observed. During the late Holocene between 3 to 0.8 kyr a net increase in productivity has been observed. Also, the nitrogen isotope ratios δ¹⁵N, from the same core shows an increasing trend during the early Holocene which further increased during the late Holocene. Stable Oxygen isotope values and Mg/Ca values of selected surface and deep dwelling planktic foraminifera has been carried out to reconstruct the degree of water column stratification, sea surface temperature and sea surface salinity. We compared our generated records with the previously published records from the eastern Arabian sea to analyse spatial and temporal heterogeneity in surface hydrography and productivity in two different oceanographic settings (upwelling and non-upwelling system).
 

Indian monsoon, Arabian Sea, planktic foraminifera, surface hydrography, productivity