A multi-proxy approach to understand the monsoon driven changes in the eastern Arabian Sea during the Holocene

Multiproxy records of benthic foraminifera, pteropods, and total organic carbon (TOC) of sediment samples from Core SK291/GC17 (water depth 182 meter), eastern Arabian Sea, indicate changes in monsoonal conditions and associated oceanographic variabilities during ~13000 to 3400 calibrated years before present (cal yr BP). During ~8000 cal yr BP, decreased abundance of pteropod Limacina trochiformis as well as the lower value of TOC, might be a proxy for a dry phase of monsoon. The interval from ~7800 to 6400 cal yr BP can be characterized by favorable bottom water conditions, as suggested by higher value of number of species (S), Information Function (H) and alpha index (α) of the benthic foraminiferal assemblage. The middle Holocene (~6200 to 4200 cal yr BP) interval is marked by a significant increase in the number of epipelagic pteropods caused by higher surface productivity and decreasing abundance of mesopelagic pteropods caused by the shoaling and intensification of the OMZ. The oxic group of benthic foraminifera decreased drastically while dysoxic group of benthic foraminifera increased during this interval, due to the intensified OMZ. After ~4200 cal yr BP, the oxic assemblage of benthic foraminifera and pteropods, coincide with a pronounced arid phase (4.2 ka event) in the Indian subcontinent. The oxic assemblage of benthic foraminifera shows high frequency cycles centered at 692, 440 and 358 yr driven by solar variability; while Uvigerina peregrina, a benthic foraminifer sensitive to OMZ variability, shows high frequency cycles of 403 and 745 yr.