Stable oxygen isotope ratios of the planktonic foraminifera Globigerina bulloides of ODP Hole 117-723A in the Arabian Sea (Table 2)

Oxygen and carbon isotopic analyses have been performed on the tests of Globigerina bulloides and Pulleniatina obliquiloculata (planktonic foraminifera) and Uvigerina excellens (benthic foraminifer) to study the evolution of surface and bottom water hydrographic changes associated with summer monsoon upwelling process at the Oman Margin over the last 19 kyr. Globigerina bulloides, P. obliquiloculata and U. excellens show sharp depleted delta18O excursions around 9 ka, ascribed to the distribution of melt water flux of Termination IB in this region. A synchronous delta18O shift in surface, subsurface and bottom water-living foraminifera around 9 ka reveals a rapid transfer of the Termination IB signal through the vertical circulation of the Arabian Sea in response to peak monsoon intensity. A steep increase in delta13C values of U. excellens between 9 and 8 ka reveals advection of Red Sea intermediate water into the Arabian Sea during peak monsoon intensity. For the first time a drastic climatic shift at ~4 ka is noticed in the Arabian Sea as evidenced by the lowest delta18O values of both P. obliquiloculata (-1.10 ‰) and G. bulloides (-2.29 ‰). This points to reduced upwelling strength. Both planktonic foraminifer species delta18O records suggest the establishment of modern surface water conditions after 3 ka at the Oman Margin.