Carbon and oxygen isotope time series records of planktonic and benthic foraminifera from the Arabian Sea: Implications on upwelling processes

Abstract

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. G. bulloides, P. obliquiloculata and U. excellens show sharp depleted delta super(18)O excursions around 9 ka, ascribed to the distribution of melt water flux of Termination IB in this region. A synchronous delta super(18)O 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 delta super(13)C 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 approx. 4 ka is noticed in the Arabian Sea as evidenced by the lowest delta super(18)O values of both P. obliquiloculata (-1.10 ppt) and G. bulloides (-2.29 ppt). This points to reduced upwelling strength. Both planktonic foraminifer speciesdelta super(18)O records suggest the establishment of modern surface water conditions after 3 ka at the Oman Margin.