ABSTRACT

To understand carbonate dissolution and/or preservation on the sea floor since the Last Glacial Maximum (LGM), we measured shell weights of planktonic foraminifera Globigerinoides ruber from four sediment cores retrieved from different water depths (~800 to 3300 m) across the northern Indian Ocean. G. ruber shell weight pattern shows an overall decrease starting from the LGM, with a spike, also termed as the ‘mystery interval’, during the early deglaciation (~17.5 to 14.5 ka). This shell weight maximum is a feature noted across the world oceans and considered to signify carbonate preservation, although it is missing from many sediment cores from the eastern equatorial Pacific, tropical Atlantic and subtropical Indian Ocean. The carbonate preservation spike during deglaciation in the northern Indian Ocean documented in this study suggests increased deep-water carbonate ion concentrations during the early deglaciation which in turn favored preservation. This study sheds new light on the preservation of carbonate and associated deep water circulation during deglaciation in the northern Indian Ocean.