Oxygen and carbon stable isotope studies onGloborotalia menardii from Pleistocene DSDP Cores in northern Indian Ocean and their paleoclimatic and paleoceanographic implications |
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| Authors: | Ashish Sarkar Asit K Guha Supriyo Chakraborty |
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| Institution: | (1) Department of Geology and Geophysics, Indian Institute of Technology, 721 302 Kharagpur, India;(2) Physical Research Laboratory, 380 009 Ahmedabad, India |
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| Abstract: | Stable isotope ratios of oxygen (δ18O) and carbon (δ13C) in tests ofGloborotalia menardii from samples at 25 cm intervals of top 900 cm cores, representing different thicknesses of the Pleistocene, from DSDP Sites
219, 220 and 241 in the northern Indian Ocean have been measured. Based on the δ18O stratigraphy, glacial and interglacial phases during the Pleistocene have been recognized, which are in good agreement with
the standard Quaternary planktonic foraminiferal/climatic zones i.e., Ericson zones at these sites, based onG. menardii abundances. The GIA (glacial interglacial amplitude) at Sites 241, 219 and 220 are of the order of 1·2, 1·4 and 1·9‰ respectively.
The last glacial and interglacial maxima (18 ka BP and 125 ka BP respectively) could be identified in DSDP Cores 241, and
219 with some precision. ‘Isotopic ages’ could be assigned to the different levels of these core sections based on the correlation
of δ18O record from these sites with the SPECMAP record (Imbrieet al 1984). Changes in sediment accumulation rates at different levels of the Pleistocene have been worked out on the basis of
changes in oxygen isotopic ratio.
Oscillations in δ13C stratigraphy at Site 241 indicated southwest monsoon induced increase in upwelling and productivity during warmer periods.
At Sites 219 and 220, variations in the δ13C record were due to the mixing of bottom water. |
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| Keywords: | Quaternary stratigraphy Ericson zones glacial-interglacial amplitude (GIA) last glacial maxima (LGM) upwelling stable isotope |
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