Record of carbonate preservation and the Mid‐Brunhes climatic shift from a seamount top with low sedimentation rates in the Central Indian Basin |
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| Authors: | Bejugam Nagender Nath Adukkam V Sijinkumar Dnyandev V Borole Shyam M Gupta Lina P Mergulhao Maria B L Mascarenhas‐Pereira Venkitasubramani Ramaswamy Medimi V S Guptha Göran Possnert Ala Aldahan Nandkumar H Khadge Rahul Sharma |
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| Institution: | 1. Department of Post Graduate Studies & Research in Geology, Govt. College Kasaragod, , Kerala, 671123 India;2. 62, Sagar Society, Dona Paula, , Goa, 403004 India;3. Tandem Laboratory, Uppsala University, , Uppsala, Sweden;4. Department of Earth Sciences, Uppsala University, , Uppsala, Sweden;5. Department of Geology, United Arab Emirates University, , Al Ain, UAE;6. Geological Oceanography Division, National Institute of Oceanography (CSIR), Dona Paula, , Goa, 403?004 India |
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| Abstract: | In the present investigation, an age model of carbonate‐rich cores from a seamount top in the Central Indian Basin (CIB) was constructed using both isotopic (230Thexcess, AMS 14C, oxygen isotopes) and biostratigraphic methods. The chronologies using the two methods are in good agreement, yielding a record of the late Middle Pleistocene to the Pleistocene–Holocene transition (550 to 11.5 ka). The first appearance datum (FAD) of the radiolarian Buccinosphaera invaginata (180 ka) and coccolith Emiliania huxleyi (268 ka) and the last appearance datum (LAD) of the radiolarian Stylatractus universus (425 ka) were used. A monsoon‐induced productivity increase was inferred from carbonate, organic carbon and δ13C records in response to the Mid‐Brunhes Climatic Shift (MBCS), consistent with an increased global productivity. While the coccolith diversity increased, a decrease in coccolith productivity was found during the MBCS. At nearly the same time period, earlier records from the equatorial Indian Ocean, western Indian Ocean and eastern Africa have shown an increased productivity in response to the influence of westerlies and increased monsoon. The influence of easterlies from Australia and the intensification of aridity are evidenced by increased kaolinite content and clay‐sized sediments in response to the MBCS. An increased abundance of Globorotalia menardii and other resistant species beginning from marine isotope stage (MIS) 11 and the proliferation of coccolith Gephyrocapsa spp. indicate increased dissolution, which is consistent with the widespread global carbonate dissolution during this period. The relatively high carbonate dissolution during the transition period of MIS 3/2 and glacial to interglacial periods (MIS 6, 7 and 8) may be due to the enhanced flow of corrosive Antarctic Bottom Water (AABW) into the CIB. |
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