期刊
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
卷 20, 期 3, 页码 1592-1608出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2018GC008179
关键词
Bay of Bengal; intermediate water masses; glacial Holocene; benthic foraminiferal assemblages; carbon and oxygen stable isotopes; B-P C-14 age
资金
- National Natural Science Foundation of China [41806060]
- China Scholarship Council
- INSU-LEFE-IMAGO-CITRON GLACE program
Benthic foraminiferal assemblages and geochemical tracers (delta O-18, delta C-13 and C-14) have been analyzed on benthic and planktonic foraminifera from core MD77-176, located in the northern Bay of Bengal, in order to reconstruct the evolution of intermediate circulation in the northern Indian Ocean since the last glaciation. Results indicate that during the Last Glacial Maximum (LGM), Southern Sourced Water masses were dominant at the core site. A high relative abundance of intermediate and deep infaunal species during the LGM reflects low oxygen concentration and/or mesotropic to eutrophic deep water conditions, associated with depleted benthic delta C-13 values. During the Holocene, benthic foraminiferal assemblages indicate an oligotropic to mesotrophic environment with well-ventilated bottom water conditions compared with LGM. Higher values for benthic foraminifera delta C-13 and B-P C-14 age offsets suggest an increased contribution of North Atlantic Deep Water to the northern Bay of Bengal during the Late Holocene compared to the LGM. Millennial-scale events punctuated the last deglaciation, with a shift in the delta C-13 and the epsilon(Nd) values coincident with low B-P C-14 age offsets, providing strong evidence for an increased contribution of Antarctic Intermediate Water at the studied site. This was associated with enhanced upwelling in the Southern Ocean, reflecting a strong sea-atmospheric CO2 exchange through Southern Ocean ventilation during the last deglaciation.
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