| Title | Surface and deep water changes in the northeast Indian Ocean during the last 60 ka inferred from carbon and oxygen isotopes of planktonic and benthic Foraminifera |
| Author | Ahmad, S.M.; Babu, G.A.; Padmakumari, V.M.; Raza, W. |
| Author Affil | Ahmad, S.M., National Geophysical Research Institute, Hyderabad, India |
| Source | Palaeogeography, Palaeoclimatology, Palaeoecology, 262(3-4), p.182-188, . Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0031-0182 |
| Publication Date | Jun. 4, 2008 |
| Notes | In English. 42 refs. GeoRef Acc. No: 285170 |
| Index Terms | radioactive age determination; age determination; radioactive age determination; carbon isotopes; climatic change; correlation; geochemistry; isotopes; ocean environments; oxygen; paleoclimatology; paleoecology; radioactive isotopes; statistical analysis; Indian Ocean-- Ninetyeast Ridge; absolute age; Anomalinidae; benthic taxa; biochemistry; C-13/C-12; C-14; carbon; Cassidulinacea; Cenozoic; chronostratigraphy; Cibicidoides; Cibicidoides wuellerstorfi; climate change; cores; dates; deep-sea environment; Foraminifera; glacial environment; glaciomarine environment; Globigerinacea; Globigerinidae; Globigerinoides; Globigerinoides ruber; Holocene; Indian Ocean; Invertebrata; isotope ratios; last glacial maximum; marine environment; microfossils; monsoons; Ninetyeast Ridge; O- 18/O-16; paleo-oceanography; paleocirculation; planktonic taxa; Protista; Quaternary; Rotaliina; stable isotopes; time series analysis; upper Quaternary |
| Abstract | Stable carbon and oxygen isotopic records of planktonic (Globigerinoides ruber) and benthic foraminifera (mostly Cibicidoides wuellerstorfi) from a deep-sea core in the northeast Indian Ocean are used to infer surface and deep water characteristics for the last ~60 kyr. The gravity core (SK-157- 14) studied here was retrieved from the Ninetyeast Ridge (5°11'N; 90°05'E) at a water- depth of 3306 m. Chronology of the core was established using nine radiocarbon dates and oxygen isotope stratigraphy. Significant variations in delta 18O during the last 2-60 kyr BP are suggestive of large changes in monsoonal precipitation over the Indian sub- continent. The last glacial maximum (LGM) to Holocene shift in planktonic foraminifera delta 18O (1.64 per mil) is less than documented earlier from the Bay of Bengal cores. Two prominent negative delta 18O excursions at ~8-7 and ~20-18 kyr BP are attributed to the sudden influx of freshwater as a result of intensified monsoonal precipitation. Large fluctuations in delta 18O of G. ruber during the Holocene suggest variability in riverine input. Planktonic delta 18O values show a combined effect of increased sea surface salinity and decreased sea surface temperature (SST) during the LGM. In contrast, the planktonic delta 13C values are not linked to the glacial-to-Holocene transition. Comparison of the benthic delta 18O and delta 13C time series with those of a Pacific core (RC13-110) suggests a similar glacial deep water evolution. The LGM to Holocene delta 18O shift in benthic foraminifera (mostly C. wuellerstorfi) exceeds the ice volume effect by ~0.5 per mil, indicating a glacial deep water cooling of ~2°C, assuming no salinity change. Variations in the distribution of delta 13C in the glacial northeast Indian Ocean (NEIO) are most likely the result of deep ocean circulation changes. The glacial deep NEIO delta 13C characteristics clearly point to reduced North Atlantic Deep Water (NADW) input. Consequently the contribution from the Southern Ocean deep water may have increased resulting in low delta 13C. A positive shift in delta 13C during the early deglaciation is consistent with other records from this region. Deglacial delta 13C fluctuations appear to have been caused by the switch "on" and "off" of NADW production. |
| URL | http://hdl.handle.net/10.1016/j.palaeo.2008.03.007 |
| Publication Type | journal article |
| Record ID | 62005347 |