TY - JOUR T1 - Glacial to deglacial ventilation and productivity changes in the southern Okhotsk Sea JF - Palaeogeography, Palaeoclimatology, Palaeoecology Y1 - 2014 A1 - Okazaki, Yusuke A1 - Kimoto, Katsunori A1 - Asahi, Hirofumi A1 - Sato, Miyako A1 - Nakamura, Yuriko A1 - Harada, Naomi KW - Glacial–deglacial change KW - Okhotsk Sea KW - productivity KW - ventilation AB - As a source region of North Pacific Intermediate Water, the Okhotsk Sea plays an important role in the ventilation of the North Pacific. To understand the detailed oceanographic changes in this marginal sea since the last glaciation, we studied decadal to centennial scale proxy records from new sediment cores from the southwestern Okhotsk Sea. Glacial to Holocene Δ14C records of benthic foraminiferal shells suggested enhanced ventilation in the Okhotsk Sea during the early deglacial period between 18 and 15 ka, corresponding to Heinrich Event 1. Although the Δ14C reconstruction has considerable uncertainties, the Okhotsk Sea may have acted as a source for vigorous ventilation of the subarctic Pacific during this period. CaCO3 preservation events appear to be better explained by the ventilation history of the Okhotsk Sea than by coccolithophores and foraminifera production. CaCO3 preservation started to improve during 18 to 15 ka, and pronounced peaks in the CaCO3 content corresponded to the Bølling–Allerød (15 to 13 ka) and Preboreal (11.5 to 10 ka) warm periods. Diatom and coccolithophore productivity remained low in the Okhotsk Sea throughout the glacial to deglacial periods, different from the situation in the open subarctic Pacific, where high productivity was observed during the Bølling–Allerød period. After the Preboreal period, biogenic opal gradually increased and δ15N decreased in the southern Okhotsk Sea, suggesting that productivity was enhanced by a relaxation of the nitrate limitation. VL - 395 UR - https://doi.org/10.1016/j.palaeo.2013.12.013 ER - TY - JOUR T1 - Late Quaternary benthic foraminifera from Ocean Drilling Program Hole 716A, Maldives Ridge, southeastern Arabian Sea JF - Micropaleontology Y1 - 2009 A1 - Sarkar, S. A1 - De, S. A1 - Gupta, A. K. KW - benthonic foraminifera KW - equatorial indian-ocean KW - Holocene KW - late neogene KW - monsoon KW - Oxygen minimum zone KW - productivity KW - red-sea KW - south atlantic-ocean KW - Water masses AB - A study on deep-sea benthic foraminifera from the interval similar to 445 ka BP to the Present of the Ocean Drilling Program (ODP) Hole 716A (4 degrees 56.0'N, 73 degrees 17.0'E; preser t water depth 533.3m), Maldives Ridge. southeastern Arabian Sea, documented 201 species belonging to 105 genera. These taxa were examined under scanning electron microscope (SEM) to illustrate their interspecific morphological variations. Several of these species are dominant showing significant down core fluctuations in their abundances whereas some are rare and sporadic. VL - 55 SN - 0026-2803 IS - 1 N1 - 424cdTimes Cited:5 Cited References Count:47 JO - Micropaleontology ER - TY - JOUR T1 - Oxygen and carbon isotope records of calcareous nannofossils from the west Philippine Sea during the last 190ka JF - Earth Science.Journal of China University of Geoscience Y1 - 2008 A1 - Jingtao, Zhao A1 - Li, Tiegang A1 - Chang, Fengming A1 - Li, Jun KW - 02D KW - 24 KW - algae KW - biochemistry KW - C-13/C-12 KW - carbon KW - Cenozoic KW - Foraminifera KW - Geochemistry KW - Holocene KW - Invertebrata KW - Isotope geochemistry KW - isotope ratios KW - isotopes KW - Last glacial maximum KW - microfossils KW - nannofossils KW - north pacific KW - Northwest Pacific KW - O-18/O-16 KW - oxygen KW - Pacific Ocean KW - paleo-oceanography KW - Philippine Sea KW - Plantae KW - Pleistocene KW - productivity KW - Protista KW - Quaternary KW - Quaternary geology KW - Stable isotopes KW - upper Pleistocene KW - West Pacific AB - The piston core Ph05-5 recovered from the West Philippine Sea(16.049 degrees N, 124.344 degrees E, water depth 3382m) was used to study the delta (super 18) O and delta (super 13) C variations of calcareous nannofossils. The delta (super 18) O values of calcareous nannofossils were obviously lower in Holocene and the last interglaciation than those in the last and the penultimate glaciation. During the last 190 ka the nannofossil delta (super 18) O values were positively correlated with those of planktonic and benthic foraminifera from the same core. But the average delta (super 18) O value of nannofossils was 0.431X10 (super -3) , higher than that of planktonic foraminifera Globigerinoides rubber, and was 0.410X10 (super -3) , lower than that of planktonic foraminifera Neogloboquadrina dutertrei. All the above three average delta (super 18) O values were much lower than those of benthic foraminifera Cibicides wullerstorfi. The change of nannofossil delta (super 13) C values showed similar trends with the absolute abundance of calcareous nannofossils in core Ph05-5, which also indicates the primary productivity variations in the West Philippine Sea. The primary productivity stayed at a stable but relatively low level at MIS 6 and MIS 5e.There was an abrupt rise at the beginning of MIS 5d for the primary productivity which retained high value until 25 ka BP. The primary productivity showed a slight decline during MIS 2 and MIS 1, but still higher than that of MIS 6 and MIS 5e. VL - 33 SN - 1000-2383, 1000-2383 IS - 2 N1 - id: 1933; NO: Source type: scholarlyjournals; Object type: Article; Copyright: GeoRef in Process, Copyright 2011, American Geosciences Institute. After editing and indexing, this record will be added to Georef.; CSAUnique: 570969-5; AccNum: 570969-5; ISSN: 1000-2383; Peer Reviewed: true ER -