摘要
A piston sediment core E017 from the middle-southern Okinawa Trough was investigated. A preliminary study of the deep-water evolution since 18 cal. ka BP was performed basedon the quantitative census data of benthic foraminiferal fauna, together with planktonic foraminiferal oxygen and carbon isotope, AMS14C dating, and the previous results achieved in thesouthern Okinawa Trough. The result shows that the benthic fauna was dominated by Buliminaaculeata (d′Orbigny), Uvigerina peregrina (Cushman), Hispid Uvigerina and Uvigerina dirupta(Todd) during the glaciation-deglaciation before 9.2 cal. ka BP, while Epistominella exigua(Brady), Pullenia bulloides (d′Orbigny), Cibicidoides hyalina (Hofker), Sphaeroidina bulloides(d’Orbigny) and Globocassidulina subglobosa (Brady) predominated the fauna in the post-glaciaperiod after 9.2 cal. ka BP. The benthic foraminifera accumulation rate (BFAR), paleoproductivityestimates and benthic foraminiferal assemblage conformably indicate that surface water paleoproductivity and organic matter flux during the glaciation-deglaciation were higher than those othe post-glacial period in the middle-southern Okinawa Trough, and gradually enhanced from thesouthern to the central Okinawa Trough during the glaciation-deglaciation, which could becaused by the discrepancy of the terrigenous nutrients supply. High abundances of E. exigua, anindicator of pulsed organic matter input, after 9.2 cal. ka BP may indicate that the intensity oseasonally riverine pulsed flux during the post-glacial period was stronger than that of the glaciation-deglaciation period, and the seasonal influx in the central trough might be stronger than inthe south. The temporal distributions of the typical species indicating bottom water oxygen content and ventilation condition show that the ventilation of the bottom water during the post-glaciaperiod is more active than the glaciation-deglaciation, which reflects that the evolution of the intermediate and deep waters of the northwestern Pacific during the last glaciation has no evideninfluence on the deep-water of the middle-southern Okinawa Trough. Additionally, the variationsin agglutinated benthic foraminiferal abundance and other carbonate dissolution proxies indicatethat carbonate dissolution gradually increased since the last 18 ka in the Okinawa Trough andrapidly enhanced at 9.2 cal. ka BP. The modern shallow carbonate lysocline could form at 3 calka BP.
A piston sediment core E017 from the middle-southern Okinawa Trough was investigated. A preliminary study of the deep-water evolution since 18 cal. ka BP was performed basedon the quantitative census data of benthic foraminiferal fauna, together with planktonic foraminiferal oxygen and carbon isotope, AMS14C dating, and the previous results achieved in thesouthern Okinawa Trough. The result shows that the benthic fauna was dominated by Buliminaaculeata (d′Orbigny), Uvigerina peregrina (Cushman), Hispid Uvigerina and Uvigerina dirupta(Todd) during the glaciation-deglaciation before 9.2 cal. ka BP, while Epistominella exigua(Brady), Pullenia bulloides (d′Orbigny), Cibicidoides hyalina (Hofker), Sphaeroidina bulloides(d'Orbigny) and Globocassidulina subglobosa (Brady) predominated the fauna in the post-glaciaperiod after 9.2 cal. ka BP. The benthic foraminifera accumulation rate (BFAR), paleoproductivityestimates and benthic foraminiferal assemblage conformably indicate that surface water paleoproductivity and organic matter flux during the glaciation-deglaciation were higher than those othe post-glacial period in the middle-southern Okinawa Trough, and gradually enhanced from thesouthern to the central Okinawa Trough during the glaciation-deglaciation, which could becaused by the discrepancy of the terrigenous nutrients supply. High abundances of E. exigua, anindicator of pulsed organic matter input, after 9.2 cal. ka BP may indicate that the intensity oseasonally riverine pulsed flux during the post-glacial period was stronger than that of the glaciation-deglaciation period, and the seasonal influx in the central trough might be stronger than inthe south. The temporal distributions of the typical species indicating bottom water oxygen content and ventilation condition show that the ventilation of the bottom water during the post-glaciaperiod is more active than the glaciation-deglaciation, which reflects that the evolution of the intermediate and deep waters of the northwestern Pacific during the last glaciation has no evideninfluence on the deep-water of the middle-southern Okinawa Trough. Additionally, the variationsin agglutinated benthic foraminiferal abundance and other carbonate dissolution proxies indicatethat carbonate dissolution gradually increased since the last 18 ka in the Okinawa Trough andrapidly enhanced at 9.2 cal. ka BP. The modern shallow carbonate lysocline could form at 3 calka BP.
基金
the CAS Pilot Project of the National Knowledge Innovation Program(Project No.KZCFX3-SW-220)
the National Natural Science Foundation of China(Grant Nos.40176019 , 90411014)
the National Major Fundamental Research and Development Project(Grant No.G20000467).
