Benthic foraminifera and bottom water evolution in the middle-southern Okinawa Trough during the last 18 ka |
| |
| Authors: | Email author" target="_blank">Li?Tiegang?Email author Rong?Xiang Rongtao?Sun Qiyuan?Cao |
| |
| Institution: | 1. Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
2. Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;College of Geosciences, Ocean University of China, Qingdao 266003, China |
| |
| Abstract: | 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 based on the quantitative census data of benthic foraminiferal fauna, together
with planktonic foraminiferal oxygen and carbon isotope, AMS14C dating, and the previous results achieved in the southern Okinawa Trough. The result shows that the benthic fauna was dominated
by Bulimina aculeata (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-glacial period after 9.2 cal. ka BP. The benthic foraminifera accumulation rate
(BFAR), paleoproductivity estimates and benthic foraminiferal assemblage conformably indicate that surface water paleoproductivity
and organic matter flux during the glaciation-deglaciation were higher than those of the post-glacial period in the middle-southern
Okinawa Trough, and gradually enhanced from the southern to the central Okinawa Trough during the glaciation-deglaciation,
which could be caused by the discrepancy of the terrigenous nutrients supply. High abundances of E. exigua, an indicator of pulsed organic matter input, after 9.2 cal. ka BP may indicate that the intensity of seasonally 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 in the 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-glacial
period 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 evident influence on the deep-water of the middle-southern Okinawa
Trough. Additionally, the variations in agglutinated benthic foraminiferal abundance and other carbonate dissolution proxies
indicate that carbonate dissolution gradually increased since the last 18 ka in the Okinawa Trough and rapidly enhanced at
9.2 cal. ka BP. The modern shallow carbonate lysocline could form at 3 cal. ka BP. |
| |
| Keywords: | benthic foraminifera the Okinawa Trough deep-water evolution |
| 本文献已被 CNKI 万方数据 SpringerLink 等数据库收录！ |
|
