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Late Quaternary changes of warm current system in the northwestern Pacific Ocean from the equator to the Ryukyu Island Arc region.

西北太平洋赤道至琉球岛弧区暖流系统晚第四纪变化.

基本信息

批准号：
05455019
负责人：
UJIIE Hiroshi
金额：
$ 3.52万
依托单位：
UNIVERSITY OF THE RYUKYUS
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1995
项目状态：
已结题

项目摘要

1) Variable analyzes of three piston cores taken from the Ryukyu Trench slope area revealed that down-core change of Florisphaera profunda, a calcareous nannoplankton, indicate sea-water turbidity (=primary production) change during the late Quaternary. 2) Prototypes of the Okinawa Trough and the Ryukyu Island Arc appeared during the Middle Pleistocene. Afterward, the Kuroshio Current has entered into the Trough. 3)Benthic foraminiferal changes in two cores taken from the south of Ishigaki Island reflected bottom water changes during the past 210 ka. 4) To more precisely understand the faunal change through sedimentary sequences, the detailed and multivariate analyzes of Recent benthic foraminiferal assemblages were completed for a coral reef area (62 sediment samples used) and for the batyal environment (56 real surface samples used). 5) To know the relationship between sedimentary materials carried by the Kuroshio Current and by Asiatic continental rivers during the post-glacial period, nine cores were collected from the Okinawa Trough and investigated by variable methods.Only a terrigenous plant fragment supply indicate steady decrease toward Recent according to the down-core changes of organic carbon/nitrogen ratio and lignin-phenol content. This means the gradual disappearance of a land-bridge connected Taiwan through Okinawa to Amami-ohshima during the last glacial episode. This disappearance mode was supported by a upward increase of pulleniatina group, planktonic foraminifera characteristic of the Kuroshio Current. This group suddenly disappeared during a few hundred years at - 3,800 yr.BP., suggesting a temporary formation of the above land-bridge or of similar situation.

1)对琉球海沟斜坡区3个活塞柱状样的变量分析表明，深部浮游植物--深部浮游植物的向下变化指示了第四纪晚期海水浊度(=初级产品)的变化。2)冲绳海槽和琉球岛弧的原型出现在中更新世。之后，黑潮进入低谷。3)石垣岛南部两个岩心的底栖有孔虫变化反映了过去210ka以来底水的变化。4)为了通过沉积序列更准确地了解动物群的变化，对珊瑚礁地区(使用62个沉积物样品)和巴塔尔环境(使用56个真实表层样品)的现代底栖有孔虫组合进行了详细的多变量分析。5)为了了解冰后期黑潮与亚洲大陆河流携带的沉积物质之间的关系，在冲绳海槽采集了9个岩心，并用不同的方法进行了研究，根据岩心下部有机碳/氮比和木质素-苯酚含量的变化，只有陆源植物碎屑的供应在最近呈现稳定减少的趋势。这意味着，在上一次冰川事件中，一座连接台湾经冲绳到大岛的陆桥逐渐消失。这种消失模式得到了以黑潮特征的浮游有孔虫Pulleniatina群的向上增加的支持。这一群在-3800年前的几百年间突然消失，表明上述大陆桥的临时形成或类似情况。