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冲绳海槽西南端作为黑潮路径下一个高速沉降中心一直受到地球科学界的关注.在实验室对2005年5月中法合作航次在冲绳海槽南部取得的原状无搅动的深海沉积柱状样MD05-2908岩芯进行了沉积通量与沉积特征分析,并对物质来源进行了探讨.样品在分割后分别进行了AMS14C分析、粗颗粒组分(>63μm)的提取及含水量的测定.结果显示,该34m长柱状岩芯底部年龄仅为6.8kaBP,其平均线性沉积速率达到了5m/ka,揭示出冲绳海槽西南端自中全新世以来具有非常高的沉积速率;结合含水量数据,其沉积通量也与研究区现代沉积通量相符合.根据17个AMS14C数据识别出了5期快速沉积事件(6790～6600,5690～5600,4820～4720,1090～880以及260～190aBP),其持续时间为70～200a不等,快速沉积期间其最大沉积速率可以达到21.2m/ka.通过与相邻的ODP1202站对比后发现,研究区沉积物皆以细颗粒的黏土与粉砂质为主,粗颗粒组分所占比重总体不到5%.台湾岛东北部丰富的降雨量使得宜兰境内的兰阳溪可以携带大量陆源物质进入宜兰陆架并进一步向冲绳海槽输运,成为研究区重要的物质来源.这5期快速堆积事件主要是与气候变化引起的区域性降水增加有关,另外岩芯也记录到由地震、风暴等因素引起的小时间尺度的沉积增强事件.由地震、风暴等引起的侧向与底层传输使得研究区的沉积环境更为复杂,但同时也为冲绳海槽提供了丰富的物质供应.
The southwestern tip of the Okinawa Trough, as the next high-speed settlement center under the Kuroshio Path, has drawn the attention of the Earth science community. In the laboratory, the undisturbed deep-sea sedimentary column-like MD05 made in the Sino-French cooperative voyage in the southern Okinawa Trough in May 2005 -2908 core sediment flux and sedimentary characteristics of the analysis of the source of the material were discussed after the sample was separated AMS14C analysis, the coarse particle fraction (> 63μm) extraction and determination of water content results show . The bottom of the 34m long columnar core is only 6.8kaBP in age with an average linear sedimentation rate of 5m / ka. It shows that the sedimentary rate is very high at the southwestern tip of the Okinawa Trough since Mid-Holocene. Combined with the water content data, Sediment flux is also consistent with modern depositional fluxes in the study area. Five rapid sedimentary events (6790-6600, 5690-5600, 4820-4720, 1090-850, and 260-190aBP) were identified based on 17 AMS14C data, With a duration of 70 ~ 200a, the maximum deposition rate can reach 21.2m / ka during rapid deposition.Comparing with the adjacent ODP1202 station, it is found that the sediments in the study area are mainly fine-grained clay and silty sand ,Crude The proportion of particulate fraction is less than 5% in total.The abundant rainfall in northeastern Taiwan Island makes LanYangxi in Ilan carry a large amount of terrestrial material into Ilan shelf and further transport it to the Okinawa Trough, making it an important material in the study area The five rapid accumulation events are mainly related to the increase of regional precipitation caused by climate change, and the core also records the small-scale sedimentation enhancement events caused by factors such as earthquakes and storms caused by earthquakes and storms Lateral and subtropic transport makes the depositional environment in the study area more complicated, but it also provides abundant supplies of material for the Okinawa Trough.