台湾峡谷HD133和HD77柱状样的沉积构成和发育背景

分别对南海东北部台湾峡谷内水深3 280 m的HD133和峡谷外水深3 378 m的HD77重力活塞柱状样进行了沉积物粒度、古生物和碳酸钙含量分析，利用AMS14C同位素测年和沉积速率初步认定是属于MIS3a以来的沉积。按沉积物粒度和碳酸钙含量可将两支柱状样划分为3套沉积层段:上部层段1和下部层段3均以粉砂质黏土为主，夹薄层粉砂，深水底栖有孔虫含量高，碳酸钙低于10%，代表受重力流作用较弱的正常深海沉积；中部层段2发育一套以中-细粒为主的厚砂层，含大量浅水底栖有孔虫，碳酸钙含量可高达60%，AMS14C测年出现倒置现象，表明主要为浅水重力流沉积。柱状样的沉积构成响应同期海平面变化，特别表现在深水砂层沉积的两大控制因素:在时间上，低海平面时期大量浅水和陆源碎屑物质直接输送到陆坡之下的深水区，形成富砂的层段2；在空间上，峡谷水道是重力流的物质输送通道，地形优势使得重力流携带物优先在水道中发生沉积，造成HD133柱的含砂量明显高于HD77柱状样。

Depositional Elements and Settings of HD133 and HD77 Cores in the Taiwan Canyon

Located within and outside the Taiwan Canyon in the northeastern South China Sea, with the water depths of 3 280 m and 3 378 m separately, two sediment cores HD133 and HD77 are carefully investigated through analysis of grain size, paleontology and calcium carbonate content. In combination with the sea level history during the LGM (Last Glacial Maximum), the sedimentary elements and responses are discussed. Based on sediment grain size and carbonate content, the two cores can be subdivided into three sediment layers. The layer 2 is consisted of medium to fine grained thick bedded sands which is interpreted to be terrigenous gravity flow deposits, evidenced by the abundant shallow water benthic foraminifera, the carbonate content reaching 60% and the internal chaos of AMS14C isotope dating. Layers 1 and 3 are dominated by silt mud with silt interbeds, with few shallow water benthic foraminifera and carbonate content less than 10%, indicating a decrease of sediment gravity flows. The controlling factors for the deep water sands within these two sediment cores are as the following: temporally, terrigenous sediments are directly delivered into the deep water settings, forming sand rich deposits layer 2; spatially, submarine canyons are the conduits for terrigenous gravity flow, making the deposition occur firstly within the canyon. Thus, HD133 is richer in sand than HD77. 