Sediment Transport by Unconfined Turbidity Currents: Aleutian Forearc, North Pacific Ocean

本项目重点研究浊流对弧前沉积物的运移。研究区位于北太平洋阿留申火山弧以南。本文将讨论两个重要的沉积现象：(1)无约束浊度流的上坡流动，以及(2)横向流入海沟与轴向流动之间的交错现象。上坡泥沙搬运是一个需要考虑的极其重要的过程，因为即使在没有大型侵蚀特征（即海底峡谷）的情况下，它也可以绕过水深障碍。需要三个独立的研究阶段以令人信服的细节记录弧前沉积物的搬运模式：(1)浊积砂碎屑矿物学的量化，并确定物源；(2)陆架砂碎屑矿物学定量及物源鉴定；(3)解释水深/地震数据，连同GLORIA声纳图像，作为绘制浊流所有潜在流动路径的一种手段。浊度流是负责将砂质碎屑输送到深海沉积环境的唯一最重要的物理过程。今后对浊度流的研究应集中在：(1)单个流动事件的物理特征和水动力演化；(2)浊积岩沉积在特定亚环境下的地层旋回性。后一个目标只有通过深海钻探才能实现。前一个目标将在一定程度上通过这项研究得到满足。

This project focuses on forearc sediment transport by turbidity currents. The study area is located south of the Aleutian volcanic arc, North Pacific Ocean. Two important sedimentologic phenomena will be addressed: (1) upslope flow of unconfined turbidity currents, and (2) interdigitation between transverse influx into the trench and axial flows. Upslope sediment transport is an extremely important process to consider because it allows bypassing of bathymetric obstructions even in the absence of large erosional features (i.e., submarine canyons). Three independent phases of research are required to document patterns of forearc sediment transport in convincing detail: (1) quantification of detrital mineralogy for turbidite sands, and identification of provenance; (2) quantification of detrital mineralogy for continental shelf sands, and identification of provenance; (3) interpretation of bathymetric/seismic data, together with GLORIA sonar images, as a means of charting all potential flow paths for turbidity currents. %%% Turbidity currents represent the single most important physical process responsible for transport of sandy epiclastic detritus into deep-marine depositional environments. Future research on turbidity currents should concentrate on: (1) the physical character and hydrodynamic evolution of individual flow events; and (2) the stratigraphic cyclicity of turbidite deposits within specific sub-environments of deposition. The latter goal will be satisfied only through deep ocean drilling. The former goal will be satisfied, in part, by this study.