琼东南盆地深水区浊流与块体搬运交互沉积演化过程及其控制因素

The study on turbidity flow deposits and mass transport deposits (MTDs) are important parts of studies about sediment gravity flows on the continental margin. In recent years, studies have found that deposition in deepwater in Qiongdongnan Basin has been greatly affected by interplay of turbidity flow deposits and MTDs of different direction, scale and stages. However, studies carried out recently are mainly focused on MTDs or turbidity flow deposits, and there is less research related to interplay of turbidity flow deposits and MTDs. Based on detailed description of lithology and characteristics of MTDs and turbidite in deepwater area in Qiongdongnan Basin since the Late Miocene, this project will indentify stages of turbidite as well as MTDs.Distribution of turbidity flow deposits and MTDs of different stages, scales and directions will be detailed indentified, which would help to analyze interplay processes of them. Combined with comprehensive analysis of controlling factors of gravity flows and geological background of the basin, controlling factors of interplay progresses of turbidity flow deposits and MTDs will be studied. The results will not only deepen the understanding of the deepwater depositional process, but also provide certain instruction and reference for the deepwater hydrocarbon exploration in the South China Sea.

浊流沉积和块体搬运沉积是深水重力流沉积研究的重要内容。近年来研究发现，琼东南盆地深水区受到不同方向、不同规模、不同期次浊流和块体搬运交互沉积作用的影响。目前的研究多针对以上某一种重力流沉积开展，而对于两者之间的交互沉积过程及其控制因素尚缺乏比较深入的认识。本项目以晚中新世以来盆地深水区发育的浊流和块体搬运沉积为研究对象，识别浊流和块体搬运沉积的钻井岩芯及地震反射特征，厘定深水区块体搬运和浊流沉积的发育期次；查明不同期次、不同规模和不同方向浊流和块体搬运沉积的空间耦合特征，进而分析浊流和块体搬运的交互沉积过程；通过重力流沉积控制因素的综合分析，结合盆地发育的地质背景，阐明浊流和块体搬运交互沉积过程的控制因素。课题研究成果不仅能够深化对深水沉积动力学过程的认识，同时也将为南海的深水油气勘探提供一定指导和借鉴。

浊流沉积和块体搬运沉积是深水重力流沉积研究的重要内容。近年来研究发现，琼东南盆地深水区受到不同方向、不同规模、不同期次块体搬运和浊流交互沉积作用的影响。目前的研究多针对以上某一种重力流沉积开展，而对于两者之间的交互沉积过程及其控制因素尚缺乏比较深入的认识。本项目通过晚中新世以来琼东南盆地深水区不同类型沉积物重力流的沉积演化过程分析，认为研究区内主要发育块体流沉积和浊流沉积两种沉积物重力流。其中，块体流沉积主要可分为9个期次，其中前三个期次主要发育于中央峡谷内，后6个期次发育于盆地中央凹陷区。浊流沉积在盆地中央峡谷内特征明显，主要可分为6期。浊流主要源自盆地西部，块体流主要源自盆地北部。中央峡谷内早期以浊流沉积主导，侵蚀作用强烈，在琼东南盆地中央形成大规模的海底峡谷；晚期块体流沉积比较发育，其对早期形成的峡谷具有明显的充填作用，同时，块体流沉积对早期浊流沉积形成的浊积扇体具有明显的侵蚀和限制作用。海平面升降与沉积物供给对于西部浊流沉积控制明显，进而控制了二者交互沉积过程。课题研究成果不仅能够深化对深水沉积动力学过程的认识，同时也将为南海的深水油气勘探提供一定指导和借鉴。