深水重力流与底流交互作用研究进展

摘要

The turbidity and bottom currents are two basic flowing mechanisms in deep-water basins, and the study about interaction between them is the leading edge and weak point of present sedimentology. Bottom current and bottom-current-reworked deposits have special sedimentary structures such as truncated tops, double mud layers and traction origin beddings, and lenticular units, migrating sediment waves are typical characteristics of the drifts in seismic profiles. According to the research about the interplay of gravity and bottom currents, and the leading sedimentation mechanism in different geological periods, there are four different patterns of the interaction between the two currents; ① bottom current reforms prophase gravity flow deposits; ② the turbidite reworks the prophase bottom current sediment; ③ gravity flow and the bottom current dominate the sedimentation respectively in the same area, and ④ the turbidite and bottom current affect the sediments together. The relative sea level change, climate (glacial-interglacial) change, tectonic activity, topography and other factors control the interplay between the gravity flow and bottom current by means of affecting the relative strength of the two sedimentation mechanisms. The South China Sea has favorable geological conditions for the development of interaction between gravity flow and bottom current, and the one-way migrating canyons and sediment waves are excellent interaction geological products. Intensifying the observation of the present bottom currents means a lot To the bottom current framework construction in South China Sea.%重力流和底流是深水环境下的两大基本流动体制,对二者交互作用的研究是当前沉积学研究的前缘和薄弱环节.底流及底流改造沉积物在岩芯上具有上部侵蚀面、双泥层、牵引流成因的各种层理等识别标志；底流成因的漂积体在剖面上呈现透镜状单元、迁移性特征及波状发射等地震反射特征.本文通过综述重力流与底流交互作用的研究成果,认为依据某段地质时期内深水盆地中主导沉积机制的不同,将重力流与底流的交互作用分为以下4种表现形式:①底流对前期重力流沉积进行改造；②重力流对前期底流沉积进行改造；③重力流与底流交互主导同一地区的沉积以及④底流与重力流同时作用于沉积物.相对海平面变化、气候(冰期～间冰期)变化、构造活动、地形地貌等因素,主要通过影响重力流与底流机制的相对强度大小,控制深水重力流与底流交互作用的进行.中国南海具有重力流与底流交互沉积的优越地质条件,发育有单向迁移水道、沉积物波等特色沉积记录.加强现今海流观测,对于南海底流循环格架的建立意义重大.