珠江口盆地白云凹陷陆坡限制型海底峡谷群成因机制探讨

发布时间：2018-05-03 04:08

本文选题：陆坡限制型海底峡谷群 + 沉积物供给　；参考：《沉积学报》2016年05期

【摘要】：珠江口盆地白云凹陷北部陆坡发育着17条近似NNW—SSE走向的海底峡谷,构成了区域内的陆坡限制型海底峡谷群。基于研究区内高密度覆盖的2D地震资料,通过外部形态、内部结构等反射特征的描述和刻画,建立了第四纪以来的高精度层序地层格架,将沉积充填序列划分为三个体系域,即低位体系域(LST)、海侵体系域(TST)和高位体系域(HST)。根据陆坡进积特征、垂向地层叠加样式、侵蚀特征变化、连续性强振幅同相轴的识别和空间追踪,将高位体系域进一步划分为两个沉积旋回单元,HST-I和HST-II。研究表明,白云凹陷陆坡限制型海底峡谷群发育在高位体系域晚期沉积旋回(HST-II)中。在此基础上,分别讨论了沉积物供给、沉积物失稳作用、限制型地形和流体渗漏作用对峡谷群形成和演化的影响。第四纪以来珠江水系携带的大量沉积物经由陆架进入到陆坡区域,为海底峡谷群的发育和演化提供了充足的沉积物来源。在第四纪高位体系域早期水道形成的限制型"负地形"基础上,大量的沉积物在沿着陆坡坡降方向自北向南的输送过程中发生向下的侵蚀、沉积物失稳,导致了陆坡限制型海底峡谷群的发育。研究区内广泛分布的气烟囱构造,暗示了含气流体的垂向运移和渗漏,可能促进了海底峡谷群的进一步演化。
[Abstract]:There are 17 submarine canyons similar to NNW-SSE strike on the northern slope of Baiyun Sag in the Pearl River mouth basin, which form the continental slope restricted submarine canyon group. Based on 2D seismic data covered by high density in the study area, the high precision sequence stratigraphic framework since Quaternary is established by describing and characterizing the reflection characteristics such as external morphology and internal structure, and the sedimentary filling sequence is divided into three system tracts. They are LSTL, TST and HST. According to the characteristics of continental slope precession, vertical stratigraphic superposition style, erosion feature change, identification and spatial tracing of continuous strong amplitude cophase axis, the high position system tract is further divided into two sedimentary cycle units, HST-I and HST-II. The results show that the restricted submarine canyons in Baiyun Sag are developed in the late stage of high system tract (HST-II). On this basis, the effects of sediment supply, sediment instability, restricted topography and fluid leakage on the formation and evolution of canyons are discussed respectively. Since the Quaternary, a large number of sediments carried by the Pearl River system have entered the continental slope through the continental shelf, which provides sufficient sediment sources for the development and evolution of submarine canyons. On the basis of the restricted "negative topography" formed in the early Quaternary high system tracts, a large number of sediments have been eroded downwards from north to south along the slope of the continental slope, resulting in instability of the sediments. It leads to the development of restricted submarine canyons on the continental slope. The widely distributed gas chimney structure in the study area implies the vertical migration and leakage of gas-bearing fluids and may promote the further evolution of submarine canyons.
【作者单位】：中国科学院天然气水合物重点实验室;中国科学院广州天然气水合物研究中心;广州海洋地质调查局;
【基金】：国家自然科学基金项目(41576048) 油气藏地质及开发工程国家重点实验室(成都理工大学)开放基金项目(PLC201402) 中科院可再生能源重点实验室开放基金项目(y507j61001) 中国科学院青年创新促进会(2016312) 中国石油—中国科学院科技合作项目(2015A-4813)~~
【分类号】：P618.13;P736

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