白云深水区块体搬运沉积体系与水合物分解的相关性研究

Study of correlationship between mass transport deposits and the dissociation of gas hydrate in Baiyun deepwater area

块体搬运沉积体系(MTDs)作为一种在重力作用下发育的深水沉积体系,在全球大陆边缘广泛分布。鉴于其重要的学术意义和工程意义,近年来成为国内外学者关注的热点。利用南海北部珠江口盆地白云深水区海底多波束地形地貌资料和高分辨率地震反射资料,识别了白云深水区大型块体搬运沉积体系,其分布面积逾10000km2,具有典型块体搬运的结构单元和沉积构造特征,对其开展研究具有重要的理论意义和应用价值。为了进一步探讨MTDs与天然气水合物分解的相关性,分析了水合物的分解机理及其对海底沉积地层的强度产生的影响。建立了研究区海底地质力学模型,并采用极限平衡法对海底斜坡是否稳定做出评价。研究结果表明,白云凹陷北侧的海底峡谷为南侧大型MTDs的发育提供了充足的物源保障,区内水合物的分解对海底MTDs的发育具有诱发作用。

Mass transport deposits(MTDs) are one kind of deepwater sedimentary system driven by gravitation,which widely distributed in the global continental margins.Considering the important academic significance and engineering meaning,MTDs have become a focus of concern by scholars.Based on the multi-beam bathymetric data and high resolution seismic data in Baiyun sag,Pearl river basin,north of South China Sea,we identified large scale MTDs covering over 10,000km2 on the seabed.As Baiyun large scale MTDs with typical structural units,sedimentary and structural features,the research and analysis are of theoretical and applied value.In order to clear further the correlationship between mass transport deposits and the dissociation of gas hydrate,we analysed mechanisms of gas hydrate dissociation and effects on the strength change of submarine sediments.We established geomechanical model and estimated the stability of submarine slope through ultimate equilibrium method.The results show that canyons on the north of Baiyun sag ensure abundant sediment supply while the dissociation of gas hydrate induced the development of MTDs.