西非下刚果盆地海底麻坑特征及与盐岩活动的关系

Seabed pockmarks and their bearing on salt movement in Lower Congo Basin of western African

以高精度三维地震资料为基础,系统研究了下刚果盆地深海麻坑的形态特征及其与盐构造活动的关系。研究发现,该区海底麻坑几何形态主要有平面上圆形、剖面上深V型和平面上条形、剖面浅U型两大类,并分别分布于由浅水到深水的东西两个不同区带。进一步分析认为,该区麻坑的发育、分布与下部盐岩构造活动有密切关系,东部盐岩底辟构造带上发育由压扭应力作用下的海底地层挤压破裂并诱发流体高压喷射而形成的深V型麻坑,西部盐岩挤压逆冲构造带上发育由拉张应力作用下的沿盐岩体边界上海底地层拉张破裂而形成的U型麻坑。该区产生麻坑的海底地层破裂和流体高压均由下部盐岩构造活动所控制。

Based on high resolution 3 D seismic data,the characteristics of seabed pockmarks and their relationship with salt movement are systematically studied in this paper.There are two types of pockmarks,i.e.the deep V-shaped and the shallow U-shaped pockmarks,distributed in the east and west of the study area respectively.The distribution pattern of pockmarks depends upon underlying salt movement.The V-type pockmark is resulted indirectly from the compressive stress on seabed caused by salt diapers in the east area,while the U-type pockmark resulted indirectly from the extensional stress on seabed caused by salt canopy in the west area.Both the pockmarks are formed by seabed rupturing and erupting of high pressure strata water directly triggered by underlying salt structure movements.