孟加拉盆地东部褶皱带差异构造变形及成因

基于野外地质调查和地震资料分析,证实了孟加拉盆地东部褶皱带发育底部和中部两套滑脱层。底部滑脱层在整个褶皱带均发育,而中部滑脱层仅发育于北段—中段的陆上和陆架区,在中段的陆坡-洋盆区及南段则不发育。中部滑脱层的发育受古陆坡富泥沉积控制。北段—中段主要发育滑脱褶皱及被断层突破的滑脱褶皱,而南段主要发育泥底辟和泥火山构造。孟加拉盆地东部褶皱带滑脱层系及构造样式的差异变形特征主要受区域挤压作用、沉积作用以及地层流体超压等方面存在着差异的共同影响。

Differential Structural Deformation and Its Mechanism of Fold Belt in the Eastern Part of Bengal Basin

Based on the field observation and 2D seismic data interpretation, it is illustrated that the basal and intermediate detachment levels developed in NS-trending fold belt in the eastern part of Bengal Basin. The basal detachment level is developed below the whole fold belt, while the intermediate detachment level is only formed in the onshore and shelf area in the north-central segment of the fold belt. The analysis result shows that the intermediate detachment level is primarily controlled by the paleoslope, where mud-rich sediments were deposited, and detachment folds and faulted detachment folds are dominant in the north-central segment, while mud diapirs and mud volcanoes are dominant in the south segment. It is suggested that the differential décollement and structural style of the fold belt in eastern part of Bengal Basin is mainly controlled by the along-strike variations of tectonic shortening, sedimentary processes, and fluid overpressure.