东非鲁武马盆地海底水道—朵体体系粗粒浊流沉积物波特征及主控因素

Characteristics and Controlling Factors of Coarse-Grained Turbidite Sediment Waves in Submarine Channel-Lobe System of the Ruvuma Basin,East Africa

海底水道—朵体体系内粗粒沉积物波的研究可以深化浊流搬运过程的认识。利用先进的地球物理成像技术,通过地震地貌分析,对东非鲁武马盆地海底水道—朵体体系内这种后期易被改造的特殊沉积体进行识别和解释,结合粗粒沉积物波的形态、尺度、移动方式、厚度变化、平面分布等特征,探讨其成因和影响因素。鲁武马盆地近海底水道—朵体体系内的粗粒浊流沉积物波具有多变的地貌和逆行砂丘的底形。水道内粗粒沉积物波规模较小,分布范围局限;水道—朵体过渡带的粗粒沉积物波规模大,波高约45~110 m,波长可达一千余米,总体规模大于其他地区已识别出的粗粒深水沉积物波。构造活动、超临界流产生的水跃作用、地形地貌的变化以及底流作用是鲁武马盆地粗粒浊流沉积物波形成的主控因素。

Research of coarse-grained turbidite sediment waves in submarine channel-lobe system can deepen the geological understanding of deep-water transporting process. The special sedimentary bodies,which are easy to be reworked later found in a submarine channel-lobe system of the Ruvuma Basin,East Africa,are identified and explained through the use of advanced geophysical imaging technologies and the analysis of the seismic relief. The causes and influencing factors are discussed by describing the shape,scale,migration style,thickness variations,and distribution of the coarse sediment waves. The coarse-grained turbidite sediment waves which are found in submarine channel-lobe system in Ruvuma Basin have various morphology and antidune bedforms. The small scale sediment waves with limited extension are mainly developed in the channel. While,large inclusive sediment waves distributes in channel-lobe transition zone,wave heights are in the region of 45 - 110 m,and wavelengths are up to over one thousand meters. The overall scale is larger than the coarse-grained sediment waves that have been identified in worldwide other regions. The coarse-grained turbidite sediments waves in the Ruvuma Basin were mainly controlled by tectonic deformation,hydraulic jumps of the supercritical flow,topography and bottom current activities.