Tanganyika盆地南部断裂特征及其对沉积的控制作用

东非裂谷系盆地近年来相继取得油气发现,Tanganyika盆地与已发现含油气盆地的构造及沉积特征相似,具有较大的勘探潜力。文中利用地震资料开展构造解释,对盆地断裂系统的成因及特征、调节带的类型及对沉积的控制作用开展了研究。结果表明:研究区主要受新生代裂谷拉伸作用及元古代克拉通-古缝合线影响,发育以NW—SE向为主的断裂系统;研究区断层类型以非旋转正断层和走滑断层为主,根据规模可划分为3级;受断层控制,研究区表现为“一缓一洼一剪切”的构造格局。根据断层倾向和叠覆关系,在研究区共识别出5类调节带类型,对沉积起到不同的控制作用。其中,同向接近型调节带控制了扇三角洲及滑塌沉积的发育位置,同向叠覆型调节带控制了轴向河流沉积的发育范围,对向叠覆型调节带控制了洼陷中心轴向河流三角洲及浊流沉积体系的发育范围。

Fracture characteristics and its control on sedimentation in south of Tanganyika basin

In recent years,oil and gas discoveries had been achieved successively in East Africa Rift System.Tanganyika basin is similar in structure and sedimentary characteristics with these petroliferous basins,and has great exploration potential.Based on seismic data,the structural interpretation was carried out,and the origin and characteristics of faults system,accommodation zone types and its controls on the sedimentation were studied.The results show that the study area was affected by the Cenozoic rifting tension and Proterozoic Craton-ancient suture,and developed NW—SE-oriented fault system.The faults systems,mainly non-rotating normal faults and strike-slip faults,were classified into three levels by size.Controlled by faults,the tectonic framework of study area includes a gentle slope belt,a sag subsidence center and a shear zone.Based on faults tendency and overlapping relation,five types accommodation zones were summarized,which control sedimentation in different ways.Synthetic approaching accommodation zones control development of fan delta and collapse deposits,synthetic overlapping accommodation zones control development of fluvial deposits in the axial direction,and antithetic overlapping accommodation zones control fluvial delta and turbidity current sedimentary system in the axial direction in sag center.