西非Rio Muni盆地深水水道特征与成因

摘要

深水水道沉积构型及其演化一直是沉积学界研究的热点。基于Rio Muni盆地深水区470 km2高分辨率三维地震数据，在精细地震解释的基础上，对研究区发育的深水水道的沉积构型、演化进行探讨。主要取得4点认识：（1）深水水道的弯曲度主要受控于物源供给和海底坡度，研究区发育弯曲水道、顺直水道2类深水水道；（2）起源于陆架边缘的深水水道，物源供给相对充分，弯曲度高，其剖面往往不对称，水道壁发育滑塌或阶地，垂向演化具有侧向迁移特征，发育废弃水道；（3）而起源于中上陆坡的深水水道，其弯曲度低，剖面具有U形特征，水道壁光滑无滑塌或阶地，主要以垂向加积为主。由于物源供给不足，顺直水道逐渐被深海泥质披覆沉积充填；（4）同一条深水水道，由上陆坡向下陆坡，随着海底坡度的降低，其弯曲度呈增大趋势。%Study on the sedimentary architecture and evolution of deep-water channel is one of the most interest-ing fields in sedimentology.Based on high-resolution three-dimensional seismic data sets which cover 470 km2 , the sedimentary architecture and evolution of submarine channels are discussed in deep-water Rio Muni basin. Four conclusions can be drawn in this paper:(1 )The sinuosity of submarine channels are main dominated by the sediment supply and the seafloor gradient.Two main types of submarine channels:straight channels and sin-uous channels have been recognized in the study area.(2 )The high sinuosity submarine channel indents the shelf margin and is linked to areas of high coarse-grained sediment supply.Their mophologies often show asym-metrical cross-sections,terraces,slumped edges,lateral migration and abandoned channel.(3 )The submarine channels heading on middle or upper continental slopes have a low sinuosity.Straight channels’ morphologies commonly include a U-shaped cross-section,smooth walls lacking slumps or terraces,aggradational evolution. The straight channels with low sediment supply were draped by hemipelagic deposition.(4)The sinuosity of a submarine increases as the shelf gradient decreases.