江西赣江下游中支现代网状河流沉积

赣江下游中支网状河位于赣江现代三角洲平原上 ,它们具有重复分叉合并、快速加积、低坡降、低弯度等特点 ,其河道具有较高的侧向稳定性 ,并且发育天然堤、决口扇、废弃河道、河间漫滩、湖泊、沼泽和江心洲等地貌单元。网状河道的沉积物多以沙砾石和中细沙为主 ,概率累积曲线多为三段式 ,并以跳跃组分为主。砂体内部主要发育槽状交错层理。河道间其他地貌单元 (如河漫滩、湖泊和沼泽等 )以细粒沉积物为主。河口盆地的上升、三角洲地带水流的扩散、长江倒灌水流的顶托、坡降很低以及江心洲稳定等是赣江网状河形成的主要因素

MODERN ANASTOMOSED FLUVIAL DEPOSITS OF THE MIDDLE TRIBUTARY OF THE LOWER GANJIANG RIVER IN JIANGXI PROVINCE

Anastomosing stream is distinct from the well|known meandering and braided river. The aim of studying modern anastomosing river is to recognize the regularity of sand body deposits and future regularity of oil and gas exploration. Ganjiang anastomosing river systems are in the Ganjiang modern deltaplain. They are multi|channel systems showing high aggradation rates, low gradients, low|curvature and channel with high stability. Channels, natural levees, crevasse|splay, abandoned channels, floodplain, lakes, marshes and river islands are important morphological and sedimentary units. Anastomosing channel filling sediments are mainly composed of pebbly sands and medium to fine sands. Grain|size probability cumulative curve of channel filling deposition is composed of three segments, dominated by saltation. Internal channel sandbody mainly consists of trough cross|strata. The other morphological units (floodplain, lakes, marshes) are mainly composed of fine grained sediments. A rising river mouth basin, current spread in delta plain, blockage of encroached current from Yangtze river, very low gradients and stable river island have caused the development of Ganjiang anastomosing river system.