关键词: 决口扇, 识别标志, 沉积构造, 粒度特征, 沉积模式

Abstract:

Intermittent flood crevasse is the main factor in the formation to Wencunjia crevasplayi adeep crevasse pond and the directional extansion of braided channels passing by hills and holows is the important geomorphic feature of the crevasse splay.The sediments of the splay are primarily graded-suspension transported.Sediments in water channels hawe distinct binary texture,but the binary texture of the sediments between the channels are not clear.This has resulted in fine sediments of the former than the later in the upper parts. The maim sedimentary structures include large scale of wash-filling bedding,trough cross bedding,Parallel bedding,sand ripple,homogeneous bedding.As for its grain size curves,type-Ⅰ is usually coarse and well-sorted, representing sediments deposted in lower parts of braided channels in the root and central parts of the splay;type-Ⅱ is relatively fine and better sorted, representing sediments deposited in the lower parts of the root and central sections of the splay between the channels,type-Ⅲ is fine but poor sorted.representing sediments in.splay margin. In consideration to the above mentioned,three sub factes such as deep pond,main body and margin subfacies have been subdivided.