文村甲决口扇沉积

阵发性洪水决口是文村甲决口扇形成的主要因素。决口深潭和岗洼相间辫状水道断续定向延伸是其重要的地貌标志。沉积物以悬浮递交搬运为主。水道沉积具明显的二元结构；水道问沉积二元结构不明显,形成上部沉积物前者比后者细的特点。以大型冲刷充填和小型槽状交错、平行、沙纹、均匀层理为主要沉积构造。在粒度曲线上,Ⅰ类沉积物较粗,分选好,代表扇根扇中辫状水道下部沉积；Ⅱ类沉积物较细,分选较好,代表扇根扇中水道间下部沉积；Ⅲ类沉积物细,分选较差,代表扇缘沉积。并据此划分出了深潭、主体、边缘三个微相。

SEDIMENTS OF CREVASSE SPLAY IN WENCUNJIA

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.