海安凹陷安丰退积型辫状三角洲沉积模式及建筑结构分析

受晚白垩世仪征运动影响，苏北盆地拉张断陷沉积基准面上升，形成了比较完整的安丰退积型辫状三角洲沉积体系。平原亚相中的分流河道具有高度沟道化特征，具有辫状河道3个沉积单元结构的特点，前缘亚相中反韵律的河口坝、前三角洲亚相中水下滑塌重力流和浊流发育，纵向上与半深湖相伴生，总体表现为向上变细、逐渐萎缩的垂向序列。在沉积体系内，细分出11种建筑结构单元，平面上有2种拼合形式，剖面上有3种拼合形式。

Sedimentary mode and formational structure analysis in Anfeng retrograding type braided delta of Hai'an depression

Influenced by late Cretaceous Yizheng movement,Subei basin was extended and faulted,and then it depressed,the sedimentary base level rose,so the pretty perfect sedimentary system of retrograding type braided delta in Anfeng area is formed. The distributary channel in plain subfacies possesses much better channelized feature,3 sedimentary units in the braided channel are well developed and so do the inverted-layered river mouth bar in front subfacies and the underwater slump gravity flow & turbid flow in front delta subfacies.Vertically accompanied by hypabyssal lake facies and in a whole the sedimentary system displays such a vertical sequence: becoming thinner upward and gradually shrink.The system can be further divided into 11 kinds of formational structure units;2 kinds of combinations in horizon and 3 in cross section.