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新疆伊宁盆地早侏罗世为一内陆坳陷盆地 ,沉积了一套冲积—湖泊环境下的碎屑岩沉积体 ,其中三工河期盆地周缘广泛发育辫状河进积到湖泊中而形成的辫状河三角洲。三角洲三层结构清楚 ,由下而上出现前辫状河三角洲亚相、辫状河三角洲前缘亚相及辫状河三角洲平原亚相 ,呈明显的进积层序。辫状河三角洲特征显著 ,明显有别于其它类型的三角洲 ,可见到九种特征各异的微相。辫状河三角洲的主体是由含砾砂岩及中、粗粒砂岩组成的辫状河道砂坝及水下分流砂坝 ,单一砂坝呈下粗上细的透镜状 ,透镜体最大厚度在 0 .5～ 3m不等。垂向上许多砂坝透镜体相互叠置而成巨厚砂体。三角洲中交错层理丰富 ,其中尤以水道砂坝侧向迁移加积而形成的侧积交错层异常发育为标志。
The Early Jurassic in the Yün basin of Xinjiang is an inland depression basin and a set of clastic sedimentary bodies deposited in the alluvial-lacustrine environment, in which the braided river is extensively developed into lakes in the periphery of the Sangong Hechi Basin Braided river delta formed. The three-layer structure of the delta is clear. From the bottom up, the braided river delta subfacies, the braided river delta front subfacies and the braided river delta plain subfacies show obvious accretion sequence. Braided river delta features are significantly different from other types of delta, showing nine distinct microfacies. The main body of the braided delta is a braided channel sand bar and a subaqueous distributary bar dam which are composed of gravel sandstones and medium and coarse sandstones. The single sand bar is lenticular in shape with fine upper and thinnest, and the maximum thickness of the lens body is zero. 5 ~ 3m range. Many sand-dam lens bodies vertically overlap each other to form a giant sand body. In the Delta, there are richly stratified strata, of which the abnormal development of the side-fold strata formed by the lateral migration and accretion of the channel sand bar is especially marked.