基于下寺湾地区的区域地质、沉积相、测井、钻井和岩心资料，以Cross 高分辨率层序地层学理论 及其方法为指导，采用多级旋回层序划分方案，结合测井相分析技术，将研究区长8 段划分为中期、短期和超短期3 个级次的基准面旋回层序。各级次基准面旋回又可进一步分为向上“变深”的非对称型、向上 “变浅”的非对称型和对称型3 种结构类型。该文重点论述了超短期基准面旋回层序沉积背景、叠加式样和沉积动力学过程， 并以短期基准面旋回作为等时地层对比单元， 建立了长8 段高分辨率地层-时间格架，为本区砂体纵、横向展布规律的认识及下一步勘探开发方案提供了理论依据。

Under the guide of Cross high resolution sequence stratigraphy theory, based on areal geology, sedimentary facies, well logging, well drilling and core data in Xiasiwan area, the multistage cyclic sequence division scheme and electrofacies analysis technology are adopted to divide the eighth member of Yanchang Formation intomid-term, shortterm and super-short-term base level cyclic sequences. Every base level cyclic sequence can be subdivided into asymmetric upward-deepening, asymmetric upward-shallowing and symmetric base level cycles. The depositional setting，superposition style and sedimentary dynamics process of the super-short-term base level cyclic sequence are emphatically discussed. Isochronous stratigraphic framework of the eighth member of Yanchang Formation is established by making the short-term base level cycle as isochronous stratigraphic unit. This study provides geologic foundation for the cognition of sand body distribution lawand the planning of exploration and development scheme.