鄂尔多斯盆地上古生界层序地层划分及演化

Sequence Division and Evolution of Upper Paleozoic in the Ordos Basin

利用露头、岩心、钻测井、地震资料,进行层序界面识别,建立鄂尔多斯盆地上古生界的层序地层格架,将其划分为5个二级层序、19个三级层序,并分析了层序的体系域构成及其基本特征。二级层序对应于特定的构造—沉积演化阶段:SS1—裂陷海湾与局限海共存阶段;SS2—统一陆表海阶段;SS3—近海平原沼泽、三角洲阶段;SS4—近海湖盆沉积阶段;SS5—内陆红色碎屑岩沉积阶段。建立了三种层序格架中的沉积砂体发育模式(包括太原组的海陆交互相潮坪—三角洲模式,山西组的近海平原沼泽—三角洲模式、下石盒子组的辫状河—辫状三角洲模式),并对层序格架中的主要砂体类型及分布进行分析预测。

Through integrated studies of outcrops, cores, drilling, well logging and seismic data, sequence interfaces are identified and sequence framework of the Upper Palaeozoic of Ordos Basin is established. The Upper Paleozoic of Ordos Basin can be divided into 5 second order sequences and 19 third order sequences, the basic characteristics and constitution of system tracts of which are also analyzed. Each second order sequence corresponds to specific tectonicdeposition evolution stages ： SS1 corresponds to rift bay and restricted epiric sea coexistence stage; SS2 corresponds to unified epicontinental sea stage; SS3 corresponds to offshore plain swamp-deha stage; SS4 corresponds to seaside lake basin deposition stage; SS5 corresponds to inland red clastic rock deposition stage. Three models are established for the development of sedimentary sandbodies in sequence frameworks （ including tidal flat-delta model of marine-continental alternative deposition in Taiyuan Formation, offshore plain swamp-deha model in Shanxi Formation and braided river-braided delta model in lower Shihezi Formation）. The main sandbody types and their distribution in sequence frameworks are analyzed and predicated.