鄂尔多斯盆地东部边界的构造学分析:以石楼北地区为例

Tectonic analysis of the eastern boundary of Ordos Basin:a case study of northern region of Shilou area

通常认为鄂尔多斯东部边界带由晋西挠褶带和离石断裂组成,但这一边界为残余边界,并非原始的沉积边界。文中以石楼北区域为例,过该区域构建了1条鄂尔多斯盆地东部盆-山尺度的区域地质大剖面,运用2D-Move软件进行构造演化的反演与正演模拟,对其构造变形进行定量分析,并根据研究结果对鄂尔多斯盆地东部边界进行重新厘定。研究认为:(1)石楼北地区在加里东晚期受深部基底断裂活动影响,奥陶系膏盐岩层中形成盐滑脱褶皱,之后沉积石炭系—白垩系,至燕山期受到东西向的挤压应力,地层整体发生掀斜,最终在新生代吕梁隆起加速隆升,遭受差异风化剥蚀形成现今构造格局。(2)构建的区域地质大剖面现今长度为263.76 km,海拔最高可达2000 m,从加里东晚期到白垩纪地层缩短量为3.14 km,缩短率为1.18%,地层抬升高度为3.82 km。(3)根据地层、构造、演化特征对燕山运动期鄂尔多斯盆地的东部边界进行重新厘定,认为东部边界应向东延伸至吕梁隆起东侧。该成果可为鄂尔多斯盆地东缘范围、构造变形研究以及晋西挠褶带煤层气勘探开发提供参考与新思路。

The boundary belt of the eastern margin of Ordos Basin is believed to be composed of the Jinxi flexural fold belt and Lishi fault,but this boundary is a residual boundary and not the original sedimentary boundary.Taking the northern region of Shillou as an example,a regional geological profile was constructed at the basin-mountain scale in the eastern part of the Ordos Basin.The 2D-Move software was used for inversion and forward simulation of tectonic evolution,and quantitative analysis of structural deformation was conducted.Based on theseresults,the eastern boundary of the Ordos Basin was redefined.(1)In the late Caledonian period,the northern part of the Shiliouarea was affected by deep basement fault activity,and salt detachment folds were formed in the Ordovician gypsum salt rock layers,followed by the deposition of the Carboniferous,Permian,Triassic,Jurassic and Cretaceous systems.During the Yanshanian,the strata were subjected to E-W compressive stress,causing the overall strata to tilt.In the Cenozoic Lvliang uplift,they accelerated and underwent differential weathering and erosion,forming the present tectonic pattern.(2)The present length of the regional geological profile is 263.76 km,with an altitude of up to 2000 m.The shortening of strata from the late Caledonian to the Cretaceous sedimentary period is 3.14 km,with a shortening rate of 1.18%.The elevation of the formation uplift is 3.82 km.(3)Based on the characteristics of stratigraphy,structure,and evolution,the eastern boundary of the Ordos Basin during the Yanshan Movement is redefined,and it is believed that the eastern boundary should extend easternward to the east side of Lvliang Uplift.This paper can provide a reference and new ideas for studying the eastern margin of the Ordos Basin,structural deformation,and coalbed methane exploration and development in the western Shanxi flexural fold belt.