鄂尔多斯盆地西北部早-中侏罗世延安期沉积边界恢复

Restoration of the Sedimentary Boundary of the Yan′an Period of Early-Middle Jurassic,the Northwest of Ordos Basin

从鄂尔多斯盆地西北部及其邻区残存的沉积建造、现今构造格局出发,在大量野外露头观测、钻井资料分析和实验测试的基础上,通过对该盆地西北部(贺兰山、桌子山和狼山地区)残留延安期及对应地层进行地层对比、边缘相分析、区域构造演化和构造环境分析,指出贺兰山及其东侧的银川盆地,在早-中侏罗世延安期属相对稳定的沉积环境,为鄂尔多斯盆地的一部分;狼山地区的对应地层与鄂尔多斯盆地西北部属于不同的沉积环境;认为早-中侏罗世延安期盆地西北缘边界大致在贺兰山西缘断裂至桌子山一线。

The restoration of the sedimentary boundary of Ordos Basin in the Yan’an period of Jurassic is a key problem of restoration for its original basin.The sedimentary boundary has not been concluded due to different kind of structural transformation.Aiming at residual sedimentation and current tectonic framework of the northwest of the basin and its adjacent areas,and based on a large amount of field observation,drilling data,and lab assays,it is pointed out that Helanshan and Yinchuan graben located in the eastern side of Helanshan belong to Ordos Basin in the Yan’an period of Early-Middle Jurassic by comparing the remaining strata of Yan’an period in the northwest of Ordos Basin and analysing the border facies,regional tectonic evolution and structural setting.The sedimentary environment in the Yan’an period of Early-Middle Jurassic,the northwest of Ordos Basin is different from the corresponding strata of Langshan region.Based on these multidisciplinary analysis and research,the northwest sedimentary boundary of Ordos Basin in the Yan’an period of Jurassic is along the fault zone in west margin of Helanshan to Zhuozishan.