鄂尔多斯盆地中侏罗统延安组软沉积变形构造特征研究

On the characteristics of the deformation structure about soft sediment object of the Middle Jurassic Extension in the Ordos Basin

以安塞区延河西侧阳光小区以及延安裴庄两处延安组出露地层为研究对象,通过对露头地层层位的确定、变形构造的描述、成因机制的分析等,确定出露地层的地质年代为中侏罗世延7沉积中晚期,变形构造以大小不等的球枕状构造为主,且伴有碎裂微褶皱、塑性变形纹层等软沉积物变形构造。根据变形构造的发育规模和特征,结合前人研究,首次提出鄂尔多斯盆地中侏罗统延安组延7沉积时期存在两期古地震活动,其成因可能与燕山构造活动早期的古火山喷发有关。

This article takes tow outcrops of Yan’an Formation located at Yangguang Community on the west side of Yanhe River in Ansai District and Yan’an Peizhuang as the research object. Through the determination of the horizon of the outcrop strata,the description of the deformation structure and the analysis of the genetic mechanism,the study shows: the geological age is considered as in the middle and late stages of the Middle Jurassic extension,the deformation structure is dominated by pillow structures of varying sizes,accompanied by soft sediment deformation structures such as fragmented micro-folds and fluidization deformation laminas.According to the development scale and characteristics of the deformation structure,combined with previous studies,this paper first proposed two periods of paleo-earthquake activity during the Yan 7 depositional period of the Middle Jurassic Yan’an Formation in the Ordos Basin,and its genesis may be related to the volcanic eruption in the early Yanshan tectonic activity.