大同盆地云岗组石窟段河流相沉积特征

大同盆地云岗组分布于大同云岗盆地、宁武静乐盆地、沁水盆地北部等地区.其命名地点在山西大同市云岗镇,其中石窟段为云岗组中段.经前人研究发现,大同盆地云岗组为辫状河沉积.通过对研究区野外露头中三条典型剖面的研究,全面分析了石窟段河流相沉积特征,并完成了如下工作:①制作了研究区野外露头中三条典型剖面的素描图并建立了界面划分方案;②在界面划分的基础上进行各单元内部岩相、沉积构造及沉积特征的分析;③综合各单元的沉积特征,并通过剖面之间的横向对比,明确了研究区各期次河流相沉积之间时间与空间上的联系;④明确了研究区河流相沉积模式并建立了相应沉积相模式概图.上述工作完成后,从研究区沉积模式概图可见古河流大致沿着自北向南的方向由北部山间汇入大同盆地,形成辫状河道沉积.沉积相总体按照自西向东的方向呈现出泛滥平原—河道沉积—泛滥平原的变化趋势.研究成果为大同盆地侏罗纪的进一步研究及未来大同地区的煤矿开采工作提供资料基础.

Sedimentary Features of Fluvial Facies in the Shiku Member of Yungang Formation in Datong Basin

Yungang formation in Datong Basin is distributed in Yungang Basin, Jingle Basin and Northern Qinshui Basin. Its named place is located in Yungang Town, Datong City, Shanxi Province, and the Shiku member is the middle section of Yungang formation. It has been found that the Yungang formation in Datong Basin is mainly braided river deposit. Based on the study of three typical sections in the field outcrop of the study area, this paper comprehensively analyzed the sedimentary features of the river facies in the Shiku member, and following works were completed: Firstly, the sketch map of three sections in the field outcrop of the study area is made and the interface division scheme is established. Secondly, the analysis of the internal lithofacies, sedimentary structure and sedimentary characteristics of each unit is carried out on the basis of the interface division. Thirdly, combining the sedimentary characteristics of each unit and through the horizontal comparison between sections, the horizontal change characteristics and connection of the outcrop sedimentary facies in the study area are analyzed. Finally, the fluvial facies sedimentary model of the study area is clearly defined and the sketch of it is formed. It is believed that the work completed in this paper will provide a data base for the further study of the Jurassic sedimentary environment evolution in Datong Basin and the future coal mining work in Datong area.