Cambrian Ichnofossils from the Zhoujieshan Formation(Quanji Group) Overlying Tillites in the Northern Margin of the Qaidam Basin, NW China  

作　　者：Yue Wang Xunlian Wang Ye Wang 

机构地区：[1]School of Resources and Environments, Guizhou University [2]School of Earth Sciences and Resources, China University of Geosciences

出　　处：《Journal of Earth Science》2015年第2期203-210,共8页地球科学学刊（英文版）

基　　金：jointly supported by the National Natural Science Foundation of China (No. 41162003);China Geological Survey (No. 1212011121258)

摘　　要：The Quanji Group is composed of siliciclastics and carbonates and was deposited on a relatively stable block, in the northern margin of the Qaidam Basin, NW China. It is one of the research hotspots in the Qilian-Qinling-Kunlun tectonic zones. However, it has long been argued whether the up- per Qnanji Group should be assigned to the Precambrian or the Cambrian for lack of convincing fossil evidence. The discovery of ichnofossils, including Rusophycus, Cruziana, Dimorphichnus, Treptichnus, Skolithos, Arenicolites, Palaeophycus, and Helminthopsis, indicates that the upper member of the Zhou- jieshan Formation （top Quanji Group） is Cambrian in age, and at least above the Treptichnus （Phycodes） pedum Biozone, the lowermost biozone in the Cambrian. The lower member of the Zhoujieshan Forma- tion should belong to the Cambrian. During the time when the upper member of the Zhoujieshan For- mation was deposited, the northern margin of the Qaidam Basin was dominated by the Cruziana Ichnofacies, characterizing a lower-energy shelf （shallow） sea environment with moderate-rich oxygen con- tents. In addition, the conglomerates in the Hongtiegou Formation of the Quanji Group underlying the Zhoujieshan Formation were generally regarded as tillites. However, the dolostones of the lower member of the Zhoujieshan Formation are, in lithology and geochemistry, different from the typical cap-dolostones of the Doushantuo Formation in South China, so it is necessary to further study the origins of the lower member of the Zhoujieshan Formation and the conglomerates of the Hongriegou Formarion.The Quanji Group is composed of siliciclastics and carbonates and was deposited on a relatively stable block, in the northern margin of the Qaidam Basin, NW China. It is one of the research hotspots in the Qilian-Qinling-Kunlun tectonic zones. However, it has long been argued whether the up- per Qnanji Group should be assigned to the Precambrian or the Cambrian for lack of convincing fossil evidence. The discovery of ichnofossils, including Rusophycus, Cruziana, Dimorphichnus, Treptichnus, Skolithos, Arenicolites, Palaeophycus, and Helminthopsis, indicates that the upper member of the Zhou- jieshan Formation （top Quanji Group） is Cambrian in age, and at least above the Treptichnus （Phycodes） pedum Biozone, the lowermost biozone in the Cambrian. The lower member of the Zhoujieshan Forma- tion should belong to the Cambrian. During the time when the upper member of the Zhoujieshan For- mation was deposited, the northern margin of the Qaidam Basin was dominated by the Cruziana Ichnofacies, characterizing a lower-energy shelf （shallow） sea environment with moderate-rich oxygen con- tents. In addition, the conglomerates in the Hongtiegou Formation of the Quanji Group underlying the Zhoujieshan Formation were generally regarded as tillites. However, the dolostones of the lower member of the Zhoujieshan Formation are, in lithology and geochemistry, different from the typical cap-dolostones of the Doushantuo Formation in South China, so it is necessary to further study the origins of the lower member of the Zhoujieshan Formation and the conglomerates of the Hongriegou Formarion.

关 键 词：CAMBRIAN ichnofossil Zhoujieshan Formation Quanji Group Daqaidam NW China. 

分 类 号：P534.41[天文地球—古生物学与地层学]