Discussion on Age of “Sailiyakedaban Group”in Southern Yecheng,South Xinjiang,NW China

Wang Yue; Wang Xunlian; Wang Ye

doi:10.3799/dqkx.2016.091

Abstract：In the Sailiyakedaban area (in West Kunlun Mountains),Yecheng,South Xinjiang,a series of coal-bearing clastic strata,distributed in the Mazha-Kangxiwa tectonic belt,is named as the Sailiyakedaban Group and considered as the Early-Middle Triassic strata.The Mazha-Kangxiwa tectonic belt is considered as the boundaries between the West Kunlun and the Karakoram plates,as well as between the Eurasian plate and the Paleo-Tethys domain,so the dating of the coal-bearing clastics in the Mazha-Kangxiwa tectonic belt is significant to the study on the tectonic and paleogeographic evolution in West Kunlun Mountains.Lithologically,the coal-bearing clastic strata can be divided into three parts:the lower part consists mainly of con-glomerates,the middle part is characterized by coals,and the upper part consists mainly of pebbly sandstones.Abundant plant fossils,of 1 7 genus and 20 species,were collected from the middle part of the strata.The flora is predominated by Cycado-phytes (25%),ferns (20%),Ginkgopsida (20%),and Confiers (1 5%).Similar to the Yarkant Group flora found in the West Kunlun Mountains and the margin of the Tarim basin,it shows the characteristics of both Coniopteris-Phoenicopsis flora in North China and Ptilophyllum-Conioptersis flora in South China during the Early-Middle Jurassic transition.In addition,the coal-bearing clastic deposit in the Mazha-Kangxiwa tectonic belt not only is correlated with the Yarkant Group in the strati-graphic sequences and lithostratigraphy,but also conforms to the definition of the Yarkant Group.Therefore,the stratigraphic unit “Sailiyakedaban Group”of the Early-Middle Triassic is proposed to be suspended for use and to be replaced by the Yarkant Group of the Early-Middle Jurassic.