Discovery of marine fossils in the upper part of the Permian Linxi Formation in Lopingian, Xingmeng area, China
Yongsheng Zhang;Shugang Tian;Zishun Li;Yuexuan Gong;Enyuan Xing;Zhuozhuo Wang;Daxing Zhai;Cao Jie;Su Kui;Wang Meng;Institute of Mineral Resources, Chinese Academy of Geological Sciences;Key Laboratory of Saline Lake Resources and Environment,Ministry of Land and Resources;Institute of Geology, Chinese Academy of Geological Sciences;Chinese Academy of Geological Sciences;
Two important geological issues have a long history of debate in the Xingmeng area. The first concerns the final closure of the North China plate, Siberia plate and several intermediate massifs in the area, and the other concerns the folding and lifting of the Xingmeng Trough. Disagreements arise because of issues involving the tectonicpalaeogeographical environment of the Upper Permian deposits of the Linxi Formation. The Linxi Formation(Upper Permian) is generally considered to be either an exclusively continental deposit or separated into marineterrigenous facies deposited during the Lower to Middle Linxi Period and continental deposits in the Upper Linxi Period. However, in this study, large numbers of bryozoan and sponge spicule fossils were discovered for this first time in the thick limestone layers and lenses of the upper part of the Linxi Formation found in the Guandi section of Linxi county in eastern Inner Mongolia. At the same time, abundant bryozoan fossils were also found in sedimentary tuff slices that were collected from the upper part of the Taohuayingzi Formation from the Taohuayingzi section in Ar Horqin Banner, and abundant small connecting body crinoid stem fossils were found in the dark shale of the Yangjiagou Formation from the Yangjiagou section of Jiutai county, Jilin Province. These marine fossils provide the first evidence that the Xingmeng area was still a marine or mainly marine environment at the end of the late Permian. This not only provides conclusive evidence for the recognition of the above two major geological issues but also promotes changes in the approach towards research, exploration and development of oil and gas, shale gas(oil), and other mineral resources that are preserved in the late Permian layers of the Northeast-Xingmeng area.