Study Of The Middle-Late Namurian Flora In Xiaheyan, Zhongwei (Northwest China)

The study of Namurian Flora is not so well advanced because of the limited geographic distribution of the plants in the world, even the stage had been taken place by Serpukhovian and Bashkirian due to the middle borderline between Upper and Lower Carbeniferous passing through the ammonite subzone E2 and subzone H1 of Namurian A, thus there are not so many practical papers subjected to the plants of this stage like the other periods these years. Since the most recent great piece "The Namurian and its biota in the east sector of North Qilian Mountain"(Li et al, 1993) and several other papers dealt with the fossil plants of Namurian stage in China, China seems to have made the top ones in the study of the early Namurian Flora among the world. Unfortunately, few papers considered systematically the plant elements and its vertical evolutionary development in the every subdivision unit for the high-resolution reconstruction of the Namurian Flora, nor the study of the high-resolution of correlation between the different Flora provinces, even less in the Middle-Late Namurian.The author had been to dozens of fossil localities of Namurian strata many times in the North Qilian Mountains since junior year of undergraduate study to the last summer of graduate school under the direction of Professor Guanglong Shen of the Department of Geology, Northwest University. Based on 18 boxes of fossil specimens collected by the author from Xiaheyan, Zhongwei, Ningxia Hui Minority Autonomous Region and some other geological and palaeontological data from both Xiaheyan and the adjacent sections in the east sector of North Qilian Mountains, the present paper studies the botanical characteristics of Middel-Late Namurian Flora in Locality Xiaheyan and represents the primary reconstruction of the Middle-Late Namurian Flora in the Northeast Qilian Mountains, also tries to make available accounts for the correlation between the different Flora provinces, and discusses the origin time of Cathaysian Flora based on the succession and the transmissibility of the plants through the whole Namurian stage.