Late Permian Flora From The Soron, Inner Mongolia, China

Two type floras, the Angaran and Cathayasian floras, are mainly distributed innortheastern China during the Carboniferous and Permian. They were developingseparately in different climatic zones and different latitude before the Early-MiddlePermian. Since Late Permian, the North China Plate and the Jiamusi-Mongolia Blockhad been getting more and more close to each other due to the former movednorthward; and some taxa of the two floras, which are distributed separately on thetwo blocks, had begun to migrate to each other.The fossil plants described here were collected from the Upper Permian LinxiFormation (the Soron Layer) outcropped at the roadside from the Soron to theHouhelemen near the Soron Town of Kerqin Right Wing Front Banner, InnerMongolia, China. They are composed of38species belonging to18genera, includingSphenophytes (4species of3genera): Paracalamites tubicinus Naug., Paracalamitessp., Lobatannularia lingulata (Halle) Halle, Lobatannularia multifolia Kon’no; Filices&Pteridospermopsida (25species of11genera): Sphenopteris rotunda Sze,Pecopteris anbangensis Huang, Pecopteris arcuata Halle, Pecopteris hongshanensisHuang, Pecopteris julii Radcz., Pecopteris lativenosa Halle, Pecopteris marginata Guet Zhi, Pecopteris tenuicostata Halle, Pecopteris unita Brongniart, Pecopteris yabeiKaw., Pecopteris (Prynadaeopteris) anthriscifolia (Goepp.) Zalessky, Fascipteris(Ptychocarpus) densata Gu et Zhi, Cladophlebis liulinensis Xiao, Cladophlebisnystroemii Halle, Cladophlebis (Lixotheca) permica Lee et Wang, Odontopterisorbicularis Halle, Rhachiphyllum (Callipteris) pseudoshenshuensis Huang,Rhachiphyllum sp., Compsopteris tchirkovae Zalessky, Supaia tieliensis Huang,Supaia sp., Comia cf. enisejevensis Schwedov, Iniopteris sibirica Zalessky,Taeniopteris szei Chow; Ginkgophytes (3species of1genus): Rhipidopsis ginkgoidesSchmalh., Rhipidopsis lobata Halle, Rhipidopsis panii Chow; Cordaitales (5speciesof3genera): Cordaites principalis (Germ.) Gein., Discinites orientalis Gu et Zhi,Rufloria obovata (Neub.) Meyen, Rufloria synensis (Zalessky) Meyen, Rufloria sp.；Seeds (1species of1genus): Nucicarpus piniformis Neuburg.Most of the fossil plants listed herein are aged in the Wuchiapingian andChanghsingian stages, indicating an age of Late Permian period. The flora ischaracterized by numerous Angaran-type plants, such as Paracalamites, Comia, Rhachiphyllum, Iniopteris, Rufloria, etc. Some Cathaysian elements, such asLobatannularia lingulata, L. multifolia, Fascipteris densata, Taeniopteris szei,Cladophlebis liulinensis, C. nystroemii, C. permica and Cordaites principalis, are alsomixed within the flora.Through the comparison between the present flora to the other homochronousfloras in the adjacent areas, the evolution of the Xar Moron River–Changchun–Yanji suture zone is depicted with the help of the stratigraphic and tectonic evidences.The phenomenon of the Cathaysian and Angaran mixed floras, such as thetropical-subtropical Cathaysian flora (the Kaishantun flora in Jilin) and the temperateAngaran flora (including the Jiefangcun flora in Yanji, the Hongshan flora in Yichunand Acheng and the Linxi flora in Da Hsingan Mountains) indicates that thePaleoasian Ocean, which separated the Jiamusi-Mongolia Block and the North ChinaPlate during the Early-Middle Permian, had been closed in the Late Permian.