Early Permian Hesheng Flora From Wangqing Of Jilin, China

There existed four major phytogeographic realms namely the Cathaysia,Euramerica, Angara and Gondwana during the Carboniferous-Permian period in theworld. South part and north part of Northeast China developed respectively theCathaysia and the Angara floras, which boundary lies in the Xar Moron River.However, eastern extension of the boundary in eastern Northeast China is still unclear.The last decades have witnessed a growing debate in research on Paleozoicstratigraphy in Yanbian area, Jilin Province. Some scientists even hold the opinionthat Carboniferous-Permian is dominated by ophiolite complex and turbidite-mélange rocks. The problems mentioned above seriously affect to determine theeastern extension of the Solonker-Xar Moron River suture zone.This thesis aims at fixing the boundary between Permian Cathaysia and Angaraflora in eastern Northeast China, ascertaining Paleozoic stratigraphic sequence inYanbian area, and confining the eastern extension of the Solonker-Xar Moron Riversuture. Systematic botany of a newly found Hesheng flora was done by the presentauthor and also the stratigraphy of fossil sites in the Daxinggou Town, WangqingCounty, Yanbian area, Jilin Province, NE China was investigated, and LA–ICP–MSU-Pb detrital zircon geochronology of clastic rocks from the fossil plants interbedewas analyzed. The results are as follows:The fossil plants of the Hesheng flora consist of31species of18genera, namelyLepidophylloides sp., Stigmaria ficoides (Sternb.) Brongn., Trizygia oblongifolium(Germ. et Kaulf.) Asama, Calamites cistii Brongn., C. sp., Paracalamitesstenocostatus Gu et Zhi, Annularia stellata (Schloth.) Wood, A. sp., Schizoneura sp.,Sphenopteridium pseudogermanicum (Halle) Sze, Sphenopteris rotunda Sze,Pecopteris arborescens (Schloth.) Sternb., P. candolleana Brongn., P. cyathea(Schloth.) Brongn., P. huichensis Hsü, P. marginata Gu et Zhi, P. cf. P.(Asterotheca)orientalis (Schenk) Pot., P. yabei Kaw., P. sp., Neuropteris ovata Hoffm., N. plicataSternb., Odontopteris subcrenulata (Rost) Zeill., Emplectopteris cf. E.triangularisHalle, E. sp.(cf. E. sinensis Huang), Taeniopteris cf. T. multinervis Weiss, T.yernauxii Stockm. et Math., Cordaites principalis (Germ.) Gein., C. schenkii Halle,Cardiocarpus sp., Rhabdocarpus sp., Radicites sp. The Hesheng flora is dominated byferns and seed ferns. Most of the fossil plants are important or peculiar of theCathaysia flora, such as Emplectopteris, Taeniopteris yernauxii, Pecopteris huicensisand P. maginata. This indicates the Hesheng flora has a typical Cathaysia floristiccharacter and situate in North China Province of the Cathaysia realm. The Heshengflora, which is comparative to Early Permian Emplectopteris triangularis-Emplectopteridium alatum assembles of Shanxi Formation in North China andNorthwest China, is Late Cisuralian of Permian (Artinskian-early Kungurian) in age.The plants fossil-bearing beds of the Hesheng Formation is of late Cisuralian(Artinskian-early Kungurian) in age. The formation consists of about230m of greyand dark grey conglomerate, coarse-grained sandstone, siltstone and mudstone, underlying by the Late Carboniferous–Early Permian marine carbonate of theShanxiuling Formation with an unconformable contact, and overlain by the Cisuralian-Guadalupian marine carbonate of the Dasuangou Formation.The U-Pb ages of detrital zircon grains from the Hesheng Formation are dividedinto four groups:2541-2535Ma,1897-1832Ma,458-452Ma and390-280Ma.Constrained results from detrital zircon U-Pb geochronology of clastic rock prove thatages of the Hesheng flora and Hesheng Formation is younger than280Ma.Provenance analysis shows the clast came from the North China Plate and no sourcefrom Jiamusi-Mongolia Block. Therefore, Hesheng district of Wangqing County,Yanbian area belongs to North China Plate during middle-late Cisuralian.Based on results of paleophytogeography, stratigraphy, detrital zircongeochronology and geophysical data, the boundary between Permian Cathaysia andAngara flora and the eastward extension of the Solonker-Xar Moron River sutureshould locate in the line of Wangqing-Hunchun in Yanbian area, Jilin Province.The discovery of the Hesheng flora advances the research on Cathaysia flora inNorth China Province, and the distribution of the Cathaysia flora extends northwardto Wangqing district. This confines the boundary between the Cathaysia and Angarafloristic realms in eastern Northeast China, and provides significant data for Paleozoicgeology in Northeast China, and for research on regional tectonic evolution ofNortheast Asia.