Fossil Plants From ?₁ Coal Member Of Early Permian Shanxi Formation In Yuzhou,Henan Province

Coal-forming Basin in Western Henan is well known for the“north type with southern facies”coal-bearing strata in the southern zone of the North China.The Carboniferous-Permian marine strata and flooding layer are growed,and many typical elements of Cathaysian plants grew in the tropical-subtropical humid warm climate,forming the famous Yuzhou flora.During the Carboniferous to Permian period,Gondwana polar glacier event occurred on the earth,which reached the severe ice age in the early Early Permian.It is an important period for studying the interaction between Phanerozoic vegetation and ice chamber climate.The continuous Carboniferous Permian stratigraphic sequence and abundant plant fossils in North China,as well as the significant time points of its transformation from glacial period to warm period,which provides important research materials for investigating the impact of organisms on climate in geological history.The fossil plants focused were collected from the?₁coal member of the Shanxi Formation at Madong section of Shenhou Town,Yuzhou City,Henan Province,China.Their composition of 41 species is belonging to 20 genera,including Lycopsida(1 species of 1 genus):Lepidostrobus sp.;Sphenopsida(6 species of 4 genera):Sphenophyllum emarginatum Brongn.,S.minor(Sterz.)Gu et Zhi,S.verticillatum(Schloth.)Brongn.,Bowmanites fusiformis Wang,Mesocalamites cistiformis Stur,Asterophyllites robustus Xie;Noeggerathiales(4 species of 1 genus):Tingia carbonica(Schenk)Halle,T.?gerardii Stockm.et Math,T.partita Halle,T.spiniformis Wang;Filices et Pteridospermopsida(20 species of 7 genera):Sphenopteris firmata Sze,S.nystroemii Halle,S.tenuis Schenk,Pecopteris anderssonii Halle,P.candolleana Brongn.,P.cyathea(Schloth.)Brongn.,P.heteropinna(Yabe et Shim.),P.lativenosa Halle,P.marginata Gu et Zhi,P.moneyi Zeill.,P.(Asterotheca)norinii Halle,P.(Asterotheca)orientalis(Schenk)Pot.,P.taiyuanensis Halle,Cladophlebis nystroemii Halle,Alethopteris ascendens Halle,Emplectopteris triangularis Halle,Callipteridium koraiense(Tok.)Kaw.,Taeniopteris tingii Halle,T.tongshanensis Stockm.et Math.,T.yernauxii Stockm.et Math.;Cycadopsida(2 species of 1 genus):Pterophyllum cutelliforme Sze,P.daihoense Kaw.;Cordaitopsida(3 species of 2 genera):Cordaites principalis(Germ.)Gein.,C.schenkii Halle,Cordaianthus volkmannii(Ett.)Zeill.;Semina Gymnospermarum(5 species of 4genera):Cornucarpus patulus Halle,Acanthocarpus sp.,Samaropsis deltata Wang,S.wongii Stockm.et Math.,Carpolithus taxiformis Stockm.et Math..The flora is dominated by filicopsids and pteridospermopsids.There are also numerous in Sphenopsids,noeggerathiopsids,cordaitopsids,cycadopsids and lycopsida.Typical elements appear such as Emplectopteris triangularis Halle,Tingia partita Halle,Taeniopteris yernauxii Stockm.et Math.,Pecopteris marginata Gu et Zhi,Pecopteris(Asterotheca)orientalis Halle,which indicate the flora with typical characters of Cathaysian flora in the middle phase.Based on the existence of Sweetognathus whitei,a conodont fossil in the marine limestone at the top of the underlying Taiyuan formation,which determined that the coal-bearing strata began in Artinskian(Early Permian).Compared with the comparison between the cotemporary floras phase in China,the geological age of Shanxi Formation is determined as Artinskian-Early Kungurian.A large number of plant fossils developed in the?₁coal member of Shanxi Formation record the lush coastal delta vegetation landscape in tropical subtropical warm and humid climate in the northern hemisphere.Compared with this flora,the plant fossils in the upper part of Shanxi formation above Dazhan sandstone have developed greatly,which mainly appeared in the rise of pteridospermopsids,gigantopterises,cycadopsids,the evolution of Sphenopsids,and the reappearance of Lepidodendrales.Lepidodendrales developed from 1 species of 1 genus to 8 species of 5 genera,which indicates that wet coastal swamps are widely distributed.Sphenopsids developed from 6 species of 4 genera to 13 species of 4 genera.The emergence of Lobatannularia shows that the light utilization rate of plants is greatly improved.Sphenophyllum plants have a great development at a total of 9 species.And there is also one species of Annularia.Filices and/or pteridospermopsida have 24 species of 12 genera,which have more genera compared with this flora,such as Qasimia,Zhongzhoupteris,Cathaysiopteris,Protoblechnum,Odontopteris,Emplectopteridium,Progigantonoclea.Pecopteridaceae have some changes.Meanwhile,the development of reticulate veins in pteridospermopsids and gigantopterises also shows the improvement of photosynthetic efficiency.In addition,the rise of cycadopsids:Cathsysiocycas rectanervis Yang,Procycas densiner vioides Zhang et Mo is also a response to environmental changes.Overall,the plants in the upper part of Shanxi formation are more evolved,and the paleoclimate is warmer than that in the?₁ coal member,the lower part of Shanxi Formation.The coastal marsh is more extensive and the photosynthetic efficiency is more effective.Based on the study of characters,ages and the comparison between the cotemporary floras phase in China.This flora is connected to the global climate change and sea-level undulation for the first time.As the climate changing from ice-house to green-house and the sea-level rising,floral succession was enhanced and the photosynthetic efficiency was greatly improved,with a great amount of atmospheric CO₂ was consumed and caused a sharp arising of O₂.