The Jiangchuan Biota from the Jiucheng Member(Mb.)of the Dengying Formation(Fm.),discovered in Jiangchuan,eastern Yunnan,China,is marked by copious macrofossils at the apex of the Ediacaran strata.This fauna features ...The Jiangchuan Biota from the Jiucheng Member(Mb.)of the Dengying Formation(Fm.),discovered in Jiangchuan,eastern Yunnan,China,is marked by copious macrofossils at the apex of the Ediacaran strata.This fauna features benthic algae with varied holdfasts and other fossils of indeterminate taxonomic affinity and is compositionally unique compared to the Shibantan and Gaojiashan biotas of the Dengying Fm.and the Miaohe and Wenghui biotas of the Doushantuo Fm.,elsewhere in China.One novel benthic saccular macroalgal fossil,named here Houjiashania yuxiensis gen.and sp.nov.,from the Jiangchuan Biota is based on fossils that are sausage-shaped,elongate,tubular,ranging from 0.3 to 4 cm in length,and up to 0.8 cm in diameter.One terminus is blunt and rounded to an obtuse angle,the other is bent with a spread-out surface resembling a holdfast,suggesting a three-dimensional thallus.Thin,stipe-shaped outgrowths,likely vestiges of sessile saccular life forms,are prevalent in macroalgal fossils of analogous size and shape,as well as present brown algae Scytosiphonaceae,such as Colpomenia and Dactylosiphon.The new findings augment the diversity of benthic algae,such as those known from the Early Neoproterozoic Longfengshan Biota in North China.The benthic algal macrofossils in the Jiucheng Mb.add to knowledge of Late Ediacaran metaphyte diversification and offer more clues about the evolutionary positioning of primitive macroalgae.The co-occurrence of numerous planktonic and benthic multicellular algae and planktonic microbes might have facilitated ecologically the more extensive later Cambrian explosion evidenced by the Chengjiang Biota in Yunnan.展开更多
The algal dolostone of the Upper Sinian Dengying Formation(corresponding to the Ediacaran system)in the Upper Yangtze Platform of China possesses a rich diversity of microorganisms and is an ideal site for the study o...The algal dolostone of the Upper Sinian Dengying Formation(corresponding to the Ediacaran system)in the Upper Yangtze Platform of China possesses a rich diversity of microorganisms and is an ideal site for the study of ancient microbial dolomite.We focused on algal dolostone and its microbial dolomite in the Hanyuan area of Sichuan Province,China.The macroscopic petrological features,microscopic morphology,texture characteristics of the fossil microorganisms and microbial dolomite,and geochemical characteristics were investigated.We found rich fossil microorganisms and microbial dolomites in the laminated,stromatolithic,uniform and clotted(algal)dolostones.The microorganisms present were mainly body fossils of cyanobacteria(including Renalcis,Girvanella,Nanococcus,and Epiphyton)and their trace fossils(including microbial mats(biofilms),algal traces,and spots).In addition,there was evidence of sulfate-reducing bacteria(SRB),moderately halophilic aerobic bacteria,and red algae.The microbial dolomites presented cryptocrystalline textures under polarizing microscope and nanometer-sized granular(including spherulitic and pene-cubical granular)and(sub)micron-sized sheet-like,irregular,spherical and ovoidal morphologies under scanning electron microscope(SEM).The microbial dolomites were formed by microbialiy induced mineralization in the intertidal zone and lagoon environments during the depositional and syngenetic stages and microbially influenced mineralization in the supratidal zone environment during the penecontemporaneous stage.The microbial metabolic activities and extracellular polymeric substances(EPS)determined the morphology and element composition of microbial dolomite.During the depositional and syngenetic stages,the metabolic activities of cyanobacteria and SRB were active and EPS,biofilms and microbial mats were well-developed.EPS provided a large number of nucleation sites.Accordingly,many nanometer-sized pene-cubical granular and(sub)micron-sized sheet-like microbial dolomites were formed.During the penecontemporaneous stage,SBR,cyanobacteria,and moderately halophilic aerobic bacteria were inactive.Furthermore,nucleation sites reduced significantly and were derived from both the EPS of surviving microorganisms and un-hydrolyzed EPS from dead microorganisms.Consequently the microbial dolomites present nanometer-sized spherulitic and micron-sized irregular,spherical,and ovoidal morphologies.Overall,the microbial dolomites evolved from nanometer-sized granular(including spherulitic and pene-cubical granular)dolomites to(sub)micron-sized sheet-like,irregular,spherical and ovoidal dolomites,and then to macroscopic laminated,stromatolithic,uniform,and clotted dolostones.These findings reveal the correlation between morphological evolution of microbial dolomite and microbial activities showing the complexity and diversity of mineral(dolomite)-microbe interactions,and providing new insight into microbial biomineralization and microbial dolomite in the Precambrian era.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42172035,42062005 and 41572024)the China Geological Survey(Grant No.DD20221648)+1 种基金Yunnan Province Science and Technology Department(Grant No.202305AD160031,202401AT070012)the project entitled 1:50000 Regional Geological Survey of Dazhuang,Fabiao,Ditu,and Dianzhong Sheets in Yunnan Province(Grant No.D202207).
文摘The Jiangchuan Biota from the Jiucheng Member(Mb.)of the Dengying Formation(Fm.),discovered in Jiangchuan,eastern Yunnan,China,is marked by copious macrofossils at the apex of the Ediacaran strata.This fauna features benthic algae with varied holdfasts and other fossils of indeterminate taxonomic affinity and is compositionally unique compared to the Shibantan and Gaojiashan biotas of the Dengying Fm.and the Miaohe and Wenghui biotas of the Doushantuo Fm.,elsewhere in China.One novel benthic saccular macroalgal fossil,named here Houjiashania yuxiensis gen.and sp.nov.,from the Jiangchuan Biota is based on fossils that are sausage-shaped,elongate,tubular,ranging from 0.3 to 4 cm in length,and up to 0.8 cm in diameter.One terminus is blunt and rounded to an obtuse angle,the other is bent with a spread-out surface resembling a holdfast,suggesting a three-dimensional thallus.Thin,stipe-shaped outgrowths,likely vestiges of sessile saccular life forms,are prevalent in macroalgal fossils of analogous size and shape,as well as present brown algae Scytosiphonaceae,such as Colpomenia and Dactylosiphon.The new findings augment the diversity of benthic algae,such as those known from the Early Neoproterozoic Longfengshan Biota in North China.The benthic algal macrofossils in the Jiucheng Mb.add to knowledge of Late Ediacaran metaphyte diversification and offer more clues about the evolutionary positioning of primitive macroalgae.The co-occurrence of numerous planktonic and benthic multicellular algae and planktonic microbes might have facilitated ecologically the more extensive later Cambrian explosion evidenced by the Chengjiang Biota in Yunnan.
基金supported by the open fund of Key Laboratory of Sedimentary Basin and Oil and Gas Resources,Ministry of Land and Resources(China)(NO.zdsys2015002)
文摘The algal dolostone of the Upper Sinian Dengying Formation(corresponding to the Ediacaran system)in the Upper Yangtze Platform of China possesses a rich diversity of microorganisms and is an ideal site for the study of ancient microbial dolomite.We focused on algal dolostone and its microbial dolomite in the Hanyuan area of Sichuan Province,China.The macroscopic petrological features,microscopic morphology,texture characteristics of the fossil microorganisms and microbial dolomite,and geochemical characteristics were investigated.We found rich fossil microorganisms and microbial dolomites in the laminated,stromatolithic,uniform and clotted(algal)dolostones.The microorganisms present were mainly body fossils of cyanobacteria(including Renalcis,Girvanella,Nanococcus,and Epiphyton)and their trace fossils(including microbial mats(biofilms),algal traces,and spots).In addition,there was evidence of sulfate-reducing bacteria(SRB),moderately halophilic aerobic bacteria,and red algae.The microbial dolomites presented cryptocrystalline textures under polarizing microscope and nanometer-sized granular(including spherulitic and pene-cubical granular)and(sub)micron-sized sheet-like,irregular,spherical and ovoidal morphologies under scanning electron microscope(SEM).The microbial dolomites were formed by microbialiy induced mineralization in the intertidal zone and lagoon environments during the depositional and syngenetic stages and microbially influenced mineralization in the supratidal zone environment during the penecontemporaneous stage.The microbial metabolic activities and extracellular polymeric substances(EPS)determined the morphology and element composition of microbial dolomite.During the depositional and syngenetic stages,the metabolic activities of cyanobacteria and SRB were active and EPS,biofilms and microbial mats were well-developed.EPS provided a large number of nucleation sites.Accordingly,many nanometer-sized pene-cubical granular and(sub)micron-sized sheet-like microbial dolomites were formed.During the penecontemporaneous stage,SBR,cyanobacteria,and moderately halophilic aerobic bacteria were inactive.Furthermore,nucleation sites reduced significantly and were derived from both the EPS of surviving microorganisms and un-hydrolyzed EPS from dead microorganisms.Consequently the microbial dolomites present nanometer-sized spherulitic and micron-sized irregular,spherical,and ovoidal morphologies.Overall,the microbial dolomites evolved from nanometer-sized granular(including spherulitic and pene-cubical granular)dolomites to(sub)micron-sized sheet-like,irregular,spherical and ovoidal dolomites,and then to macroscopic laminated,stromatolithic,uniform,and clotted dolostones.These findings reveal the correlation between morphological evolution of microbial dolomite and microbial activities showing the complexity and diversity of mineral(dolomite)-microbe interactions,and providing new insight into microbial biomineralization and microbial dolomite in the Precambrian era.
