Apart from previously reported Small Shelly Fossils （SSFs）, a macroscopic fossil assemblage, comprising abundant algae, cone-shaped tubular fossil forms, and probable impressions of a megascopic metazoan, comes from...Apart from previously reported Small Shelly Fossils （SSFs）, a macroscopic fossil assemblage, comprising abundant algae, cone-shaped tubular fossil forms, and probable impressions of a megascopic metazoan, comes from the Lower Cambrian Yanjiahe Formation in the Yangtze Gorges area of western Hubei Province, south China. The visible fossils are preserved in thinlaminated siltstone or muddy siltstone intercalated between 8-15 ram-thick carbonate deposits, probably representing sedimentary settings of a constrained local depression in the shallow water carbonate platform during the Early Cambrian Meishucunian Stage. The macroscopic fossil association provides significant fossil evidence about the evolution of life from the late Precambrian to the ＇Cambrian explosion＇ interval.展开更多
Hexangulaconulariids,an extinct family of medusozoan small shelly fossils(SSFs),were a conspicuous component of early Cambrian,shallow marine platform communities in South China.Described herein is Septuconularia cras...Hexangulaconulariids,an extinct family of medusozoan small shelly fossils(SSFs),were a conspicuous component of early Cambrian,shallow marine platform communities in South China.Described herein is Septuconularia crassiformis sp.nov.from Bed 5 of the Yanjiahe Formation(Cambrian Stage 2)in the Three Gorges area of Hubei Province.The new species differs from the type and only other known species,S.yanjiaheensis,in the shape of the abapical portion and in the degree of curvature of the adapertural margin.The anatomy of the apical portion of the new species is unknown.The diagnosis of the genus Septuconularia is emended and the spatio-temporal distribution of hexangulaconulariids in South China is summarized.Finally,S.yanjiaheensis,with its slit-like aperture and very narrow transverse cross-section,may have been better adapted to the shallow platform environment than the broader S.crassiformis,which appears to have been less common than the type species.展开更多
Silica-phosphatic nodules are abundant in black shales of the Yanjiahe Formation in the Three Gorges Area of South China,which is correlated to the Fortunian Stage,Terreneuvian Series,Cambrian System.The nodules are r...Silica-phosphatic nodules are abundant in black shales of the Yanjiahe Formation in the Three Gorges Area of South China,which is correlated to the Fortunian Stage,Terreneuvian Series,Cambrian System.The nodules are rich in small shelly fossils and hence attract the attention of numerous paleontologists and sedimentary geologists.However,the genesis of the nodules and the preservation of the small shelly fossils are poorly understood.Here we analyze morphological,structural,mineralogical and chemical features of the nodules in multiscale using a combination of micro-X-ray fluorescence spectroscopy,X-ray diffraction,scanning electron microscopy and confocal laser Raman spectroscopy.Results reveal that nodules are concentric in chemical and mineralogical compositions,comprising a silica-phosphatic core encrusted sequentially by a phosphatic zone,a siliceous zone and a very thin pyrite outer rim.The black shales hosting the nodules demonstrate a laminated texture of alternating clayey and silty laminae,which were respectively deposited in sulfidic/less sulfidic,high/low production,intense/weak chemical weathering conditions.The phosphogenesis of the nodules resulted in the phosphatization of small shelly fossils,which prevented the fossils from being dissolved during diagenesis,whereas the silica encrustation sealed the fossils within the nodules and thus protected the fossils from alteration by deep burial and surface weathering.展开更多
基金funded by the National Natural Science Foundation of China(40332016,04062003,40702005)National"973"Project(2006CB806401)"as well as by the Program for Changjiang Scholars and Innovative Research Team in Universities(G2000077702) and the Sino-Japan Cooperative Project
文摘Apart from previously reported Small Shelly Fossils （SSFs）, a macroscopic fossil assemblage, comprising abundant algae, cone-shaped tubular fossil forms, and probable impressions of a megascopic metazoan, comes from the Lower Cambrian Yanjiahe Formation in the Yangtze Gorges area of western Hubei Province, south China. The visible fossils are preserved in thinlaminated siltstone or muddy siltstone intercalated between 8-15 ram-thick carbonate deposits, probably representing sedimentary settings of a constrained local depression in the shallow water carbonate platform during the Early Cambrian Meishucunian Stage. The macroscopic fossil association provides significant fossil evidence about the evolution of life from the late Precambrian to the ＇Cambrian explosion＇ interval.
基金This study was financially supported by the Natural Science Foundation of China(Grant Nos.42172016,41890844,41890840,41621003,41772010,41720104002)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB26000000)the Key Scientific and Technological Innovation Team Project in Shaanxi Province and the State Key Laboratory of Palaeobiology and Stratigraphy(Nanjing Institute of Geology and Palaeontology,CAS,Grant Nos.203106,163107).
文摘Hexangulaconulariids,an extinct family of medusozoan small shelly fossils(SSFs),were a conspicuous component of early Cambrian,shallow marine platform communities in South China.Described herein is Septuconularia crassiformis sp.nov.from Bed 5 of the Yanjiahe Formation(Cambrian Stage 2)in the Three Gorges area of Hubei Province.The new species differs from the type and only other known species,S.yanjiaheensis,in the shape of the abapical portion and in the degree of curvature of the adapertural margin.The anatomy of the apical portion of the new species is unknown.The diagnosis of the genus Septuconularia is emended and the spatio-temporal distribution of hexangulaconulariids in South China is summarized.Finally,S.yanjiaheensis,with its slit-like aperture and very narrow transverse cross-section,may have been better adapted to the shallow platform environment than the broader S.crassiformis,which appears to have been less common than the type species.
基金financially supported by the National Natural Science Foundation of China(grant nos.41890843 and 41920104009)the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(Grant No.311021003)。
文摘Silica-phosphatic nodules are abundant in black shales of the Yanjiahe Formation in the Three Gorges Area of South China,which is correlated to the Fortunian Stage,Terreneuvian Series,Cambrian System.The nodules are rich in small shelly fossils and hence attract the attention of numerous paleontologists and sedimentary geologists.However,the genesis of the nodules and the preservation of the small shelly fossils are poorly understood.Here we analyze morphological,structural,mineralogical and chemical features of the nodules in multiscale using a combination of micro-X-ray fluorescence spectroscopy,X-ray diffraction,scanning electron microscopy and confocal laser Raman spectroscopy.Results reveal that nodules are concentric in chemical and mineralogical compositions,comprising a silica-phosphatic core encrusted sequentially by a phosphatic zone,a siliceous zone and a very thin pyrite outer rim.The black shales hosting the nodules demonstrate a laminated texture of alternating clayey and silty laminae,which were respectively deposited in sulfidic/less sulfidic,high/low production,intense/weak chemical weathering conditions.The phosphogenesis of the nodules resulted in the phosphatization of small shelly fossils,which prevented the fossils from being dissolved during diagenesis,whereas the silica encrustation sealed the fossils within the nodules and thus protected the fossils from alteration by deep burial and surface weathering.
