An early Norian flora from the Partizansk River Basin of Primorye, Far-East of Russia, is described in detail for the first time, in which over 25 taxa are reported. The flora is dominated by cycadoalean, bennettitale...An early Norian flora from the Partizansk River Basin of Primorye, Far-East of Russia, is described in detail for the first time, in which over 25 taxa are reported. The flora is dominated by cycadoalean, bennettitalean and coniferous plants, associated with a lot of ferns and czekanowskialean plants, and with a few ginkgoalean. In floristic characteristics, the flora can be well comparable with Late Triassic Mongugai flora of southwestern Primorye and its neighboring Tianqiaoling flora of eastern Jilin, China, as well with the Yamanoi and Nariwa floras from southwestern Japan. As the plant-bearing strata are sandwiched in the lower Norian marine beds yielding marine fauna, the age of the Partizansk flora is well evidenced as the early Norian. Paleophytogeographically, the flora appears to be in the ecotone of the Medio-Triassic and Arcto-Triassic floristic regions in Eurasia, and indicates probably warm temperate or subtropic vegetation in nature. Four new species are reported in this paper, including Ctenis elegantus sp. nov, Ixostrobus pacificus sp. nov., Elatocladus elegantus sp. nov. and E. prynadae sp. nov.展开更多
This study presents the results of the conodont biostratigraphy and microfacies analysis carried out on the pelagic limestones of the Upper Triassic Dov?ko Section in Slovenia,which represents the eastern part of the ...This study presents the results of the conodont biostratigraphy and microfacies analysis carried out on the pelagic limestones of the Upper Triassic Dov?ko Section in Slovenia,which represents the eastern part of the Slovenian Basin.The age of the section ranges from the Lacian 1 to the Alaunian 1.The Lacian part of the succession is predominantly characterized by the representatives of the genus Ancyrogondolella.Transitional morphologies towards Alaunian faunas first appear in the Lacian 3 and become common during the Lacian-Alaunian transition.This evolutionary development coincides with a shift in microfacies from a dominantly radiolarian-bearing mudstone-wackestone-packstone to a filament-dominated wackestone-packstone,and the formation of small neptunian dykes,which may reflect environmental perturbations and/or a change in basin geometry.The proliferation of the genera Epigondolella and Mockina is observed in the Alaunian part of the section,though the genus Ancyrogondolella is still present in this interval.Systematic description of the conodont taxa is provided,and seven new species and two new subspecies are established.The new advances will be of great value in further biostratigraphic studies,especially in areas without ammonoid faunas,and in the reconstruction of the paleogeography of the Slovenian Basin.展开更多
The Norian represents the longest stage of the Triassic,nevertheless,its precise subdivision is an unresolved matter.Conodonts might be useful in the establishment of an accurate biozonation to avoid common scientific...The Norian represents the longest stage of the Triassic,nevertheless,its precise subdivision is an unresolved matter.Conodonts might be useful in the establishment of an accurate biozonation to avoid common scientific misinterpretations.Understanding the Norian evolutionary trends and morphological changes of the Ancyrogondolella lineage(genus Ancyrogondolella and descendant genera Epigondolella,Orchardella and Mockina)is of key importance in this issue.The forward shifting of the pit and the posterior prolongation of the keel and the carina characterize the main trend that corresponds to the faunal turnover around the Lacian-Alaunian transition.A gradual decrease in overall element width and length can be observed from that time on,which couples with a decrease in the length of the free blade and an increase in the height of the anterior platform denticles.The presence of secondary carinae is characteristic for the mid-Lacian 1 to Alaunian 1,but their development shows no trends and has no taxonomic value.Adult specimens of the Lacian generally have an arched lower profile,whereas in the Alaunian and Sevatian the lower profile is dominantly stepped or straight.The thorough documentation of the Tethyan assemblages is needed for any detailed taxonomic and paleobiogeographic comparisons with other regions.展开更多
Many well-preserved silicified megalodontids found from the Jiapila Formation of the Upper Triassic in western China show great variations in the amorphous teeth and the massive hinge plate,making the internal molds v...Many well-preserved silicified megalodontids found from the Jiapila Formation of the Upper Triassic in western China show great variations in the amorphous teeth and the massive hinge plate,making the internal molds vary greatly in size and shape.Thus,the internal molds of megalodontids do not always provide reliable taxonomic characters.As a result,about 3/4 of the 132 species and 6 of 9 genera of Triassic Megalodontidae erected on the basis of internal molds have to be revised.The revised definitions of genera Neomegalodon,Triadomegalodon,and Conchodon are given in this paper.展开更多
The Qinling orogen in central China contains several black shale-hosted gold deposits,but the age of their formation and a possible relation between gold mineralization and regional tectonism remain undetermined.Here ...The Qinling orogen in central China contains several black shale-hosted gold deposits,but the age of their formation and a possible relation between gold mineralization and regional tectonism remain undetermined.Here we present results of in situ monazite U-Th-Pb dating and sericite Rb-Sr dating of the Xiajiadian black shale-hosted gold deposit to provide tight constraints on the time of gold deposition and information on the tectonic setting under which the deposit formed.The Xiajiadian gold deposit is mainly hosted in black shales of the Lower Cambrian Shuigoukou formation,with minor ores contained in sandy conglomerate of the Lower Devonian Xichahe formation.Gold ores in the black shales have been intensively oxidized and consist mainly of hematite,goethite,gypsum,quartz,calcite,native gold,and unrecognized iron oxides.However,gold ores in the sandy conglomerate are free of oxidation and thus provide an opportunity to date the formation of the Xiajiadian gold deposit.The ores consist of pyrite,marcasite,sericite,and quartz,which are associated with a variety of accessory minerals,including monazite,apatite,and titanite.Gold is mainly present as structure-bound ions or nanoparticles in pyrite and marcasite,but minor native gold grains also occur as inclusions in pyrite.Monazite is well developed in the ores,and has close textural association with Au-bearing pyrite and marcasite.Most monazite grains have zoned textures consisting of a core area(Mnz1)and an overgrowth zone(Mnz2).Mnz1 contains 4.8–13 wt.%ThO_(2)and shows large variations in HREE and prominent negative Eu anomalies in the chondrite-normalized REE patterns.It yields common lead-corrected^(208)Pb/^(232)Th dates ranging from 910±10 to416±4 Ma(2σ).These dates are interpreted in terms of a detrital origin for monazite in the core area.Mnz2 has much lower ThO_(2)contents of 0.8–1.7 wt.%and shows weak negative Eu anomalies in the chondrite-normalized REE patterns.It yields common lead-corrected^(208)Pb/^(232)Th dates of 229–209 Ma(2σ)with a weig展开更多
基金Supported by PP RAS Projects 06-1-P11-022 , 06-1-P18-081 , Russia and NSFC-RFBR Proj .30511120003 , Key Lab Modern Paleont . Stratig.(NIGPAS) Proj .903109 , China
文摘An early Norian flora from the Partizansk River Basin of Primorye, Far-East of Russia, is described in detail for the first time, in which over 25 taxa are reported. The flora is dominated by cycadoalean, bennettitalean and coniferous plants, associated with a lot of ferns and czekanowskialean plants, and with a few ginkgoalean. In floristic characteristics, the flora can be well comparable with Late Triassic Mongugai flora of southwestern Primorye and its neighboring Tianqiaoling flora of eastern Jilin, China, as well with the Yamanoi and Nariwa floras from southwestern Japan. As the plant-bearing strata are sandwiched in the lower Norian marine beds yielding marine fauna, the age of the Partizansk flora is well evidenced as the early Norian. Paleophytogeographically, the flora appears to be in the ecotone of the Medio-Triassic and Arcto-Triassic floristic regions in Eurasia, and indicates probably warm temperate or subtropic vegetation in nature. Four new species are reported in this paper, including Ctenis elegantus sp. nov, Ixostrobus pacificus sp. nov., Elatocladus elegantus sp. nov. and E. prynadae sp. nov.
基金partially supported by the Slovenian Research Agency(No.P1-0011)partially by the NKFIH PD-131536 Project。
文摘This study presents the results of the conodont biostratigraphy and microfacies analysis carried out on the pelagic limestones of the Upper Triassic Dov?ko Section in Slovenia,which represents the eastern part of the Slovenian Basin.The age of the section ranges from the Lacian 1 to the Alaunian 1.The Lacian part of the succession is predominantly characterized by the representatives of the genus Ancyrogondolella.Transitional morphologies towards Alaunian faunas first appear in the Lacian 3 and become common during the Lacian-Alaunian transition.This evolutionary development coincides with a shift in microfacies from a dominantly radiolarian-bearing mudstone-wackestone-packstone to a filament-dominated wackestone-packstone,and the formation of small neptunian dykes,which may reflect environmental perturbations and/or a change in basin geometry.The proliferation of the genera Epigondolella and Mockina is observed in the Alaunian part of the section,though the genus Ancyrogondolella is still present in this interval.Systematic description of the conodont taxa is provided,and seven new species and two new subspecies are established.The new advances will be of great value in further biostratigraphic studies,especially in areas without ammonoid faunas,and in the reconstruction of the paleogeography of the Slovenian Basin.
基金Funding for this research was provided through the NKFIH PD-131536 Project and the Hantken Miksa Foundation。
文摘The Norian represents the longest stage of the Triassic,nevertheless,its precise subdivision is an unresolved matter.Conodonts might be useful in the establishment of an accurate biozonation to avoid common scientific misinterpretations.Understanding the Norian evolutionary trends and morphological changes of the Ancyrogondolella lineage(genus Ancyrogondolella and descendant genera Epigondolella,Orchardella and Mockina)is of key importance in this issue.The forward shifting of the pit and the posterior prolongation of the keel and the carina characterize the main trend that corresponds to the faunal turnover around the Lacian-Alaunian transition.A gradual decrease in overall element width and length can be observed from that time on,which couples with a decrease in the length of the free blade and an increase in the height of the anterior platform denticles.The presence of secondary carinae is characteristic for the mid-Lacian 1 to Alaunian 1,but their development shows no trends and has no taxonomic value.Adult specimens of the Lacian generally have an arched lower profile,whereas in the Alaunian and Sevatian the lower profile is dominantly stepped or straight.The thorough documentation of the Tethyan assemblages is needed for any detailed taxonomic and paleobiogeographic comparisons with other regions.
基金supported by National Natural Science Foundation of China (Gant No. 41172025)China Geological Survey Project (Grant No. 1212011120116)
文摘Many well-preserved silicified megalodontids found from the Jiapila Formation of the Upper Triassic in western China show great variations in the amorphous teeth and the massive hinge plate,making the internal molds vary greatly in size and shape.Thus,the internal molds of megalodontids do not always provide reliable taxonomic characters.As a result,about 3/4 of the 132 species and 6 of 9 genera of Triassic Megalodontidae erected on the basis of internal molds have to be revised.The revised definitions of genera Neomegalodon,Triadomegalodon,and Conchodon are given in this paper.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.42130814 and 42321001)。
文摘The Qinling orogen in central China contains several black shale-hosted gold deposits,but the age of their formation and a possible relation between gold mineralization and regional tectonism remain undetermined.Here we present results of in situ monazite U-Th-Pb dating and sericite Rb-Sr dating of the Xiajiadian black shale-hosted gold deposit to provide tight constraints on the time of gold deposition and information on the tectonic setting under which the deposit formed.The Xiajiadian gold deposit is mainly hosted in black shales of the Lower Cambrian Shuigoukou formation,with minor ores contained in sandy conglomerate of the Lower Devonian Xichahe formation.Gold ores in the black shales have been intensively oxidized and consist mainly of hematite,goethite,gypsum,quartz,calcite,native gold,and unrecognized iron oxides.However,gold ores in the sandy conglomerate are free of oxidation and thus provide an opportunity to date the formation of the Xiajiadian gold deposit.The ores consist of pyrite,marcasite,sericite,and quartz,which are associated with a variety of accessory minerals,including monazite,apatite,and titanite.Gold is mainly present as structure-bound ions or nanoparticles in pyrite and marcasite,but minor native gold grains also occur as inclusions in pyrite.Monazite is well developed in the ores,and has close textural association with Au-bearing pyrite and marcasite.Most monazite grains have zoned textures consisting of a core area(Mnz1)and an overgrowth zone(Mnz2).Mnz1 contains 4.8–13 wt.%ThO_(2)and shows large variations in HREE and prominent negative Eu anomalies in the chondrite-normalized REE patterns.It yields common lead-corrected^(208)Pb/^(232)Th dates ranging from 910±10 to416±4 Ma(2σ).These dates are interpreted in terms of a detrital origin for monazite in the core area.Mnz2 has much lower ThO_(2)contents of 0.8–1.7 wt.%and shows weak negative Eu anomalies in the chondrite-normalized REE patterns.It yields common lead-corrected^(208)Pb/^(232)Th dates of 229–209 Ma(2σ)with a weig
