Conodonts and fusulinids are the two most widely used biotic groups for subdividing and correlating Bashkirian and Moscovian strata. The definition of the base of the Global Moscovian Stage is undecided because there ...Conodonts and fusulinids are the two most widely used biotic groups for subdividing and correlating Bashkirian and Moscovian strata. The definition of the base of the Global Moscovian Stage is undecided because there are many disagreements among existing boundary definition proposals,each of which has disadvantages. Declinognathodus donetzianus is easily recognized but somewhat limited in its paleogeographic distribution. Idiognathoides postsulcatus is slightly more widespread, but it is less easily identified and its occurrences may be diachronous from region to region. Diplognathodus ellesmerensis is easily recognized and even more widespread, but it is usually rare and its ancestry is not adequately known. The Naqing Section of South Guizhou, South China contains diverse conodont evolutionary lineages among different taxa, including Idiognathoides, Idiognathodus, Diplognathodus,Neognathodus, Gondolella and Mesogondolella. There are numerous transitional forms in almost every lineage of the Naqing section, which shows that the prospects for South China to play a critical role in determining the basal Moscovian Stage definition are good.展开更多
Various microbial fabrics characterize late Moscovian mounds in Houchang Town,southern Guizhou,South China.The dominant components of the mounds are microbial boundstones with stromatolitic structures,irregular oncoid...Various microbial fabrics characterize late Moscovian mounds in Houchang Town,southern Guizhou,South China.The dominant components of the mounds are microbial boundstones with stromatolitic structures,irregular oncoid-like forms,and wrinkle structures.Calcimicrobes recognized in the mounds include Girvanella,Ortonella,Wetheredella-like,Palaeomicrocodium-like,and some problematic calcimicrobes occurring in deposits between microbial boundstones,in thrombolitic textures,and in some intraclasts.Microbial carbonates are common in the substrate and interior of the mounds,including thrombolitic textures,microstromatolites,microbial ooids,oncoids,irregular encrusted layers,microbial mat debris,and microbial micrite.Calcimicrobes and microbial carbonates played an important role in the construction of the mounds:Girvanella might have contributed as a source of lime mud that formed the mound and stabilized the coral frame;thrombolitic mats could trap and fix sediments and bioclasts,contributing to the stabilization of substrate and mound limestones;and,microbial boundstone,clotted micrite and micritized bioclast could provide a hard substrate for encrusting metazoans(e.g.,bryozoans,Ivanovia).The abundant microbial fabrics in the mounds indicate that microbial activity was widespread in Moscovian reef mounds in southern Guizhou,and this suggests that microbial organisms were the primary mound builders in the study area.展开更多
The Upper Carboniferous Benxi Formation of the Ordos Basin is the lowest strata overlying Middle Ordovician above the major ca.150-Myr sedimentary gap that characterizes the entire North China Block(NCB).We apply an i...The Upper Carboniferous Benxi Formation of the Ordos Basin is the lowest strata overlying Middle Ordovician above the major ca.150-Myr sedimentary gap that characterizes the entire North China Block(NCB).We apply an integrated analysis of stratigraphy,petrography,and U-Pb dates and Hf isotopes on detrital zircons to investigate its provenance and relationships to the progressive collisions that formed the Xing’an-Mongolia Orogenic Belt to the north and the Qinling Orogenic Belt to the south.The results show that,in addition to regional patterns of siliciclastic influx from these new uplifted sources,the Benxi Formation is composed of two sequences corresponding to long-term glacial-interglacial cycles during the Moscovian to lower Gzhelian stages which drove global changes of eustatic sea level and weathering.The spatio-temporal distribution of sediment isopachs and facies indicate there were two sediment-infilling pulses,during which the southern and the northern Ordos Basin developed tidal-reworked deltas.The age spectra from detrital zircons,trace element patterns and εNd(t)values reveal that the siliciclastics forming the southern delta was sourced in the Qinling Orogenic Belt,whereas the northern delta was derived from the Xing’an-Mongolia Orogenic Belt.The source-to-sink evolution of this Upper Paleozoic system records the progressive development of orogenic belts and uplifts forming on the southern and northern margins of the NCB prior to its collisions with the South China and the Siberian plates,respectively.展开更多
基金supported by the Ministry of Science and Technology of China (2006FY120300-8)the Chinese Academy of Sciences (KZCX2-YW-122, KZCX2-YW-Q050603)National Natural Science Foundation of China (NSFC), and the CAS/SAFEA International Partnership Program for Creative Research Teams
文摘Conodonts and fusulinids are the two most widely used biotic groups for subdividing and correlating Bashkirian and Moscovian strata. The definition of the base of the Global Moscovian Stage is undecided because there are many disagreements among existing boundary definition proposals,each of which has disadvantages. Declinognathodus donetzianus is easily recognized but somewhat limited in its paleogeographic distribution. Idiognathoides postsulcatus is slightly more widespread, but it is less easily identified and its occurrences may be diachronous from region to region. Diplognathodus ellesmerensis is easily recognized and even more widespread, but it is usually rare and its ancestry is not adequately known. The Naqing Section of South Guizhou, South China contains diverse conodont evolutionary lineages among different taxa, including Idiognathoides, Idiognathodus, Diplognathodus,Neognathodus, Gondolella and Mesogondolella. There are numerous transitional forms in almost every lineage of the Naqing section, which shows that the prospects for South China to play a critical role in determining the basal Moscovian Stage definition are good.
基金supported by the National Natural Science Foundation of China(Grant No.41572004)
文摘Various microbial fabrics characterize late Moscovian mounds in Houchang Town,southern Guizhou,South China.The dominant components of the mounds are microbial boundstones with stromatolitic structures,irregular oncoid-like forms,and wrinkle structures.Calcimicrobes recognized in the mounds include Girvanella,Ortonella,Wetheredella-like,Palaeomicrocodium-like,and some problematic calcimicrobes occurring in deposits between microbial boundstones,in thrombolitic textures,and in some intraclasts.Microbial carbonates are common in the substrate and interior of the mounds,including thrombolitic textures,microstromatolites,microbial ooids,oncoids,irregular encrusted layers,microbial mat debris,and microbial micrite.Calcimicrobes and microbial carbonates played an important role in the construction of the mounds:Girvanella might have contributed as a source of lime mud that formed the mound and stabilized the coral frame;thrombolitic mats could trap and fix sediments and bioclasts,contributing to the stabilization of substrate and mound limestones;and,microbial boundstone,clotted micrite and micritized bioclast could provide a hard substrate for encrusting metazoans(e.g.,bryozoans,Ivanovia).The abundant microbial fabrics in the mounds indicate that microbial activity was widespread in Moscovian reef mounds in southern Guizhou,and this suggests that microbial organisms were the primary mound builders in the study area.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.41872109 and 41702108)China Postdoctoral Science Foundation(Grant No.2019M650833)Everest Scientific Research Program of Chengdu University of Technology。
文摘The Upper Carboniferous Benxi Formation of the Ordos Basin is the lowest strata overlying Middle Ordovician above the major ca.150-Myr sedimentary gap that characterizes the entire North China Block(NCB).We apply an integrated analysis of stratigraphy,petrography,and U-Pb dates and Hf isotopes on detrital zircons to investigate its provenance and relationships to the progressive collisions that formed the Xing’an-Mongolia Orogenic Belt to the north and the Qinling Orogenic Belt to the south.The results show that,in addition to regional patterns of siliciclastic influx from these new uplifted sources,the Benxi Formation is composed of two sequences corresponding to long-term glacial-interglacial cycles during the Moscovian to lower Gzhelian stages which drove global changes of eustatic sea level and weathering.The spatio-temporal distribution of sediment isopachs and facies indicate there were two sediment-infilling pulses,during which the southern and the northern Ordos Basin developed tidal-reworked deltas.The age spectra from detrital zircons,trace element patterns and εNd(t)values reveal that the siliciclastics forming the southern delta was sourced in the Qinling Orogenic Belt,whereas the northern delta was derived from the Xing’an-Mongolia Orogenic Belt.The source-to-sink evolution of this Upper Paleozoic system records the progressive development of orogenic belts and uplifts forming on the southern and northern margins of the NCB prior to its collisions with the South China and the Siberian plates,respectively.
