The Ordovician graptolite sequence of the Yongxin-Chongyi area in southern Jiangxi was suggested as a standard for the correlation of Ordovician in the Zhujiang region of South China. Based on a restudy of the Upper O...The Ordovician graptolite sequence of the Yongxin-Chongyi area in southern Jiangxi was suggested as a standard for the correlation of Ordovician in the Zhujiang region of South China. Based on a restudy of the Upper Ordovician graptolites, the Shikou and Huamianlong formations are recognized herein as a part of the Hanjiang Formation, corresponding only to the Dipla-canthograptus caudatus-Diplacanthograptus spiniferus Zone. Two graptolite zones in the Longxi Formation of Yongxin and Chongyi, the Nemagraptus gracilis Zone and Climacograptus bicornis Zone, are redefined here. A rapid replacement of facies from the typical deep-water graptolitic black shale of Longxi Formation to the rapidly-accumulated, shallow-water clastic deposits of Hanjiang Formation indicates the tectonic initiation of the Kwangsian Orogeny. The thick clastic deposits of the Han-jiang Formation are proposed to come from a nearby source area that rose during the Kwangsian Orogeny. The D. caudatus-D. spiniferus graptolite Zone of the Hanjiang Formation indicates the initiation time of this tectonic event.展开更多
The Kwangsian Orogeny originated along the southeast coast of China and stepwise developed in a northwest direction.It includes two stages,a long locally varying uplift from the Late Ordovician to the early Silurian a...The Kwangsian Orogeny originated along the southeast coast of China and stepwise developed in a northwest direction.It includes two stages,a long locally varying uplift from the Late Ordovician to the early Silurian and a finally tectonic movement near the Silurian and Devonian transition.The Kwangsian uplift event shows a stepwise delay northwestwards from the southeastern coast area in Nemagraptus gracilis Biozone(Sa1)to the south side of the Xuefeng Mountains in or later than Cystograptus vesiculosus Biozone(R3)to Coronograptus cyphus Biozone(R4).In the southern of Yangtze Platform,the Yichang Uplift was droved by the Kwangsian Orogeny forming a diachronous stratigraphical break through Rhuddanian and Aeronian.The distribution of the early Telychian lower marine red beds indicates a northwestward increase of the Cathaysian Oldland.Stratigraphical evidence may explain why the Kwangsian movement was marked by an angular disconformity during the Pridoli to earliest Devonian interval.展开更多
Early Paleozoic black organic sediments and bentonites occur widely in the craton basin within the Yangtze block and are generally believed to be genetically related to a specific tectonic setting on the cratonic boun...Early Paleozoic black organic sediments and bentonites occur widely in the craton basin within the Yangtze block and are generally believed to be genetically related to a specific tectonic setting on the cratonic boundary.However,the intimate relationship between their origins and the dynamic mechanisms are unclear,as exemplified by the genesis of the black shale series and bentonites from the Wufeng Formation during the Ordovician–Silurian transition(OST).In order to reveal the relationship between the Wufeng Formation and the convergence of the Yangtze and Cathaysia blocks(i.e.,the intracontinental Kwangsian Orogeny),two stratigraphic sections respectively in Zhaotong area(Northeast Yunnan)and Puyi area(Northwestern Guizhou)that were located in the semi-restricted inner Yangtze Sea during the OST were systematically studied,on the basis of whole-rock geochemical composition,pyriteδ^(34)S(δ^(34)Spy),total organic carbon(TOC),stable Sr isotope,pyrite framboid size distribution and zircon U-Pb age,trace elements.The evidence shows that the paleo-oceanic environment changed significantly at the turn of the early–late Katian and formed the black shale series in the Wufeng Formation.These acritarch assemblages were formed in the transition process of the Upper Yangtze Basin from passive continental margin basin to foreland basin during this interval.Based on previous research on the genetic relationship between black shale series and plate tectonic movement,a basin-mountain evolution model suitable for South China in the Late Ordovician is presented.The two bentonites in the Wufeng Formation with U-Pb ages of 445.5±0.8 Ma and 441.9±2.4 Ma primarily originated from the intermediate–acid volcanic eruption during the collision and convergence between the Yangtze and Cathaysia blocks in the Late Ordovician,the provenance region probably being located in the Jiangnan orogenic belt.Thus,we believe that the appearance of the black shale series and bentonite in the Wufeng Formation at the turn of the early–late Katian may represent the initiation of basin-mountain transformation and the Kwangsian Orogeny in South China,which provides important evidence for the collision and convergence of the Yangtze and Cathaysia blocks in the Late Ordovician.展开更多
The present paper deals with a tectonic event of Late Ordovician age affecting three blocks of China,i.e.South China,North China and Tarim.In the North China and the Tarim platforms,as well as their marginal belts,the...The present paper deals with a tectonic event of Late Ordovician age affecting three blocks of China,i.e.South China,North China and Tarim.In the North China and the Tarim platforms,as well as their marginal belts,there was a regional uplift during the early Katian Stage of the Ordovician.The uplift was indicated by the unconformities between the Ordovician successions and overlying late Paleozoic strata.New biostratigraphic studies of conodonts and graptolites from many sections at Longxian and Yaoxian,North China shows that the youngest Ordovician strata are of the early Katian age corresponding to graptolite Diplacanthograptus spiniferus Biozone.The same level has been recognized to represent the uppermost Ordovician in the platform area of Tarim,whereas in the marginal belt the top boundary of the Ordovician is slightly younger,corresponding to the graptolite Dicellograptus complanatus Biozone.Thus,the regional uplift in North China and Tarim is shown by the disconformity between the early Katian strata and Late Paleozoic strata,the onset coinciding with that of the Kwangsian Orogeny in South China.The designation Kwangsian Orogeny later fell into disuse and was replaced by the term Caledonian Orogeny.However,in terms of geographic location,tectonic nature,and the timing of activity,the Caledonian Orogeny differs significantly from the orogenic event in South China,and the continued use of this term in South China is inappropriate and misleading.展开更多
基金supported by Chinese Academy of Sciences (Grant Nos.KZCX2-YW-122,2008ZX05008-001-001)Ministry of Science and Technology (Grant No.2006CB806402)National Natural Science Foundation of China (Grant No.40772002)
文摘The Ordovician graptolite sequence of the Yongxin-Chongyi area in southern Jiangxi was suggested as a standard for the correlation of Ordovician in the Zhujiang region of South China. Based on a restudy of the Upper Ordovician graptolites, the Shikou and Huamianlong formations are recognized herein as a part of the Hanjiang Formation, corresponding only to the Dipla-canthograptus caudatus-Diplacanthograptus spiniferus Zone. Two graptolite zones in the Longxi Formation of Yongxin and Chongyi, the Nemagraptus gracilis Zone and Climacograptus bicornis Zone, are redefined here. A rapid replacement of facies from the typical deep-water graptolitic black shale of Longxi Formation to the rapidly-accumulated, shallow-water clastic deposits of Hanjiang Formation indicates the tectonic initiation of the Kwangsian Orogeny. The thick clastic deposits of the Han-jiang Formation are proposed to come from a nearby source area that rose during the Kwangsian Orogeny. The D. caudatus-D. spiniferus graptolite Zone of the Hanjiang Formation indicates the initiation time of this tectonic event.
基金supported by Chinese Academy of Sciences(Grant No.KZCX2-EW-111)the State Key Laboratory of Palaeontology and Stratigraphy and Key Laboratory of Economic Stratigraphy and Paleogeography(Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences)National Natural Science Foundation of China(Grant No.41272042)
文摘The Kwangsian Orogeny originated along the southeast coast of China and stepwise developed in a northwest direction.It includes two stages,a long locally varying uplift from the Late Ordovician to the early Silurian and a finally tectonic movement near the Silurian and Devonian transition.The Kwangsian uplift event shows a stepwise delay northwestwards from the southeastern coast area in Nemagraptus gracilis Biozone(Sa1)to the south side of the Xuefeng Mountains in or later than Cystograptus vesiculosus Biozone(R3)to Coronograptus cyphus Biozone(R4).In the southern of Yangtze Platform,the Yichang Uplift was droved by the Kwangsian Orogeny forming a diachronous stratigraphical break through Rhuddanian and Aeronian.The distribution of the early Telychian lower marine red beds indicates a northwestward increase of the Cathaysian Oldland.Stratigraphical evidence may explain why the Kwangsian movement was marked by an angular disconformity during the Pridoli to earliest Devonian interval.
基金funded by the China Geological Survey Basic Public Welfare Comprehensive Geological Survey Project(DD20191012,ZD20220504)the Chinese National Natural Science Foundation(42102065)。
文摘Early Paleozoic black organic sediments and bentonites occur widely in the craton basin within the Yangtze block and are generally believed to be genetically related to a specific tectonic setting on the cratonic boundary.However,the intimate relationship between their origins and the dynamic mechanisms are unclear,as exemplified by the genesis of the black shale series and bentonites from the Wufeng Formation during the Ordovician–Silurian transition(OST).In order to reveal the relationship between the Wufeng Formation and the convergence of the Yangtze and Cathaysia blocks(i.e.,the intracontinental Kwangsian Orogeny),two stratigraphic sections respectively in Zhaotong area(Northeast Yunnan)and Puyi area(Northwestern Guizhou)that were located in the semi-restricted inner Yangtze Sea during the OST were systematically studied,on the basis of whole-rock geochemical composition,pyriteδ^(34)S(δ^(34)Spy),total organic carbon(TOC),stable Sr isotope,pyrite framboid size distribution and zircon U-Pb age,trace elements.The evidence shows that the paleo-oceanic environment changed significantly at the turn of the early–late Katian and formed the black shale series in the Wufeng Formation.These acritarch assemblages were formed in the transition process of the Upper Yangtze Basin from passive continental margin basin to foreland basin during this interval.Based on previous research on the genetic relationship between black shale series and plate tectonic movement,a basin-mountain evolution model suitable for South China in the Late Ordovician is presented.The two bentonites in the Wufeng Formation with U-Pb ages of 445.5±0.8 Ma and 441.9±2.4 Ma primarily originated from the intermediate–acid volcanic eruption during the collision and convergence between the Yangtze and Cathaysia blocks in the Late Ordovician,the provenance region probably being located in the Jiangnan orogenic belt.Thus,we believe that the appearance of the black shale series and bentonite in the Wufeng Formation at the turn of the early–late Katian may represent the initiation of basin-mountain transformation and the Kwangsian Orogeny in South China,which provides important evidence for the collision and convergence of the Yangtze and Cathaysia blocks in the Late Ordovician.
基金supported by the project of the State Key Laboratory of Palaeobiology and Stratigraphy(Y126040124)the National Natural Science Foundation of China(41172034 and 41221001)the project of the Ministry of Science and Technology of China(2011ZX05008-001-10)
文摘The present paper deals with a tectonic event of Late Ordovician age affecting three blocks of China,i.e.South China,North China and Tarim.In the North China and the Tarim platforms,as well as their marginal belts,there was a regional uplift during the early Katian Stage of the Ordovician.The uplift was indicated by the unconformities between the Ordovician successions and overlying late Paleozoic strata.New biostratigraphic studies of conodonts and graptolites from many sections at Longxian and Yaoxian,North China shows that the youngest Ordovician strata are of the early Katian age corresponding to graptolite Diplacanthograptus spiniferus Biozone.The same level has been recognized to represent the uppermost Ordovician in the platform area of Tarim,whereas in the marginal belt the top boundary of the Ordovician is slightly younger,corresponding to the graptolite Dicellograptus complanatus Biozone.Thus,the regional uplift in North China and Tarim is shown by the disconformity between the early Katian strata and Late Paleozoic strata,the onset coinciding with that of the Kwangsian Orogeny in South China.The designation Kwangsian Orogeny later fell into disuse and was replaced by the term Caledonian Orogeny.However,in terms of geographic location,tectonic nature,and the timing of activity,the Caledonian Orogeny differs significantly from the orogenic event in South China,and the continued use of this term in South China is inappropriate and misleading.
