Twenty-three ichnotaxa have been found in the Silurian and Carboniferous turbidites of the Tianshan orogenic belt and the Triassic turbidites of the East Kunlun-West Qinling erogenic belt of northwestern China. They a...Twenty-three ichnotaxa have been found in the Silurian and Carboniferous turbidites of the Tianshan orogenic belt and the Triassic turbidites of the East Kunlun-West Qinling erogenic belt of northwestern China. They are Acanthorhaphe isp., ?Arthrophycus isp., Aulichnites parkerensis, Chondrites isp., C. intricatus, C. targionii, Cochlichnus anguineus, coprolite, Dendrotichnium haentzscheli, Helminthopsis isp., Helminthopsis abeli, H. hiero-glyphica, H. cf. irregularis, Imbrichnus isp., Kunlunichnus qinghaiensis, Laevicyclus rotaeformis, Lophoctenium tianshanensis, Megagrapton isp., Micatuba verso?, Muensteria isp., Neonereites, Palaeophycus, and Zoophycos cau-dagalli, two of which, namely, Kunlunichnus qinghaiensis and Lophoctenium tianshanensis, are new icnnospecies. The described trace fossils can be grouped into five ichno-assemblages: the Aulichnites-Imbrichnus ichno-assemblage representing turbidity current deposits of a restricted anoxic deep-sea basin, the Lophoctenium ichno-assemblage showing展开更多
The provenance and paleogeography of the Upper Triassic deep-sea flysch Langjiexue Group(LG)of the Shannan Terrane in the northeastern Himalaya orogen,south of Yarlung Zangbo,have been disputed in recent years since i...The provenance and paleogeography of the Upper Triassic deep-sea flysch Langjiexue Group(LG)of the Shannan Terrane in the northeastern Himalaya orogen,south of Yarlung Zangbo,have been disputed in recent years since its affinity to the Tethys Himalaya was suspected during the early 2000 s.Based on the earlier discoveries of the Upper Permian–Triassic basalts and mafic dykes from the LG and of coeval detrital zircons from the Qulonggongba Formation(QF)in shallow shelf sediments of the Tethys Himalaya,the previous viewpoints on the basin and tectonics of the LG have been recently rejected.We compared the two units of the Upper Triassic,and our results reveal a number of differences,discrepancies,and inconsistencies in the debate,raising crucial questions on the postulation and provenance model of the remote Gondwanide Orogen for the LG.It is suggested that more observations and evidence are needed to further improve the paleogeographic understanding and relationship of the two units.展开更多
Tributaries are one of the most important factors contributing to variability in the downstream evolution of bed sediment grain size.The primary aim of this work is to evaluate the response of the bed sediment texture...Tributaries are one of the most important factors contributing to variability in the downstream evolution of bed sediment grain size.The primary aim of this work is to evaluate the response of the bed sediment texture in the recipient channel induced by ten tributaries of the?ernáOstravice stream and find reach-scale and catchment-scale parameters that would be able to predict this response.The research was based on collecting information on the grain size distributions at sites adjacent to confluence zones.A significant change in sediment texture occurred in the vicinity of five confluences.Considering the other factors contributing to grain size variability(e.g.,local channel geometry,lithology,and lateral sediment sources),it was assumed that only four of them were associated with a sufficient bedload influx to alter the sediment calibre below the junction.Moreover,a significant morphological effect in the form of a large confluence bar was observed in one case.These tributaries had several common features:(i)they had a larger relative catchment area than that of nonsignificant tributaries;(ii)they were characterized by different bed grain sizes,with some exceptions;and(iii)they had a higher unit stream power close to the confluence in relation to that of the mainstream.These characteristics were represented by the proposed relative parameters,including the relative unit stream power and bed material texture,which allowed the best classification of significant and nonsignificant tributaries.In their simplified form,the parameters described the transport capacity and grain size distribution,which were generally considered to be primary factors responsible for a redefinition of the sediment texture in the recipient channel.However,it should be noted that these results are subject to some degree of uncertainty due to the relatively small sample size of only 10 tributaries.展开更多
In early Late Carboniferous only the South Junggaru-Bogeda area of the ancient North Xinjiang geosynclinal region was still in the geosynclinal stage,when it was the critical Period for closing of the geosynclinal reg...In early Late Carboniferous only the South Junggaru-Bogeda area of the ancient North Xinjiang geosynclinal region was still in the geosynclinal stage,when it was the critical Period for closing of the geosynclinal region. The crust movement was in a special form with frequent rhythm,and there developed a typical flysch formation in Liushugou-Urho in Late Carboniferous. A thorough investigation and study on the flysch formation have been carried out,based on a great number of the firsthand field information and experiment analytical data.The Late Carboniferous flysch formation in Liushugou-Urho,Xinjiang,formed in the Bashkirian .consisting mainly of the Baogutu Formation. There are outcrops if the flysch at Liushugou ,Kesongertai, Kayinte, Hatu, Dongfeng Wudui, Urho, etc. The outcrops at Kesongertai and Urho, 422m and 1228m thick respectively,are more typical and complete flysch formation.The Late Carbonilerous flysch formation in Liushugou-Urho consists mainly of the rhythmic series of sandstone and shale. The shale (or mudstone) component increases southeastward to Urho and sandstone component increases southwestward to Liushugou-Kayinte. Body fossils are seldom in the formation but the Nereites ichnofacies are common. The distribution of trace elements is stable and belongs to the regular pattern. THe flysch formation at the Urho formed chiefly in a bathyal sedimentary environment,possessing a complete transgressive-and-regressive sequence. At Liushugou -Kayinte, the formation can obviously be divided into the upper and lower parts. The upper formed in a littoral-neritic oscillatory environment,while the lower deposited in a bathyal turbidite basin. The two parts constitute a transgressive sequence.展开更多
The Late Caledonian to Early Hercynian North Qilian orogenic belt in no rthwestern China is an elongate tectonic unit situated between the North China p late in the north and the Qaidam plate in the south. North Qilia...The Late Caledonian to Early Hercynian North Qilian orogenic belt in no rthwestern China is an elongate tectonic unit situated between the North China p late in the north and the Qaidam plate in the south. North Qilian started in the latest Proterozoic to Cambrian as a rift basin on the southern margin of North China, and evolved later to an archipelagic ocean and active continental margin during the Ordovician and a foreland basin from Silurian to the Early and Middle Devonian. The Early Silurian flysch and submarine alluvial fan, the Middle to L ate Silurian shallow marine to tidal flat deposits and the Early and Middle Devo nian terrestrial molasse are developed along the corridor Nanshan. The shallowin g upward succession from subabyssal flysch, shallow marine, tidal flat to terre strial molasse and its gradually narrowed regional distribution demonstrate that the foreland basin experienced the transition from flysch stage to molasse stag e during the Silurian and Devonian time.展开更多
We used iilite and chlorite crystallinities,index minerals,mineral assemblages,polytype and domain size of white mica,electron microprobe analysis(EMPA),b_0 geobarometer and chlorite geothermometer to quantify the dia...We used iilite and chlorite crystallinities,index minerals,mineral assemblages,polytype and domain size of white mica,electron microprobe analysis(EMPA),b_0 geobarometer and chlorite geothermometer to quantify the diagenetic and metamorphic overprint on the Triassic flysch formations in the Songpan-Garzêorogen along profile Zoigê-Lushan,northwest Sichuan.Two anchizones,two epizones,one diagenetic zone and a transition belt in-between them are defined on the basis of the obtained data.Illite crystallinity correlates strongly with the best mean domain size of mica and moderately with chlorite crystallinity.2M_1 white mica polytype are observed within the epizone whilst 2M_1 and 1M polytypes occur in the anchizone and diagenetic zone.Epizonal metamorphism reached maximum temperatures of 370℃±21℃at low-to intermediate pressure conditions.Clay minerals underwent Ostwald ripening during metamorphism.Rocks from both sides of the Longmenshan fault reveal contrasting degrees of metamorphic overprint:on the northwest side of the Longmenshan fault,epimetamorphic conditions contrast with diagenetic rocks on the southeast side.展开更多
Flysch formations are generally characterised by evident heterogeneity in the presence of low strength and tectonically disturbed structures.The complexity of these geological materials demands a more specialized geoe...Flysch formations are generally characterised by evident heterogeneity in the presence of low strength and tectonically disturbed structures.The complexity of these geological materials demands a more specialized geoengineering characterisation.In this regard,the paper tries to discuss the standardization of the engineering geological characteristics,the assessment of the behaviour in underground excavations,and the instructionseguidelines for the primary support measures for flysch layer qualitatively.In order to investigate the properties of flysch rock mass,12 tunnels of Egnatia Highway,constructed in Northern Greece,were examined considering the data obtained from the design and construction records.Flysch formations are classified thereafter in 11 rock mass types(IeXI),according to the siltstone esandstone proportion and their tectonic disturbance.A special geological strength index(GSI)chart for heterogeneous rock masses is used and a range of geotechnical parameters for every flysch type is presented.Standardization tunnel behaviour for every rock mass type of flysch is also presented,based on its site-specific geotechnical characteristics such as structure,intact rock strength,persistence and complexity of discontinuities.Flysch,depending on its types,can be stable even under noticeable overburden depth,and exhibit wedge sliding and wider chimney type failures or cause serious deformation even under thin cover.Squeezing can be observed under high overburden depth.The magnitude of squeezing and tunnel support requirements are also discussed for various flysch rock mass types under different overburdens.Detailed principles and guidelines for selecting immediate support measures are proposed based on the principal tunnel behaviour mode and the experiences obtained from these 12 tunnels.Finally,the cost for tunnel support from these experiences is also presented.展开更多
A considerable number of in situ permeability tests in flysch are processed to a depth of 120m with a good spatial distribution. The distribution of permeability values for the different litho-types of this formation,...A considerable number of in situ permeability tests in flysch are processed to a depth of 120m with a good spatial distribution. The distribution of permeability values for the different litho-types of this formation, their comparison and their decrease with depth is discussed. The depth where a permeability of 3 to 5×10-7m/sec can be retained (the limit of a reasonable grouting under a high dam) may be twofold if the geological history of the formation could not contain a compressional tectonic process. This depth may reach 100m in some cases. The differences in the mean values of permeability among the various litho-types are minor, while the presence of siltstones, always present although with varied participation, dramatically controls the global permeability.展开更多
The Xianshuihe-Anninghe fault extends SE–S and constitutes the southeastern margin of the Tibetan Plateau.However,the Dadu River which is associated with the fault does not flow following the path,but makes a 90º...The Xianshuihe-Anninghe fault extends SE–S and constitutes the southeastern margin of the Tibetan Plateau.However,the Dadu River which is associated with the fault does not flow following the path,but makes a 90ºturn within a distance of 1 km at Shimian,heading east,and joins the Yangtze River,finally flowing into the East China Sea.Adjacent to the abrupt turn,a low and wide pass near the Daqiao reservoir at Mianning separates the N–S course of the Dadu River from the headwater of the Anning River which then flows south into the Yunnan Province along the Anninghe fault.Therefore,many previous studies assumed southward flow of the paleo-Dadu River from the Shimian to the Anning River.However,evidences for the capture of the integrated N–S paleo-Dadu-Anning River,its timing,and causes are still insufficient.This study explored the paleo-drainage pattern of the Dadu and Anning Rivers based on bulk mineral and geochemical analyses of the large quantities of fluvial/lacustrine sediments along the trunk of the Dadu and Anning Rivers.Similar with sands in the modern Dadu River,the Xigeda sediments also exhibit a granitoid affinity with the bulk major mineral compositions of quartz(>50%),anorthite(about 10%),orthoclase(about 5%),muscovite(about 5%),and clinochlore(about 4%).Correspondingly,bulk major elements show high SiO_(2),with all samples>60%,and some of them>70%,low TiO_(2)(≤0.75%),P_(2)O_(5)(≤0.55%),FeO*(≤5%),and relatively high CaO(1.02%–8.51%),Na_(2)O(1.60%–2.52%),and K_(2)O(2.17%–2.71%),with a uniform REE patterns.Therefore,synthesizing all these results indicate that these lacustrine sediments have similar material sources,which are mainly derived from its course in the Songpan-Ganzi flysch block,implying that the paleo-Dadu originally flowed southward into the Anning River and provided materials to the Xigeda ancient lake.The rearrangement of the paleo-Dadu River appears to be closely related to the locally focused uplift driven by strong activities of the XianshuiheXiaojiang fault system.展开更多
文摘Twenty-three ichnotaxa have been found in the Silurian and Carboniferous turbidites of the Tianshan orogenic belt and the Triassic turbidites of the East Kunlun-West Qinling erogenic belt of northwestern China. They are Acanthorhaphe isp., ?Arthrophycus isp., Aulichnites parkerensis, Chondrites isp., C. intricatus, C. targionii, Cochlichnus anguineus, coprolite, Dendrotichnium haentzscheli, Helminthopsis isp., Helminthopsis abeli, H. hiero-glyphica, H. cf. irregularis, Imbrichnus isp., Kunlunichnus qinghaiensis, Laevicyclus rotaeformis, Lophoctenium tianshanensis, Megagrapton isp., Micatuba verso?, Muensteria isp., Neonereites, Palaeophycus, and Zoophycos cau-dagalli, two of which, namely, Kunlunichnus qinghaiensis and Lophoctenium tianshanensis, are new icnnospecies. The described trace fossils can be grouped into five ichno-assemblages: the Aulichnites-Imbrichnus ichno-assemblage representing turbidity current deposits of a restricted anoxic deep-sea basin, the Lophoctenium ichno-assemblage showing
基金the National Natural Science Foundation of China(NSFC 41072075 and 41872104)for funding this study。
文摘The provenance and paleogeography of the Upper Triassic deep-sea flysch Langjiexue Group(LG)of the Shannan Terrane in the northeastern Himalaya orogen,south of Yarlung Zangbo,have been disputed in recent years since its affinity to the Tethys Himalaya was suspected during the early 2000 s.Based on the earlier discoveries of the Upper Permian–Triassic basalts and mafic dykes from the LG and of coeval detrital zircons from the Qulonggongba Formation(QF)in shallow shelf sediments of the Tethys Himalaya,the previous viewpoints on the basin and tectonics of the LG have been recently rejected.We compared the two units of the Upper Triassic,and our results reveal a number of differences,discrepancies,and inconsistencies in the debate,raising crucial questions on the postulation and provenance model of the remote Gondwanide Orogen for the LG.It is suggested that more observations and evidence are needed to further improve the paleogeographic understanding and relationship of the two units.
基金supported by the University of Ostrava(Grant no.SGS02/P?F/2019–2020)。
文摘Tributaries are one of the most important factors contributing to variability in the downstream evolution of bed sediment grain size.The primary aim of this work is to evaluate the response of the bed sediment texture in the recipient channel induced by ten tributaries of the?ernáOstravice stream and find reach-scale and catchment-scale parameters that would be able to predict this response.The research was based on collecting information on the grain size distributions at sites adjacent to confluence zones.A significant change in sediment texture occurred in the vicinity of five confluences.Considering the other factors contributing to grain size variability(e.g.,local channel geometry,lithology,and lateral sediment sources),it was assumed that only four of them were associated with a sufficient bedload influx to alter the sediment calibre below the junction.Moreover,a significant morphological effect in the form of a large confluence bar was observed in one case.These tributaries had several common features:(i)they had a larger relative catchment area than that of nonsignificant tributaries;(ii)they were characterized by different bed grain sizes,with some exceptions;and(iii)they had a higher unit stream power close to the confluence in relation to that of the mainstream.These characteristics were represented by the proposed relative parameters,including the relative unit stream power and bed material texture,which allowed the best classification of significant and nonsignificant tributaries.In their simplified form,the parameters described the transport capacity and grain size distribution,which were generally considered to be primary factors responsible for a redefinition of the sediment texture in the recipient channel.However,it should be noted that these results are subject to some degree of uncertainty due to the relatively small sample size of only 10 tributaries.
文摘In early Late Carboniferous only the South Junggaru-Bogeda area of the ancient North Xinjiang geosynclinal region was still in the geosynclinal stage,when it was the critical Period for closing of the geosynclinal region. The crust movement was in a special form with frequent rhythm,and there developed a typical flysch formation in Liushugou-Urho in Late Carboniferous. A thorough investigation and study on the flysch formation have been carried out,based on a great number of the firsthand field information and experiment analytical data.The Late Carboniferous flysch formation in Liushugou-Urho,Xinjiang,formed in the Bashkirian .consisting mainly of the Baogutu Formation. There are outcrops if the flysch at Liushugou ,Kesongertai, Kayinte, Hatu, Dongfeng Wudui, Urho, etc. The outcrops at Kesongertai and Urho, 422m and 1228m thick respectively,are more typical and complete flysch formation.The Late Carbonilerous flysch formation in Liushugou-Urho consists mainly of the rhythmic series of sandstone and shale. The shale (or mudstone) component increases southeastward to Urho and sandstone component increases southwestward to Liushugou-Kayinte. Body fossils are seldom in the formation but the Nereites ichnofacies are common. The distribution of trace elements is stable and belongs to the regular pattern. THe flysch formation at the Urho formed chiefly in a bathyal sedimentary environment,possessing a complete transgressive-and-regressive sequence. At Liushugou -Kayinte, the formation can obviously be divided into the upper and lower parts. The upper formed in a littoral-neritic oscillatory environment,while the lower deposited in a bathyal turbidite basin. The two parts constitute a transgressive sequence.
基金TheresearchissponsoredbytheNationalNaturalScienceFoundationofChina (No .4 9972 0 78)
文摘The Late Caledonian to Early Hercynian North Qilian orogenic belt in no rthwestern China is an elongate tectonic unit situated between the North China p late in the north and the Qaidam plate in the south. North Qilian started in the latest Proterozoic to Cambrian as a rift basin on the southern margin of North China, and evolved later to an archipelagic ocean and active continental margin during the Ordovician and a foreland basin from Silurian to the Early and Middle Devonian. The Early Silurian flysch and submarine alluvial fan, the Middle to L ate Silurian shallow marine to tidal flat deposits and the Early and Middle Devo nian terrestrial molasse are developed along the corridor Nanshan. The shallowin g upward succession from subabyssal flysch, shallow marine, tidal flat to terre strial molasse and its gradually narrowed regional distribution demonstrate that the foreland basin experienced the transition from flysch stage to molasse stag e during the Silurian and Devonian time.
基金This study was supported by the National Natural Science Foundation of China （Grant No. 40572032）；the open fund of the central laboratory of Peking University （No. 14 and 15）.
文摘We used iilite and chlorite crystallinities,index minerals,mineral assemblages,polytype and domain size of white mica,electron microprobe analysis(EMPA),b_0 geobarometer and chlorite geothermometer to quantify the diagenetic and metamorphic overprint on the Triassic flysch formations in the Songpan-Garzêorogen along profile Zoigê-Lushan,northwest Sichuan.Two anchizones,two epizones,one diagenetic zone and a transition belt in-between them are defined on the basis of the obtained data.Illite crystallinity correlates strongly with the best mean domain size of mica and moderately with chlorite crystallinity.2M_1 white mica polytype are observed within the epizone whilst 2M_1 and 1M polytypes occur in the anchizone and diagenetic zone.Epizonal metamorphism reached maximum temperatures of 370℃±21℃at low-to intermediate pressure conditions.Clay minerals underwent Ostwald ripening during metamorphism.Rocks from both sides of the Longmenshan fault reveal contrasting degrees of metamorphic overprint:on the northwest side of the Longmenshan fault,epimetamorphic conditions contrast with diagenetic rocks on the southeast side.
文摘Flysch formations are generally characterised by evident heterogeneity in the presence of low strength and tectonically disturbed structures.The complexity of these geological materials demands a more specialized geoengineering characterisation.In this regard,the paper tries to discuss the standardization of the engineering geological characteristics,the assessment of the behaviour in underground excavations,and the instructionseguidelines for the primary support measures for flysch layer qualitatively.In order to investigate the properties of flysch rock mass,12 tunnels of Egnatia Highway,constructed in Northern Greece,were examined considering the data obtained from the design and construction records.Flysch formations are classified thereafter in 11 rock mass types(IeXI),according to the siltstone esandstone proportion and their tectonic disturbance.A special geological strength index(GSI)chart for heterogeneous rock masses is used and a range of geotechnical parameters for every flysch type is presented.Standardization tunnel behaviour for every rock mass type of flysch is also presented,based on its site-specific geotechnical characteristics such as structure,intact rock strength,persistence and complexity of discontinuities.Flysch,depending on its types,can be stable even under noticeable overburden depth,and exhibit wedge sliding and wider chimney type failures or cause serious deformation even under thin cover.Squeezing can be observed under high overburden depth.The magnitude of squeezing and tunnel support requirements are also discussed for various flysch rock mass types under different overburdens.Detailed principles and guidelines for selecting immediate support measures are proposed based on the principal tunnel behaviour mode and the experiences obtained from these 12 tunnels.Finally,the cost for tunnel support from these experiences is also presented.
文摘A considerable number of in situ permeability tests in flysch are processed to a depth of 120m with a good spatial distribution. The distribution of permeability values for the different litho-types of this formation, their comparison and their decrease with depth is discussed. The depth where a permeability of 3 to 5×10-7m/sec can be retained (the limit of a reasonable grouting under a high dam) may be twofold if the geological history of the formation could not contain a compressional tectonic process. This depth may reach 100m in some cases. The differences in the mean values of permeability among the various litho-types are minor, while the presence of siltstones, always present although with varied participation, dramatically controls the global permeability.
基金financially supported by the Natural Science Foundation of China(41941016,42072240,41830217)Ministry of Science and Technology of China(2019QZKK0901,2021FY100101)+2 种基金Key Special Project for Introduced Talents Team of the Southern Marine Science and Engineering Guangdong Laboratory(GML2019ZD0201)China Geological Survey(DD20221630)Special Fund of the Institute of Geophysics,China Earthquake Administration(DQJB20B21).
文摘The Xianshuihe-Anninghe fault extends SE–S and constitutes the southeastern margin of the Tibetan Plateau.However,the Dadu River which is associated with the fault does not flow following the path,but makes a 90ºturn within a distance of 1 km at Shimian,heading east,and joins the Yangtze River,finally flowing into the East China Sea.Adjacent to the abrupt turn,a low and wide pass near the Daqiao reservoir at Mianning separates the N–S course of the Dadu River from the headwater of the Anning River which then flows south into the Yunnan Province along the Anninghe fault.Therefore,many previous studies assumed southward flow of the paleo-Dadu River from the Shimian to the Anning River.However,evidences for the capture of the integrated N–S paleo-Dadu-Anning River,its timing,and causes are still insufficient.This study explored the paleo-drainage pattern of the Dadu and Anning Rivers based on bulk mineral and geochemical analyses of the large quantities of fluvial/lacustrine sediments along the trunk of the Dadu and Anning Rivers.Similar with sands in the modern Dadu River,the Xigeda sediments also exhibit a granitoid affinity with the bulk major mineral compositions of quartz(>50%),anorthite(about 10%),orthoclase(about 5%),muscovite(about 5%),and clinochlore(about 4%).Correspondingly,bulk major elements show high SiO_(2),with all samples>60%,and some of them>70%,low TiO_(2)(≤0.75%),P_(2)O_(5)(≤0.55%),FeO*(≤5%),and relatively high CaO(1.02%–8.51%),Na_(2)O(1.60%–2.52%),and K_(2)O(2.17%–2.71%),with a uniform REE patterns.Therefore,synthesizing all these results indicate that these lacustrine sediments have similar material sources,which are mainly derived from its course in the Songpan-Ganzi flysch block,implying that the paleo-Dadu originally flowed southward into the Anning River and provided materials to the Xigeda ancient lake.The rearrangement of the paleo-Dadu River appears to be closely related to the locally focused uplift driven by strong activities of the XianshuiheXiaojiang fault system.
