Microspherules are found in different facies at the Lower-Middle Devonian boundary, Guangxi, South China. There are more than 20 grains per kilogram rock sample. Composition and form of the microspherules are very sim...Microspherules are found in different facies at the Lower-Middle Devonian boundary, Guangxi, South China. There are more than 20 grains per kilogram rock sample. Composition and form of the microspherules are very similar to those of the microtektites from modern deposits of South Pacific Ocean and F-F boundary (Devonian). This may indicate that the microspherules from Guangxi are most likely the products of an extraterrestrial impact event that occurred at the end of Early Devonian Epoch. The event may be responsible for the biomass reduction and extinction of benthic organisms at the end of Early Devonian. The impact products (ejecta) can be used as a potential tool for stratigraphic correlation.展开更多
The controversies on the division and correlation of the Devonian have never stopped since Lonsodale found and named the Devonian at Devonshire, Britain, especially on the determination and correlation of the Lower-Mi...The controversies on the division and correlation of the Devonian have never stopped since Lonsodale found and named the Devonian at Devonshire, Britain, especially on the determination and correlation of the Lower-Middle Devonian Boundary. The correlation between the different areas and sedimentary facies are still an international question although the international stratotype section has already been established. Recently,展开更多
The Yingshan Formation of the Lower-Middle Ordovician in the Tarim Basin(NW China)was mainly deposited in a shallow platform,which was intensely bioturbated with burrows filled with both dolomites and calcites.This st...The Yingshan Formation of the Lower-Middle Ordovician in the Tarim Basin(NW China)was mainly deposited in a shallow platform,which was intensely bioturbated with burrows filled with both dolomites and calcites.This study aims to figure out the controls on the dolomitization of burrow infills and the effects on petroleum reservoir quality based on petrographic examination,fluid inclusion microthermometry,and isotopic(C-O-Sr)geochemical analyses.The differentiation of burrow-associated carbonates(dolomites and calcites)was likely controlled by the interactions of sea-level oscillations of variable orders and depositional environments.The burrow-associated dolomites(BADs)were precipitated in a relatively restricted(i.e.,lagoon)depositional environment during the lowstand of long-term sea level.In contrast,the burrow-associated calcites(BACs)were formed in a water circulation-improved lagoonal environment during the transgression of long-term sea level.Isotopic geochemical data indicate that the BADs in the Yingshan Formation were formed from slightly saline(i.e.,mesosaline to penesaline)seawater,whereas the BACs were precipitated from nearly normal seawater.In addition to the anoxic condition,the presence of marine-sourced organic matter and sulfate-reducing bacteria,and a sufficient supply of dolomitizing fluids enriched in magnesium ions(Mg^(2+))and their Mg^(2+)concentration may have played a critical role in the formation of BADs.In the more permeable and disturbed burrow sediments as a result of burrowing,penetrating fluids with higher salinities and higher Mg^(2+)concentration relative to seawater favored dolomite precipitation.The fluids with seawater-like Mg^(2+)concentration,however,would lead to calcite precipitation.The progressive dolomitization of these burrowed sediments could have propagated the dolomitizing fronts and extended into ambient limestones,leading to the development of extensive dolomites.This dolomitization process can improve the petrophysical properties(porosity and permeability)and the potential as hydrocarbon reservoirs during the emplacement of hydrocarbons from underlying source rocks of the Cambrian to Lower Ordovician.展开更多
The detrital modes of the sandstones from the south basin of Dabie（大别） orogenic belt during the Early-Middle Jurassic are complex due to multiple supplying.Detrital compositions of medium-coarse sandstones from th...The detrital modes of the sandstones from the south basin of Dabie（大别） orogenic belt during the Early-Middle Jurassic are complex due to multiple supplying.Detrital compositions of medium-coarse sandstones from the Lower-Middle Jurassic,Huangshi（黄石）,show three main provenances：recycled ororgen,volcanic arc（arc orogen）,and continental block on the bases of the Dickinson discriminating diagrams of modal composition and analysis of sandstone petrofacies.Combined with sparse published paleocurrent data,geotectonic setting of the study area,and the unpublished detrital zircon age data,the positions of the main provenances are inferred as follows：coastal orogenic belt（COB） in the East China provided detritus as the recycled orogen provenance;Dabie orogenic belt（DOB） to the north was the source of volcanic arc（arc orogen） materials;and the continental block clasts were likely from the uplift of the Yangtze basement（UYB）（Jiangnan（江南） uplift）.Six sedimentary cycles are recognized in the studied section,one in Wuchang（武昌） Formation,and five in Huajiahu（花家湖） Formation.During the deposition,the three main provenances play different roles.The quantitative petrofacies analysis revealed distinct changes of the effect from each source,that is,61.9%（Cycle Ⅰ）→54.5%（Cycle Ⅲ）→50%（Cycle Ⅳ）→57.9%（Cycle Ⅴ）→14.3%（Cycle Ⅵ）,14.3%（Cycle Ⅰ）→21.2%（ Cycle Ⅲ）→40%（Cycle Ⅳ）→36.8%（Cycle Ⅴ）→14.3%（Cycle Ⅵ）,and 23.8%（Cycle Ⅰ）→24.2%（Cycle Ⅲ）→10%（Cycle Ⅳ）→5.3%（Cycle Ⅴ）→71.4%（Cycle Ⅵ） from COB,DOB,and UYB,respectively.The results show that（1） COB behaved in considerable activation during the EarlyJurassic but weakened in the Middle Jurassic;（2） the vigorous tectonic uplift of DOB initiated in Middle Jurassic;and（3） UYB was in stabilization basically from the Early to Middle Jurassic.展开更多
BACKGROUND While Crohn’s disease has been studied extensively in high-income countries,its epidemiology and care in low and lower-middle income countries(LLMICs)is not well established due to a lack of disease regist...BACKGROUND While Crohn’s disease has been studied extensively in high-income countries,its epidemiology and care in low and lower-middle income countries(LLMICs)is not well established due to a lack of disease registries and diagnostic capacity.AIM To describe the published burden,diagnostic/treatment capacity,service utilization,challenges/barriers to individuals with Crohn’s in LLMICs and their providers.METHODS We conducted a scoping review utilizing a full search strategy was developed and conducted in PubMed,Embase and World Health Organization Global Index Medicus.Two independent reviewers screened the titles and abstracts of all of the publications found in this search,reviewed selected publications,and extracted relevant data,which underwent descriptive review and was analyzed in Excel.RESULTS The database search yielded 4486 publications,216 of which were determined to be relevant to the research questions.Of all 79 LLMICs,only 21(26.6%)have publications describing individuals with Crohn’s.Overall,the highest number of studies came from India,followed by Tunisia,and Egypt.The mean number of Crohn’s patients reported per study is 57.84 and the median is 22,with a wide range from one to 980.CONCLUSION This scoping review has shown that,although there is a severe lack of populationbased data about Crohn’s in LLMICs,there is a signal of Crohn’s in these settings around the world.展开更多
Here we report a left cheek plate of Psarolepis,a postparietal shield of Youngolepis,a skull of Diabolepis,and a scale of Styloichthys from the Lianhuashan and Nahkaoling formations(Lochkovian,Lower Devonian)of Nannin...Here we report a left cheek plate of Psarolepis,a postparietal shield of Youngolepis,a skull of Diabolepis,and a scale of Styloichthys from the Lianhuashan and Nahkaoling formations(Lochkovian,Lower Devonian)of Nanning,Guangxi.This marks the first report of Diabolepis and Styloichthys beside Qujing,Yunnan,and the latest occurrence of Psarolepis to date.The fossil community displays significant similarities to the Xujiachong Assemblage,and provides new data for the Lower Devonian stratigraphic correlation between southwestern China and northern Vietnam.Given the latest dating constraint based on the conodont evidence,we regard that the Xujiachong Assemblage has a much longer range than previously supposed,extending from the latest Lochkovian to the end of Pragian.We propose that the transition of the Nahkaoling and Lianhuashan formations in Nanning might correspond to the Guijiatun Formation in Qujing.The relatively large size of fish individuals from Guangxi is probably attributed to the increase in the oxygen content of the ocean.展开更多
A genus within the family Douvillinidae of the order Strophomenida from the Erdaogou Memberof the Xibiehe Formation in the Early Devonian of central Jilin has been re-examined, with considerationgiven to the 56 specim...A genus within the family Douvillinidae of the order Strophomenida from the Erdaogou Memberof the Xibiehe Formation in the Early Devonian of central Jilin has been re-examined, with considerationgiven to the 56 specimens collected and described by Liu and Huang (1977). Based on its distinct externalornamentation and internal characteristics, it has been classified as Cymostrophia (Protocymostrophia). It isconcluded that the three specices described by Liu and Huang (1977), Idioglyptus alatus, I. semicircularis,I. subquadratus, as well as the Mesodouvillina jilinensis Su, 1980 should be considered synonyms and benamed Cymostrophia (Protocymostrophia) alatus (Liu) Li.展开更多
Well-preserved and diversified spores,cryptospores,and acritarchs have been recorded from a relatively continuous sequence that encompasses the Silurian-Devonian boundary in Qujing, Yunnan,southwest China.Four spore a...Well-preserved and diversified spores,cryptospores,and acritarchs have been recorded from a relatively continuous sequence that encompasses the Silurian-Devonian boundary in Qujing, Yunnan,southwest China.Four spore assemblage zones from Late Silurian to Early Devonian in age are proposed based on the first appearance datum（FAD）of characteristic spore species.In ascending stratigraphic order,they are Ambitisporites dilutus-Apiculiretusispora synorea（DS;Late Ludfordian to Early Pridoli）,Synorisporites verrucatus-Apiculiretusispora plicata（VP;Pridoli）,Apiculiretusispora minuta-Leiotriletes ornatus（MO;Lochkovian）,and Verrucosisporites polygonalis-Dibolisporites wetteldorfensis（PW;Pragian）.The acritarch assemblage from the upper part of the Yulongsi Formation,the Xiaxishancun Formation,and the lower-middle parts of the Xitun Formation indicates an age of Late Silurian.Based on palynological evidence,the upper part of the Yulongsi Formation is considered Late Ludfordian to Early Pridoli in age;the Xiaxishancun Formation is believed to be Pridoli in age;the Xitun Formation is considered Late Pridoli to Early Lochkovian in age;the Guijiatun Formation is considered Lochkovian in age;and the Xujiachong Formation is Late Lochkovian to Pragian in age.The Silurian-Devonian boundary is recognized between the VP and the MO spore biozones,and occurs within the middle part of the Xitun Formation.展开更多
Devonian in the North Qilian orogenic belt and Hexi Corridor developed terrestrial molasse of later stage of foreland basin caused by collision between the North China plate and Qaidam microplate. The foreland basin t...Devonian in the North Qilian orogenic belt and Hexi Corridor developed terrestrial molasse of later stage of foreland basin caused by collision between the North China plate and Qaidam microplate. The foreland basin triggered a intense earthquake, and formed seismites and earthquake-related soft-sediment deformation. The soft-sediment deformation structures of Devonian in the eastern North Qilian Mts. consist of seismo-cracks, sandstone dykes, syn-depositional faults, microfoids （micro-corrugated lamination）, fluidized veins, load casts, flame structures, pillow structures and brecciation. The seismo-cracks, syn-depositional faults and microfolds are cracks, faults and folds formed directly by oscillation of earthquake. The seismic dykes formed by sediment instilling into seismic cracks. Fluidized veins were made by instilling into the seismo-fissures of the fluidized sands. The load casts, flame structures and pillow structures were formed by sinking and instilling caused from oscillation of earthquake along the face between sandy and muddy beds. The brecciation resulted from the oscillation of earthquake and cracking of sedimentary layers. The seismites and soft-sediment deformations in Devonian triggered the earthquake related to tectonic activities during the orogeny and uplift of North Qilian Mts.展开更多
A group of radiolarian fossils with a complete morphological gradient of increasing polarization are reported from upper Devonian successions in southwestern Tianshan, China. Specifically, the important transitional m...A group of radiolarian fossils with a complete morphological gradient of increasing polarization are reported from upper Devonian successions in southwestern Tianshan, China. Specifically, the important transitional mophotypes, Pylentonema transitorum sp. nov., Archocyrtium medium sp. nov. and Quadrapesus transitivus sp. nov, were found. Based on the fact that the new transitional radiolarian fossils resemble more closely to pylentonemids （cyrtoid nassellarians） than to entactinids （spumellarians） in morphology, they are assigned to pylentonemids. Pylentonemids share characters of both the Nassellaria （e.g., horned cephalis, basal opening with pylome） and Spumellaria （e.g., system of trabecular spicules）, and they are thus of evolutionary significance. The evolutionary trend from spumellarians to nassellarians is characterized by （1） internal spicule： from simple trabecular spicules to complicate components （A;Ir,II;D;V;Lr,Li;MB）; （2） polarization of the radiolarian tests due to rearrangment of spine, from radial to an axial symmetry; （3） the gradual formation of a basal opening （aperture, pylome, or podome）; and the transition from a pseudopylome, a primative pylome with a narrow margin on the outer shell, to a true pylome rimmed with a narrow, elevated impermite wall.展开更多
The Caiziyan Middle and Upper Devonian boundary section is located approximately 30 km northeast of Guilin. It hosts relatively abundant benthic and common-rare pelagic fossils, including brachiopods, corals, tentacul...The Caiziyan Middle and Upper Devonian boundary section is located approximately 30 km northeast of Guilin. It hosts relatively abundant benthic and common-rare pelagic fossils, including brachiopods, corals, tentaculites, and conodonts, which may serve as a better suitable section for pelagic and neritic stratigraphic correlation. In this section, 10 ＂standard＂ conodont zones are recognized across the Givetian-Frasnian boundary, including, in descending order, the Lower hassi Zone, punctata Zone, transitans Zone, the Upperfalsiovalis Zone, the Lowerfalsiovalis Zone, disparilis Zone, the Upper hermanni-cristatus Zone, the Lower hermanni-cristatus Zone, the Upper varcus Zone, and the Middle varcus Zone, all of which are defined by the first occurrence of their defining conodont species. The Middle-Upper Devonian （Givetian-Frasnian） boundary is defined by the first occurrence of Ancyrodella pristina in accordance with the Global Stratotype Section and Point （GSSP）, which is assigned at 6.2m above the base of bed 19 in the Caiziyan section.展开更多
In South China four depositional sequences are recognized in the upper part of Upper Devonian and Tournaisian. They are named SQ0 SQ1, SQ2 and SQ3 in ascending order. SQ0 is Strunian (uppermost Devonian), and the othe...In South China four depositional sequences are recognized in the upper part of Upper Devonian and Tournaisian. They are named SQ0 SQ1, SQ2 and SQ3 in ascending order. SQ0 is Strunian (uppermost Devonian), and the other three Tournaisian in age. These four depositional sequences appear to correlate fairly well with the four sequence recognized in Europe, North America and other areas. This may suggest that these sequences are synchronous depos- its resulted from the eustatic changes. The present study on sequence stratigraphy, biostratigraphy and event stratigraphy indicates that in neritic facies areas of South China, the Devonian-Carboniferous boundary, matching the boundary between Siphonodella praesulcata zone and S. sulcata zone in pelagic facies areas, is not only higher than the top of the Cystophrentis zone, but also higher than the top of the Devonian-Carboniferous boundary event bed. In neritic facies areas, the Devonian-Carbonifrerous boundary is marked by the most distinct transgressive surface within the Cystophrentiseudouralina interval zone, i. e. at the base of the TST of the SQ1. This boundary coincides with the top surface of the event bed resulted from the eustatic fall, and approximately corresponds to the basal part of Rseudouralina assemblage zone.展开更多
Two zosterophyll plants are described from the Lower Devonian （Lochkovian） Xitun Formation of Qujing, Yunnan, China. Xitunia spinitheca gen. et sp. nov. has stalked sporangia laterally attached on the axis in a heli...Two zosterophyll plants are described from the Lower Devonian （Lochkovian） Xitun Formation of Qujing, Yunnan, China. Xitunia spinitheca gen. et sp. nov. has stalked sporangia laterally attached on the axis in a helical arrangement. Sporangia are dorsoventrally flattened and composed of two unequal valves; the adaxial valve is round in face view, while the abaxial valve is larger than the former, triangular or wedge-shaped, and radially bears long spiny appendages along the distal margin. Xitunia shows new variation of sporangial morphology within the zosterophylls. Zosterophyllum minorstachyum sp. nov. has K-shaped branchings at the basal parts and small-sized terminal spikes, which consist of round to elliptical sporangia arranged helically. This paper provides new data on the diversity of plant types during Lochkovian when rare vascular plants were reported. As for various species of Zosterophyllum in South China, their apparent evolutionary trend of features from the Late Silurian to Early Devonian （Emsian） is discussed.展开更多
The Wangchengpo Frasnian section of Dushan County contains two atrypid brachiopod assemblages. The lower is characterized by the Atryparia （Costatrypa） dushanensis fauna that appears at the base of the Hejiazhai Mem...The Wangchengpo Frasnian section of Dushan County contains two atrypid brachiopod assemblages. The lower is characterized by the Atryparia （Costatrypa） dushanensis fauna that appears at the base of the Hejiazhai Member approximately in the falsiovalis to transitans conodont zones： the upper is characterized by the Radiatrypa yangi fauna, which appears in the Lujiazhai Member approximately correspondent with the hassi to Upper rhenana conodont zones. Atrypid brachiopods, together with other brachiopods from the Dushan section show that the Hejiazhai Member is of Frasnian age. Preliminary analyses of Frasnian atrypid brachiopods from sections of South China indicate that there are nine genera and subgenera including Atryparia （Costatrypa）, Kyrtatrypa, Spinatrypa, lsospinatrypa, Spinatrypina, lowatrypa, Desquamatia （Desquamatia）. Desquamatia （Seratrypa）, and Radiatr）pa. Atrypid species diversity did not change much through the Frasnian. On a regional scale in South China, most atrypid species went extinct prior to the Frasnian/Famennian boundary. At any specific locality or section, these atrypids became extinct about 20-40 m below the Frasnian/Famennian （F/F） boundary, within the linguiformis conodont Zone, marking this as the major extinction level. Three new atrypid species are described： Atryparia （Costatrypa） dushanensis, lowatrypa pseudobodini, and Radiatrypa yangi.展开更多
Phanerozoic strata are distributed in several north-south trending zones in the central part of the Changning-Menglian Belt. Four types of Devonian to Triassic stratigraphic successions can be identified: (1) elastics...Phanerozoic strata are distributed in several north-south trending zones in the central part of the Changning-Menglian Belt. Four types of Devonian to Triassic stratigraphic successions can be identified: (1) elastics with limestone lenses in the mid-section, changing up-section into alternations of fine elastics and cherts; (2) elastics with chert intercalations and limestone lenses, and topped by Permian basic volcanics; (3) elastics-basic volcanics-carbonates-clastics; and (4) limestones, dolomitic limestones-dark gray thin-bedded limestones, argillaceous limestones, mudstones and siliceous mudstones. Devonian to Triassic cherts occur in different horizons and different zones from east to west. These cherts are usually transitional to their neighboring elastics. There is no continuous Devonian to Middle Triassic chert sequence in the central zone of the Changning-Menglian Belt as Liu et al. (1991,1993) reported. Volcanics and the overlying carbonates described by some workers as 'seamount' sequences are more likely to have formed in a marine environment on continental crust. Succession (4) is newly recognized in the area from Menglai to Yong'an in Cangyuan County and further north to Padi of Gengma County. Basalts, cherts and elastics also appear in this area. Mid-Triassic (very probably Ladinian) radiolarians extracted from bedded cherts in the Ganzhejidi section indicate that they are in higher stratigraphic positions. The change from bedded cherts via siltstones to thick-bedded sandstones with thin-bedded fine intercalations in the Ganzhejidi section and (some other outcrops along the road from Cangyuan to Gengma) suggests a fundamental change of sedimentary environment caused by a rapid increase of a large quantity of detritus supply. These siliciclastic sediments are possibly syn-orogenic deposits.展开更多
A new plant, Zhenglia radiata gen. et sp. nov., from the Posongchong Formation （Early Devonian, Pragian age） of the Wenshan District of southeastern Yunnan Province, China is a small herbaceous lycopsid. The aerial ...A new plant, Zhenglia radiata gen. et sp. nov., from the Posongchong Formation （Early Devonian, Pragian age） of the Wenshan District of southeastern Yunnan Province, China is a small herbaceous lycopsid. The aerial branches divide into foliar and fertile stems. The arrangement of the leaf bases on the stem shows lepidodendroid-like phyllotaxy. Possibly the leaf base bears a ligulate pit. The microphyll consists of a swollen, decurrent base, and an entire, linear lamina. The fertile axis is composed of sporophylls arranged helically, forming a compact area similar to cone-like structure. Each sporophyll consists of a widened lateral extension and a distal lamina. The ovoid-elongate sporangia are attached adaxially on the surface of sporophylls. Based on morphological similarities, especially the undivided microphylls, the style of phyllotaxy, the form of the cone-like structures and sporangia, the new lycopsid Zhenglia radiata is placed in the order Protolepidodendrales and a possible evolutionary relationship with the arborescent lycopsids of the Late Devonian and Carboniferous is considered.展开更多
Twenty orthosequences and their corresponding sea-level change (SLC) cycles have been recognized in the Devonian overlying the Caledonian unconformity, of which 9, 5.5 and 5.5 occurred in the Lower, Middle and Upper D...Twenty orthosequences and their corresponding sea-level change (SLC) cycles have been recognized in the Devonian overlying the Caledonian unconformity, of which 9, 5.5 and 5.5 occurred in the Lower, Middle and Upper Devonian respectively. They can be grouped into 4 orthosequence sets, in which the maximum flooding surfaces lie in the sulcutus Zone (D12), perbonus Zone (D13), Middle and Upper varcus Zone (D22) and gigas Zone (D21) respectively. Four instant palaeogeographical reconstructions of South China have been made in the Emsian and Givetian. Devonian sea-level change rhythms of South China can be divided into 3 categories: the autorhythmic, the worldwide and regional allorhythmic, and the coupling-rhythmic. They developed respectively in the Famennian, Pragian, Eifelian, Lochkovian, Emsian, Givetian, Frasnian and the F / F (between the Frasnian and Famennian) event. The cause of the worldwide allorhythmic SLC of the Pragian and Eifelian under comparatively dry, warm and tranquil conditions may be related to the pulsating expanding and contracting of the oceanic basin volume or the earth volume pulsation, rather than the common glaciation and plate tectonism. The coupling-rhythmic SLC related to the F/ F event is a sensitive indicator of the interaction between terrestrial and extraterrestrial factors, and coordinated action among the earth-spheres.展开更多
文摘Microspherules are found in different facies at the Lower-Middle Devonian boundary, Guangxi, South China. There are more than 20 grains per kilogram rock sample. Composition and form of the microspherules are very similar to those of the microtektites from modern deposits of South Pacific Ocean and F-F boundary (Devonian). This may indicate that the microspherules from Guangxi are most likely the products of an extraterrestrial impact event that occurred at the end of Early Devonian Epoch. The event may be responsible for the biomass reduction and extinction of benthic organisms at the end of Early Devonian. The impact products (ejecta) can be used as a potential tool for stratigraphic correlation.
基金Project supported by the National Natural Science Foundation of China Doctoral Foundation of National Education Committee
文摘The controversies on the division and correlation of the Devonian have never stopped since Lonsodale found and named the Devonian at Devonshire, Britain, especially on the determination and correlation of the Lower-Middle Devonian Boundary. The correlation between the different areas and sedimentary facies are still an international question although the international stratotype section has already been established. Recently,
基金supported by Guizhou Provincial Science and Technology Projects(No.ZK[2021]ordinary 199)the National Natural Science Foundation of China(Nos.42262019,92062221)the National Key R&D Program of China(No.2017YFC0603103)。
文摘The Yingshan Formation of the Lower-Middle Ordovician in the Tarim Basin(NW China)was mainly deposited in a shallow platform,which was intensely bioturbated with burrows filled with both dolomites and calcites.This study aims to figure out the controls on the dolomitization of burrow infills and the effects on petroleum reservoir quality based on petrographic examination,fluid inclusion microthermometry,and isotopic(C-O-Sr)geochemical analyses.The differentiation of burrow-associated carbonates(dolomites and calcites)was likely controlled by the interactions of sea-level oscillations of variable orders and depositional environments.The burrow-associated dolomites(BADs)were precipitated in a relatively restricted(i.e.,lagoon)depositional environment during the lowstand of long-term sea level.In contrast,the burrow-associated calcites(BACs)were formed in a water circulation-improved lagoonal environment during the transgression of long-term sea level.Isotopic geochemical data indicate that the BADs in the Yingshan Formation were formed from slightly saline(i.e.,mesosaline to penesaline)seawater,whereas the BACs were precipitated from nearly normal seawater.In addition to the anoxic condition,the presence of marine-sourced organic matter and sulfate-reducing bacteria,and a sufficient supply of dolomitizing fluids enriched in magnesium ions(Mg^(2+))and their Mg^(2+)concentration may have played a critical role in the formation of BADs.In the more permeable and disturbed burrow sediments as a result of burrowing,penetrating fluids with higher salinities and higher Mg^(2+)concentration relative to seawater favored dolomite precipitation.The fluids with seawater-like Mg^(2+)concentration,however,would lead to calcite precipitation.The progressive dolomitization of these burrowed sediments could have propagated the dolomitizing fronts and extended into ambient limestones,leading to the development of extensive dolomites.This dolomitization process can improve the petrophysical properties(porosity and permeability)and the potential as hydrocarbon reservoirs during the emplacement of hydrocarbons from underlying source rocks of the Cambrian to Lower Ordovician.
基金supported by the National Natural Science Foundation of China (Nos. 40672080, 40621002)the Program for Innovative Research Team in University of the Ministry of Education of China (No. IRT00546)
文摘The detrital modes of the sandstones from the south basin of Dabie（大别） orogenic belt during the Early-Middle Jurassic are complex due to multiple supplying.Detrital compositions of medium-coarse sandstones from the Lower-Middle Jurassic,Huangshi（黄石）,show three main provenances：recycled ororgen,volcanic arc（arc orogen）,and continental block on the bases of the Dickinson discriminating diagrams of modal composition and analysis of sandstone petrofacies.Combined with sparse published paleocurrent data,geotectonic setting of the study area,and the unpublished detrital zircon age data,the positions of the main provenances are inferred as follows：coastal orogenic belt（COB） in the East China provided detritus as the recycled orogen provenance;Dabie orogenic belt（DOB） to the north was the source of volcanic arc（arc orogen） materials;and the continental block clasts were likely from the uplift of the Yangtze basement（UYB）（Jiangnan（江南） uplift）.Six sedimentary cycles are recognized in the studied section,one in Wuchang（武昌） Formation,and five in Huajiahu（花家湖） Formation.During the deposition,the three main provenances play different roles.The quantitative petrofacies analysis revealed distinct changes of the effect from each source,that is,61.9%（Cycle Ⅰ）→54.5%（Cycle Ⅲ）→50%（Cycle Ⅳ）→57.9%（Cycle Ⅴ）→14.3%（Cycle Ⅵ）,14.3%（Cycle Ⅰ）→21.2%（ Cycle Ⅲ）→40%（Cycle Ⅳ）→36.8%（Cycle Ⅴ）→14.3%（Cycle Ⅵ）,and 23.8%（Cycle Ⅰ）→24.2%（Cycle Ⅲ）→10%（Cycle Ⅳ）→5.3%（Cycle Ⅴ）→71.4%（Cycle Ⅵ） from COB,DOB,and UYB,respectively.The results show that（1） COB behaved in considerable activation during the EarlyJurassic but weakened in the Middle Jurassic;（2） the vigorous tectonic uplift of DOB initiated in Middle Jurassic;and（3） UYB was in stabilization basically from the Early to Middle Jurassic.
文摘BACKGROUND While Crohn’s disease has been studied extensively in high-income countries,its epidemiology and care in low and lower-middle income countries(LLMICs)is not well established due to a lack of disease registries and diagnostic capacity.AIM To describe the published burden,diagnostic/treatment capacity,service utilization,challenges/barriers to individuals with Crohn’s in LLMICs and their providers.METHODS We conducted a scoping review utilizing a full search strategy was developed and conducted in PubMed,Embase and World Health Organization Global Index Medicus.Two independent reviewers screened the titles and abstracts of all of the publications found in this search,reviewed selected publications,and extracted relevant data,which underwent descriptive review and was analyzed in Excel.RESULTS The database search yielded 4486 publications,216 of which were determined to be relevant to the research questions.Of all 79 LLMICs,only 21(26.6%)have publications describing individuals with Crohn’s.Overall,the highest number of studies came from India,followed by Tunisia,and Egypt.The mean number of Crohn’s patients reported per study is 57.84 and the median is 22,with a wide range from one to 980.CONCLUSION This scoping review has shown that,although there is a severe lack of populationbased data about Crohn’s in LLMICs,there is a signal of Crohn’s in these settings around the world.
文摘Here we report a left cheek plate of Psarolepis,a postparietal shield of Youngolepis,a skull of Diabolepis,and a scale of Styloichthys from the Lianhuashan and Nahkaoling formations(Lochkovian,Lower Devonian)of Nanning,Guangxi.This marks the first report of Diabolepis and Styloichthys beside Qujing,Yunnan,and the latest occurrence of Psarolepis to date.The fossil community displays significant similarities to the Xujiachong Assemblage,and provides new data for the Lower Devonian stratigraphic correlation between southwestern China and northern Vietnam.Given the latest dating constraint based on the conodont evidence,we regard that the Xujiachong Assemblage has a much longer range than previously supposed,extending from the latest Lochkovian to the end of Pragian.We propose that the transition of the Nahkaoling and Lianhuashan formations in Nanning might correspond to the Guijiatun Formation in Qujing.The relatively large size of fish individuals from Guangxi is probably attributed to the increase in the oxygen content of the ocean.
基金Supported by the National Natural Science Foundation of China Nos.41702011 and 41372019.
文摘A genus within the family Douvillinidae of the order Strophomenida from the Erdaogou Memberof the Xibiehe Formation in the Early Devonian of central Jilin has been re-examined, with considerationgiven to the 56 specimens collected and described by Liu and Huang (1977). Based on its distinct externalornamentation and internal characteristics, it has been classified as Cymostrophia (Protocymostrophia). It isconcluded that the three specices described by Liu and Huang (1977), Idioglyptus alatus, I. semicircularis,I. subquadratus, as well as the Mesodouvillina jilinensis Su, 1980 should be considered synonyms and benamed Cymostrophia (Protocymostrophia) alatus (Liu) Li.
基金supported by the Chinese Academy of Sciences(noKZCX2-YW-105, KZCX2-SW-130)the National Natural Science Foundation of China(no40523004 and 40072005)
文摘Well-preserved and diversified spores,cryptospores,and acritarchs have been recorded from a relatively continuous sequence that encompasses the Silurian-Devonian boundary in Qujing, Yunnan,southwest China.Four spore assemblage zones from Late Silurian to Early Devonian in age are proposed based on the first appearance datum（FAD）of characteristic spore species.In ascending stratigraphic order,they are Ambitisporites dilutus-Apiculiretusispora synorea（DS;Late Ludfordian to Early Pridoli）,Synorisporites verrucatus-Apiculiretusispora plicata（VP;Pridoli）,Apiculiretusispora minuta-Leiotriletes ornatus（MO;Lochkovian）,and Verrucosisporites polygonalis-Dibolisporites wetteldorfensis（PW;Pragian）.The acritarch assemblage from the upper part of the Yulongsi Formation,the Xiaxishancun Formation,and the lower-middle parts of the Xitun Formation indicates an age of Late Silurian.Based on palynological evidence,the upper part of the Yulongsi Formation is considered Late Ludfordian to Early Pridoli in age;the Xiaxishancun Formation is believed to be Pridoli in age;the Xitun Formation is considered Late Pridoli to Early Lochkovian in age;the Guijiatun Formation is considered Lochkovian in age;and the Xujiachong Formation is Late Lochkovian to Pragian in age.The Silurian-Devonian boundary is recognized between the VP and the MO spore biozones,and occurs within the middle part of the Xitun Formation.
基金supported by the National Natural Science Foundation of China(NO,40672080,40621002)the Program for Innovative Research Team in University of the Ministry of Education of China(IRT00546)"111 Project"(Grant No.B08030)
文摘Devonian in the North Qilian orogenic belt and Hexi Corridor developed terrestrial molasse of later stage of foreland basin caused by collision between the North China plate and Qaidam microplate. The foreland basin triggered a intense earthquake, and formed seismites and earthquake-related soft-sediment deformation. The soft-sediment deformation structures of Devonian in the eastern North Qilian Mts. consist of seismo-cracks, sandstone dykes, syn-depositional faults, microfoids （micro-corrugated lamination）, fluidized veins, load casts, flame structures, pillow structures and brecciation. The seismo-cracks, syn-depositional faults and microfolds are cracks, faults and folds formed directly by oscillation of earthquake. The seismic dykes formed by sediment instilling into seismic cracks. Fluidized veins were made by instilling into the seismo-fissures of the fluidized sands. The load casts, flame structures and pillow structures were formed by sinking and instilling caused from oscillation of earthquake along the face between sandy and muddy beds. The brecciation resulted from the oscillation of earthquake and cracking of sedimentary layers. The seismites and soft-sediment deformations in Devonian triggered the earthquake related to tectonic activities during the orogeny and uplift of North Qilian Mts.
基金This work was supported by the National Nature Science Foundation of China(No.40232019).
文摘A group of radiolarian fossils with a complete morphological gradient of increasing polarization are reported from upper Devonian successions in southwestern Tianshan, China. Specifically, the important transitional mophotypes, Pylentonema transitorum sp. nov., Archocyrtium medium sp. nov. and Quadrapesus transitivus sp. nov, were found. Based on the fact that the new transitional radiolarian fossils resemble more closely to pylentonemids （cyrtoid nassellarians） than to entactinids （spumellarians） in morphology, they are assigned to pylentonemids. Pylentonemids share characters of both the Nassellaria （e.g., horned cephalis, basal opening with pylome） and Spumellaria （e.g., system of trabecular spicules）, and they are thus of evolutionary significance. The evolutionary trend from spumellarians to nassellarians is characterized by （1） internal spicule： from simple trabecular spicules to complicate components （A;Ir,II;D;V;Lr,Li;MB）; （2） polarization of the radiolarian tests due to rearrangment of spine, from radial to an axial symmetry; （3） the gradual formation of a basal opening （aperture, pylome, or podome）; and the transition from a pseudopylome, a primative pylome with a narrow margin on the outer shell, to a true pylome rimmed with a narrow, elevated impermite wall.
基金supported by the National Natural Science Foundation ofChina(Grants 40472009,40872007,and 40830211)the Major Basic Research Projects of the Ministry ofScience and Technology,China(2006CB806400)
文摘The Caiziyan Middle and Upper Devonian boundary section is located approximately 30 km northeast of Guilin. It hosts relatively abundant benthic and common-rare pelagic fossils, including brachiopods, corals, tentaculites, and conodonts, which may serve as a better suitable section for pelagic and neritic stratigraphic correlation. In this section, 10 ＂standard＂ conodont zones are recognized across the Givetian-Frasnian boundary, including, in descending order, the Lower hassi Zone, punctata Zone, transitans Zone, the Upperfalsiovalis Zone, the Lowerfalsiovalis Zone, disparilis Zone, the Upper hermanni-cristatus Zone, the Lower hermanni-cristatus Zone, the Upper varcus Zone, and the Middle varcus Zone, all of which are defined by the first occurrence of their defining conodont species. The Middle-Upper Devonian （Givetian-Frasnian） boundary is defined by the first occurrence of Ancyrodella pristina in accordance with the Global Stratotype Section and Point （GSSP）, which is assigned at 6.2m above the base of bed 19 in the Caiziyan section.
文摘In South China four depositional sequences are recognized in the upper part of Upper Devonian and Tournaisian. They are named SQ0 SQ1, SQ2 and SQ3 in ascending order. SQ0 is Strunian (uppermost Devonian), and the other three Tournaisian in age. These four depositional sequences appear to correlate fairly well with the four sequence recognized in Europe, North America and other areas. This may suggest that these sequences are synchronous depos- its resulted from the eustatic changes. The present study on sequence stratigraphy, biostratigraphy and event stratigraphy indicates that in neritic facies areas of South China, the Devonian-Carboniferous boundary, matching the boundary between Siphonodella praesulcata zone and S. sulcata zone in pelagic facies areas, is not only higher than the top of the Cystophrentis zone, but also higher than the top of the Devonian-Carboniferous boundary event bed. In neritic facies areas, the Devonian-Carbonifrerous boundary is marked by the most distinct transgressive surface within the Cystophrentiseudouralina interval zone, i. e. at the base of the TST of the SQ1. This boundary coincides with the top surface of the event bed resulted from the eustatic fall, and approximately corresponds to the basal part of Rseudouralina assemblage zone.
基金supportedby the National Natural Science Foundation of China(Nos.40672001,40802003,40830211)China PostdoctoralScience Foundation(20070420245)
文摘Two zosterophyll plants are described from the Lower Devonian （Lochkovian） Xitun Formation of Qujing, Yunnan, China. Xitunia spinitheca gen. et sp. nov. has stalked sporangia laterally attached on the axis in a helical arrangement. Sporangia are dorsoventrally flattened and composed of two unequal valves; the adaxial valve is round in face view, while the abaxial valve is larger than the former, triangular or wedge-shaped, and radially bears long spiny appendages along the distal margin. Xitunia shows new variation of sporangial morphology within the zosterophylls. Zosterophyllum minorstachyum sp. nov. has K-shaped branchings at the basal parts and small-sized terminal spikes, which consist of round to elliptical sporangia arranged helically. This paper provides new data on the diversity of plant types during Lochkovian when rare vascular plants were reported. As for various species of Zosterophyllum in South China, their apparent evolutionary trend of features from the Late Silurian to Early Devonian （Emsian） is discussed.
基金Th is work is supported by the Major Basic Research Project(G2000077700)the National Natural Science Foundation of China(Grant No.401 72006,40232019,and 40472009).
文摘The Wangchengpo Frasnian section of Dushan County contains two atrypid brachiopod assemblages. The lower is characterized by the Atryparia （Costatrypa） dushanensis fauna that appears at the base of the Hejiazhai Member approximately in the falsiovalis to transitans conodont zones： the upper is characterized by the Radiatrypa yangi fauna, which appears in the Lujiazhai Member approximately correspondent with the hassi to Upper rhenana conodont zones. Atrypid brachiopods, together with other brachiopods from the Dushan section show that the Hejiazhai Member is of Frasnian age. Preliminary analyses of Frasnian atrypid brachiopods from sections of South China indicate that there are nine genera and subgenera including Atryparia （Costatrypa）, Kyrtatrypa, Spinatrypa, lsospinatrypa, Spinatrypina, lowatrypa, Desquamatia （Desquamatia）. Desquamatia （Seratrypa）, and Radiatr）pa. Atrypid species diversity did not change much through the Frasnian. On a regional scale in South China, most atrypid species went extinct prior to the Frasnian/Famennian boundary. At any specific locality or section, these atrypids became extinct about 20-40 m below the Frasnian/Famennian （F/F） boundary, within the linguiformis conodont Zone, marking this as the major extinction level. Three new atrypid species are described： Atryparia （Costatrypa） dushanensis, lowatrypa pseudobodini, and Radiatrypa yangi.
基金support by the Chinese Geological Survey(Grant No.200210000009)the National Natural Science Foundation of China(Grant No.40232024)
文摘Phanerozoic strata are distributed in several north-south trending zones in the central part of the Changning-Menglian Belt. Four types of Devonian to Triassic stratigraphic successions can be identified: (1) elastics with limestone lenses in the mid-section, changing up-section into alternations of fine elastics and cherts; (2) elastics with chert intercalations and limestone lenses, and topped by Permian basic volcanics; (3) elastics-basic volcanics-carbonates-clastics; and (4) limestones, dolomitic limestones-dark gray thin-bedded limestones, argillaceous limestones, mudstones and siliceous mudstones. Devonian to Triassic cherts occur in different horizons and different zones from east to west. These cherts are usually transitional to their neighboring elastics. There is no continuous Devonian to Middle Triassic chert sequence in the central zone of the Changning-Menglian Belt as Liu et al. (1991,1993) reported. Volcanics and the overlying carbonates described by some workers as 'seamount' sequences are more likely to have formed in a marine environment on continental crust. Succession (4) is newly recognized in the area from Menglai to Yong'an in Cangyuan County and further north to Padi of Gengma County. Basalts, cherts and elastics also appear in this area. Mid-Triassic (very probably Ladinian) radiolarians extracted from bedded cherts in the Ganzhejidi section indicate that they are in higher stratigraphic positions. The change from bedded cherts via siltstones to thick-bedded sandstones with thin-bedded fine intercalations in the Ganzhejidi section and (some other outcrops along the road from Cangyuan to Gengma) suggests a fundamental change of sedimentary environment caused by a rapid increase of a large quantity of detritus supply. These siliciclastic sediments are possibly syn-orogenic deposits.
基金This work was supported by the National Natural Science Foundation of China （No. 40232019 No. 40302001）.
文摘A new plant, Zhenglia radiata gen. et sp. nov., from the Posongchong Formation （Early Devonian, Pragian age） of the Wenshan District of southeastern Yunnan Province, China is a small herbaceous lycopsid. The aerial branches divide into foliar and fertile stems. The arrangement of the leaf bases on the stem shows lepidodendroid-like phyllotaxy. Possibly the leaf base bears a ligulate pit. The microphyll consists of a swollen, decurrent base, and an entire, linear lamina. The fertile axis is composed of sporophylls arranged helically, forming a compact area similar to cone-like structure. Each sporophyll consists of a widened lateral extension and a distal lamina. The ovoid-elongate sporangia are attached adaxially on the surface of sporophylls. Based on morphological similarities, especially the undivided microphylls, the style of phyllotaxy, the form of the cone-like structures and sporangia, the new lycopsid Zhenglia radiata is placed in the order Protolepidodendrales and a possible evolutionary relationship with the arborescent lycopsids of the Late Devonian and Carboniferous is considered.
基金Jointly supported by the Special Research Foundation for Doctorate Programme of CollegesUniversities of the State Education Commission of China (No. 9549111), Fundamental Research Project from the State Commission of Science and Technology of ChinaNa
文摘Twenty orthosequences and their corresponding sea-level change (SLC) cycles have been recognized in the Devonian overlying the Caledonian unconformity, of which 9, 5.5 and 5.5 occurred in the Lower, Middle and Upper Devonian respectively. They can be grouped into 4 orthosequence sets, in which the maximum flooding surfaces lie in the sulcutus Zone (D12), perbonus Zone (D13), Middle and Upper varcus Zone (D22) and gigas Zone (D21) respectively. Four instant palaeogeographical reconstructions of South China have been made in the Emsian and Givetian. Devonian sea-level change rhythms of South China can be divided into 3 categories: the autorhythmic, the worldwide and regional allorhythmic, and the coupling-rhythmic. They developed respectively in the Famennian, Pragian, Eifelian, Lochkovian, Emsian, Givetian, Frasnian and the F / F (between the Frasnian and Famennian) event. The cause of the worldwide allorhythmic SLC of the Pragian and Eifelian under comparatively dry, warm and tranquil conditions may be related to the pulsating expanding and contracting of the oceanic basin volume or the earth volume pulsation, rather than the common glaciation and plate tectonism. The coupling-rhythmic SLC related to the F/ F event is a sensitive indicator of the interaction between terrestrial and extraterrestrial factors, and coordinated action among the earth-spheres.
