This work deals with the evolution of carbon isotope composition in the Luoyixi (罗依溪) Section, a candidate of the Global Standard Stratotype-section and Point (GSSP), defining the base of the as-yet-undefined s...This work deals with the evolution of carbon isotope composition in the Luoyixi (罗依溪) Section, a candidate of the Global Standard Stratotype-section and Point (GSSP), defining the base of the as-yet-undefined seventh stage of Cambrian System at the first appearance of the cosmopolitan agnostoid Lejopyge iaevigata. This level is favored in a vote of International Subcommission on Cambrian Stratigraphy (ISCS) as the biohorizon for defining the base of a global stage. Two hundred and sixty-four samples for carbon and oxygen isotope analysis have been collected from the carbonate successions at an interval of 0.25 to 0.5 m in this section. Results of the carbon isotope data exhibit a remarkable disciplinarian trend. The pattern of the carbon isotope evolution is gently undulant with a relatively long period during the underlying Drumian Stage, and then the values of δ13C fluctuate sharply with a short period in provisional seventh stage. The onset of sharp fluctuation in the δ13C values begins at the proposed GSSP level, defining the base of the global seventh stage, where δ13C values change from a gentle trend to a sharp trend. Distinct covariant-relationships among δ13C,δ18O, and sea level fluctuations suggest that a warming change in paleoclimate took place during the early global seventh stage, which led to a positive shift in δ13C values.展开更多
A polymetallic layer is usually developed at the bottom of the early Cambrian black shale in Guizhou Province.The mineral that makes up the polymetallic layer is related to the sedimentary facies.To analyze the differ...A polymetallic layer is usually developed at the bottom of the early Cambrian black shale in Guizhou Province.The mineral that makes up the polymetallic layer is related to the sedimentary facies.To analyze the differentiation mechanism between polymetallic deposits(Ni-Mo and V),the Zhijin Gezhongwu profile located in the outer shelf and the Sansui Haishan V deposit located in the lower slope are selected to study the in situ sulfur isotopes and trace elements of pyrite.The results show that δ^(34)S values of pyrite vary widely from−7.8‰to 28‰in the Gezhongwu profile,while the δ^(34)S values are relatively uniform(from 27.8‰to 38.4‰)in the Haishan profile.The isotopic S composition is consistent with the transition that occurs in the sedimentary phase from the shelf to the deep sea on the transgressive Yangtze platform;this indicates that the δ^(34)SO_(4)^(2−)values in seawater must be differently distributed in depositional environments.The sulfur in the Ni-Mo layer is produced after the mixing of seawater and hydrothermal fluid,while the V layer mainly originates from seawater.Overall,the Ni-Mo and V deposits have been differentiated primarily on the basis of the combined effect of continental weathering and hydrothermal fluid.展开更多
The Early Cambrian represents a critical time period characterized by extraordinary biological innovations and dynamic redox conditions in seawaters.Nitrogen isotopic signatures of ancient sediments have the potential...The Early Cambrian represents a critical time period characterized by extraordinary biological innovations and dynamic redox conditions in seawaters.Nitrogen isotopic signatures of ancient sediments have the potential to elucidate the evolutionary path of marine redox states and the biogeochemical nitrogen cycle within the water column of the Early Cambrian ocean.While existing research on this topic has predominantly focused on South China,the exploration of other continental margins has been limited,leaving contradictory hypotheses untested.In this study,pairedδ^(15)N andδ^(13)C org analyses were performed on the Lower Cambrian successions from the Shiairike section(inner ramp)and Well Tadong 2(deep shelf/basin)in the northwestern and eastern Tarim Basin,respectively.Our data from the Shiairike section reveal a discernible shift in the operation of different nitrogen cycles for the black chert-shale unit,also referred to as the black rock series in Chinese literature,of the Yurtus Formation(Fortunian stage to lower Stage 3).Oscillatingδ^(15)N values for its lower part are suggestive of alternating anaerobic assimilation of NH 4+and denitrification/anammox.This is likely attributed to a shallow,unstable chemocline consistent with the upwelling and incursion of deep,anoxic waters during a major transgression.In contrast,aerobic nitrogen cycling,indicated by positiveδ^(15)N values of>2‰,dominated the upper part alongside a reduction in upwelling intensity.On the other hand,theδ^(15)N signatures of Xishanbulake and Xidashan Formations of Well Tadong 2,which encompass a time interval from the Cambrian Fortunian Age to Age 4,are indicative of N_(2)fixation by diazotrophs as the major nitrogen source.The two studied intervals,although not time-equivalent,exhibit separated states of nitrogen cycling at least during the deposition of the Yurtus black rock series.The spatially different nitrogen cycling of the studied sections is compatible with a redox-stratified ocean during the deposition of the Yurtus black rock series.The build-up of a NO_(3)−reservoir and aerobic nitrogen cycling in seawater was largely restricted to near-shore settings whereas anaerobic nitrogen cycling dominated by N_(2)fixation served as the main nitrogen uptake pathway in off-shore settings.展开更多
Cambrian carbonates with abundant fossils of agnostoid trilobites deposited on the southern slope (Jiangnan slope belt) of the Yangtze Platform and in the Jiangnan deepwater basin are well exposed in the Wangeun Sec...Cambrian carbonates with abundant fossils of agnostoid trilobites deposited on the southern slope (Jiangnan slope belt) of the Yangtze Platform and in the Jiangnan deepwater basin are well exposed in the Wangeun Section of western Hunan, South China, and in the Duibian A Section of western Zhejiang, southeastern China, respectively. To better understand the response of carbonisotope excursions to depositional environment changes, mass extinctions and eustatic events, we collected 530 carbonate samples in fresh roadcut exposures of the two measured sections for analysis of carbon and oxygen isotopic compositions. Data of δ^13C from the Wangcun Section, western Hunan, South China, demonstrate that the Cambrian carbon-isotope profile includes three remarkable positive excursions CPEwc-1, 2, 3 in the Upper Series 2, in the Lower and in the Middle Furongian Series. Three distinctive negative excursions CNEwc,-1, 2, 3 were separately tested in the Lower Terreneuvian Series, Lower Series 3 and in the Upper Furongian Series. Similarly, in the corresponding horizons in the Duibian A Section, Zhejiang Province, southeastern China, three positive excursions CPEdb-1, 2, 3 and three negative excursions CNEdb-1, 2, 3 also have been discovered. We interpret these significant carbon-isotope excursions as being associated with enhanced biogenic prodnctivity, mass extinctions and eustatic events.展开更多
Based on the latest drilling, seismic and field outcrop data, the geological characteristics(e.g. strata, development and sedimentary evolution) of the southern segment of the Late Sinian–Early Cambrian Deyang–Anyue...Based on the latest drilling, seismic and field outcrop data, the geological characteristics(e.g. strata, development and sedimentary evolution) of the southern segment of the Late Sinian–Early Cambrian Deyang–Anyue rift trough in the Sichuan Basin are analyzed. First, the strata in the southern segment are complete. The first to second members of Dengying Formation(Deng 1 + Deng 2) are found with relatively stable thickness(400–550 m), and the third to fourth members(Deng 3+ Deng 4) show great thickness difference between the marginal trough and the inner trough, which is up to 250 m. The Cambrian Maidiping Formation and Qiongzhusi Formation in southern Sichuan Basin are relatively thin, with the thickness changing greatly and frequently. Second, the Deyang–Anyue rift trough extended southward during the Deng 4 period, affecting southern Sichuan Basin. Compared to the middle and northern segments of the rift trough, the southern segment is generally wide, gentle and shallow, with multiple steps, and alternating uplifts and sags, which are distributed in finger shape. Third, the Deng 1 + Deng 2 in southern Sichuan Basin records the dominance of carbonate platform and unobvious sedimentary differentiation, and the Deng 4 exhibits obvious sedimentary differentiation, namely, basin–slope–secondary slope–slope–secondary slope–platform margin–restricted platform, from the inner trough to the marginal trough. Fourth, the rift trough in southern Sichuan Basin has evolved in four stages: stabilization of Deng 1–Deng 2, initialization of Deng 3–Deng 4, filling of Maidiping–Qiongzhusi, and extinction of Canglangpu Formation.展开更多
Important ecological changes of the Earth (oxidization of the atmosphere and the ocean) increase in nutrient supply due to the break-up of the super continent (Rodinia) and the appearance of multi-cellular organis...Important ecological changes of the Earth (oxidization of the atmosphere and the ocean) increase in nutrient supply due to the break-up of the super continent (Rodinia) and the appearance of multi-cellular organisms (macroscopic algae and metazoan) took place in the Ediacaran period, priming the Cambrian explosion. The strong perturbations in carbon cycles in the ocean are recorded as excursions in carbonate and organic carbon isotope ratio (δ13Ccarb and δ13Corg) from the Ediacaran through early Cambrian periods. The Ediacaran-early Cambrian sediment records of δ13Ccarb and δ13Corg, obtained from the drill-core samples in Three Gorges in South China, are compared with the results of numerical simulation of a sim- ple one-zone model of the carbon cycle of the ocean, which has two reservoirs (i.e., dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC). The fluxes from the reservoirs are assumed to be proportional to the mass of the carbon reservoirs. We constructed a model, referred to here as the Best Fit Model (BFM), which reproduce δ13Ccarb and δ13Corg records in the Ediacaran-early Cambrian period noted above. BFM reveals that the Shuram excursion is related to three major changes in the carbon cycle or the global ecological system of the Earth: (1) an increase in the coefficient of remineralization by a factor of ca. 100, possibly corresponding to a change in the dominant metabolism from anaerobic respiration to aerobic respiration, (2) an increase of carbon fractionation index from 25‰, to 33‰, possibly corresponding to the change in the primary producer from rock-living cyanobacteria to free-living macro algae, and (3) an in- crease in the coefficient of the organic carbon burial by a factor of ca. 100, possibly corresponding to the onset of a biological pump driven by the flourishing metazoan and zooplankton. The former two changes took place at the start of the Shuram excursion, while the third occurred at the end of the Shuram excursion. The other two excursions are explained by the tentative decrease in primary production due to cold periods, which correspond to the Gaskiers (ca. 580 Ma) and Bikonor (ca. 542 Ma) glaciations.展开更多
The Xixiangchi Group in eastern Sichuan Basin has great potential for natural gas exploration.However,there is a lack of in-depth studies of the hydrocarbon sources and the formation and evolution of gas reservoirs in...The Xixiangchi Group in eastern Sichuan Basin has great potential for natural gas exploration.However,there is a lack of in-depth studies of the hydrocarbon sources and the formation and evolution of gas reservoirs in this Group.Systematic investigation about the gas reservoir in Pingqiao anticline was consequently carried out in terms of characteristics of reservoir bitumen,the geochemical characteristics of natural gas,diagenetic minerals,and fluid inclusions.Based on this,combined with the reconstruction of the burial history,thermal evolution history and uplifting history of strata,and analysis of the regional tectonic settings,the hydrocarbon sources were identified and the formation and evolutionary processes of the gas reservoirs in Xixiangchi Group was revealed in this study.It was shown that the gas reservoirs have mixed gas sources from the shale source rocks in the Lower Cambrian Qiongzhusi Formation and in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation,and experienced several evolutionary stages,including the paleo-oil reservoir stage from the Late Siliurian to the Middle Permian,the paleo-gas reservoir stage from the Late Permian to the Early Cretaceous,and the superimposed accumulation and mixed-source gas reservoir stage since the Late Cretaceous.The mixed-source gas reservoir is formed by the adjustment of the Xixiangchi Group paleo-gas reservoirs and depressurization of the overpressure Wufeng-Longmaxi shale gas reservoirs and the charging of gas into the Xixiangchi Group reservoir of the Pingqiao anticline since the Late Cretaceous,which show obvious superimposed accumulation characteristics.There are different accumulation patterns in different geological periods.The accumulation pattern of the“old source-young reservoir”(i.e.hydrocarbons generated from older source rocks accumulating in younger reservoirs)dominates before the Late Cretaceous,and that of“juxtaposed young source-old reservoir”(i.e.hydrocarbons generated from younger source rocks accumulating in juxtaposed older reservoirs)dominates after the Early Cretaceous.Moreover,faults acted as critical vertical pathways for hydrocarbon migration during the evolution of the Xixiangchi Group gas reservoirs.This model provides new insights and theoretical basis for evaluation and mapping of the Xixiangchi Group play fairway in eastern Sichuan Basin.展开更多
A study of the morphological and microstructural characteristics of helcionelloids from the Nanjiang area(north Sichuan,China)at the northern Yangtze Platform was undertaken,in order to understand their phylogenetic p...A study of the morphological and microstructural characteristics of helcionelloids from the Nanjiang area(north Sichuan,China)at the northern Yangtze Platform was undertaken,in order to understand their phylogenetic position.Helcionelloids fossils from the Kuanchuanpu Formation of the Changtanhe–Maolinzi section include 7 genera and 11 species.There are distinct differences in the degree of shell bending,the apical morphology and apex position,the outline of the aperture and the height of the shell,all of which constitute important identification features.Although helcionelloid apices exhibit varying degrees of rotation towards the aperture,they do not show any signs of evident distortion.A pair of basally-symmetrical muscle scars are discovered on the shells of helcionelloids(such as Bemella simplex),showing a distinct difference when compared with those of the stem-group gastropod(e.g.,Pelagiella).The prismatic shell layer of helcionelloids has been observed,which are common components in Cambrian molluscs,but differ significantly from the dense layer microstructure found in contemporary molluscs.The microstructures,muscle scars and morphological characteristics demonstrate that helcionelloids represent a stem-group of molluscs.展开更多
Some trace elements(TEs),both bio-essential and redox-sensitive,are promising tracers of Earth’s surface processes.As an essential sedimentary organic matter,kerogen may have inherited and retained the key TEs from o...Some trace elements(TEs),both bio-essential and redox-sensitive,are promising tracers of Earth’s surface processes.As an essential sedimentary organic matter,kerogen may have inherited and retained the key TEs from organisms.In this study,the distribution of TEs in kerogens from two sections(Dongkanshang and Fengtan) in South China was analyzed to explore its biogeochemical significance during Ediacaran-Lower Cambrian.Compared with V and Zn,the relative concentrations of Co,Ni,Cu,and Mo were generally higher in kerogens than in the whole rocks.Enrichment of TEs in the kerogen was involved in the selective utilization of TEs by different organic precursors and the competition of sulfide in the depositional environment.The significant content of TEs in the kerogens from deep-water facies corresponded to a more negative δ^(13) Ckeras a result of the dominant taxa of chemo autotrophs with tremendous bioaccumulation potential for trace metals and the reduction conditions favorable for organic matter preservation.Furthermore,the content variations of trace elements in the kerogens coincided with the rise and fall of the Ediacaran biota,implying that the trace elements might have played an important role in early life evolution.展开更多
Early Cambrian shale is an important petroleum source rock around the world.Because of little drilling data and poor seismic data,until recently,organic matter enrichment of the Lower Cambrian Yuertusi and Xishanbulak...Early Cambrian shale is an important petroleum source rock around the world.Because of little drilling data and poor seismic data,until recently,organic matter enrichment of the Lower Cambrian Yuertusi and Xishanbulake formations shale is still an enigma in the Tarim Basin,northwestern China.Total organic carbon(TOC),major and trace element data of Cambrian shale samples from five boreholes have been analyzed to decipher the mechanism of the organic matter enrichment.The results show that the shales deposited in the western restricted intraplatform have much higher TOC contents(3.2%-19.8%,on average 11.0%)than those from the eastern basin(2.2%-10.2%,on average 4.5%).The paleoproductivity proxies(Ba,Ba/Al,P/Al)in the western restricted platform are much higher than those in the eastern basin.The trace element indicators such as V/Cr,Ni/Co,Mo-TOC and Mo_(EF)-U_(EF)suggest an anoxic environment across the basin,but a more restricted environment in the western intraplatform.The paleoproductivity rather than anoxic condition and hydrothermal activity are concluded to have resulted in the differentiation of the organic matter enrichment from the western intraplatform to eastern basin in the early Cambrian shales;the restricted environment was favorable for paleoproductivity and preservation of organic matter.展开更多
The Moroccan Anti-Atlas is a vast geological region composed of a Precambrian basement covered by a late-Neoproterozoic to Paleozoic sedimentary sequences. More than 200 copper occurrences are listed in these sequence...The Moroccan Anti-Atlas is a vast geological region composed of a Precambrian basement covered by a late-Neoproterozoic to Paleozoic sedimentary sequences. More than 200 copper occurrences are listed in these sequences. The copper mineralization of the Jbel N’Zourk (Central Anti-Atlas) is observed into the lower Limestones of the lower Cambrian (Adoudou formation), just above the volcanic formations of the Jbel Boho between Bou Azzer El Graara and Zenaga inliers. The region is by an E-W shortening resulting in an overlapping structure with vergence associated with folds. Generally, the mineralization is hosted along the principal fault of Jbel N’Zourk and sometimes in the anticlines hinges. The petrographic study showed that the mineralization can be observed in several aspects, either in the fractures and veins, in small karsts or rarely disseminated in calcite and dolomite minerals. These observations host new arguments who contribute to a later reconcentration of the copper mineralization of Jbel N’Zourk, trapped on faulted and folded structures attributed to Variscan deformation.展开更多
This paper briefly summarizes an officially ratified Global Standard Stratotype-section and Point (GSSP) and a proposed GSSP for global stages of the Cambrian System. The Luoyixi section near Luoyixi town, Guzhang, ...This paper briefly summarizes an officially ratified Global Standard Stratotype-section and Point (GSSP) and a proposed GSSP for global stages of the Cambrian System. The Luoyixi section near Luoyixi town, Guzhang, northwestern Hunan is ratified as the boundary stratotype for the base of the global Guzhangian Stage, which is the upmost stage of an unnamed series termed provisionally as Cambrian Series 3. The GSSP position lies 121.3 m above the base of the Huaqiao Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Lejopyge leavigata.The Duibian B section at Duibian village, Jiangshan, western Zhejiang, is proposed as the boundary stratotype for the base of the proposed global Jiangshanian Stage that is the second stage of the Furongian Series. The proposed GSSP position lies 108.12 m above the base of the Huayansi Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalius. This horizon is also with the first appearance of the cosmopolitan polymerid trilobite lrvingella angustilimbata.展开更多
Based on analyses of characteristics,hydrocarbon charging history and geological conditions for the formation of Sinian-Cambrian reservoirs in the north slope area of central Sichuan paleo-uplift,the natural gas origi...Based on analyses of characteristics,hydrocarbon charging history and geological conditions for the formation of Sinian-Cambrian reservoirs in the north slope area of central Sichuan paleo-uplift,the natural gas origin,accumulation evolution,accumulation pattern and formation conditions of large lithologic gas reservoirs have been investigated.Through comprehensive analyses of natural gas composition,carbon and hydrogen isotopic compositions,fluid inclusions,reservoir bitumen,and geological conditions such as lithofacies paleogeography and beach body characterization,it is concluded that:(1)The natural gas in the Sinian-Cambrian of the north slope area is mainly oil cracking gas,and different contribution ratios of multiple sets of source rocks lead to different geochemical characteristics of natural gas in different reservoirs.(2)Although the both Sinian and Cambrian gas reservoirs in this area are lithologic gas reservoirs under monocline background,the former has normal-pressure and the latter has high-pressure.There are three types of source-reservoir-caprock combinations:single source with lower generation and upper reservoir,double sources with lower generation and upper reservoir or with side source and lateral reservoir,double sources with lower generation and upper reservoir or with upper generation and lower reservoir.The Permian-Triassic is the main generation period of oil,Early-Middle Jurassic is the main generation period of oil cracking gas and wet gas,and Late Jurassic-Cretaceous is the main generation period of dry gas.(3)The Sinian-Cambrian system of the north slope area has two favorable conditions for formation of large lithologic gas reservoirs,one is that the large scale beach facies reservoirs are located in the range of ancient oil reservoirs or near the source rocks,which is conducive to the"in-situ"large-scale accumulation of cracked gas in the paleo-oil reservoirs,the other is that the large scale mound-beach complex reservoirs and sealing layers of inter beach tight zones match effectively to form large lithologic traps under the slope background.The research results confirm that the north slope area has large multi-layer lithologic gas reservoirs with more than one trillion cubic meters of natural gas resources and great exploration potential.展开更多
A Burgess Shale-type biota is, in part, characterized by a wide diversity of taxa and soft-part preservation. Each provides unique historical insights into early metazoan evolution. Among the more than 40 globally dis...A Burgess Shale-type biota is, in part, characterized by a wide diversity of taxa and soft-part preservation. Each provides unique historical insights into early metazoan evolution. Among the more than 40 globally distributed biotas, the early Cambrian Chengjiang and Middle Cambrian Burgess-type biotas are the largest. The Kaili Biota, from the earliest Middle Cambrian of Guizhou, China, contains representatives of 110 metazoan genera belonging to 10 phyla. It contains many well-persevered soft-bodied specimens. This Chinese biota has become the third most taxonomically diverse Burgess Shale-type fauna. Because the Kaili Biota formed in an outer-shelf environment, its main faunal character is large numbers of eocrinoids and planktoic trilobites. The Kaili is younger than the Chengjiang Biota but older than the Canadian Burgess Shale Biota; it shares 30 genera with the Chengjiang and 38 genera with the Burgess Biota. The Kaili Biota displays a taphonomic window to the diversification and evolution of marine offshore organisms covering 5.13 million years between the Early and Middle Cambrian.展开更多
Since 1985, samples with a total weight of more than 14,000 kg, mainly from three key sections in western and northwestern Hunan, South China, have been processed for conodonts. In strata older than the late Late Camb...Since 1985, samples with a total weight of more than 14,000 kg, mainly from three key sections in western and northwestern Hunan, South China, have been processed for conodonts. In strata older than the late Late Cambrian paraconodonts have proved useful for stratigraphic subdivision and correlation. Thirteen conodont zones are proposed in the Middle Cambrian through lowermost Ordovician. The correlation between these zones and those of North China, western U. S.A., western Newfoundland, Canada, and Iran is discussed. In ascending order, these 13 zones are as follows: The Gapparodus bisulcatus-Westergaardodina brevidens Zone, Shandongodus priscus-Hunanognathus tricuspidatus Zone, Westergaardodina quadrata Zone, Westergaardodina matsushitai-W. grandidens Zone, Westergaardodina lui-W. am Zone, Westergaardodina cf. calix-Prooneotodus rotundatus Zone, Proconodontus tenuiserratus Zone, Proconodontus Zone, Eoconodontus Zone, Cordylodus proavus Zone, Cordylodus intermedius Zone, Cordylodus lindstromi Zone, and Cordylodus angulatus Zone (lower part). The Westergaardodina lui-W. ani and Westergaardodina cf. calix-Prooneotodus rotundatus Zones replace the Westergaardodina proligula and Westergaardodina cf. behrae-Prooneotodus rotundatus Zones, respectively, in the lowermost Upper Cambrian. Two new species (Westergaardodina Iui and Westergaardodina ani) and one conditionally identified species (Westergaardodina cf. calix) are described.展开更多
The Guanshan Fauna, a soft-bodied fauna intermediate between the Chengjiang Fauna and the Kaili Fauna and also the Burgess Shale Fauna stratigraphically, consists of trilobites, trilobitoides, Tuzoia, Vetulicola, Pale...The Guanshan Fauna, a soft-bodied fauna intermediate between the Chengjiang Fauna and the Kaili Fauna and also the Burgess Shale Fauna stratigraphically, consists of trilobites, trilobitoides, Tuzoia, Vetulicola, Paleoscolex, brachiopods and sponges. The discovery and research of this fauna is of great significance in understading the 'Cambrian Explosion' and the evolution of early life. The occurrence of vetulicoliids from the Guanshan Fauna not only adds new members to the taxonomic list, but also provides new information to the evolution of this animal group. This paper describe Vetulicola gantoucunensis Luo, Fu et Hu sp. nov. from the Lower Cambrian Wulongqing Formation in the Kunming area. Also presented are the amended description of Vetulicola and the comparisons with related genera within Vetulicoliids. The affinity, distribution, as well as evolution of vetulicoliids are discussed.展开更多
The Lower Cambrian Chengjiang Lagerstatte provides a good window to explorethe origin and radiation of early bilaterians. Here we describe a netted sclerite-bearing wormTabelliscolex hexagonus gen. et sp. nov., and te...The Lower Cambrian Chengjiang Lagerstatte provides a good window to explorethe origin and radiation of early bilaterians. Here we describe a netted sclerite-bearing wormTabelliscolex hexagonus gen. et sp. nov., and tentatively assign it to palaeoscolecidans ofpriapulids. The cuticle of the animal is covered with two kinds of platy sclerites which areconstructed by hexagonally arranged tubercles Similar structures of the sclerites can be seen onsome Cambrian palaeoscolecidans and lobopods, so, this new species is critical for understanding therelationships between lobopods and palaeoscolecidans.展开更多
The genus and species Yuyuanozoon magnificissimi gen. et sp. nov., a new fossil vetulicolian, is reported from the Early Cambrian Chengjiang Fauna in Yunnan of China. It has a bipartite body plan and five pairs of cha...The genus and species Yuyuanozoon magnificissimi gen. et sp. nov., a new fossil vetulicolian, is reported from the Early Cambrian Chengjiang Fauna in Yunnan of China. It has a bipartite body plan and five pairs of chain-formed gill sacs, showing the general characteristics of Ventulicolia. However, the exclusive 'atrial cavity' and external gill observed indicate that the new form is different from those previously described as vetulicolians, probably representing a lineage developed within deuterostomes and more primitive than urochordates.展开更多
基金the National Natural Science Foundation of China (Nos. 40672023, 40332018)Chinese Academy of Sciences (KZCX2-YW-122) and the Major Basic Research Project of MST (2006CB806400).
文摘This work deals with the evolution of carbon isotope composition in the Luoyixi (罗依溪) Section, a candidate of the Global Standard Stratotype-section and Point (GSSP), defining the base of the as-yet-undefined seventh stage of Cambrian System at the first appearance of the cosmopolitan agnostoid Lejopyge iaevigata. This level is favored in a vote of International Subcommission on Cambrian Stratigraphy (ISCS) as the biohorizon for defining the base of a global stage. Two hundred and sixty-four samples for carbon and oxygen isotope analysis have been collected from the carbonate successions at an interval of 0.25 to 0.5 m in this section. Results of the carbon isotope data exhibit a remarkable disciplinarian trend. The pattern of the carbon isotope evolution is gently undulant with a relatively long period during the underlying Drumian Stage, and then the values of δ13C fluctuate sharply with a short period in provisional seventh stage. The onset of sharp fluctuation in the δ13C values begins at the proposed GSSP level, defining the base of the global seventh stage, where δ13C values change from a gentle trend to a sharp trend. Distinct covariant-relationships among δ13C,δ18O, and sea level fluctuations suggest that a warming change in paleoclimate took place during the early global seventh stage, which led to a positive shift in δ13C values.
基金supported by the National Natural Science Foundation of China(Grant Nos.42272103,92062221,42063009,U1812402)the Guizhou Provincial Science and Technology Projects(Grant No.Qiankehejichu–ZK[2022]common 213)the Higher Education Scientific Research Projects of the Education Department of Guizhou Province(Grant No.Qianjiaoji[2022]157).
文摘A polymetallic layer is usually developed at the bottom of the early Cambrian black shale in Guizhou Province.The mineral that makes up the polymetallic layer is related to the sedimentary facies.To analyze the differentiation mechanism between polymetallic deposits(Ni-Mo and V),the Zhijin Gezhongwu profile located in the outer shelf and the Sansui Haishan V deposit located in the lower slope are selected to study the in situ sulfur isotopes and trace elements of pyrite.The results show that δ^(34)S values of pyrite vary widely from−7.8‰to 28‰in the Gezhongwu profile,while the δ^(34)S values are relatively uniform(from 27.8‰to 38.4‰)in the Haishan profile.The isotopic S composition is consistent with the transition that occurs in the sedimentary phase from the shelf to the deep sea on the transgressive Yangtze platform;this indicates that the δ^(34)SO_(4)^(2−)values in seawater must be differently distributed in depositional environments.The sulfur in the Ni-Mo layer is produced after the mixing of seawater and hydrothermal fluid,while the V layer mainly originates from seawater.Overall,the Ni-Mo and V deposits have been differentiated primarily on the basis of the combined effect of continental weathering and hydrothermal fluid.
基金supported by the Fundamental Research Funds for the Central Universities(No.B200202009).
文摘The Early Cambrian represents a critical time period characterized by extraordinary biological innovations and dynamic redox conditions in seawaters.Nitrogen isotopic signatures of ancient sediments have the potential to elucidate the evolutionary path of marine redox states and the biogeochemical nitrogen cycle within the water column of the Early Cambrian ocean.While existing research on this topic has predominantly focused on South China,the exploration of other continental margins has been limited,leaving contradictory hypotheses untested.In this study,pairedδ^(15)N andδ^(13)C org analyses were performed on the Lower Cambrian successions from the Shiairike section(inner ramp)and Well Tadong 2(deep shelf/basin)in the northwestern and eastern Tarim Basin,respectively.Our data from the Shiairike section reveal a discernible shift in the operation of different nitrogen cycles for the black chert-shale unit,also referred to as the black rock series in Chinese literature,of the Yurtus Formation(Fortunian stage to lower Stage 3).Oscillatingδ^(15)N values for its lower part are suggestive of alternating anaerobic assimilation of NH 4+and denitrification/anammox.This is likely attributed to a shallow,unstable chemocline consistent with the upwelling and incursion of deep,anoxic waters during a major transgression.In contrast,aerobic nitrogen cycling,indicated by positiveδ^(15)N values of>2‰,dominated the upper part alongside a reduction in upwelling intensity.On the other hand,theδ^(15)N signatures of Xishanbulake and Xidashan Formations of Well Tadong 2,which encompass a time interval from the Cambrian Fortunian Age to Age 4,are indicative of N_(2)fixation by diazotrophs as the major nitrogen source.The two studied intervals,although not time-equivalent,exhibit separated states of nitrogen cycling at least during the deposition of the Yurtus black rock series.The spatially different nitrogen cycling of the studied sections is compatible with a redox-stratified ocean during the deposition of the Yurtus black rock series.The build-up of a NO_(3)−reservoir and aerobic nitrogen cycling in seawater was largely restricted to near-shore settings whereas anaerobic nitrogen cycling dominated by N_(2)fixation served as the main nitrogen uptake pathway in off-shore settings.
基金supported by the National Natural Science Foundation of China(Nos.41672028,41672002,41330101,41221001)
文摘Cambrian carbonates with abundant fossils of agnostoid trilobites deposited on the southern slope (Jiangnan slope belt) of the Yangtze Platform and in the Jiangnan deepwater basin are well exposed in the Wangeun Section of western Hunan, South China, and in the Duibian A Section of western Zhejiang, southeastern China, respectively. To better understand the response of carbonisotope excursions to depositional environment changes, mass extinctions and eustatic events, we collected 530 carbonate samples in fresh roadcut exposures of the two measured sections for analysis of carbon and oxygen isotopic compositions. Data of δ^13C from the Wangcun Section, western Hunan, South China, demonstrate that the Cambrian carbon-isotope profile includes three remarkable positive excursions CPEwc-1, 2, 3 in the Upper Series 2, in the Lower and in the Middle Furongian Series. Three distinctive negative excursions CNEwc,-1, 2, 3 were separately tested in the Lower Terreneuvian Series, Lower Series 3 and in the Upper Furongian Series. Similarly, in the corresponding horizons in the Duibian A Section, Zhejiang Province, southeastern China, three positive excursions CPEdb-1, 2, 3 and three negative excursions CNEdb-1, 2, 3 also have been discovered. We interpret these significant carbon-isotope excursions as being associated with enhanced biogenic prodnctivity, mass extinctions and eustatic events.
基金Supported by the PetroChina Science and Technology Project (2021DJ0605,2022KT0101)the CNPC Major Science and Technology Project (2021DJ0501)。
文摘Based on the latest drilling, seismic and field outcrop data, the geological characteristics(e.g. strata, development and sedimentary evolution) of the southern segment of the Late Sinian–Early Cambrian Deyang–Anyue rift trough in the Sichuan Basin are analyzed. First, the strata in the southern segment are complete. The first to second members of Dengying Formation(Deng 1 + Deng 2) are found with relatively stable thickness(400–550 m), and the third to fourth members(Deng 3+ Deng 4) show great thickness difference between the marginal trough and the inner trough, which is up to 250 m. The Cambrian Maidiping Formation and Qiongzhusi Formation in southern Sichuan Basin are relatively thin, with the thickness changing greatly and frequently. Second, the Deyang–Anyue rift trough extended southward during the Deng 4 period, affecting southern Sichuan Basin. Compared to the middle and northern segments of the rift trough, the southern segment is generally wide, gentle and shallow, with multiple steps, and alternating uplifts and sags, which are distributed in finger shape. Third, the Deng 1 + Deng 2 in southern Sichuan Basin records the dominance of carbonate platform and unobvious sedimentary differentiation, and the Deng 4 exhibits obvious sedimentary differentiation, namely, basin–slope–secondary slope–slope–secondary slope–platform margin–restricted platform, from the inner trough to the marginal trough. Fourth, the rift trough in southern Sichuan Basin has evolved in four stages: stabilization of Deng 1–Deng 2, initialization of Deng 3–Deng 4, filling of Maidiping–Qiongzhusi, and extinction of Canglangpu Formation.
基金partly supported by grants for "Secular variation of seawater composition(No. 16740284)""Coevolution of surface environment and solid Earth from the Neoproterozoic Snowball Earth to Cambrian explosion events(No.18740318)"+1 种基金the 21st Century COE Program "How to build habitable planets" at the Tokyo Institute of Technology from the Ministry of Education,Culture,Sports,Science and Technology,Japanthe Mitsubishi Foundation (T.K.)
文摘Important ecological changes of the Earth (oxidization of the atmosphere and the ocean) increase in nutrient supply due to the break-up of the super continent (Rodinia) and the appearance of multi-cellular organisms (macroscopic algae and metazoan) took place in the Ediacaran period, priming the Cambrian explosion. The strong perturbations in carbon cycles in the ocean are recorded as excursions in carbonate and organic carbon isotope ratio (δ13Ccarb and δ13Corg) from the Ediacaran through early Cambrian periods. The Ediacaran-early Cambrian sediment records of δ13Ccarb and δ13Corg, obtained from the drill-core samples in Three Gorges in South China, are compared with the results of numerical simulation of a sim- ple one-zone model of the carbon cycle of the ocean, which has two reservoirs (i.e., dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC). The fluxes from the reservoirs are assumed to be proportional to the mass of the carbon reservoirs. We constructed a model, referred to here as the Best Fit Model (BFM), which reproduce δ13Ccarb and δ13Corg records in the Ediacaran-early Cambrian period noted above. BFM reveals that the Shuram excursion is related to three major changes in the carbon cycle or the global ecological system of the Earth: (1) an increase in the coefficient of remineralization by a factor of ca. 100, possibly corresponding to a change in the dominant metabolism from anaerobic respiration to aerobic respiration, (2) an increase of carbon fractionation index from 25‰, to 33‰, possibly corresponding to the change in the primary producer from rock-living cyanobacteria to free-living macro algae, and (3) an in- crease in the coefficient of the organic carbon burial by a factor of ca. 100, possibly corresponding to the onset of a biological pump driven by the flourishing metazoan and zooplankton. The former two changes took place at the start of the Shuram excursion, while the third occurred at the end of the Shuram excursion. The other two excursions are explained by the tentative decrease in primary production due to cold periods, which correspond to the Gaskiers (ca. 580 Ma) and Bikonor (ca. 542 Ma) glaciations.
基金supported by the National Key R&D Program of China grant(2017YFC0603105).
文摘The Xixiangchi Group in eastern Sichuan Basin has great potential for natural gas exploration.However,there is a lack of in-depth studies of the hydrocarbon sources and the formation and evolution of gas reservoirs in this Group.Systematic investigation about the gas reservoir in Pingqiao anticline was consequently carried out in terms of characteristics of reservoir bitumen,the geochemical characteristics of natural gas,diagenetic minerals,and fluid inclusions.Based on this,combined with the reconstruction of the burial history,thermal evolution history and uplifting history of strata,and analysis of the regional tectonic settings,the hydrocarbon sources were identified and the formation and evolutionary processes of the gas reservoirs in Xixiangchi Group was revealed in this study.It was shown that the gas reservoirs have mixed gas sources from the shale source rocks in the Lower Cambrian Qiongzhusi Formation and in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation,and experienced several evolutionary stages,including the paleo-oil reservoir stage from the Late Siliurian to the Middle Permian,the paleo-gas reservoir stage from the Late Permian to the Early Cretaceous,and the superimposed accumulation and mixed-source gas reservoir stage since the Late Cretaceous.The mixed-source gas reservoir is formed by the adjustment of the Xixiangchi Group paleo-gas reservoirs and depressurization of the overpressure Wufeng-Longmaxi shale gas reservoirs and the charging of gas into the Xixiangchi Group reservoir of the Pingqiao anticline since the Late Cretaceous,which show obvious superimposed accumulation characteristics.There are different accumulation patterns in different geological periods.The accumulation pattern of the“old source-young reservoir”(i.e.hydrocarbons generated from older source rocks accumulating in younger reservoirs)dominates before the Late Cretaceous,and that of“juxtaposed young source-old reservoir”(i.e.hydrocarbons generated from younger source rocks accumulating in juxtaposed older reservoirs)dominates after the Early Cretaceous.Moreover,faults acted as critical vertical pathways for hydrocarbon migration during the evolution of the Xixiangchi Group gas reservoirs.This model provides new insights and theoretical basis for evaluation and mapping of the Xixiangchi Group play fairway in eastern Sichuan Basin.
基金funded by the National Natural Science Foundation of China(Grant Nos.41872007,41972026)the Sichuan Science and Technology Program(2018JY0491)。
文摘A study of the morphological and microstructural characteristics of helcionelloids from the Nanjiang area(north Sichuan,China)at the northern Yangtze Platform was undertaken,in order to understand their phylogenetic position.Helcionelloids fossils from the Kuanchuanpu Formation of the Changtanhe–Maolinzi section include 7 genera and 11 species.There are distinct differences in the degree of shell bending,the apical morphology and apex position,the outline of the aperture and the height of the shell,all of which constitute important identification features.Although helcionelloid apices exhibit varying degrees of rotation towards the aperture,they do not show any signs of evident distortion.A pair of basally-symmetrical muscle scars are discovered on the shells of helcionelloids(such as Bemella simplex),showing a distinct difference when compared with those of the stem-group gastropod(e.g.,Pelagiella).The prismatic shell layer of helcionelloids has been observed,which are common components in Cambrian molluscs,but differ significantly from the dense layer microstructure found in contemporary molluscs.The microstructures,muscle scars and morphological characteristics demonstrate that helcionelloids represent a stem-group of molluscs.
基金financially supported by the National Natural Science Foundation of China (42072145)the National Oil and Gas Special Project of China (2017ZX05008002)。
文摘Some trace elements(TEs),both bio-essential and redox-sensitive,are promising tracers of Earth’s surface processes.As an essential sedimentary organic matter,kerogen may have inherited and retained the key TEs from organisms.In this study,the distribution of TEs in kerogens from two sections(Dongkanshang and Fengtan) in South China was analyzed to explore its biogeochemical significance during Ediacaran-Lower Cambrian.Compared with V and Zn,the relative concentrations of Co,Ni,Cu,and Mo were generally higher in kerogens than in the whole rocks.Enrichment of TEs in the kerogen was involved in the selective utilization of TEs by different organic precursors and the competition of sulfide in the depositional environment.The significant content of TEs in the kerogens from deep-water facies corresponded to a more negative δ^(13) Ckeras a result of the dominant taxa of chemo autotrophs with tremendous bioaccumulation potential for trace metals and the reduction conditions favorable for organic matter preservation.Furthermore,the content variations of trace elements in the kerogens coincided with the rise and fall of the Ediacaran biota,implying that the trace elements might have played an important role in early life evolution.
基金partly supported by the National Natural Science Foundation of China(Grant No.42241206,91955204)the Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(Grant No.4224100017,2020CX010101)。
文摘Early Cambrian shale is an important petroleum source rock around the world.Because of little drilling data and poor seismic data,until recently,organic matter enrichment of the Lower Cambrian Yuertusi and Xishanbulake formations shale is still an enigma in the Tarim Basin,northwestern China.Total organic carbon(TOC),major and trace element data of Cambrian shale samples from five boreholes have been analyzed to decipher the mechanism of the organic matter enrichment.The results show that the shales deposited in the western restricted intraplatform have much higher TOC contents(3.2%-19.8%,on average 11.0%)than those from the eastern basin(2.2%-10.2%,on average 4.5%).The paleoproductivity proxies(Ba,Ba/Al,P/Al)in the western restricted platform are much higher than those in the eastern basin.The trace element indicators such as V/Cr,Ni/Co,Mo-TOC and Mo_(EF)-U_(EF)suggest an anoxic environment across the basin,but a more restricted environment in the western intraplatform.The paleoproductivity rather than anoxic condition and hydrothermal activity are concluded to have resulted in the differentiation of the organic matter enrichment from the western intraplatform to eastern basin in the early Cambrian shales;the restricted environment was favorable for paleoproductivity and preservation of organic matter.
文摘The Moroccan Anti-Atlas is a vast geological region composed of a Precambrian basement covered by a late-Neoproterozoic to Paleozoic sedimentary sequences. More than 200 copper occurrences are listed in these sequences. The copper mineralization of the Jbel N’Zourk (Central Anti-Atlas) is observed into the lower Limestones of the lower Cambrian (Adoudou formation), just above the volcanic formations of the Jbel Boho between Bou Azzer El Graara and Zenaga inliers. The region is by an E-W shortening resulting in an overlapping structure with vergence associated with folds. Generally, the mineralization is hosted along the principal fault of Jbel N’Zourk and sometimes in the anticlines hinges. The petrographic study showed that the mineralization can be observed in several aspects, either in the fractures and veins, in small karsts or rarely disseminated in calcite and dolomite minerals. These observations host new arguments who contribute to a later reconcentration of the copper mineralization of Jbel N’Zourk, trapped on faulted and folded structures attributed to Variscan deformation.
基金supported by the Ministry of Science and Technology of China (2006FY120300)the State Key Laboratory of Palaeobiology and Stratigraphy (20091103)funded by the National Natural Science Foundation of China (40072003, 40023002, 40332018, 40672023, 40602002)
文摘This paper briefly summarizes an officially ratified Global Standard Stratotype-section and Point (GSSP) and a proposed GSSP for global stages of the Cambrian System. The Luoyixi section near Luoyixi town, Guzhang, northwestern Hunan is ratified as the boundary stratotype for the base of the global Guzhangian Stage, which is the upmost stage of an unnamed series termed provisionally as Cambrian Series 3. The GSSP position lies 121.3 m above the base of the Huaqiao Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Lejopyge leavigata.The Duibian B section at Duibian village, Jiangshan, western Zhejiang, is proposed as the boundary stratotype for the base of the proposed global Jiangshanian Stage that is the second stage of the Furongian Series. The proposed GSSP position lies 108.12 m above the base of the Huayansi Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalius. This horizon is also with the first appearance of the cosmopolitan polymerid trilobite lrvingella angustilimbata.
基金Chinese Academy of Sciences Strategic Pilot Science and Technology Project(Class A)(XDA14010403)National Science and Technology Major Project(2016ZX05007)PetroChina Science and Technology Project(2021DJ0604,kt2020-01-03)。
文摘Based on analyses of characteristics,hydrocarbon charging history and geological conditions for the formation of Sinian-Cambrian reservoirs in the north slope area of central Sichuan paleo-uplift,the natural gas origin,accumulation evolution,accumulation pattern and formation conditions of large lithologic gas reservoirs have been investigated.Through comprehensive analyses of natural gas composition,carbon and hydrogen isotopic compositions,fluid inclusions,reservoir bitumen,and geological conditions such as lithofacies paleogeography and beach body characterization,it is concluded that:(1)The natural gas in the Sinian-Cambrian of the north slope area is mainly oil cracking gas,and different contribution ratios of multiple sets of source rocks lead to different geochemical characteristics of natural gas in different reservoirs.(2)Although the both Sinian and Cambrian gas reservoirs in this area are lithologic gas reservoirs under monocline background,the former has normal-pressure and the latter has high-pressure.There are three types of source-reservoir-caprock combinations:single source with lower generation and upper reservoir,double sources with lower generation and upper reservoir or with side source and lateral reservoir,double sources with lower generation and upper reservoir or with upper generation and lower reservoir.The Permian-Triassic is the main generation period of oil,Early-Middle Jurassic is the main generation period of oil cracking gas and wet gas,and Late Jurassic-Cretaceous is the main generation period of dry gas.(3)The Sinian-Cambrian system of the north slope area has two favorable conditions for formation of large lithologic gas reservoirs,one is that the large scale beach facies reservoirs are located in the range of ancient oil reservoirs or near the source rocks,which is conducive to the"in-situ"large-scale accumulation of cracked gas in the paleo-oil reservoirs,the other is that the large scale mound-beach complex reservoirs and sealing layers of inter beach tight zones match effectively to form large lithologic traps under the slope background.The research results confirm that the north slope area has large multi-layer lithologic gas reservoirs with more than one trillion cubic meters of natural gas resources and great exploration potential.
基金This research was supported in part by grants from the National Natural Sciences Foundation of China(40162002,40372023,40232020)from the Foundation of the Key and Basic Project of Science and Technology of Guizhou(Gui No.2002-309)+1 种基金from the Early and Special Projects of the Key and Basic Projects of the Ministry of Technology and Science of China(2002 CCC 02600)to Zhaofrom the U S.National Science Foundation(0106883,0229757)to Babcock.
文摘A Burgess Shale-type biota is, in part, characterized by a wide diversity of taxa and soft-part preservation. Each provides unique historical insights into early metazoan evolution. Among the more than 40 globally distributed biotas, the early Cambrian Chengjiang and Middle Cambrian Burgess-type biotas are the largest. The Kaili Biota, from the earliest Middle Cambrian of Guizhou, China, contains representatives of 110 metazoan genera belonging to 10 phyla. It contains many well-persevered soft-bodied specimens. This Chinese biota has become the third most taxonomically diverse Burgess Shale-type fauna. Because the Kaili Biota formed in an outer-shelf environment, its main faunal character is large numbers of eocrinoids and planktoic trilobites. The Kaili is younger than the Chengjiang Biota but older than the Canadian Burgess Shale Biota; it shares 30 genera with the Chengjiang and 38 genera with the Burgess Biota. The Kaili Biota displays a taphonomic window to the diversification and evolution of marine offshore organisms covering 5.13 million years between the Early and Middle Cambrian.
基金This study was supported by the National Natural Science Foundation of China(Grants 4037200140072007+3 种基金49772083 to Dong Xiping)by the Laboratory of Paleobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences(Grant 023106 to Dong Xiping)by the Research Fund for Doctoral Program of High Education(Grant 2000000127 to Dong Xiping)by a travel grant from the Ohio State University(to Stig M.Bergstrom).
文摘Since 1985, samples with a total weight of more than 14,000 kg, mainly from three key sections in western and northwestern Hunan, South China, have been processed for conodonts. In strata older than the late Late Cambrian paraconodonts have proved useful for stratigraphic subdivision and correlation. Thirteen conodont zones are proposed in the Middle Cambrian through lowermost Ordovician. The correlation between these zones and those of North China, western U. S.A., western Newfoundland, Canada, and Iran is discussed. In ascending order, these 13 zones are as follows: The Gapparodus bisulcatus-Westergaardodina brevidens Zone, Shandongodus priscus-Hunanognathus tricuspidatus Zone, Westergaardodina quadrata Zone, Westergaardodina matsushitai-W. grandidens Zone, Westergaardodina lui-W. am Zone, Westergaardodina cf. calix-Prooneotodus rotundatus Zone, Proconodontus tenuiserratus Zone, Proconodontus Zone, Eoconodontus Zone, Cordylodus proavus Zone, Cordylodus intermedius Zone, Cordylodus lindstromi Zone, and Cordylodus angulatus Zone (lower part). The Westergaardodina lui-W. ani and Westergaardodina cf. calix-Prooneotodus rotundatus Zones replace the Westergaardodina proligula and Westergaardodina cf. behrae-Prooneotodus rotundatus Zones, respectively, in the lowermost Upper Cambrian. Two new species (Westergaardodina Iui and Westergaardodina ani) and one conditionally identified species (Westergaardodina cf. calix) are described.
基金the joint project between the Yunnan Institute of Geological Sciences the Shenzhen Palaeontological Museum the Natural Science Foundation of Yunnan Province(2002D0033Q).
文摘The Guanshan Fauna, a soft-bodied fauna intermediate between the Chengjiang Fauna and the Kaili Fauna and also the Burgess Shale Fauna stratigraphically, consists of trilobites, trilobitoides, Tuzoia, Vetulicola, Paleoscolex, brachiopods and sponges. The discovery and research of this fauna is of great significance in understading the 'Cambrian Explosion' and the evolution of early life. The occurrence of vetulicoliids from the Guanshan Fauna not only adds new members to the taxonomic list, but also provides new information to the evolution of this animal group. This paper describe Vetulicola gantoucunensis Luo, Fu et Hu sp. nov. from the Lower Cambrian Wulongqing Formation in the Kunming area. Also presented are the amended description of Vetulicola and the comparisons with related genera within Vetulicoliids. The affinity, distribution, as well as evolution of vetulicoliids are discussed.
基金supported by the Natural Science Foundation of China(NSFC)the Ministry of Science and Technology(CMST)of China
文摘The Lower Cambrian Chengjiang Lagerstatte provides a good window to explorethe origin and radiation of early bilaterians. Here we describe a netted sclerite-bearing wormTabelliscolex hexagonus gen. et sp. nov., and tentatively assign it to palaeoscolecidans ofpriapulids. The cuticle of the animal is covered with two kinds of platy sclerites which areconstructed by hexagonally arranged tubercles Similar structures of the sclerites can be seen onsome Cambrian palaeoscolecidans and lobopods, so, this new species is critical for understanding therelationships between lobopods and palaeoscolecidans.
基金supported by the National Natural Science Foundation of China(Grants 40073007,40173002,40232020)the Natural Scienee Foundation of Yunnan Province(Grant 97D007Z)
文摘The genus and species Yuyuanozoon magnificissimi gen. et sp. nov., a new fossil vetulicolian, is reported from the Early Cambrian Chengjiang Fauna in Yunnan of China. It has a bipartite body plan and five pairs of chain-formed gill sacs, showing the general characteristics of Ventulicolia. However, the exclusive 'atrial cavity' and external gill observed indicate that the new form is different from those previously described as vetulicolians, probably representing a lineage developed within deuterostomes and more primitive than urochordates.