We report a new eusauropod dinosaur,Huashanosaurus qini gen.et sp.nov.,based on a partial skeleton recovered from a bed in the Lower to Middle Jurassic Wangmen Formation(Fm.)from Huqiu Quarry near Mingjiang River,Ning...We report a new eusauropod dinosaur,Huashanosaurus qini gen.et sp.nov.,based on a partial skeleton recovered from a bed in the Lower to Middle Jurassic Wangmen Formation(Fm.)from Huqiu Quarry near Mingjiang River,Ningming County,Guangxi Zhuang Autonomous Region,southern China.The new taxon can be diagnosed by the following autapomorphies:posterior process of the ulna hook-shaped;the cross-section of the proximal part of the ulna crescent-shaped;groove structure present at the posterodistal surface of the fibula.Phylogenetic analysis reveals that H.qini is later-diverging than the Middle Jurassic Shunosaurus.Previous work showed that the Wangmen Fm.is early Early Jurassic in age whereas the new eusauropod discovery indicates that the Wangmen Fm.is probably somewhat younger Early-Middle Jurassic in age.The find increases the diversity of Jurassic eusauropods in China.展开更多
The Central Yunnan Basin(CYB)that tectonically located on the southwest margin of the Yangtze Block and to the eastern segment of the Paleo-Tethys tectonic domain,is a typical‘red bed'sedimentary basin formed sin...The Central Yunnan Basin(CYB)that tectonically located on the southwest margin of the Yangtze Block and to the eastern segment of the Paleo-Tethys tectonic domain,is a typical‘red bed'sedimentary basin formed since Late Triassic.The CYB is composed of mega-thick fluvial and lacustrine facies successions.However,the tectonic evolution and sedimentary provenance studies on this basin are scarce.In this study,we report new detrital zircon ages of four sandstones from the Lower Jurassic Fengjiahe Formation(FJF),including four major clusters of 2060-1810,870-760,485-430,and 280-254 Ma,with sporadic Archean,Cambrian,and Triassic ages.We interpret that the Archaean and Proterozoic zircons were mainly derived from the western Yangtze Block,which may recycle from the Jiangnan Orogen,the Cathaysia Block and the Proterozoic igneous rocks.Ordovician and Silurian zircons were probably from the Ailaoshan orogenic belt,and the Lancang Group in western Yunnan,as well as the Yangtze,Cathaysia and Indosinian blocks.Permian zircons probably came from the Ailaoshan orogenic belt and the Emeishan basalt.The youngest zircon age of~212.9 Ma indicates that the depositional age of the FJF is younger than the Norian stage.We also proposed a geodynamic model of the CYB and the Ailaoshan orogenic belt during the Mesozoic.The Simao Block to the west of the CYB constituted the Ailaoshan orogenic belt and collaged with the Yangtze Block during the Early Triassic,provided sedimentary provenance to the CYB.The Changning-Menglian zone that composed of the Baoshan and the Simao Blocks,uplifted in the Late Triassic and provided provenance to the CYB.Collapse of the Ailaoshan orogenic belt in Late Triassic probably provided channel for source materials that transported from the Lincang granites to the CYB.We propose a transtensional tectonic setting of the central Yunnan during the Early Jurassic,after a short collision during the Indosinian Movement in the Late Triassic.展开更多
Better understanding of shoshonitic rocks is vital to unravel the formation process and spatial distribution of their associated ore deposits.Here,we conducted analyses on the shoshonitic granodiorite and its mafic mi...Better understanding of shoshonitic rocks is vital to unravel the formation process and spatial distribution of their associated ore deposits.Here,we conducted analyses on the shoshonitic granodiorite and its mafic microgranular enclaves(MMEs)from the Chadi Cu-Pb-Zn polymetallic deposit(South China),with the aim to investigate their petrogenesis and tectonic setting.Zircon U-Pb age of the MMEs(165.0±1.2 Ma)is coeval with that of the host granodiorite(164.8±0.63 Ma).The Chadi granitoids are enriched in large ion lithophile elements and light rare earth elements,but depleted in high-field-strength elements.The granodiorite displays low(^(87)Sr/^(86)Sr)_(i)(0.7069-0.7072),and negative ε_(Nd)(t)(−5.8 to−5.5)and zircon ε_(Hf)(t)(−3.6 to−0.4)values.These isotopic characteristics of the granodiorite and MMEs indicate the mixing of a mafic magma(formed from the subduction-related,metasomatically-enriched lithospheric mantle)and a felsic magma(formed from the partial melting of crustal materials),which is closely related to the Paleo-Pacific subduction.The Chadi granodioritic magma has likely low oxygen fugacity(<ΔFMQ+1),low whole-rock Sr/Y ratio(mostly<30),and low S(0.04±0.02 wt%)and Cl(0.23±0.04 wt%)contents,suggesting that the potential of forming large-scale Cu mineralization is low.展开更多
Based on the detrital zircon U-Pb dating data,this paper discusses the provenance and constructs source-to-sink system of the Upper Jurassic in the North Yellow Sea Basin(NYSB),eastern North China Craton(ENCC).In addi...Based on the detrital zircon U-Pb dating data,this paper discusses the provenance and constructs source-to-sink system of the Upper Jurassic in the North Yellow Sea Basin(NYSB),eastern North China Craton(ENCC).In addition,to avoid the bias of detrital zircon ages caused by variations in zircon fertility,we collected 1709 whole rock zirconium content values(ppm)from granitic rocks with different ages in the North China Craton(NCC).Based on mean Zr content of granitic rocks in each age,these granitic rocks can be divided into four groups:Group A consists of Jurassic,Group B consists of Paleozoic,Neo-Mesoproterozoic and Neoarchean,Group C consists of Early Cretaceous and Triassic,and Group D consists of Paleoproterozoic.This research assigns to these groups zircon fertility factors(ZFF)of 1,1.4,1.8 and 2.2.The U-Pb age of detrital zircons from Late Jurassic sediments corrected by ZFF is statistically analyzed(K-S test,similarity,crosscorrelation,linkeness,and multidimensional scaling).And combining with paleocurrent and paleogeography,we construct two source-to-sink systems:(1)Jiaodong uplift and Sulu Orogenic Belt as the source area and the North Yellow Sea Basin as the sink area;(2)Liaodong Peninsula as the source area and the North Yellow Sea Basin as the sink area.展开更多
The Jurassic tight sandstone oil and gas exploration and development in the eastern Yangxia Sag is a new field.To elucidate the origin,accumulation process and potential of tight oil and gas,the authors have conducted...The Jurassic tight sandstone oil and gas exploration and development in the eastern Yangxia Sag is a new field.To elucidate the origin,accumulation process and potential of tight oil and gas,the authors have conducted comprehensive analyses employing methodologies encompassing source rocks,oil geochemistry,and fluid inclusions.The results show that the abundance of organic matter of Jurassic source rocks is high,and the type of organic matter is ofⅡ-Ⅲand in mature evolution stage.The main source rocks of oil and gas are Huangshanjie Formation and Jurassic coal-bearing source rocks.Ahe Formation developed two stages of hydrocarbon charging,and the period is later than the reservoir densification time.Yangxia Formation oil charged before the reservoir densified,and the late gas charged after the reservoir densified.Hydrocarbon generation intensity of Jurassic source rocks has reached the basic conditions for the formation of tight gas reservoirs.Controlled by the difference of source rocks distribution and accumulation process,tight sandstone oil and gas accumulation conditions are better in the depression direction than in the southeast margin area.This study is of practical importance for expanding the exploration field and selecting favorable areas in the eastern Yangxia sag.展开更多
Recently identified hydrothermal monazite from the Sidaogou deposit in the Liaodong Peninsula,is co-genetic with gold-bearing ore minerals and thus can serve as ideal proxy for dating the gold-mineralization event.Our...Recently identified hydrothermal monazite from the Sidaogou deposit in the Liaodong Peninsula,is co-genetic with gold-bearing ore minerals and thus can serve as ideal proxy for dating the gold-mineralization event.Our study effectively solved the dilemma of lack of any accurate age for the Sidaogou deposit.The Sidaogou deposit is hosted mainly by Paleoproterozoic metamorphic rocks of the Liaohe Group,and hydrothermal monazite therein occurs within voids or along micro-fractures in syn-ore pyrite and quartz.First in situ SIMS U-Th-Pb isotope data on this monazite from the Sidaogou deposit yielded an inverse Concordia age of 184±20 Ma,which is much younger than an^(40)Ar-^(39)Ar age of 1858.9±25.4 Ma obtained on muscovite from the host rock(Gaixian Formation),thus supporting a prominent Early Jurassic gold mineralization event in the Wulong gold field,which is distinct from previously established Early Cretaceous gold mineralization,held responsible for the nearby large Wulong gold deposit.Our new findings make it possible,together with previous studies,to formulate a model for the Early Jurassic magmatic-hydrothermal gold system in the area,for which a compressional setting during the westward subduction of the Paleo-Pacific Plate beneath the North China Craton is postulated.展开更多
The deep geologic processes between the Xing’an-Mongolian Orogenic Belt and the North China Craton in the Mesozoic are crucial to reveal the magmatic and tectonic evolution and their constraints on mineralization in ...The deep geologic processes between the Xing’an-Mongolian Orogenic Belt and the North China Craton in the Mesozoic are crucial to reveal the magmatic and tectonic evolution and their constraints on mineralization in the Jiapigou-Haigou collage zone.In this paper,We have presented the geochronology,geochemistry and Sr-Nd-Hf isotopic compositions of the Middle Jurassic granitic complexes in the Songjianghe area,Jilin Province.The granitic complexes can be categorized into four groups based on their geologic characteristics,with corresponding zircon U-Pb isotope ages of 177 Ma,172 Ma,169 Ma and 168-167 Ma,respectively.These granitoids exhibit calcalkaline to high-K calc-alkaline,metaluminous to weakly peraluminous Ⅰ-type characteristics,which show relative enrichment in LILEs(Rb,Sr,Ba)and depletion in HFSEs(Nb,Zr).Geochemical analyses reveal high initial^(87)Sr/^(86)Sr ratios of 0.70633-0.70740,coupled with lowεNd(t)values ranging from−10.65 to−13.23.The zircon analyses show similarly negativeεHf(t)values ranging from−16.9 to−3.2.The integrated elemental and Hf-Sr-Nd isotopic signatures demonstrate that the primitive magmas of the four group rocks were primarily derived from partial melting of thickened Archean lower crust,with the exception of the Group Ⅳ rocks,which exhibit significant evidence of crustal contamination.The residual mineral assemblages during the magma-forming process varied from amphibole to eclogite facies.These findings indicate that magmatism in the Songjianghe region likely resulted from the accretion and delamination of the Archean crust in the collage zone during the subduction of the Paleo-Pacific Plate beneath the Eurasian continent.展开更多
Oxygen isotope(δ^(18)O)of paleolake water is a key indicator for reconstructing the formation temperature and diagenetic history of lacustrine carbonate minerals.In this study,we use clumped isotopes(Δ_(47))of lacus...Oxygen isotope(δ^(18)O)of paleolake water is a key indicator for reconstructing the formation temperature and diagenetic history of lacustrine carbonate minerals.In this study,we use clumped isotopes(Δ_(47))of lacustrine shell limestones to determine the surface erosion thickness and δ^(18)O of Early Jurassic lake water in the northern Sichuan Basin.We analyzed nine shell limestone and seventeen shale samples from the Early Jurassic Da'anzhai Member(J_(1)z^(4))in the Yuanba area.Whether the shell's shapes are well or partially preserved,the J_(1)z^(4)shell limestones in the Yuanba area show no significant recrystallization and dull cathodoluminescence.These characteristics suggest that the shell limestones did not undergo significant diagenetic alteration during late burial.The Δ_(47)values of the J_(1)z^(4)shell limestones range from 0.448±0.005‰to 0.463±0.006‰,yielding clumped isotope temperature(T_(Δ47))of 64.4±0.8 to 69.7±1.4℃,which is significantly higher than the Early Jurassic paleotemperature.It suggests that the Δ_(47)of shell limestones was altered by solid-state reordering,meaning the T_(Δ47)does not reflect the initial formation temperatures.By integrating organic matter's maturation model(Easy%R_(o))of coexisting shales with Δ_(47)solid-state reordering model of calcite,we constrained the maximum burial temperature(~170℃)and the initial formation temperature(~28℃)of these shell limestones.Based on reported paleotemperature gradient,we estimated that the surface erosion thickness was about 1500 m.Furthermore,using the determined initial formation temperatures and conventional oxygen isotope thermometer,we determined that the δ^(18)O values of the Early Jurassic lake water in the Sichuan Basin,which ranged from-10.8‰to-8.0‰(SMOW).The reconstructed paleo temperature and δ^(18)O of lake water suggest that the Early Jurassic in the Sichuan Basin was warm and humid,which was favorable for the deposition of organic-rich lacustrine shale.The methods developed in this study,which employ Δ_(47)of shell limestones to reconstruct the maximum burial temperature and paleolake environmental conditions,demonstrate broad applicability to the Sichuan Basin and similar lacustrine basins.展开更多
The genus Beipiaoserphus gen. nov. is established and referred to Mesoserphidae with Beipiaoserphus elegans sp. nov. as its type species. The type specimens were collected from the lower part of the Upper Jura...The genus Beipiaoserphus gen. nov. is established and referred to Mesoserphidae with Beipiaoserphus elegans sp. nov. as its type species. The type specimens were collected from the lower part of the Upper Jurassic Yixian Formation at Huangbanjigou Village near Shangyuan Town, Beipiao, Liaoning Province, China and are housed at Nanjing Institute of Geology and Palaeontology, Academia Sinica, Nanjing.展开更多
Eighty-one species of fossil spores and pollen assigned to 52 genera are found from the Middle Jurassic Xishanyao, Sanjianfang and Qiketai Formations of boreholes Le 1, Mi 1, Shan 1 and Dun 1 in the northern Turpan De...Eighty-one species of fossil spores and pollen assigned to 52 genera are found from the Middle Jurassic Xishanyao, Sanjianfang and Qiketai Formations of boreholes Le 1, Mi 1, Shan 1 and Dun 1 in the northern Turpan Depression, Xinjiang, northwest China. Three assemblages have been proposed as: Cyathidites-Psophosphaera-Cycadopites assemblage, Cyathidites-Quadraceculina-Classopollis assemblage and Cyathidites-Callialasporites-Classopollis assemblage obtained from the Xishanyao Formation, the Sanjianfang Formation and Qiketai Formation respectively. Based on the sporo-pollen assemblage features and con-elation, their geological ages are regarded as of Middle Jurassic, probably Aalenian to Bathonian. The results of the study indicate that the vegetation of early Middle Jurassic in this region consisted mainly of Gymnospermae of Ginkgoaceae of Cycadales, Podocarpaceae, Pinaceae and Pteridophyta of Cyatheacene, Osmundaceae, Lycopodiaceae and Dicksoniaceae, etc. They reflect a warm-moist subtropic climate. To the middle-late Middle Jurassic, Cheirolepidaceae was dominant in the vegetation, which indicates that the climate was in the trend of becoming dry.展开更多
A better theoretical and practical understanding of the linkage between paleo-CO2 and climate during geological history is important to enhance the sustainable development of modern human society. Development in plant...A better theoretical and practical understanding of the linkage between paleo-CO2 and climate during geological history is important to enhance the sustainable development of modern human society. Development in plant physiology since the 1980s has led to the realization that fossil plants can serve as a proxy for paleoatmosphere and paleobiosphere. As a relict gymnosperm with evolutionary stasis, Ginkgo is well suited for paleoenvironmental reconstruction. This paper analyzes fossil Ginkgo species from integrated strata in the north of China using anatomic data of plant physiology. Using stomatal parameters, a trend for the paleo-CO2 level during the Early-Middle Jurassic and the Early Cretaceous was obtained, which is consistent with the estimates by GEOCARB. The trend is also similar to that of Mean Global Surface Temperature in geological time. Compared with three other atmospheric CO2 concentration parameters, the trend of paleo-CO2 level based on the stomatal parameter of the fossil Ginkgo specimens from three contiguous strata is more exact.展开更多
The origin of angiosperms has been tantalizing botanists for centuries. Despite the efforts of palaeobotanists, most of the pre-Cretaceous angiosperms are regarded either non-convincing or misdated. The applications o...The origin of angiosperms has been tantalizing botanists for centuries. Despite the efforts of palaeobotanists, most of the pre-Cretaceous angiosperms are regarded either non-convincing or misdated. The applications of SEM and LM （light microscope） enable us to recognize a coalified fossil plant, Xingxueanthus sinensis gen. et sp. nov., from the Haifanggou Formation （Middle Jurassic, 〉160 Ma） in western Liaoning, China. Xingxueanthus is an ＂inflorescence＂ with more than 20 female units spirally arranged. Each female unit is situated in the axii of a bract. The female unit is composed of an ovule-container and a style-like projection at the top. There is a vertical column bearing several ovules in the ovule-container. The general morphology and the internal structure of Xingxueanthus distinguish itself from any known fossil and extant gymnosperms, and its structures are more comparable to those of angiosperms. Xingxueanthus, if taken as a gymnosperm, would represent a new class, demonstrate an evolutionarily advanced status of ovule-protection in gymnosperms never seen before, and provide new insights into the origin of angiospermy. Alternatively, if taken as an angiosperm, together with Schmeissneria, it would increase the diversity of Jurassic angiosperms, which has been underestimated for a long time, and suggest a much earlier origin of angiospermy than currently accepted.展开更多
Four new fossil genera and species of true bugs from the family Pachymeridiidae, Beipiaocoris multifurcus, Bellicoris mirabilis, Nitoculus regiUus, and Viriosinervis stolidus, are described. New specimens were collect...Four new fossil genera and species of true bugs from the family Pachymeridiidae, Beipiaocoris multifurcus, Bellicoris mirabilis, Nitoculus regiUus, and Viriosinervis stolidus, are described. New specimens were collected from the Middle and Upper Jurassic non-marine sedimentary strata from the Jiulongshan and Yixian Formations of northeast China. The species Karatavocoris asiatica Becker-Migdisova, 1963, which was considered to be a member of the family Coreidae is transferred to the Pachymeridiidae. A new map of all known and newly discovered fossil pachymeridiid localities is given. The diagnosis of the family is modified.展开更多
This paper gives a synthetic view on the Jurassic tectonics of North China, with an attempt to propose a framework for the stepwise tectonic evolution history. Jurassic sedimentation, deformation and magmatism in Nort...This paper gives a synthetic view on the Jurassic tectonics of North China, with an attempt to propose a framework for the stepwise tectonic evolution history. Jurassic sedimentation, deformation and magmatism in North China have been divided into three stages. The earliest Jurassic is marked by a period of magmatism quiescence （in 205-190 Ma） and regional uplift, which are considered to be the continuation of the “Indosinian movement” characterized by continent-continent collision between the North and South China blocks. The Early to Middle Jurassic （in 190-170 Ma） was predominated by weak lithospheric extension expressed by mantle-derived plutonism and volcanism along the Yanshan belt and alongside the Tan-Lu fault zone, normal faulting and graben formation along the Yinshan- Yanshan tectonic belt, depression and resuming of coal-bearing sedimentation in vast regions of the North China block （NCB）. The Middle to Late Jurassic stage started at 165y.5 Ma and ended up before 136 Ma; it was dominated by intensive intraplate deformation resulting from multi-directional compressions. Two major deformation events have been identified. One is marked by stratigraphic unconformity beneath the thick Upper Jurassic molasic series in the foreland zones of the western Ordos thrust-fold belt and along the Yinshan-Yanshan belt; it was predated 160 Ma. The other one is indicated by stratigraphic unconformity at the base of the Lower Cretaceous and predated 135 Ma. During this last stage, two latitudinal tectonic belts, the Yinshan-Yanshan belt in the north and the Qinling-Dabie belt in the south, and the western margin of the Ordos basin were all activated by thrusting; the NCB itself was deformed by the NE to NNE-trending structural system involving thrusting, associated folding and sinistral strike-slip faulting, which were spatially partitioned. Foliated S-type granitic plutons aged 160-150 Ma were massively emplaced in the Jiao-Liao massif east of the Tan-Lu fault zone and indicate important crustal thickening in this part of the NCB. The Jurassic deformation patterns, different tectonic systems and multi-directional contractions in North China recorded far-field effects of synchronous convergences, toward the East Asian continent, of three different plates, the Siberian plate in the north, the paleo-Pacific oceanic plate in the east and the Lhasa block in the southwest. This Middle to Late Jurassic intraplate orogenesis and pervasive shortening deformation preceded lithospheric attenuation and thinning in East China, which most possibly started by the Early Cretaceous around 135 Ma.展开更多
Lacustrine deposits exposed at Daohugou, Inner Mongolia, China, have yielded superbly preserved vertebrate fossils. The fossil beds were first misinterpreted as of Early Cretaceous age, based on alleged occurrences of...Lacustrine deposits exposed at Daohugou, Inner Mongolia, China, have yielded superbly preserved vertebrate fossils. The fossil beds were first misinterpreted as of Early Cretaceous age, based on alleged occurrences of key fossils of the Jehol Biota. Compelling evidence revealed by more rigorous research involving regional biostratigraphy, radiometric dating, and paleontology supports the Middle Jurassic age of the fossil beds. Despite the awesome evidence for the Middle Jurassic age of the Daohugou beds, the age dispute has been resurrected recently by invoking an overturned stratigraphic sequence. A careful review of the data, however, found no evidence that this sequence has been overturned. In addition, many of the assumptions, on which the conjecture of the fossil beds being post- Middle Jurassic is imprudently based, are self-contradictory or otherwise misleading. Thus, the post- Middle Jurassic age of the Daohugou beds as an unfounded conclusion can readily be dismissed.展开更多
Cherts in the Zhongba melange of the western Yarlung Zangbo Suture Zone(YZSZ) contain well preserved radiolarian assemblages. These radiolarian assemblages indicate that the Zhongba melange has middle Jurassic-early C...Cherts in the Zhongba melange of the western Yarlung Zangbo Suture Zone(YZSZ) contain well preserved radiolarian assemblages. These radiolarian assemblages indicate that the Zhongba melange has middle Jurassic-early Cretaceous remnant, are coeval with those from the central and eastern parts of the YZSZ. Cherts from the Najiu area yield Aalenian to Aptian radiolarians, while cherts interbedded with siliceous mudstones from the Bielongjiala area yield Aptian radiolarians, indicating that terrigenousderived sediments were deposited during early Aptian. The above observations indicate that the entire YZSZ have a similar geochronological framework and thus they underwent similar geological evolution:(1) during the Jurassic, the Neo-Tethys was a wide ocean with pelagic sediments distal from continents;(2) during the Cretaceous(around 130-120 Ma), the Neo-Tethys started to subduct along the southern margin of the Lhasa block, and terrigenous-derived siliceous mudstone began deposition.展开更多
The early Jurassic soft-sediment deformation occurring within lacustrine sandstone is distributed mainly in the Wuqia region of SW Tianshan Mountains, Xinjiang, western China. Triggered by earthquakes, such deformatio...The early Jurassic soft-sediment deformation occurring within lacustrine sandstone is distributed mainly in the Wuqia region of SW Tianshan Mountains, Xinjiang, western China. Triggered by earthquakes, such deformation was found to occur in three beds overlying the lower Jurassic Kangsu Formation. The main styles of deformation structures comprise load cast, ball-and- pillow, droplet, cusps, homogeneous layer, and liquefied unconformity. The deformation layers reflect a series of three strong earthquakes at the end of early Jurassic in the Wuqia region. The differences of deformation mechanisms undergone might represent the varying magnitudes of the earthquake events. During the early Jurassic, the Wuqia region was located in a pull-apart basin controlled by the significant Talas-Ferghana strike-slip fault in central Asia, which initiated the soft-sediment deformation induced by earthquakes. Our research suggests that the paleoseismic magnitudes could have ranged from Ms 6.5 to 7.展开更多
The newly discovered large(350 m^2) Yantan dinosaur tracksite, in the Lower Jurassic Ziliujing Formation of Guizhou Province, China, reveals at least 250 footprints of which ~97 can be resolved into trackways of sauro...The newly discovered large(350 m^2) Yantan dinosaur tracksite, in the Lower Jurassic Ziliujing Formation of Guizhou Province, China, reveals at least 250 footprints of which ~97 can be resolved into trackways of sauropodomorphs. All the trackways are sub parallel likely indicating gregarious behavior. One theropod track(cf. Grallator) was recorded. The sauropodomorph tracks predominantly represent quadrupedal progression(Morphotype A), and footprint morphology is similar to the ichnospecies Liujianpusshunan, characterized by outward pes rotation. Three trackways indicate bipedal progression, and two of these(Morphotype B) indicate inward pes rotation, accompanied by elongate pes digit scratch marks. For the latter phenomenon three possible scenarios are discussed:(1) significant rotation changes accompanying changes in gait,(2) swimming behavior,(3) formation of undertracks.Sedimentological evidence indicates the tracks were made on a linguloid rippled, muddy, immature sandstone substrate characterized by significant differences in substrate consistency across the trackbearing surface. Microbially induced sedimentary structures(MISS) characterized by distinctive wrinkle marks indicate a stressed, probably semi-arid, paleoenvironment that was not conducive to habitation by invertebrate organisms. This is consistent with other evidence that Lower Jurassic sauropodomorph tracks are often associated with semi-arid paleoenvironments.展开更多
In this paper two new species of fossil Pseudopolycentropus Handlirsch, 1906 are described： Pseudopolycentropus janeannae sp. nov. and P. novokshonovi, sp. nov. All of them were recovered from the Middle Jurassic non...In this paper two new species of fossil Pseudopolycentropus Handlirsch, 1906 are described： Pseudopolycentropus janeannae sp. nov. and P. novokshonovi, sp. nov. All of them were recovered from the Middle Jurassic non-marine sedimentary strata of northeastern China. The new material from China reveals that the early diversification of pseudopolycentropodids was well underway by the Middle Jurassic.展开更多
基金supported by the Natural Science Foundation of Guangxi(Grant No.2023GXNSFAA026496)the Natural Science Foundation of China(Grant No.42288201)the Yunnan Revitalization Talent Support Program(Grant No.202305AB350006).
文摘We report a new eusauropod dinosaur,Huashanosaurus qini gen.et sp.nov.,based on a partial skeleton recovered from a bed in the Lower to Middle Jurassic Wangmen Formation(Fm.)from Huqiu Quarry near Mingjiang River,Ningming County,Guangxi Zhuang Autonomous Region,southern China.The new taxon can be diagnosed by the following autapomorphies:posterior process of the ulna hook-shaped;the cross-section of the proximal part of the ulna crescent-shaped;groove structure present at the posterodistal surface of the fibula.Phylogenetic analysis reveals that H.qini is later-diverging than the Middle Jurassic Shunosaurus.Previous work showed that the Wangmen Fm.is early Early Jurassic in age whereas the new eusauropod discovery indicates that the Wangmen Fm.is probably somewhat younger Early-Middle Jurassic in age.The find increases the diversity of Jurassic eusauropods in China.
基金supported by the Open Foundation of the State Key Laboratory of Continental Dynamics,Northwest University,China(No.16LCD06)the Basic Research Program from Department of Science and Technology Yunnan Province(No.202101AU070132)+1 种基金Jun Wang was also supported by the‘Double Top’Construction Projects(No.C176220100135)at Yunnan Universitysupported by the open fund from the Key Laboratory of Deep-Earth Dynamics of the Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing,10037,China(No.J1901)。
文摘The Central Yunnan Basin(CYB)that tectonically located on the southwest margin of the Yangtze Block and to the eastern segment of the Paleo-Tethys tectonic domain,is a typical‘red bed'sedimentary basin formed since Late Triassic.The CYB is composed of mega-thick fluvial and lacustrine facies successions.However,the tectonic evolution and sedimentary provenance studies on this basin are scarce.In this study,we report new detrital zircon ages of four sandstones from the Lower Jurassic Fengjiahe Formation(FJF),including four major clusters of 2060-1810,870-760,485-430,and 280-254 Ma,with sporadic Archean,Cambrian,and Triassic ages.We interpret that the Archaean and Proterozoic zircons were mainly derived from the western Yangtze Block,which may recycle from the Jiangnan Orogen,the Cathaysia Block and the Proterozoic igneous rocks.Ordovician and Silurian zircons were probably from the Ailaoshan orogenic belt,and the Lancang Group in western Yunnan,as well as the Yangtze,Cathaysia and Indosinian blocks.Permian zircons probably came from the Ailaoshan orogenic belt and the Emeishan basalt.The youngest zircon age of~212.9 Ma indicates that the depositional age of the FJF is younger than the Norian stage.We also proposed a geodynamic model of the CYB and the Ailaoshan orogenic belt during the Mesozoic.The Simao Block to the west of the CYB constituted the Ailaoshan orogenic belt and collaged with the Yangtze Block during the Early Triassic,provided sedimentary provenance to the CYB.The Changning-Menglian zone that composed of the Baoshan and the Simao Blocks,uplifted in the Late Triassic and provided provenance to the CYB.Collapse of the Ailaoshan orogenic belt in Late Triassic probably provided channel for source materials that transported from the Lincang granites to the CYB.We propose a transtensional tectonic setting of the central Yunnan during the Early Jurassic,after a short collision during the Indosinian Movement in the Late Triassic.
基金granted by the Basic Scientific Research Fund of Chinese Academy of Geological Sciences[Grant No.JKY202505,JYYWF20180601,KK2207]the National Natural Science Foundation of China(Grant No.41702083,41820104010)China Scholarship Council(Grant No.CSC 201908110163)。
文摘Better understanding of shoshonitic rocks is vital to unravel the formation process and spatial distribution of their associated ore deposits.Here,we conducted analyses on the shoshonitic granodiorite and its mafic microgranular enclaves(MMEs)from the Chadi Cu-Pb-Zn polymetallic deposit(South China),with the aim to investigate their petrogenesis and tectonic setting.Zircon U-Pb age of the MMEs(165.0±1.2 Ma)is coeval with that of the host granodiorite(164.8±0.63 Ma).The Chadi granitoids are enriched in large ion lithophile elements and light rare earth elements,but depleted in high-field-strength elements.The granodiorite displays low(^(87)Sr/^(86)Sr)_(i)(0.7069-0.7072),and negative ε_(Nd)(t)(−5.8 to−5.5)and zircon ε_(Hf)(t)(−3.6 to−0.4)values.These isotopic characteristics of the granodiorite and MMEs indicate the mixing of a mafic magma(formed from the subduction-related,metasomatically-enriched lithospheric mantle)and a felsic magma(formed from the partial melting of crustal materials),which is closely related to the Paleo-Pacific subduction.The Chadi granodioritic magma has likely low oxygen fugacity(<ΔFMQ+1),low whole-rock Sr/Y ratio(mostly<30),and low S(0.04±0.02 wt%)and Cl(0.23±0.04 wt%)contents,suggesting that the potential of forming large-scale Cu mineralization is low.
基金supported by the National Natural Science Foundation of China(Nos.41872101 and 41790453-4)。
文摘Based on the detrital zircon U-Pb dating data,this paper discusses the provenance and constructs source-to-sink system of the Upper Jurassic in the North Yellow Sea Basin(NYSB),eastern North China Craton(ENCC).In addition,to avoid the bias of detrital zircon ages caused by variations in zircon fertility,we collected 1709 whole rock zirconium content values(ppm)from granitic rocks with different ages in the North China Craton(NCC).Based on mean Zr content of granitic rocks in each age,these granitic rocks can be divided into four groups:Group A consists of Jurassic,Group B consists of Paleozoic,Neo-Mesoproterozoic and Neoarchean,Group C consists of Early Cretaceous and Triassic,and Group D consists of Paleoproterozoic.This research assigns to these groups zircon fertility factors(ZFF)of 1,1.4,1.8 and 2.2.The U-Pb age of detrital zircons from Late Jurassic sediments corrected by ZFF is statistically analyzed(K-S test,similarity,crosscorrelation,linkeness,and multidimensional scaling).And combining with paleocurrent and paleogeography,we construct two source-to-sink systems:(1)Jiaodong uplift and Sulu Orogenic Belt as the source area and the North Yellow Sea Basin as the sink area;(2)Liaodong Peninsula as the source area and the North Yellow Sea Basin as the sink area.
基金supported by Joint Fund Project of National Natural Science Foundation(No.U22B6002)CNPC Scientific Research and Technology Development Project(No.2023ZZ14YJ02).
文摘The Jurassic tight sandstone oil and gas exploration and development in the eastern Yangxia Sag is a new field.To elucidate the origin,accumulation process and potential of tight oil and gas,the authors have conducted comprehensive analyses employing methodologies encompassing source rocks,oil geochemistry,and fluid inclusions.The results show that the abundance of organic matter of Jurassic source rocks is high,and the type of organic matter is ofⅡ-Ⅲand in mature evolution stage.The main source rocks of oil and gas are Huangshanjie Formation and Jurassic coal-bearing source rocks.Ahe Formation developed two stages of hydrocarbon charging,and the period is later than the reservoir densification time.Yangxia Formation oil charged before the reservoir densified,and the late gas charged after the reservoir densified.Hydrocarbon generation intensity of Jurassic source rocks has reached the basic conditions for the formation of tight gas reservoirs.Controlled by the difference of source rocks distribution and accumulation process,tight sandstone oil and gas accumulation conditions are better in the depression direction than in the southeast margin area.This study is of practical importance for expanding the exploration field and selecting favorable areas in the eastern Yangxia sag.
基金supported by the National Natural Science Foundation of China(No.42302079)Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(No.2024ZD1001301)Geological Surveying Project of CGS(No.DD20230356)。
文摘Recently identified hydrothermal monazite from the Sidaogou deposit in the Liaodong Peninsula,is co-genetic with gold-bearing ore minerals and thus can serve as ideal proxy for dating the gold-mineralization event.Our study effectively solved the dilemma of lack of any accurate age for the Sidaogou deposit.The Sidaogou deposit is hosted mainly by Paleoproterozoic metamorphic rocks of the Liaohe Group,and hydrothermal monazite therein occurs within voids or along micro-fractures in syn-ore pyrite and quartz.First in situ SIMS U-Th-Pb isotope data on this monazite from the Sidaogou deposit yielded an inverse Concordia age of 184±20 Ma,which is much younger than an^(40)Ar-^(39)Ar age of 1858.9±25.4 Ma obtained on muscovite from the host rock(Gaixian Formation),thus supporting a prominent Early Jurassic gold mineralization event in the Wulong gold field,which is distinct from previously established Early Cretaceous gold mineralization,held responsible for the nearby large Wulong gold deposit.Our new findings make it possible,together with previous studies,to formulate a model for the Early Jurassic magmatic-hydrothermal gold system in the area,for which a compressional setting during the westward subduction of the Paleo-Pacific Plate beneath the North China Craton is postulated.
基金supported by the Natural Science Foundation of Jilin Province of China(grant no.20230101075JC)the National Natural Science Foundation of China(grant no.42072085).
文摘The deep geologic processes between the Xing’an-Mongolian Orogenic Belt and the North China Craton in the Mesozoic are crucial to reveal the magmatic and tectonic evolution and their constraints on mineralization in the Jiapigou-Haigou collage zone.In this paper,We have presented the geochronology,geochemistry and Sr-Nd-Hf isotopic compositions of the Middle Jurassic granitic complexes in the Songjianghe area,Jilin Province.The granitic complexes can be categorized into four groups based on their geologic characteristics,with corresponding zircon U-Pb isotope ages of 177 Ma,172 Ma,169 Ma and 168-167 Ma,respectively.These granitoids exhibit calcalkaline to high-K calc-alkaline,metaluminous to weakly peraluminous Ⅰ-type characteristics,which show relative enrichment in LILEs(Rb,Sr,Ba)and depletion in HFSEs(Nb,Zr).Geochemical analyses reveal high initial^(87)Sr/^(86)Sr ratios of 0.70633-0.70740,coupled with lowεNd(t)values ranging from−10.65 to−13.23.The zircon analyses show similarly negativeεHf(t)values ranging from−16.9 to−3.2.The integrated elemental and Hf-Sr-Nd isotopic signatures demonstrate that the primitive magmas of the four group rocks were primarily derived from partial melting of thickened Archean lower crust,with the exception of the Group Ⅳ rocks,which exhibit significant evidence of crustal contamination.The residual mineral assemblages during the magma-forming process varied from amphibole to eclogite facies.These findings indicate that magmatism in the Songjianghe region likely resulted from the accretion and delamination of the Archean crust in the collage zone during the subduction of the Paleo-Pacific Plate beneath the Eurasian continent.
基金supported by National Natural Science Foundation of China(42372148)。
文摘Oxygen isotope(δ^(18)O)of paleolake water is a key indicator for reconstructing the formation temperature and diagenetic history of lacustrine carbonate minerals.In this study,we use clumped isotopes(Δ_(47))of lacustrine shell limestones to determine the surface erosion thickness and δ^(18)O of Early Jurassic lake water in the northern Sichuan Basin.We analyzed nine shell limestone and seventeen shale samples from the Early Jurassic Da'anzhai Member(J_(1)z^(4))in the Yuanba area.Whether the shell's shapes are well or partially preserved,the J_(1)z^(4)shell limestones in the Yuanba area show no significant recrystallization and dull cathodoluminescence.These characteristics suggest that the shell limestones did not undergo significant diagenetic alteration during late burial.The Δ_(47)values of the J_(1)z^(4)shell limestones range from 0.448±0.005‰to 0.463±0.006‰,yielding clumped isotope temperature(T_(Δ47))of 64.4±0.8 to 69.7±1.4℃,which is significantly higher than the Early Jurassic paleotemperature.It suggests that the Δ_(47)of shell limestones was altered by solid-state reordering,meaning the T_(Δ47)does not reflect the initial formation temperatures.By integrating organic matter's maturation model(Easy%R_(o))of coexisting shales with Δ_(47)solid-state reordering model of calcite,we constrained the maximum burial temperature(~170℃)and the initial formation temperature(~28℃)of these shell limestones.Based on reported paleotemperature gradient,we estimated that the surface erosion thickness was about 1500 m.Furthermore,using the determined initial formation temperatures and conventional oxygen isotope thermometer,we determined that the δ^(18)O values of the Early Jurassic lake water in the Sichuan Basin,which ranged from-10.8‰to-8.0‰(SMOW).The reconstructed paleo temperature and δ^(18)O of lake water suggest that the Early Jurassic in the Sichuan Basin was warm and humid,which was favorable for the deposition of organic-rich lacustrine shale.The methods developed in this study,which employ Δ_(47)of shell limestones to reconstruct the maximum burial temperature and paleolake environmental conditions,demonstrate broad applicability to the Sichuan Basin and similar lacustrine basins.
基金Supported by the National Natural Science foundation of China (49832 0 2 0 NIGPAS990 50 2 ) and CMBRP(G2 0 0 0 0 7770 0 )
文摘The genus Beipiaoserphus gen. nov. is established and referred to Mesoserphidae with Beipiaoserphus elegans sp. nov. as its type species. The type specimens were collected from the lower part of the Upper Jurassic Yixian Formation at Huangbanjigou Village near Shangyuan Town, Beipiao, Liaoning Province, China and are housed at Nanjing Institute of Geology and Palaeontology, Academia Sinica, Nanjing.
文摘Eighty-one species of fossil spores and pollen assigned to 52 genera are found from the Middle Jurassic Xishanyao, Sanjianfang and Qiketai Formations of boreholes Le 1, Mi 1, Shan 1 and Dun 1 in the northern Turpan Depression, Xinjiang, northwest China. Three assemblages have been proposed as: Cyathidites-Psophosphaera-Cycadopites assemblage, Cyathidites-Quadraceculina-Classopollis assemblage and Cyathidites-Callialasporites-Classopollis assemblage obtained from the Xishanyao Formation, the Sanjianfang Formation and Qiketai Formation respectively. Based on the sporo-pollen assemblage features and con-elation, their geological ages are regarded as of Middle Jurassic, probably Aalenian to Bathonian. The results of the study indicate that the vegetation of early Middle Jurassic in this region consisted mainly of Gymnospermae of Ginkgoaceae of Cycadales, Podocarpaceae, Pinaceae and Pteridophyta of Cyatheacene, Osmundaceae, Lycopodiaceae and Dicksoniaceae, etc. They reflect a warm-moist subtropic climate. To the middle-late Middle Jurassic, Cheirolepidaceae was dominant in the vegetation, which indicates that the climate was in the trend of becoming dry.
基金supported by the National Basic Research Program of China(No.2006CB701400)the National Natural Science Foundation of China(No.40372012,40772012)the Foundation of the State Key Laboratory of Paleobiology and Stratigraphy,Nanjing Institute of Geology and Paleontology,Chinese Academy of Sciences(No.063101).
文摘A better theoretical and practical understanding of the linkage between paleo-CO2 and climate during geological history is important to enhance the sustainable development of modern human society. Development in plant physiology since the 1980s has led to the realization that fossil plants can serve as a proxy for paleoatmosphere and paleobiosphere. As a relict gymnosperm with evolutionary stasis, Ginkgo is well suited for paleoenvironmental reconstruction. This paper analyzes fossil Ginkgo species from integrated strata in the north of China using anatomic data of plant physiology. Using stomatal parameters, a trend for the paleo-CO2 level during the Early-Middle Jurassic and the Early Cretaceous was obtained, which is consistent with the estimates by GEOCARB. The trend is also similar to that of Mean Global Surface Temperature in geological time. Compared with three other atmospheric CO2 concentration parameters, the trend of paleo-CO2 level based on the stomatal parameter of the fossil Ginkgo specimens from three contiguous strata is more exact.
基金supported by National Natural Science Foundation of China Programs (No. 40772006, 30670140, 40372008, 40632010 and J0630967),the State Key Laboratory of Systematic and Evolutionary Botany at the Institute of Botany, and SRF for ROCS, SEM
文摘The origin of angiosperms has been tantalizing botanists for centuries. Despite the efforts of palaeobotanists, most of the pre-Cretaceous angiosperms are regarded either non-convincing or misdated. The applications of SEM and LM （light microscope） enable us to recognize a coalified fossil plant, Xingxueanthus sinensis gen. et sp. nov., from the Haifanggou Formation （Middle Jurassic, 〉160 Ma） in western Liaoning, China. Xingxueanthus is an ＂inflorescence＂ with more than 20 female units spirally arranged. Each female unit is situated in the axii of a bract. The female unit is composed of an ovule-container and a style-like projection at the top. There is a vertical column bearing several ovules in the ovule-container. The general morphology and the internal structure of Xingxueanthus distinguish itself from any known fossil and extant gymnosperms, and its structures are more comparable to those of angiosperms. Xingxueanthus, if taken as a gymnosperm, would represent a new class, demonstrate an evolutionarily advanced status of ovule-protection in gymnosperms never seen before, and provide new insights into the origin of angiospermy. Alternatively, if taken as an angiosperm, together with Schmeissneria, it would increase the diversity of Jurassic angiosperms, which has been underestimated for a long time, and suggest a much earlier origin of angiospermy than currently accepted.
基金This research is partly supported by grants from the National Natural Science Foundation of China （Grant No. 30430100）；Beijing Natural Science Foundation Program （Nos 6042014, 5082002, 6083023） ；PHR Project of Beijing Municipal Commission of Education.
文摘Four new fossil genera and species of true bugs from the family Pachymeridiidae, Beipiaocoris multifurcus, Bellicoris mirabilis, Nitoculus regiUus, and Viriosinervis stolidus, are described. New specimens were collected from the Middle and Upper Jurassic non-marine sedimentary strata from the Jiulongshan and Yixian Formations of northeast China. The species Karatavocoris asiatica Becker-Migdisova, 1963, which was considered to be a member of the family Coreidae is transferred to the Pachymeridiidae. A new map of all known and newly discovered fossil pachymeridiid localities is given. The diagnosis of the family is modified.
文摘This paper gives a synthetic view on the Jurassic tectonics of North China, with an attempt to propose a framework for the stepwise tectonic evolution history. Jurassic sedimentation, deformation and magmatism in North China have been divided into three stages. The earliest Jurassic is marked by a period of magmatism quiescence （in 205-190 Ma） and regional uplift, which are considered to be the continuation of the “Indosinian movement” characterized by continent-continent collision between the North and South China blocks. The Early to Middle Jurassic （in 190-170 Ma） was predominated by weak lithospheric extension expressed by mantle-derived plutonism and volcanism along the Yanshan belt and alongside the Tan-Lu fault zone, normal faulting and graben formation along the Yinshan- Yanshan tectonic belt, depression and resuming of coal-bearing sedimentation in vast regions of the North China block （NCB）. The Middle to Late Jurassic stage started at 165y.5 Ma and ended up before 136 Ma; it was dominated by intensive intraplate deformation resulting from multi-directional compressions. Two major deformation events have been identified. One is marked by stratigraphic unconformity beneath the thick Upper Jurassic molasic series in the foreland zones of the western Ordos thrust-fold belt and along the Yinshan-Yanshan belt; it was predated 160 Ma. The other one is indicated by stratigraphic unconformity at the base of the Lower Cretaceous and predated 135 Ma. During this last stage, two latitudinal tectonic belts, the Yinshan-Yanshan belt in the north and the Qinling-Dabie belt in the south, and the western margin of the Ordos basin were all activated by thrusting; the NCB itself was deformed by the NE to NNE-trending structural system involving thrusting, associated folding and sinistral strike-slip faulting, which were spatially partitioned. Foliated S-type granitic plutons aged 160-150 Ma were massively emplaced in the Jiao-Liao massif east of the Tan-Lu fault zone and indicate important crustal thickening in this part of the NCB. The Jurassic deformation patterns, different tectonic systems and multi-directional contractions in North China recorded far-field effects of synchronous convergences, toward the East Asian continent, of three different plates, the Siberian plate in the north, the paleo-Pacific oceanic plate in the east and the Lhasa block in the southwest. This Middle to Late Jurassic intraplate orogenesis and pervasive shortening deformation preceded lithospheric attenuation and thinning in East China, which most possibly started by the Early Cretaceous around 135 Ma.
基金The research was supported by the National Natural Science Foundation of China （grant #40272006, 30430100, 30370184）RFDP of the Chinese Ministry of Education, and RCQJ Project of Beijing Municipal Commission of Education. Thanks are given to Prof. R. C. Fox （University of Alberta） for reading and improving the manuscript.
文摘Lacustrine deposits exposed at Daohugou, Inner Mongolia, China, have yielded superbly preserved vertebrate fossils. The fossil beds were first misinterpreted as of Early Cretaceous age, based on alleged occurrences of key fossils of the Jehol Biota. Compelling evidence revealed by more rigorous research involving regional biostratigraphy, radiometric dating, and paleontology supports the Middle Jurassic age of the fossil beds. Despite the awesome evidence for the Middle Jurassic age of the Daohugou beds, the age dispute has been resurrected recently by invoking an overturned stratigraphic sequence. A careful review of the data, however, found no evidence that this sequence has been overturned. In addition, many of the assumptions, on which the conjecture of the fossil beds being post- Middle Jurassic is imprudently based, are self-contradictory or otherwise misleading. Thus, the post- Middle Jurassic age of the Daohugou beds as an unfounded conclusion can readily be dismissed.
基金supported by the Research Center for Tibetan Plateau Geology, China Geological Survey(201401)Funds for the Central Universities (Grant No. 292016004)China Geological Survey(Grant Nos. 12112011086037 and 1212011221072)
文摘Cherts in the Zhongba melange of the western Yarlung Zangbo Suture Zone(YZSZ) contain well preserved radiolarian assemblages. These radiolarian assemblages indicate that the Zhongba melange has middle Jurassic-early Cretaceous remnant, are coeval with those from the central and eastern parts of the YZSZ. Cherts from the Najiu area yield Aalenian to Aptian radiolarians, while cherts interbedded with siliceous mudstones from the Bielongjiala area yield Aptian radiolarians, indicating that terrigenousderived sediments were deposited during early Aptian. The above observations indicate that the entire YZSZ have a similar geochronological framework and thus they underwent similar geological evolution:(1) during the Jurassic, the Neo-Tethys was a wide ocean with pelagic sediments distal from continents;(2) during the Cretaceous(around 130-120 Ma), the Neo-Tethys started to subduct along the southern margin of the Lhasa block, and terrigenous-derived siliceous mudstone began deposition.
文摘The early Jurassic soft-sediment deformation occurring within lacustrine sandstone is distributed mainly in the Wuqia region of SW Tianshan Mountains, Xinjiang, western China. Triggered by earthquakes, such deformation was found to occur in three beds overlying the lower Jurassic Kangsu Formation. The main styles of deformation structures comprise load cast, ball-and- pillow, droplet, cusps, homogeneous layer, and liquefied unconformity. The deformation layers reflect a series of three strong earthquakes at the end of early Jurassic in the Wuqia region. The differences of deformation mechanisms undergone might represent the varying magnitudes of the earthquake events. During the early Jurassic, the Wuqia region was located in a pull-apart basin controlled by the significant Talas-Ferghana strike-slip fault in central Asia, which initiated the soft-sediment deformation induced by earthquakes. Our research suggests that the paleoseismic magnitudes could have ranged from Ms 6.5 to 7.
基金funded by the NationalNatural Science Foundation of China (Grant No. 41772008) StateKey Laboratory of Palaeobiology and Stratigraphy+1 种基金Nanjing Instituteof Geology and PalaeontologyChinese Academy of Sciences (GrantNo. 173127)
文摘The newly discovered large(350 m^2) Yantan dinosaur tracksite, in the Lower Jurassic Ziliujing Formation of Guizhou Province, China, reveals at least 250 footprints of which ~97 can be resolved into trackways of sauropodomorphs. All the trackways are sub parallel likely indicating gregarious behavior. One theropod track(cf. Grallator) was recorded. The sauropodomorph tracks predominantly represent quadrupedal progression(Morphotype A), and footprint morphology is similar to the ichnospecies Liujianpusshunan, characterized by outward pes rotation. Three trackways indicate bipedal progression, and two of these(Morphotype B) indicate inward pes rotation, accompanied by elongate pes digit scratch marks. For the latter phenomenon three possible scenarios are discussed:(1) significant rotation changes accompanying changes in gait,(2) swimming behavior,(3) formation of undertracks.Sedimentological evidence indicates the tracks were made on a linguloid rippled, muddy, immature sandstone substrate characterized by significant differences in substrate consistency across the trackbearing surface. Microbially induced sedimentary structures(MISS) characterized by distinctive wrinkle marks indicate a stressed, probably semi-arid, paleoenvironment that was not conducive to habitation by invertebrate organisms. This is consistent with other evidence that Lower Jurassic sauropodomorph tracks are often associated with semi-arid paleoenvironments.
基金supported by the National Natural Science Foundation of China (30430100,40872022)the Beijing Natural Science Foundation (5082002)Key and PHR Project of Beijing Municipal Commission of Education
文摘In this paper two new species of fossil Pseudopolycentropus Handlirsch, 1906 are described： Pseudopolycentropus janeannae sp. nov. and P. novokshonovi, sp. nov. All of them were recovered from the Middle Jurassic non-marine sedimentary strata of northeastern China. The new material from China reveals that the early diversification of pseudopolycentropodids was well underway by the Middle Jurassic.
