1.Objective,The Cretaceous succession is characteristic of the aeolian sedimentary system in the Ordos Basin,which is the major ore-bearing layer for the sandstone-type uranium deposits.Based on the research of paleon...1.Objective,The Cretaceous succession is characteristic of the aeolian sedimentary system in the Ordos Basin,which is the major ore-bearing layer for the sandstone-type uranium deposits.Based on the research of paleontology and magnetostratigraphy,formers believed it belonged to the Early Cretaceous(Huang YB,2010).However,the lack of intrusions or volcanic rocks for isotopic dating results in an unclear formation age for the Lower Cretaceous succession.Recently,tuffs were firstly discovered in the Luohandong Formation in the Zhenyuan area,Gansu Province,located in the southwestern Ordos Basin,China.The LA-ICP-MS zircon U-Pb dating of tuffs was carried out.The new ages can precisely constrain the depositional age of the Luohandong Formation and also provide significant indications for the study of regional volcanic activities,paleoclimate,basin evolution,and tectonic setting.展开更多
The Late Cretaceous Jiepailing granitoids,located at the central Nanling Range in South China,are closely associated with significant Sn-Li-Be-F polymetallic metallogeny.The Jiepailing granitoids mainly consist of gra...The Late Cretaceous Jiepailing granitoids,located at the central Nanling Range in South China,are closely associated with significant Sn-Li-Be-F polymetallic metallogeny.The Jiepailing granitoids mainly consist of granitic porphyry and zinnwaldite granite.The two granitoids have an A-type affinity,showing elevated Rb/Sr ratios and significant depletions in Ba,Sr and P.Integrated zircon and monazite U-Pb dating results suggest that granitic porphyry and zinnwaldite granite were emplaced at~89 Ma and~94 Ma,respectively.The low Ce^(4+)/Ce^(3+)ratios of the Jiepailing granitoids,together with significant negative Eu anomalies of the zircons,indicate that their formation occurred under conditions of reduced oxygen fugacity.Through the analysis of zircon Hf-O and whole-rock Nd isotopes,it has been determined that both stages of the Jiepailing granitoids originated in the lower-middle Mesoproterozoic crustal basement[ε_(Nd)(t)=−5.33 to−4.96,t^(C)_(DM)(Nd)=1289-1234 Ma,ε_(Hf)(t)=−4.13 to+2.22,t^(C)_(DM)(Hf)=1418-1015 Ma andδ^(18)O_(Zrc)=6.33‰-7.72‰],with the involvement of mantle-derived materials.Both granitic porphyry and zinnwaldite granite exhibit elevated concentrations of fluorine(F),with the positive correlation between F and Sn emphasizing the crucial role of high F sources in tin mineralization.Drawing upon the study of the Late Cretaceous magma systems in southern Hunan and through comparison with the mineralized granites observed in coastal regions during the Late Cretaceous,a genetic model for the mineralized granites in the Nanling region is developed.When the Paleo-Pacific Plate retreated to the coastal region,the continental crust in southern China underwent extensional thinning and asthenospheric upwelling due to gravitational collapse.Such processes resulted in the partial melting of the middle-lower crustal metamorphic sedimentary basement and the subsequent formation of F-rich granitic magmas,related to tin mineralization.展开更多
The Upper Cretaceous of Tantou Basin in western Henan has yielded many vertebrate fossils,which are featured by several non-avian dinosaurs.Meanwhile,studies on their eggs were yet inadequate though many eggshells hav...The Upper Cretaceous of Tantou Basin in western Henan has yielded many vertebrate fossils,which are featured by several non-avian dinosaurs.Meanwhile,studies on their eggs were yet inadequate though many eggshells have been reported.The newly discovered material 41HⅤ0199 was excavated from the Upper Cretaceous Qiupa Formation in 2021.The block preserves eight complete eggs arranged in two partial rings that form a partial clutch,and there are some scattered eggshells preserved closely with the block,showing a concave-up to concave-down ratio of 54.5:45.5,which indicates that the scattered eggshells come from the clutch and the clutch had been partially broken before it was buried.Based on morphological and microstructural characteristics,the eggs and eggshells can be assigned to Macroolithus yaotunensis(Elongatoolithidae),an oospecies known to be related to oviraptorids,which leads Yulong mini to be its probable producer.Besides,some eggshells show microstructural signs indicating egg retention,which marks the second example of egg retention in the oofamily Elongatoolithidae.展开更多
Twelve new dinosaur teeth have recently been recovered from three localities in the Upper Cretaceous Nenjiang Formation of the Songliao Basin.Although fragmentary,the material offers enough evidence to identify the fo...Twelve new dinosaur teeth have recently been recovered from three localities in the Upper Cretaceous Nenjiang Formation of the Songliao Basin.Although fragmentary,the material offers enough evidence to identify the following taxa:tyrannosaurids,dromaeosaurines,velociraptorines,hadrosauroids,and titanosaurs.In addition to the previously known dinosaurs from the basin,several new ones have been identified,extending the paleogeographic range of related taxa.The discovery of these new fossil remains provides valuable insights into dinosaur diversity and sheds light on the terrestrial ecosystem during the Late Cretaceous in the Songliao Basin.展开更多
The Upper Cretaceous successions of Wadi Umm-Khayshar,southern Galala Plateau,North Eastern Desert,Egypt,are composed of highly diversified faunas and subdivided from base to top into the Galala(Middle-Late Cenomanian...The Upper Cretaceous successions of Wadi Umm-Khayshar,southern Galala Plateau,North Eastern Desert,Egypt,are composed of highly diversified faunas and subdivided from base to top into the Galala(Middle-Late Cenomanian),Maghra El Hadida(Latest Cenomanian-Late Turonian),Matulla(Coniacian-Santonian),and Sudr(Campanian-Maastrichtian)formations.Five ammonite biozones are recorded in the studied section:Neolobites vibrayeanus,Vascoceras cauvini(late Cenomanian),Vascoceras proprium,Choffaticeras segne,and Coilopoceras requienianum(Turonian)zones.The paleoenvironments of the Upper Cretaceous succession are interpreted based on detailed study and microfacies analysis that reflect a deposition in a homoclinal ramp platform ranging from intertidal to deep subtidal.The paleoecology of the Cenomanian-Turonian succession in the studied section is explained based on a detailed study of macrofaunal associations and sedimentary facies.Quantitative analysis(Q-mode cluster analysis,using the Raup-Crick Paired group method)of 1029 macrobenthic specimens,including 45 species of mollusks and echinoids yielded five macrofaunal associations(A-E)that are described and interpreted as remnants of communities.The nektonic elements are represented by 235 cephalopod specimens of 20 species;heatmap cluster analyses show the distribution of these specimens during the Upper Cenomanian-Turonian stages.Environmental parameters(substrate consistency,rate of sedimentation,water energy,surface-water productivity,and oxygen availability)controlled the distribution of the studied macrofauna.The five associations are divided into two major groups:low-stress associations(A,B,C,and D),and a highstress association(E).The low stress associations are recorded from two different habitats:(1)a high-energy,firm substrate habitat,dominated by epifaunal bivalves,large epifaunal gastropods and a regular echinoid;(2)a low-energy,soft substrate habitat dominated by infaunal bivalves and echinoids.The high stress association is dominated by only two species and recorded from a high-energy shoal environment during a regression phase.A detailed study of macrobenthos and cephalopods provides a good paleoecological understanding of Cenomanian-Turonian succession in the Wadi Umm-Khayshar section.展开更多
Zircon U-Pb ages,major and trace elements and Sr-Nd-Hf isotope data of the diabase in the Zhangjiakou District were studied to investigate its derivation and tectonic implications.Zircon U-Pb ages indicate that the di...Zircon U-Pb ages,major and trace elements and Sr-Nd-Hf isotope data of the diabase in the Zhangjiakou District were studied to investigate its derivation and tectonic implications.Zircon U-Pb ages indicate that the diabase was emplaced at∼130 Ma or younger,and captured zircons cluster at∼147,∼240,∼430 and∼465 Ma.The diabase is characterized by minor variations in SiO_(2)(49.35 wt.%–52.10 wt.%),TiO_(2)(1.65 wt.%–1.77 wt.%),Al_(2)O_(3)(17.00 wt.%–18.26 wt.%),MgO(4.28 wt.%–4.93 wt.%),CaO(6.69 wt.%–7.90 wt.%)and Mg^(#)(48–54).It has no significant Eu anomaly and displays enrichment in large ion lithophile elements(Rb,Ba and Sr)and depletion in high field strength elements(Nb,Ta,P and Ti).The diabase exhibits homogeneous Sr((^(87)Sr/^(86)Sr)i=0.70606–0.70701)and Nd(ε_(Nd)(t)=−13.6 to−13.2)isotopic compositions.These features suggest that the parental magma was derived from partial melting of the ancient lower crust,relating to mantle upwelling that was triggered by the stagnant slabs or lithospheric detachment associated with the westward subduction of the Paleo-Pacific Plate.The Early Paleozoic inherited igneous zircons in the diabase suggest that the northern margin of the North China Craton(NCC)likely underwent southward subduction of the Paleo-Asian Ocean.展开更多
Palaeowind regime is an important component for reconstructing palaeoclimate and understanding ancient global circulation.We applied the beach-ridge thickness technique(BTT)and the longshore-bar thickness technique(LT...Palaeowind regime is an important component for reconstructing palaeoclimate and understanding ancient global circulation.We applied the beach-ridge thickness technique(BTT)and the longshore-bar thickness technique(LTT)to reconstruct the Early Cretaceous palaeowind velocities based on depositional records of Tanan Depression in Northeast Asia.The thickness of beach ridges and nearshore bars is the most important parameter for applying the BTT and the LTT methods.We identified 22 beach ridges and 23 nearshore bars based on drilling cores and wireline-log data in the Tanan Depression.Palaeowind velocities calculated by using the LTT method ranged from 10.84 to 13.66 m/s,showing a narrower range than those calculated by using the BTT method(7.58–15.93 m/s).We further analyzed the underlying factors causing the difference between the results derived from these two methods based on the sedimentary process of the beach ridge and the nearshore bar.The reconstructed wind regime was assumed to be the summer monsoon originating from the Mongol-Okhotsk Ocean before it had been completely enclosed,which provides valuable insight into the understanding of the atmospheric circulation in Northeast Asia during the Early Cretaceous.展开更多
The Late Cretaceous global transgression is one of the best documented episodes of continental submergence events.The extent of transgression of the Neotethys Ocean into the African continent is generally thought to b...The Late Cretaceous global transgression is one of the best documented episodes of continental submergence events.The extent of transgression of the Neotethys Ocean into the African continent is generally thought to be limited to north Africa.Here,we describe transgression traces in the Muglad Basin in central Africa that indicate a greater spatial extend of the Neotethys during the late Cretaceous.A series of molecular markers detected in the Upper Cretaceous Santonian-Maastrichtian sediments of the Muglad Basin are typical for marine depositional conditions and differ from those in the typical lacustrine sediments of the Lower Cretaceous Barremian-Aptian.Combining the geological-geochemical implications of these markers with the paleogeographic,paleontological and lithological records,we propose that the Muglad Basin received intermittent marine inundations during the Santonian-Maastrichtian stages(86.3-66.0 Ma)and these special molecular markers are therefore the products of seawater incursion.Consequently,this study proposes that the transgression extent of the Neotethys Ocean into the African continent southern extended to the central Africa during the Late Cretaceous.展开更多
Taking the GY8HC well in the Gulong Sag of the Songliao Basin,NE China,as an example,this study utilized high-precision zircon U-Pb ages from volcanic ashes and AstroBayes method to estimate sedimentation rates.Throug...Taking the GY8HC well in the Gulong Sag of the Songliao Basin,NE China,as an example,this study utilized high-precision zircon U-Pb ages from volcanic ashes and AstroBayes method to estimate sedimentation rates.Through spectral analysis of high-resolution total organic carbon content(TOC),laboratory-measured free hydrocarbons(S_(1)),hydrocarbons formed during pyrolysis(S_(2)),and mineral contents,the enrichment characteristics and controlling factors of shale oil in an overmature area were investigated.The results indicate that:(1)TOC,S_(1),and S_(2)associated with shale oil enrichment exhibit a significant 173×10^(3)a obliquity amplitude modulation cycle;(2)Quartz and illite/smectite mixed-layer contents related to lithological composition show a significant 405×10^(3)a long eccentricity cycle;(3)Comparative studies with the high-maturity GY3HC well and moderate-maturity ZY1 well reveal distinct in-situ enrichment characteristics of shale oil in the overmature Qingshankou Formation,with a significant positive correlation to TOC,indicating that high TOC is a key factor for shale oil enrichment in overmature areas;(4)The sedimentary thickness of 12-13 m corresponding to the 173×10^(3)a cycle can serve as the sweet spot interval height for shale oil development in the study area,falling within the optimal fracture height range(10-15 m)generated during hydraulic fracturing of the Qingshankou shale.Orbitally forced climate changes not only controlled the sedimentary rhythms of organic carbon burial and lithological composition in the Songliao Basin but also influenced the enrichment characteristics and sweet spot distribution of Gulong shale oil.展开更多
0 INTRODUCTION Orogenic belts are commonly built by multiple-stage processes involving oceanic subduction and continental collisions that result in the generation of magma with distinct geochemical compositions,as exe...0 INTRODUCTION Orogenic belts are commonly built by multiple-stage processes involving oceanic subduction and continental collisions that result in the generation of magma with distinct geochemical compositions,as exemplified by Central Asian Orogenic Belts(e.g.,Wang et al.,2024;Yin et al.,2024;Xiao et al.,2005)and the Tethyan tectonic domains(e.g.,Chen et al.,2024;Li et al.,2024;Tao et al.,2024a;Gehrels et al.,2011;Yin and Harrison,2000).展开更多
Based on the petroleum exploration in the Cretaceous Qingshankou Formation,northern Songliao Basin,NE China,integrated with seismic,drilling and logging data,this study investigates the characteristics and genetic mec...Based on the petroleum exploration in the Cretaceous Qingshankou Formation,northern Songliao Basin,NE China,integrated with seismic,drilling and logging data,this study investigates the characteristics and genetic mechanisms of orderly distribution and the differential enrichment patterns of conventional and unconventional hydrocarbons in the formation.Key findings involve five aspects.First,the conventional and unconventional hydrocarbons coexist orderly.Laterally,conventional oil,tight oil,and shale oil form a pattern of orderly accumulation from basin margins to the center.Vertically,shale oil,tight oil,and conventional oil develop progressively upward.Second,the coupled tectonic-sedimentary processes govern sedimentary facies differentiation and diagenesis,influencing reservoir physical properties and lithology,thereby controlling the orderly distribution of conventional and unconventional hydrocarbons in space.Third,the coupling of source rock hydrocarbon generation evolution,fault sealing capacity,and reservoir densification determines the orderly coexistence pattern of conventional and unconventional hydrocarbons.Fourth,sequential variations in reservoir physical properties generate distinct dynamic fields that regulate hydrocarbon orderly accumulation.Fifth,enrichment controls are different depending on hydrocarbon types:buoyancy-driven,fault-transport,sandbody-connected,and trap-concentrated,for above-source conventional oil;overpressure-driven,fault-transport,multi-stacked sandbodies,and quasi-continuous distribution for near-source tight oil and gas;self-sourced reservoirs,retention through self-sealing,in-situ accumulation or micro-migration driven by hydrocarbon-generation overpressure for inner-source shale oil.From exploration practices,these findings will effectively guide the integrated deployment and three-dimensional exploration of conventional and unconventional hydrocarbon resources in the Qingshankou Formation,northern Songliao Basin.展开更多
The Cretaceous gold deposits along the margins of the North China Craton(NCC),which formed in a craton destruction setting,display geological characteristics similar to traditional orogenic gold deposits typically ass...The Cretaceous gold deposits along the margins of the North China Craton(NCC),which formed in a craton destruction setting,display geological characteristics similar to traditional orogenic gold deposits typically associated with accretionary orogeny.These deposits,known as Jiaodong-type gold deposits,have attracted considerable attention.However,the lithospheric controls and formation mechanisms of these deposits remain unclear,as they cannot be fully explained by the supracrustal metamorphic genetic model commonly applied to classic orogenic gold deposits.In this study,the compiled S-Hg-Pb isotope ratios of gold deposits on different NCC margins display compatible variations to the Sr-Nd-Hg isotope ratios of mafic dikes spatial-temporally associated with the deposits.This implies that mantle lithosphere,metasomatized by variable proportions of oceanic and continental crust,was the source for both gold deposits and mafic dikes.Increase of oxygen fugacity and zirconεHf(t)from pre-to syn-gold granites suggests continuous basic magma underplating,which could induce concentrations of Au-rich sulfides and contribute additional Au to auriferous CO_(2)-rich fluids derived from metasomatized mantle lithosphere and basic magma.Localization of gold deposits was controlled by craton-margin sinistral shearing induced by clockwise rotation of the craton coincident with distal emplacement of metamorphic core complexes.Thus,the Cretaceous Jiaodong-type orogenic gold deposits were derived from fertilized mantle lithosphere through such crust-mantle processes within a lithosphere thinning background.展开更多
Taking the shale oil of the first member of the Cretaceous Qingshankou Formation of Changling Sag in southern Songliao Basin as an example,this paper establishes a saturation model of lacustrine shale oil considering ...Taking the shale oil of the first member of the Cretaceous Qingshankou Formation of Changling Sag in southern Songliao Basin as an example,this paper establishes a saturation model of lacustrine shale oil considering the influence of organic matter on clay-bound water conductivity.Based on the fluid characterization results of sealed samples and two-dimensional nuclear magnetic resonance,the differential influence of organic matter on clay-bound water conductivity was quantitatively revealed,and the conductivity mechanism and rock-electrical relationships of lacustrine shale were systematically analyzed.The results show that there are two conductive networks for lacustrine shales,i.e.the matrix free water and the clay-bound water.The bound water cementation index msh was introduced to reflect the impact of organic matter on clay-bound water conductivity,and it is positively correlated with the effective porosity.When there is sufficient rigid framework support and well-developed pores,organic matter is more likely to fill or adsorb onto clay interlayers.This reduces the ion exchange capacity of the electrical double layer,leading to an increase in msh and a decrease in the conductivity of clay-bound water.The overall conductivity of shale is controlled by the clay-bound water conductivity,and the relative contributions of the mentioned two conductive networks to formation conductivity are affected by the effective porosity and msh.The larger the effective porosity and msh,the more the contribution of the matrix free water to formation conductivity.According to the experimental results,the proposed saturation model yields a significantly higher interpretation accuracy in oil saturation than the Archie model and the Total-shale model.展开更多
This study focuses on tuffaceous clastic rocks of the Lower Cretaceous Qingshuihe Formation in the southern margin of Junggar Basin.It aims to explore the influence of sedimentation and parent rock on this kind of res...This study focuses on tuffaceous clastic rocks of the Lower Cretaceous Qingshuihe Formation in the southern margin of Junggar Basin.It aims to explore the influence of sedimentation and parent rock on this kind of reservoir development.The results show that the tuffaceous components formed by the denudation of ultramafic and mafic rocks can transform into chlorite coating or hematite,while those from intermediate rock denudation can be dissolved or transformed into illite.Sedimentary facies and lithofacies are essential in controlling the evolutionary result of tuffaceous components.Matrix-supported medium conglomerate and grain-supported medium-fine conglomerate that developed in the fan delta plain,with a closed original geochemical systems,have been in the oxidizing environment for a long time.The tuffaceous matrices mainly transforms into hematite or illite.These minerals occupy the primary pores and are difficult to dissolve by felsic fluids,which inhibits the development of high-quality reservoirs.The grain-supported sandy fine conglomerate developed in the fan delta front was in the underwater reductive environment with an open original geochemical system.The tuffaceous matrices not only can transform into chlorite coating to strengthen the particle's compaction resistance,but also can be fully dissolved,which promotes the formation of high-quality reservoirs.展开更多
Many Late Cretaceous-Early Paleocene high-silica igneous rocks,associated with Pb-Zn-Ag deposits,were identified in western part of southern Lhasa terrane.The Dajiacuodong muscovite granite as one of the high-silica g...Many Late Cretaceous-Early Paleocene high-silica igneous rocks,associated with Pb-Zn-Ag deposits,were identified in western part of southern Lhasa terrane.The Dajiacuodong muscovite granite as one of the high-silica granites was dated by zircon U-Pb method and determined for whole-rock major and trace elements and zircon trace elements.Combined with previous data of other high-silica igneous rocks,petrogenesis,tectonic setting,and factors controlling Pb-Zn-Ag mineralization were studied.The muscovite granite emplaced at 68.2±0.3 Ma and is peraluminous.All high-silica igneous rocks are S-type and whole-rock CaO,Na_(2)O,and Rb-Sr-Ba and zircon Hf isotopic compositions show that they were formed by partial melting of meta-sedimentary protoliths from the Lhasa terrane basement.Roll-back of the NeoTethys oceanic slab caused melting of the mantle wedge is the trigger for partial melting of basement.Zircon trace elements indicate that the high-silica igneous rocks are reduced and H_(2)O-and F-enriched.These geochemical features and magma sources of the high-silica igneous rocks are comparable with the W-Sn deposit related granites.Shallow emplacement of high-silica granites and coeval volcanic eruption induced rapid escape of fluids.This caused inefficiency of hydrothermal-magmatic interaction,which are reasons to form Pb-Zn-Ag rather than W-Sn deposits.展开更多
The high Ba-Sr rocks can provide significant clues about the evolution of the continent lithosphere,but their petrogenesis remains controversial.Identifying the Late Cretaceous high Ba-Sr granodiorites in the SE Lhasa...The high Ba-Sr rocks can provide significant clues about the evolution of the continent lithosphere,but their petrogenesis remains controversial.Identifying the Late Cretaceous high Ba-Sr granodiorites in the SE Lhasa Block could potentially provide valuable insights into the continent evolution of the Qinghai-Tibet Plateau.Zircon U-Pb ages suggest that the granodiorites were emplaced at 87.32±0.43 Ma.Geochemically,the high Ba-Sr granodiorites are characterized by elevated K_(2)O+Na_(2)O contents(8.18-8.73 wt%)and K_(2)O/Na_(2)O ratios(0.99-1.25,mostly>1),and belong to high-K calc-alkaline to shoshonitic series.The Yonglaga granodiorites show notably high Sr(653-783 ppm)and Ba(1346-1531 ppm)contents,plus high Sr/Y(30.92-38.18)and(La/Yb)_(N)(27.7-34.7)ratios,but low Y(20.0-22.8 ppm)and Yb(1.92-2.19 ppm)contents with absence of negative Eu anomalies(δEu=0.83-0.88),all similar to typical high Ba-Sr granitoids.The variable zirconεHf(t)values of-4.58 to+12.97,elevated initial^(87)Sr/^(86)Sr isotopic ratios of 0.707254 to 0.707322 and lowεNd(t)values of-2.8 to-3.6 with decoupling from the Hf system suggest that a metasomatized mantle source included significant recycled ancient materials.The occurrence of such high Ba-Sr intrusions indicates previous contributions of metasomatized mantle-derived juvenile material to the continents,which imply the growth of continental crust during the Late Cretaceous in the SE Lhasa.Together with regional data,we infer that the underplated mafic magma provides a significant amount of heat,which leads to partial melting of the juvenile crust.The melting of the metasomatized mantle could produce a juvenile mafic lower crust,from which the high Ba-Sr granitoids were derived from reworking of previous mafic crust during the Late Cretaceous(ca.100-80 Ma)in the SE Lhasa.展开更多
Jiuhua Mountain,situated in the eastern segment of the Jiangnan Orogenic Belt,is characterized by extensive granite masses,providing an ideal setting for investigating the exhumation history of the region.This study p...Jiuhua Mountain,situated in the eastern segment of the Jiangnan Orogenic Belt,is characterized by extensive granite masses,providing an ideal setting for investigating the exhumation history of the region.This study presents the first zircon(U-Th)/He thermochronological investigation utilizing an age-elevation approach for Jiuhua Mountain.Zircon(U-Th)/He analyses of six bedrock samples yielded consistent ages ranging from 89 to 74 Ma.This finding aligns with the results of thermal history simulations(90-70 Ma),indicating significant exhumation in the Jiuhua Mountain region during the late Cretaceous.Comparative analysis with adjacent orogenic belts(e.g.,the Mufu and Dabie Mountains)reveals a consistent pattern:low-temperature thermochronological ages are younger than the U-Pb zircon ages.This indicates a widespread tectonic exhumation and erosion phase affecting multiple regions within the northern part of the South China Block.The rapid exhumation observed during the late Cretaceous is primarily attributed to extensional tectonics,driven by the rollback of the Paleo-Pacific slab and accompanied by thermal upwelling of the asthenosphere beneath the South China Block.These findings establish crucial temporal constraints for the exhumation history of the eastern Jiangnan Orogenic Belt,significantly enhancing our understanding of its poorly constrained Cretaceous tectonic evolution.展开更多
The stratigraphy,sedimentary history and paleontology of the northern Eromanga Basin are reviewed in the light of extensive field effort,searching for Cretaceous vertebrate fossils,in particular dinosaurs.Prolonged no...The stratigraphy,sedimentary history and paleontology of the northern Eromanga Basin are reviewed in the light of extensive field effort,searching for Cretaceous vertebrate fossils,in particular dinosaurs.Prolonged non-marine deposition throughout the Jurassic was followed by Lower Cretaceous marine incursions which extended to the late Albian.Whilst biostratigraphy is underpinned by microfloral assemblages there are three distinct marine faunas preserved from the late Aptian,early middle Albian and late Albian.Effective regression caused by sediment oversupply in the latest Albian heralded the final phase of non-marine deposition in the Eromanga Basin which continued into the Cenomanian.A distinct floral assemblage is accompanied by a modest fossil vertebrate assemblage.展开更多
The special issue deals with the Cretaceous-Tertiary deserts in southwestern China and relevant sedimentological problems about deserts. The study area is located between 101°10＇- 107°00＇E and 28°00＇...The special issue deals with the Cretaceous-Tertiary deserts in southwestern China and relevant sedimentological problems about deserts. The study area is located between 101°10＇- 107°00＇E and 28°00＇-30°40′ N. The ancient desert study is so little in China that there has not been a systematic report about it up to now. Based on the study in many ways on Cretaceous-Tertiary deserts in southwestern China, plentiful data have been obtained. Though it is still a bit rough, the study is a good beginning of the ancient desert study in China. The main ideas and conclusions are summarized as follows.展开更多
基金supported by the Science&Technology Fundamental Resources Investigation Program of China(2022FY101800)the National Science Foundation of China(92162212)the International Geoscience Programme(IGCP 675).
文摘1.Objective,The Cretaceous succession is characteristic of the aeolian sedimentary system in the Ordos Basin,which is the major ore-bearing layer for the sandstone-type uranium deposits.Based on the research of paleontology and magnetostratigraphy,formers believed it belonged to the Early Cretaceous(Huang YB,2010).However,the lack of intrusions or volcanic rocks for isotopic dating results in an unclear formation age for the Lower Cretaceous succession.Recently,tuffs were firstly discovered in the Luohandong Formation in the Zhenyuan area,Gansu Province,located in the southwestern Ordos Basin,China.The LA-ICP-MS zircon U-Pb dating of tuffs was carried out.The new ages can precisely constrain the depositional age of the Luohandong Formation and also provide significant indications for the study of regional volcanic activities,paleoclimate,basin evolution,and tectonic setting.
基金financially supported by the National Natural Science Foundation of China(Grant No.42303073).
文摘The Late Cretaceous Jiepailing granitoids,located at the central Nanling Range in South China,are closely associated with significant Sn-Li-Be-F polymetallic metallogeny.The Jiepailing granitoids mainly consist of granitic porphyry and zinnwaldite granite.The two granitoids have an A-type affinity,showing elevated Rb/Sr ratios and significant depletions in Ba,Sr and P.Integrated zircon and monazite U-Pb dating results suggest that granitic porphyry and zinnwaldite granite were emplaced at~89 Ma and~94 Ma,respectively.The low Ce^(4+)/Ce^(3+)ratios of the Jiepailing granitoids,together with significant negative Eu anomalies of the zircons,indicate that their formation occurred under conditions of reduced oxygen fugacity.Through the analysis of zircon Hf-O and whole-rock Nd isotopes,it has been determined that both stages of the Jiepailing granitoids originated in the lower-middle Mesoproterozoic crustal basement[ε_(Nd)(t)=−5.33 to−4.96,t^(C)_(DM)(Nd)=1289-1234 Ma,ε_(Hf)(t)=−4.13 to+2.22,t^(C)_(DM)(Hf)=1418-1015 Ma andδ^(18)O_(Zrc)=6.33‰-7.72‰],with the involvement of mantle-derived materials.Both granitic porphyry and zinnwaldite granite exhibit elevated concentrations of fluorine(F),with the positive correlation between F and Sn emphasizing the crucial role of high F sources in tin mineralization.Drawing upon the study of the Late Cretaceous magma systems in southern Hunan and through comparison with the mineralized granites observed in coastal regions during the Late Cretaceous,a genetic model for the mineralized granites in the Nanling region is developed.When the Paleo-Pacific Plate retreated to the coastal region,the continental crust in southern China underwent extensional thinning and asthenospheric upwelling due to gravitational collapse.Such processes resulted in the partial melting of the middle-lower crustal metamorphic sedimentary basement and the subsequent formation of F-rich granitic magmas,related to tin mineralization.
文摘The Upper Cretaceous of Tantou Basin in western Henan has yielded many vertebrate fossils,which are featured by several non-avian dinosaurs.Meanwhile,studies on their eggs were yet inadequate though many eggshells have been reported.The newly discovered material 41HⅤ0199 was excavated from the Upper Cretaceous Qiupa Formation in 2021.The block preserves eight complete eggs arranged in two partial rings that form a partial clutch,and there are some scattered eggshells preserved closely with the block,showing a concave-up to concave-down ratio of 54.5:45.5,which indicates that the scattered eggshells come from the clutch and the clutch had been partially broken before it was buried.Based on morphological and microstructural characteristics,the eggs and eggshells can be assigned to Macroolithus yaotunensis(Elongatoolithidae),an oospecies known to be related to oviraptorids,which leads Yulong mini to be its probable producer.Besides,some eggshells show microstructural signs indicating egg retention,which marks the second example of egg retention in the oofamily Elongatoolithidae.
基金supported financially by China Geological Survey(Grant No.DD20230221)the Key Laboratory of Stratigraphy and Palaeontology,Ministry of Natural Resources(Grant No.KLSP SP202301)National Nature Science Foundation of China(Grant No.41202012).
文摘Twelve new dinosaur teeth have recently been recovered from three localities in the Upper Cretaceous Nenjiang Formation of the Songliao Basin.Although fragmentary,the material offers enough evidence to identify the following taxa:tyrannosaurids,dromaeosaurines,velociraptorines,hadrosauroids,and titanosaurs.In addition to the previously known dinosaurs from the basin,several new ones have been identified,extending the paleogeographic range of related taxa.The discovery of these new fossil remains provides valuable insights into dinosaur diversity and sheds light on the terrestrial ecosystem during the Late Cretaceous in the Songliao Basin.
文摘The Upper Cretaceous successions of Wadi Umm-Khayshar,southern Galala Plateau,North Eastern Desert,Egypt,are composed of highly diversified faunas and subdivided from base to top into the Galala(Middle-Late Cenomanian),Maghra El Hadida(Latest Cenomanian-Late Turonian),Matulla(Coniacian-Santonian),and Sudr(Campanian-Maastrichtian)formations.Five ammonite biozones are recorded in the studied section:Neolobites vibrayeanus,Vascoceras cauvini(late Cenomanian),Vascoceras proprium,Choffaticeras segne,and Coilopoceras requienianum(Turonian)zones.The paleoenvironments of the Upper Cretaceous succession are interpreted based on detailed study and microfacies analysis that reflect a deposition in a homoclinal ramp platform ranging from intertidal to deep subtidal.The paleoecology of the Cenomanian-Turonian succession in the studied section is explained based on a detailed study of macrofaunal associations and sedimentary facies.Quantitative analysis(Q-mode cluster analysis,using the Raup-Crick Paired group method)of 1029 macrobenthic specimens,including 45 species of mollusks and echinoids yielded five macrofaunal associations(A-E)that are described and interpreted as remnants of communities.The nektonic elements are represented by 235 cephalopod specimens of 20 species;heatmap cluster analyses show the distribution of these specimens during the Upper Cenomanian-Turonian stages.Environmental parameters(substrate consistency,rate of sedimentation,water energy,surface-water productivity,and oxygen availability)controlled the distribution of the studied macrofauna.The five associations are divided into two major groups:low-stress associations(A,B,C,and D),and a highstress association(E).The low stress associations are recorded from two different habitats:(1)a high-energy,firm substrate habitat,dominated by epifaunal bivalves,large epifaunal gastropods and a regular echinoid;(2)a low-energy,soft substrate habitat dominated by infaunal bivalves and echinoids.The high stress association is dominated by only two species and recorded from a high-energy shoal environment during a regression phase.A detailed study of macrobenthos and cephalopods provides a good paleoecological understanding of Cenomanian-Turonian succession in the Wadi Umm-Khayshar section.
基金supported by the National Natural Science Foundation of China(No.42003032)the State Key Laboratory of Nuclear Resources and Environment,East China University of Technology(No.2020Z10).
文摘Zircon U-Pb ages,major and trace elements and Sr-Nd-Hf isotope data of the diabase in the Zhangjiakou District were studied to investigate its derivation and tectonic implications.Zircon U-Pb ages indicate that the diabase was emplaced at∼130 Ma or younger,and captured zircons cluster at∼147,∼240,∼430 and∼465 Ma.The diabase is characterized by minor variations in SiO_(2)(49.35 wt.%–52.10 wt.%),TiO_(2)(1.65 wt.%–1.77 wt.%),Al_(2)O_(3)(17.00 wt.%–18.26 wt.%),MgO(4.28 wt.%–4.93 wt.%),CaO(6.69 wt.%–7.90 wt.%)and Mg^(#)(48–54).It has no significant Eu anomaly and displays enrichment in large ion lithophile elements(Rb,Ba and Sr)and depletion in high field strength elements(Nb,Ta,P and Ti).The diabase exhibits homogeneous Sr((^(87)Sr/^(86)Sr)i=0.70606–0.70701)and Nd(ε_(Nd)(t)=−13.6 to−13.2)isotopic compositions.These features suggest that the parental magma was derived from partial melting of the ancient lower crust,relating to mantle upwelling that was triggered by the stagnant slabs or lithospheric detachment associated with the westward subduction of the Paleo-Pacific Plate.The Early Paleozoic inherited igneous zircons in the diabase suggest that the northern margin of the North China Craton(NCC)likely underwent southward subduction of the Paleo-Asian Ocean.
基金Supported by the National Science and Technology Special Project of China(No.2017ZX05009-002)the China Scholarship Council(No.202106400055)。
文摘Palaeowind regime is an important component for reconstructing palaeoclimate and understanding ancient global circulation.We applied the beach-ridge thickness technique(BTT)and the longshore-bar thickness technique(LTT)to reconstruct the Early Cretaceous palaeowind velocities based on depositional records of Tanan Depression in Northeast Asia.The thickness of beach ridges and nearshore bars is the most important parameter for applying the BTT and the LTT methods.We identified 22 beach ridges and 23 nearshore bars based on drilling cores and wireline-log data in the Tanan Depression.Palaeowind velocities calculated by using the LTT method ranged from 10.84 to 13.66 m/s,showing a narrower range than those calculated by using the BTT method(7.58–15.93 m/s).We further analyzed the underlying factors causing the difference between the results derived from these two methods based on the sedimentary process of the beach ridge and the nearshore bar.The reconstructed wind regime was assumed to be the summer monsoon originating from the Mongol-Okhotsk Ocean before it had been completely enclosed,which provides valuable insight into the understanding of the atmospheric circulation in Northeast Asia during the Early Cretaceous.
基金supported by the National Natural Science Foundation of China(No.42202134)Science Foundation of China University of Petroleum,Beijing(No.2462023YJRC010)the postdoctoral fellowship by the Central Research and Development Fund of the University of Bremen.The authors would like to thank the editor and the two anonymous reviewers for their constructive comments and suggestions which significantly improved the quality of the manuscript.
文摘The Late Cretaceous global transgression is one of the best documented episodes of continental submergence events.The extent of transgression of the Neotethys Ocean into the African continent is generally thought to be limited to north Africa.Here,we describe transgression traces in the Muglad Basin in central Africa that indicate a greater spatial extend of the Neotethys during the late Cretaceous.A series of molecular markers detected in the Upper Cretaceous Santonian-Maastrichtian sediments of the Muglad Basin are typical for marine depositional conditions and differ from those in the typical lacustrine sediments of the Lower Cretaceous Barremian-Aptian.Combining the geological-geochemical implications of these markers with the paleogeographic,paleontological and lithological records,we propose that the Muglad Basin received intermittent marine inundations during the Santonian-Maastrichtian stages(86.3-66.0 Ma)and these special molecular markers are therefore the products of seawater incursion.Consequently,this study proposes that the transgression extent of the Neotethys Ocean into the African continent southern extended to the central Africa during the Late Cretaceous.
基金Supported by the National Natural Science Foundation of China(42372162,4244205C)Project of"Solving Problems by Listing Talents"in Heilongjiang Province(2022-JS-1740,2022-JS-1853)Project on the Theory of Oil and Gas Enrichment from the Interaction of Earth's Multiple Spheres(THEMSIE04010103).
文摘Taking the GY8HC well in the Gulong Sag of the Songliao Basin,NE China,as an example,this study utilized high-precision zircon U-Pb ages from volcanic ashes and AstroBayes method to estimate sedimentation rates.Through spectral analysis of high-resolution total organic carbon content(TOC),laboratory-measured free hydrocarbons(S_(1)),hydrocarbons formed during pyrolysis(S_(2)),and mineral contents,the enrichment characteristics and controlling factors of shale oil in an overmature area were investigated.The results indicate that:(1)TOC,S_(1),and S_(2)associated with shale oil enrichment exhibit a significant 173×10^(3)a obliquity amplitude modulation cycle;(2)Quartz and illite/smectite mixed-layer contents related to lithological composition show a significant 405×10^(3)a long eccentricity cycle;(3)Comparative studies with the high-maturity GY3HC well and moderate-maturity ZY1 well reveal distinct in-situ enrichment characteristics of shale oil in the overmature Qingshankou Formation,with a significant positive correlation to TOC,indicating that high TOC is a key factor for shale oil enrichment in overmature areas;(4)The sedimentary thickness of 12-13 m corresponding to the 173×10^(3)a cycle can serve as the sweet spot interval height for shale oil development in the study area,falling within the optimal fracture height range(10-15 m)generated during hydraulic fracturing of the Qingshankou shale.Orbitally forced climate changes not only controlled the sedimentary rhythms of organic carbon burial and lithological composition in the Songliao Basin but also influenced the enrichment characteristics and sweet spot distribution of Gulong shale oil.
基金supported by the National Key Research and Development Project(No.2022YFC2903302)the Second Tibet Plateau Scientific Expedition and Research Program(STEP),(No.2019QZKK0802)+2 种基金the National Natural Science Foundation of China(No.42361144841)the Chinese Academy of Geological Sciences Basal Research Fund(No.JKYZD202402)the Scientific Research Fund Project of BGRIMM Technology Group(No.JTKY202427822)。
文摘0 INTRODUCTION Orogenic belts are commonly built by multiple-stage processes involving oceanic subduction and continental collisions that result in the generation of magma with distinct geochemical compositions,as exemplified by Central Asian Orogenic Belts(e.g.,Wang et al.,2024;Yin et al.,2024;Xiao et al.,2005)and the Tethyan tectonic domains(e.g.,Chen et al.,2024;Li et al.,2024;Tao et al.,2024a;Gehrels et al.,2011;Yin and Harrison,2000).
基金Supported by the PetroChina Science and Technology Major Project(2023ZZ15).
文摘Based on the petroleum exploration in the Cretaceous Qingshankou Formation,northern Songliao Basin,NE China,integrated with seismic,drilling and logging data,this study investigates the characteristics and genetic mechanisms of orderly distribution and the differential enrichment patterns of conventional and unconventional hydrocarbons in the formation.Key findings involve five aspects.First,the conventional and unconventional hydrocarbons coexist orderly.Laterally,conventional oil,tight oil,and shale oil form a pattern of orderly accumulation from basin margins to the center.Vertically,shale oil,tight oil,and conventional oil develop progressively upward.Second,the coupled tectonic-sedimentary processes govern sedimentary facies differentiation and diagenesis,influencing reservoir physical properties and lithology,thereby controlling the orderly distribution of conventional and unconventional hydrocarbons in space.Third,the coupling of source rock hydrocarbon generation evolution,fault sealing capacity,and reservoir densification determines the orderly coexistence pattern of conventional and unconventional hydrocarbons.Fourth,sequential variations in reservoir physical properties generate distinct dynamic fields that regulate hydrocarbon orderly accumulation.Fifth,enrichment controls are different depending on hydrocarbon types:buoyancy-driven,fault-transport,sandbody-connected,and trap-concentrated,for above-source conventional oil;overpressure-driven,fault-transport,multi-stacked sandbodies,and quasi-continuous distribution for near-source tight oil and gas;self-sourced reservoirs,retention through self-sealing,in-situ accumulation or micro-migration driven by hydrocarbon-generation overpressure for inner-source shale oil.From exploration practices,these findings will effectively guide the integrated deployment and three-dimensional exploration of conventional and unconventional hydrocarbon resources in the Qingshankou Formation,northern Songliao Basin.
基金funded by the National Natural Science Foundation of China(42125203,42330809)the 111 project of the Ministry of Science and Technology(BP0719021).
文摘The Cretaceous gold deposits along the margins of the North China Craton(NCC),which formed in a craton destruction setting,display geological characteristics similar to traditional orogenic gold deposits typically associated with accretionary orogeny.These deposits,known as Jiaodong-type gold deposits,have attracted considerable attention.However,the lithospheric controls and formation mechanisms of these deposits remain unclear,as they cannot be fully explained by the supracrustal metamorphic genetic model commonly applied to classic orogenic gold deposits.In this study,the compiled S-Hg-Pb isotope ratios of gold deposits on different NCC margins display compatible variations to the Sr-Nd-Hg isotope ratios of mafic dikes spatial-temporally associated with the deposits.This implies that mantle lithosphere,metasomatized by variable proportions of oceanic and continental crust,was the source for both gold deposits and mafic dikes.Increase of oxygen fugacity and zirconεHf(t)from pre-to syn-gold granites suggests continuous basic magma underplating,which could induce concentrations of Au-rich sulfides and contribute additional Au to auriferous CO_(2)-rich fluids derived from metasomatized mantle lithosphere and basic magma.Localization of gold deposits was controlled by craton-margin sinistral shearing induced by clockwise rotation of the craton coincident with distal emplacement of metamorphic core complexes.Thus,the Cretaceous Jiaodong-type orogenic gold deposits were derived from fertilized mantle lithosphere through such crust-mantle processes within a lithosphere thinning background.
基金Supported by National Natural Science Foundation of China(42472217).
文摘Taking the shale oil of the first member of the Cretaceous Qingshankou Formation of Changling Sag in southern Songliao Basin as an example,this paper establishes a saturation model of lacustrine shale oil considering the influence of organic matter on clay-bound water conductivity.Based on the fluid characterization results of sealed samples and two-dimensional nuclear magnetic resonance,the differential influence of organic matter on clay-bound water conductivity was quantitatively revealed,and the conductivity mechanism and rock-electrical relationships of lacustrine shale were systematically analyzed.The results show that there are two conductive networks for lacustrine shales,i.e.the matrix free water and the clay-bound water.The bound water cementation index msh was introduced to reflect the impact of organic matter on clay-bound water conductivity,and it is positively correlated with the effective porosity.When there is sufficient rigid framework support and well-developed pores,organic matter is more likely to fill or adsorb onto clay interlayers.This reduces the ion exchange capacity of the electrical double layer,leading to an increase in msh and a decrease in the conductivity of clay-bound water.The overall conductivity of shale is controlled by the clay-bound water conductivity,and the relative contributions of the mentioned two conductive networks to formation conductivity are affected by the effective porosity and msh.The larger the effective porosity and msh,the more the contribution of the matrix free water to formation conductivity.According to the experimental results,the proposed saturation model yields a significantly higher interpretation accuracy in oil saturation than the Archie model and the Total-shale model.
基金supported by the National Natural Science Foundation of China(Grant Nos.42172109,41872113,42172108)China National Petroleum Corporation-China University of Petroleum(Beijing)Strategic Cooperation Science and Technology Project(Grant No.ZLZX2020-02)+1 种基金State's Key Project of Research and Development Plan(Grant No.2018YFA0702405)Science Foundation of China University of Petroleum(Beijing)(Grant Nos.2462020BJRC002,2462020YXZZ020)。
文摘This study focuses on tuffaceous clastic rocks of the Lower Cretaceous Qingshuihe Formation in the southern margin of Junggar Basin.It aims to explore the influence of sedimentation and parent rock on this kind of reservoir development.The results show that the tuffaceous components formed by the denudation of ultramafic and mafic rocks can transform into chlorite coating or hematite,while those from intermediate rock denudation can be dissolved or transformed into illite.Sedimentary facies and lithofacies are essential in controlling the evolutionary result of tuffaceous components.Matrix-supported medium conglomerate and grain-supported medium-fine conglomerate that developed in the fan delta plain,with a closed original geochemical systems,have been in the oxidizing environment for a long time.The tuffaceous matrices mainly transforms into hematite or illite.These minerals occupy the primary pores and are difficult to dissolve by felsic fluids,which inhibits the development of high-quality reservoirs.The grain-supported sandy fine conglomerate developed in the fan delta front was in the underwater reductive environment with an open original geochemical system.The tuffaceous matrices not only can transform into chlorite coating to strengthen the particle's compaction resistance,but also can be fully dissolved,which promotes the formation of high-quality reservoirs.
基金funded by the National Key R&D Program of China(2021YFC2900100)the Basic Research Found of Chinese Academy of Geological Sciences(KK2306)the Geological Survey Program of China Geological Survey(DD20230360 and DD20240078)。
文摘Many Late Cretaceous-Early Paleocene high-silica igneous rocks,associated with Pb-Zn-Ag deposits,were identified in western part of southern Lhasa terrane.The Dajiacuodong muscovite granite as one of the high-silica granites was dated by zircon U-Pb method and determined for whole-rock major and trace elements and zircon trace elements.Combined with previous data of other high-silica igneous rocks,petrogenesis,tectonic setting,and factors controlling Pb-Zn-Ag mineralization were studied.The muscovite granite emplaced at 68.2±0.3 Ma and is peraluminous.All high-silica igneous rocks are S-type and whole-rock CaO,Na_(2)O,and Rb-Sr-Ba and zircon Hf isotopic compositions show that they were formed by partial melting of meta-sedimentary protoliths from the Lhasa terrane basement.Roll-back of the NeoTethys oceanic slab caused melting of the mantle wedge is the trigger for partial melting of basement.Zircon trace elements indicate that the high-silica igneous rocks are reduced and H_(2)O-and F-enriched.These geochemical features and magma sources of the high-silica igneous rocks are comparable with the W-Sn deposit related granites.Shallow emplacement of high-silica granites and coeval volcanic eruption induced rapid escape of fluids.This caused inefficiency of hydrothermal-magmatic interaction,which are reasons to form Pb-Zn-Ag rather than W-Sn deposits.
基金supported by the National Natural Science Foundation of China[Grants.41802054]supported by a Royal Society SinoBritish Fellowship Trust International Exchanges Award[Grant No.IESR3213093]。
文摘The high Ba-Sr rocks can provide significant clues about the evolution of the continent lithosphere,but their petrogenesis remains controversial.Identifying the Late Cretaceous high Ba-Sr granodiorites in the SE Lhasa Block could potentially provide valuable insights into the continent evolution of the Qinghai-Tibet Plateau.Zircon U-Pb ages suggest that the granodiorites were emplaced at 87.32±0.43 Ma.Geochemically,the high Ba-Sr granodiorites are characterized by elevated K_(2)O+Na_(2)O contents(8.18-8.73 wt%)and K_(2)O/Na_(2)O ratios(0.99-1.25,mostly>1),and belong to high-K calc-alkaline to shoshonitic series.The Yonglaga granodiorites show notably high Sr(653-783 ppm)and Ba(1346-1531 ppm)contents,plus high Sr/Y(30.92-38.18)and(La/Yb)_(N)(27.7-34.7)ratios,but low Y(20.0-22.8 ppm)and Yb(1.92-2.19 ppm)contents with absence of negative Eu anomalies(δEu=0.83-0.88),all similar to typical high Ba-Sr granitoids.The variable zirconεHf(t)values of-4.58 to+12.97,elevated initial^(87)Sr/^(86)Sr isotopic ratios of 0.707254 to 0.707322 and lowεNd(t)values of-2.8 to-3.6 with decoupling from the Hf system suggest that a metasomatized mantle source included significant recycled ancient materials.The occurrence of such high Ba-Sr intrusions indicates previous contributions of metasomatized mantle-derived juvenile material to the continents,which imply the growth of continental crust during the Late Cretaceous in the SE Lhasa.Together with regional data,we infer that the underplated mafic magma provides a significant amount of heat,which leads to partial melting of the juvenile crust.The melting of the metasomatized mantle could produce a juvenile mafic lower crust,from which the high Ba-Sr granitoids were derived from reworking of previous mafic crust during the Late Cretaceous(ca.100-80 Ma)in the SE Lhasa.
基金National Natural Science Foundation of China for its support of this study(grant numbers 41972212,42030305,and W2411033).
文摘Jiuhua Mountain,situated in the eastern segment of the Jiangnan Orogenic Belt,is characterized by extensive granite masses,providing an ideal setting for investigating the exhumation history of the region.This study presents the first zircon(U-Th)/He thermochronological investigation utilizing an age-elevation approach for Jiuhua Mountain.Zircon(U-Th)/He analyses of six bedrock samples yielded consistent ages ranging from 89 to 74 Ma.This finding aligns with the results of thermal history simulations(90-70 Ma),indicating significant exhumation in the Jiuhua Mountain region during the late Cretaceous.Comparative analysis with adjacent orogenic belts(e.g.,the Mufu and Dabie Mountains)reveals a consistent pattern:low-temperature thermochronological ages are younger than the U-Pb zircon ages.This indicates a widespread tectonic exhumation and erosion phase affecting multiple regions within the northern part of the South China Block.The rapid exhumation observed during the late Cretaceous is primarily attributed to extensional tectonics,driven by the rollback of the Paleo-Pacific slab and accompanied by thermal upwelling of the asthenosphere beneath the South China Block.These findings establish crucial temporal constraints for the exhumation history of the eastern Jiangnan Orogenic Belt,significantly enhancing our understanding of its poorly constrained Cretaceous tectonic evolution.
文摘The stratigraphy,sedimentary history and paleontology of the northern Eromanga Basin are reviewed in the light of extensive field effort,searching for Cretaceous vertebrate fossils,in particular dinosaurs.Prolonged non-marine deposition throughout the Jurassic was followed by Lower Cretaceous marine incursions which extended to the late Albian.Whilst biostratigraphy is underpinned by microfloral assemblages there are three distinct marine faunas preserved from the late Aptian,early middle Albian and late Albian.Effective regression caused by sediment oversupply in the latest Albian heralded the final phase of non-marine deposition in the Eromanga Basin which continued into the Cenomanian.A distinct floral assemblage is accompanied by a modest fossil vertebrate assemblage.
文摘The special issue deals with the Cretaceous-Tertiary deserts in southwestern China and relevant sedimentological problems about deserts. The study area is located between 101°10＇- 107°00＇E and 28°00＇-30°40′ N. The ancient desert study is so little in China that there has not been a systematic report about it up to now. Based on the study in many ways on Cretaceous-Tertiary deserts in southwestern China, plentiful data have been obtained. Though it is still a bit rough, the study is a good beginning of the ancient desert study in China. The main ideas and conclusions are summarized as follows.
