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Megafossils of Betulaceae from the Oligocene of qaidam basin and their paleoenvironmental and phytogeographic implications

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Plant Diversity 2024年第1期46卷 101-115页

作者： Tao Yang Jia-Hao Cai Yan-Zhi Dai Hong-Yu Chen Lei Han Li Zhang Wei-Yu Liang Xu-Jun Li Wen-Jia Li Jing-Yu Wu San-Ping Xie De-Fei Yan School of Earth Sciences and Key Laboratory of Mineral Resources in Western China(Gansu Province) Lanzhou UniversityLanzhou 730000China Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences Institute of Vertebrate Paleontology and PaleoanthropologyChinese Academy of SciencesBeijing 100044China State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and PaleoenvironmentChinese Academy of SciencesNanjing 210008China Center for Research and Education on Biological Evolution and Environments School of Earth Sciences and EngineeringNanjing UniversityNanjing 210023China

Understanding the paleoenvironment and phytogeographical history of the Tibetan Plateau,China relies on discovering new plant fossils.The qaidam basin has long been regarded as an ideal‘field laboratory’to investigate the paleoclimate and paleobiological evolution of the northern Tibetan Plateau.However,fossil angiosperms from the qaidam basin are rare,and our knowledge of its paleovegetation is poor.Here,we report fossil leaves and fruits of Betulaceae found from the Oligocene Shangganchaigou Formation of northwestern qaidam basin(Huatugou area).Comparative morphological analysis led us to assign the fruits to the Betula subgenus Betula and the leaves to Carpinus grandis.These findings,together with other reported fossil plants from the same locality,reveal a close floristic linkage between the qaidam basin and Europe during the Oligocene.The northern pathway of this floristic exchange may have crossed through the qaidam basin during the late Paleogene.This floristic linkage may have been facilitated by the continuous narrowing of the Turgai Strait and stronger westerlies,which transported moisture and provided favorable climatic conditions.Indeed,fossil plants collected from the qaidam basin suggest that during the Oligocene this region had warm and humid deciduous broad-leaf forest,which differs from the region’s modern vegetation and indicates that the qaidam basin may have been a suitable region for these plants to flourish and spread during the Oligocene.

关键词： Paleoenvironment Biogeography Betulaceous fossil qaidam basin Tibetan Plateau Oligocene

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First Record of Cyclocarya from the Early Oligocene qaidam basin,North Tibet:Implications for the Paleogeography and Paleoecology

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Journal of Earth Science 2024年第1期35卷 201-211页

作者： Yafei Hou Bowen Song Xiangchuan Li Fang Han Xu Zhang Kexin Zhang Institute of Geological Survey China University of GeosciencesWuhan 430074China Faculty of Materials Science and Chemistry China University of GeosciencesWuhan 430074China State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesWuhan 430074China College of Earth Sciences and Resources&Key Laboratory of Western Mineral Resources and Geological Engineering of the Ministry of Education Chang'an UniversityXi'an 710054China State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and PalaeontologyChinese Academy of SciencesNanjing 210008China School of Earth Sciences East China University of TechnologyNanchang 330013China

As the largest intermontane basin in the northeastern Tibetan Plateau(TP),the qaidam basin provides unique insight into paleoclimatic change and its relationship with global change and uplift on the TP.In this study,based on morphological comparison,fossil fruit of Cyclocarya from the Early Oligocene Shangganchaigou Formation in the qaidam basin is assigned as Cyclocarya cf.weylandii.The discovery of Cyclocarya cf.weylandii demonstrates the occurrence of Cyclocarya in the Oligocene sediment in qaidam basin.This is the first record of Cyclocarya fossil of Early Oligocene Age in China and indicates that Cyclocarya has existed on the northeastern TP since at least the Early Oligocene.The living analogues of the current fossil now lives in sub-tropical China,where the East Asian Monsoon is prevalent.Integrating the new fossils and previously reported fossil remains of plants and fishes,it can be inferred that the Early Oligocene qaidam basin was primarily influenced by westerly circulation and had a relatively warm and humid climate,which was in sharp contrast to the present-day climate in qaidam basin.

关键词： biostratigraphy climate change winged-fruit fossil qaidam basin Early Oligocene paleoclimate paleogeography

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Geochemistry and Zircon U-Pb and Hf Isotopes of Early Devonian Hardawu Granites in the Eastern Segment of the Ultrahigh-Pressure Metamorphic Belt, Northern qaidam basin

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Journal of Earth Science 2024年第3期35卷 866-877页

作者： Hua Li Ming Wang Jiqing Li Haikui Tong Jiaxiang Dong Minggang Tian Xiaolin Chen Leguang Li Ting Xie Xiong Li Yuying Che Qinghai Geological Survey Xining 810000China Technology Innovation Center for Exploration and Exploitation of Strategic Mineral Resources in Plateau Desert Region Ministry of Natural ResourcesXining 810000China Qinghai Geological Survey Institute Xining 810000China Geological Exploration Institute of Shandong Zhengyuan Jinan 271000China School of Earth Science China University of GeosciencesWuhan 430074China

The Hardawu granites in the eastern segment of the ultrahigh-pressure metamorphic belt,the northern qaidam basin,were studied by whole-rock major and trace elements and in-situ zircon U-Pb geochronology and Hf isotopes to discuss the petrogenesis and tectonic evolution.Geochronological results show that the granites have a crystallization age of 401±3 Ma,suggesting that they were formed in the Early Devonian.The granites have SiO2 contents of 75.32 wt.%-76.05 wt.%,total alkali contents of 8.23 wt.%-8.36 wt.%,and K2O/Na2O ratios of 1.62-1.91.They were rich in K2O,poor in TiO2,MnO,MgO,and P2O5,and have A/CNK values of 1.05-1.07,Rittmann indexδvalues of 2.05-2.14,and differentiation index(DI)values of 92.85-94.18.They are high potassium calc-alkaline,weakperaluminum,and highly differentiated I-type granites.The granites also show enrichment of large ion lithophile elements(LILE)such as Rb,Ba,and Th,and depletion of high field strength elements(HFSE)such as Nb,Ta,and Ti.The total REE concentrations range from 169 ppm to 232 ppm,with enrichments of light rare earth elements and negative Eu anomalies(δEu=0.39-0.55).The zirconεHf(t)values range from-0.65 to-2.29,and the two-stage model ages(tDM2)changed within a small range of 1.44 to 1.54 Ga,indicating that the magma of the Hardawu granites was originated from the partial melting of Mesoproterozoic lower crustal materials.Combined with previous studies,we suggest that the Hardawu granites were formed in the extensional tectonic setting after the collision between the qaidam Block and the central and southern Qilian Block in the Early Devonian.

关键词： granite Early Devonian petrogenesis tectonic implication qaidam basin geochemistry

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Shallow subsurface habitats across the Mars-analog qaidam basin

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Science China Earth Sciences 2023年第11期66卷 2487-2496页

作者： Yan CHEN Li LIU Huiqing ZHANG Xue GUO Wensi ZHANG Chunxia ZHANG Wei LIN Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China Department of Clinical Laboratory National Clinical Research Center for Infectious DiseaseShenzhen Third People’s HospitalShenzhen 518112China State Key Laboratory of Microbial Resources Institute of MicrobiologyChinese Academy of SciencesBeijing 100101China Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China

Searching for life is one of the most important targets of Mars exploration missions. It has been considered that the Martian subsurface, away from the extreme surface environment, is a potentially habitable region for microbial growth.However, the distribution pattern of potential microbial habitats in the Martian subsurface has yet to be evaluated. Here, we investigate the subsurface habitats to depths of 20–60 cm from various landscapes, including slopes, gullies, channels, playas,and alluvial fans across the Mars-analog qaidam basin, NW China. We characterize subsurface niches by measuring microbial biomass and radiocarbon ages, and correlate them with soil properties including depth, moisture content, total organic carbon content, electric conductivity, pH, evaporite and clay mineral contents. We find more habitable niches for microbial colonization at depths of 5–25 cm as compared with the surface and deep subsurface across the hyperarid qaidam basin. Maximum biomass and biotic activity could be correlated with physical stability, limited radiation, and short-term moderate water availability in the shallow subsurface in hyperarid deserts. The findings of this study provide new perspectives on subsurface microbial habitats in Mars-analog hyperarid deserts and ongoing biosignature detection on Mars.

关键词： Mars-analog qaidam basin Shallow subsurface Microbial habitat Astrobiology

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Distribution and origin of brine-type Li-Rb mineralization in the qaidam basin,NW China

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Science China Earth Sciences 2022年第3期65卷 477-489页

作者： Jiansen LI Tingwei LI Yunqi MA Fukun CHEN School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources Qinghai Institute of Salt LakesChinese Academy of SciencesXining 810008China Qinghai Provincial Key Laboratory of Geology and Environment of Salt Lakes Xining 810008China

The qaidam basin on the Qinghai-Tibet Plateau is well endowed with a variety of critical metals,such as Li and Rb.However,little is known about the distribution,source,and enrichment mechanisms of these elements.In this paper,we present results of systematic geochemical and H-O-B isotopic analyses of brines in the Tertiary and Quaternary sediments of the qaidam basin.The results reveal that the paleobrines from oil-bearing anticlines at Dafengshan,Nanyishan,Youquanzi,Jiandingshan,and Jianshishan are significantly enriched in Li and Rb,whose contents are 81.1-128.9 mg L^(-1)and 4.5-29.2 mg L^(-1),respectively,reaching levels of economic significance.High Rb contents(up to 12.5 mg L^(-1))and well-endowment of Li also characterize the Dongtai,Xitai,Yiliping,and Senie salt lakes in the qaidam basin.The Tertiary paleobrine average inδD andδ18O at-40.7‰and 2.84‰,respectively.The paleobrine with the highest Li and Rb hasδD andδ^(18)O values close to magmatic water.Theδ^(11)B values are lower than those of river water but close to those of geothermal fluids,suggesting that replenishment by deep magmatic hydrothermal fluid is most likely the key mechanism for the anomalous enrichment of these elements in the paleobrines,though evaporation and water-rock reactions have contributed to the critical metal mineralization.The anomalous enrichment of Li and Rb in modern salt lake brines is closely related to the input of volcanic geothermal water.The relatively high Li and Rb contents of intercrystalline brines in salt lakes of the western qaidam basin and the increase of Li and Rb contents with increasing depth were caused by upwelling of local paleobrines along the fault zones.

关键词： Li and Rb resources Paleobrine Salt lake brine Hydrogen H-O-B isotopes qaidam basin

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Application of remote sensing in the description of fluvial system in dryland:A case study of Golmud distributive fluvial system,qaidam basin,NW China

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Journal of Palaeogeography 2022年第4期11卷 601-617页

作者： Xiang-Hui Zhang Chang-Min Zhang Wen-Jie Feng Rui Zhu Qing-Hai Xu School of Geosciences Yangtze UniversityWuhan430100Hubei ProvinceChina

Distributive fluvial systems(DFS)are widespread in drylands in the northwestern China.Analyzing differences in fluvial morphology in drylands is beneficial for studying ancient rock records and the extraterrestrial surface environment.The remote sensing image,characterized by real-time and possibility of repeated observations,is a vital tool for recording and comparing fluvial systems in drylands.Satellite remote sensing technology is a method of investigating fluvial morphologies.Due to the limited accuracy of satellite imagery,there are few reports on the detailed description of the fluvial system in drylands of NW China.We analyze the pattern of fluvial morphology changes in the Golmud distributive fluvial system(DFS)in the qaidam basin,northwestern China,using satellite remote sensing and unmanned aerial vehicles(UAV).Firstly,we use Google Earth real-time image data,historical image data,and radar digital elevation data to extract geomorphological information;then the UAV remote sensing image data were used to interpret fluvial network information;finally,we use the gray-scale differential vector method to describe the fluvial morphologies.Three zones have been identified in the Golmud DFS:the proximal,the medial,and the distal,by comparing the differences in topographic and geomorphic characteristics,fluvial morphologies,and sedimentary characteristics of the Golmud DFS.The proximal slope is higher than the other two zones,and the geomorphic features are mainly gravel gobi.The proximal fluvial morphologies are mainly large braided rivers,and sediments are more gravelly and less sandy.The medial slope is relatively small,and the geomorphic features are mostly oasis plains.The medial fluvial morphologies are mainly meandering rivers associating with braided rivers,and sediments are more sandy and less gravelly.The distal slope is the lowest,and the geomorphic features are mostly oasis plains,lakes,and marsh plains.The distal fluvial morphologies are mainly meandering rivers,and sediments are sandy and muddy.Co

关键词： qaidam basin Remote sensing UAV Distributive fluvial system Fluvial morphology Dryland fluvial systems

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Geological implications of elements of the Pleistocene mudstone with different organism compositions and enrichment environments in the qaidam basin,China

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Frontiers of Earth Science 2023年第2期17卷 437-454页

作者： Jinqi QIAO Qingyong LUO Chen ZHANG Zhenxue JIANG State Key Laboratory of Petroleum Resources and Prospecting China University of PetroleumBeijing 102249China basin and Reservoir Research Center China University of PetroleumBeijing 102249China Unconventional Natural Gas Research Institute China University of PetroleumBeijing 102249China

Trace elements and rare earth elements(REEs)of two kinds of organic facies samples representing marginal and more basin-center deposits from Pleistocene lacustrine mudstones in the central qaidam basin were studied to understand the provenance,palaeotectonic setting,hydrothermal activity,palaeoredox conditions and sedimentary rate.The results show that the lacustrine mudstones were mainly derived from felsic sources with little contribution from ancient crustal sediments and no ultramafic(ophiolitic)source.The mudstones were deposited in a continental island arc tectonic setting,which is consistent with the tectonic evolution of the Cenozoic basin.Both two organic facies samples were hydrothermal in origin based on the ternary diagram of Ni–Zn–Co and normalized REE patterns.However,this does not mean that the water column in paleolake was affected by hydrothermal fluids in situ.This signal might indicate hydrothermal origins from hot springs related to active faults around the basin rather than the deep hydrothermal fluids entering the sediments via deep faculties based on the comprehensive analyses of normalized REE patterns,negative E_(uanom)(Eu anomaly),Y/Ho,Sm/Yb,and Eu/Sm.Redox proxies including U/Th,Ni/Co,and Mnanom values,are more sensitive for the studied samples indicating that most of the organic facies A samples were deposited under an oxygen-depleted condition,while the organic facies B samples were deposited under oxygen-rich conditions.Redox proxies of Ceanom values are unavailable for the organic facies B samples due to hypersaline environments,and V/C_(r)and V/(V+Ni)are invalid for the organic facies A samples,possibly because of their organism composition.The low Lan/Ybn values indicate high sedimentation rates,which is consistent with the average sedimentation rates of approximately 0.43 to 1.1 km/Ma.However,the La_(n)/Yb_(n) is more likely affected by the provenance of the studied samples,so it should be used with caution.

关键词： elements lacustrine mudstone Pleistocene Qigequan Formation qaidam basin

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Geological characteristics,evaluation criteria and discovery significance of Paleogene Yingxiongling shale oil in qaidam basin,NW China

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Petroleum Exploration and Development 2022年第1期49卷 21-36页

作者： LI Guoxin ZHU Rukai ZHANG Yongshu CHEN Yan CUI Jingwei JIANG Yinghai WU Kunyu SHENG Jun XIAN Chenggang LIU He State Key Laboratory of Petroleum Resources and Prospecting China University of PetroleumBeijing 102249China PetroChina Qinghai Oilfield Company Dunhuang 736202China Research Institute of Petroleum Exploration&Development PetroChinaBeijing 100083China

Major breakthroughs of shale oil exploration have been made recently in the upper member of Paleogene Lower Ganchaigou Formation of Yingxiongling area, qaidam basin. However, the low total organic carbon content of saline-lacustrine source rock, and unclear genetic mechanism, evaluation criteria and resources potential of the shale oil have restricted the exploration and evaluation of Yingxiongling shale oil. Through analysis of large amounts of cores, well drilling, seismic, laboratory test data and integrated study, focusing on the shale and mixed types of shale oil reservoirs characterized by high-frequency interbedded organic-rich laminated shale and limy dolomite, it is concluded that the shale oil in the upper member of Lower Ganchaigou Formation in the Yingxiongling area have six geological characteristics:(1) two-stage hydrocarbon generation of hydrogen-rich source rock and large amount of retained oil;(2) multiple types of reservoir space and good reservoir properties;(3)source-reservoir integration, thick “sweet spot” and high oil-bearing grade;(4) high pressure coefficient between and under salt layers, and sufficient formation energy;(5) high content of light components, high gas-oil ratio, and good quality of the crude oil;(6) high content of brittle minerals and good fracability. The evaluation criterion of shale oil is preliminarily established based on the eight parameters: total organic carbon content, maturity, effective porosity, oil saturation, brittle mineral content,pressure coefficient, lamellation density, and burial depth. Combined with parameters of E32 source rock thickness, area, vertical distribution of oil layers, and free hydrocarbon content, the shale oil resources have been preliminarily estimated as 21×10^(8) t.The structurally stable area is the predominant objective of shale oil exploration and the favorable exploration area for Yingxiongling shale oil is nearly 800 km^(2).

关键词： Yingxiongling shale oil qaidam basin Paleogene Lower Ganchaigou Formation mixed sedimentation hydrogen-rich source rocks evaluation criterion

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Genesis of Neogene Formation Waters in the Central qaidam basin:Clues from Hydrochemistry and Stable D-O-S-Sr Isotopes

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Acta Geologica Sinica(English Edition) 2023年第6期97卷 1801-1813页

作者： HAN Guang PAN Tong LI Qingkuan FAN Qishun HU Yan LIU Jiubo ZHANG Xiying Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources Qinghai Institute of Salt LakesChinese Academy of SciencesXining 810008China Qinghai Provincial Key Laboratory of Geology and Environment of Salt Lakes Xining 810008China Qinghai Provincial Key Laboratory of Exploration Research of Salt Lake Resources in qaidam basin Qinghai Qaidam Integrated Institute of Geology and Mineral Resource ExplorationGolmudQinghai 816099China University of Chinese Academy of Sciences Beijing 100049China Bureau of Geological Exploration&Development of Qinghai Province Xining 810008China

Geological explorations have revealed plentiful Neogene formation waters in anticlines in the central qaidam basin(QB).However,the hydrochemistry and origin of these waters are obscure.In this study,the hydrochemistry and DO-S-Sr isotopes of these formation waters were determined to study their origin and evolution.The formation waters are enriched in Na-Ca-Cl,and depleted in Mg-K-SO4-HCO3ions with elevated Li-B-Br-Sr elements.The D-O isotopes prove that the formation waters originated from weak-evaporated meteoric waters,and experienced water-rock interactions.Ion comparisons and Caexcess-Nadeficitdiagrams suggest that solute sources of these waters include evaporite dissolution,waterrock interaction,and minor residual lake brines.Bacterial sulfate reduction and water-rock interactions are supported by the high S-Sr isotopes.The enriched Li-B-Br-Sr concentrations of these waters are in accord with the high geochemical background values of the QB.Regarding the genesis of the formation waters,it can be concluded that meteoric waters from the southern Kunlun Mountains were discharged into the basin,weakly evaporated,and then infiltrated into the Neogene strata through faults leaching the soluble ions and mixing with residual lake brines,and all experienced water-rock interactions and a sulphate reduction process.

关键词： hydrochemistry brine resources lake/meteoric waters D-O-S-Sr isotopes Miocene-Pliocene qaidam basin

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Salt-Lake basin Bedrock Weathered Crust Gas Reservoir in the Altun Mountains Front of the qaidam basin,Western China

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Acta Geologica Sinica(English Edition) 2023年第5期97卷 1555-1567页

作者： ZHANG Yongshu JIA Chengzao LI Guoxin LI Jiangtao WANG Bo ZHAO Fan YUE Dali SHI Zhenghao ZHU Jun WANG Yuanfei ZHANG Yi CHEN Yangyang ZHANG Fenying YU Xue XU Li Hou Lili SONG Yue School of Earth Sciences China University of Petroleum(Beijing)Beijing 102249China Qinghai Provincial Key Laboratory of Plateau Saline-Lacustrine basinal Oil&Gas Geology DunhuangGansu 736202China College of New Energy and Materials China University of Petroleum(Beijing)Beijing 102249China

The bedrock weathered crust in front of the Altun Mountains in the qaidam basin,western China,is different from others because this is a salt-lake basin,where saline water fluid infiltrates and is deposited in the overlying strata.A large amount of gypsum infills the bedrock weathered crust,and this has changed the pore structure.Using core observation,polarized light microscopy,electron probe,physical property analysis and field emission scanning electron microscopy experiments,the characteristics of the weathered bedrock have been studied.There are cracks and a small number of dissolved pores in the interior of the weathered crust.Matrix micropores are widely developed,especially the various matrix cracks formed by tectonics and weathering,as well as the stress characteristics of small dissolved pores,and physical properties such as porosity and permeability.This‘dual structure’developed in the bedrock is important for guiding the exploration of the lake basin bedrock for natural gas.

关键词： upstream gas reservoir bedrock weathered crust cracks matrix micropores salt lake qaidam basin

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