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Magnetic properties of Jiaxian red clay sequences from northern chinese Loess Plateau and its paleoclimatic significance

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Science China earth sciences 2005年第8期48卷 1234-1245页

作者： QIANG xiaoke, AN Zhisheng, LI Huamei, CHANG Hong & SONG Yougui 1. SKLLQG, institute of earth environment,{2., xi’an 710075, China 2. Guangzhou {2. of Geochemistry,{2., Guangzhou 510640, China chinese academy of {2. SKLLQG Institute of Earth Environment Xi’an China chinese academy of {2. Guangzhou Institute of Geochemistry Guangzhou China

Detailed rock magnetism investigation of the Jiaxian red clay sequences indicated that there are common magnetic mineralogy properties in red clay and loess-paleosol sequences from the chinese Loess Plateau as well as the marked properties of themselves, magnetic min-erals mainly with magnetite, maghemite, hematite, and possibly limonite/goethite contributing to the magnetic behavior. Meanwhile, it is found that the strong paleosol in red clay sequences has a lower coercivity and higher content of ultra-fine ferrimagnetic grains than that of the weak pa-leosol, which is similar to loess and paleosol in upper Wucheng Loess sequences, and indicates that humid conditions and relatively strong pedogenesis play a significant role in the increase of ultra-fine magnetic minerals and transformation of the magnetic minerals. This suggests that, like Quaternary loess-paleosols, the change of characteristics of paleoclimatic conditions of the late Tertiary red clay deposits is fluctuant. In addition, the results of magnetic hysteresis properties show that the applied saturated field for samples from the Jiaxian red clay sequences is higher than that of the samples from eastern and southern chinese Loess Plateau. It is obviously shown that there exist more hard magnetic minerals and relatively weak biochemical processes in the Jiaxian red clay sequences on northern chinese Loess Plateau. We conclude that the paleocli-matic environment is different between northern and eastern/southern chinese Loess Plateau, and it should be more arid in northern chinese Loess Plateau.

关键词： northern chinese Loess Plateau, red clay, magnetic property, paleoclimatic significance.

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General inverse of Stokes, Vening-Meinesz and Molodensky formulae

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Science China earth sciences 2006年第5期49卷 499-504页

作者： CHENG Luying1,2.& XU Houze1 1. institute of Geodesy and Geophysics, chinese academy of sciences, Wuhan 430077, China 2. {2.’an Research institute of Surveying and Mapping, xi’an 710054, China institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan China xi’an Research institute of Surveying and Mapping Xi’an China

The operator operations between the disturbing potential and the geoidal undulation, the gravity anomaly, the deflection of the vertical are defined based on the relations among the gravity potential, the normal gravity potential and the disturbing potential. With the sphere as the boundary surface, based on the solution of the external boundary value problem for the disturbing potential by the spherical harmonics in the physical geodesy, the general inverse Stokes’ formula, the general inverse Vening-Meinesz formula and the general Molodensky’s formula are derived from the operator operations defined. The general formulae can get rid of the restriction of the classical formulae only used on the geoid. If the boundary surface is defined as the geoid, the general formulas are degen- erated into the classic ones.

关键词： spherical harmonics, boundary value problem, general inverse Stokes' formula, general inverse Vening-Meinesz formula, general Molodensky's formula.

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Palaeoenvironmental implication of the Plio-Pleistocene loess deposits in southern Tarim Basin

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chinese Science Bulletin 2002年第8期47卷 700-704页

作者： ZHENG Hongbo, CHEN Huizhong & CAO JunjiLaboratory of Marine Geology, Tongji University, Shanghai 2.0092. China institute of earth environment, chinese academy of sciences,{2., China institute of environment and Engineering of Cold and Arid Regio Laboratory of Marine Geology Tongji University Shanghai 200092 China

The sedimentary characteristics, grain-size distribution, geochemical composition and surface characteristics of quartz grains, together with palaeoenvironmental reconnaissance, all point to an aeolian origin for the intercalated siltstone beds in the Plio-Pleistocene Artux and xiyu Formations along the southern margins of the Tarim Basin, indicating that loess deposition in the region started, at least, in the Early Pliocene. Loess deposition in the southern Tarim Basin was a response to the global deterioration, which might be attributed to the uplift of the Tibetan Plateau.

关键词： eolian loess Plio-Pleistocene Tarim Basin.

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Grain-size features of a Miocene loess-soil sequence at Qinan: Implications on its origin

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Science China earth sciences 2006年第7期49卷 731-738页

作者： QIAO Yansong1,3, GUO Zhengtang2.1, HAO Qingzhen1, YIN Qiuzhen1, YUAN Baoyin1 & LIU Tungsheng1 1. institute of Geology and Geophysics, chinese academy of sciences, Beijing 10002., China 2. {2., chinese academy of sciences, xi’an 710075, China 3. institute of Geomechanics, chinese academy of Geological sciences, Beijing 100081, China institute of Geology and Geophysics Chinese Academy of Sciences Beijing China institute of Geomechanics Chinese Academy of Geological Sciences Beijing China institute of earth environment Chinese Academy of Sciences Xi’an China

In this study, grain-size of 507 bulk samples from the QA-I Mioceneloess-soil sequence at Qinan were analyzed, and the grain-size features are compared with those oftypical Quaternary loess and soil samples, representative lacustrine and fluvial samples. Theresults indicate that the grain-size distribution pattern of the Miocene loess is essentiallysimilar to that of Quaternary loess, but greatly differs from the lacustrine and fluvial *** layers are regularly coarser than soil layers, indicating cyclical climate changes. Mediangrain-size along the 2.3.1 m sequence varies from 6 to 13 μm and the > 63 μm fraction representsonly 5.3% in maximum, 0.9% in average. Long-term grain-size variations are consistent with the loessaccumulation rate at Qinan and with the eolian mass accumulation rate in the North Pacific. Thesefeatures firmly indicate an eolian origin of the studied sequence, and also reveal a coeval changesbetween the long-term changes of eolian grain-size and continental aridity in the dust sourceregions.

关键词： Qinan, Miocene loess-soil sequence, grain-size, eolian origin.

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environmental characteristics of Mid-Holocene recorded by lacustrine sediments from Lake Daihai, north environment sensitive zone, China

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Science China earth sciences 2006年第9期49卷 968-981页

作者： SUN Qianli1,2. ZHOU Jie1, SHEN Ji3, CHEN Peng1,2. WU Feng1,2.& xiE xiuping1,2.1. State Key Lab of Loess and Quaternary Geology, {2., chinese academy of sciences, xi’an 710075, China 2. Graduate University of chinese academy of sciences, Beijing 100039, China 3. Nanjing institute of Geography and Limnology, chinese academy of sciences, Nanjing 2.0008, China State Key Lab of Loess and Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi’an China Graduate University of chinese academy of sciences Beijing China Nanjing institute of Geography and Limnology Chinese Academy of Sciences Nanjing China

Climate proxies, such as total organic carbon and nitrogen (TOC, TN), carbonate content (CaCO3), grain-size and pollen of the sediment core retrieved from enclosed Lake Daihai which lies in the north China environment sensitive zone are analyzed to reconstruct the environment evolution of the area based on high-resolution radiocarbon chronology. The results reveal that the TOC and TN contents of the sediments correlate well with pollen percentage and pollen flux variations during the Holocene, and both reach their peak values simultaneously at 6.7―3.5 ka BP (calendar age, 7.6―3.6 ka BP). Since 6.7 ka BP, both the CaCO3 and organic matter contents of the core have simultaneous variations, and their high values also occur during 6.7―3.5 ka BP. While during 9.0―6.7 ka BP (calendar age, 10―7.6 ka BP) relatively lower level of organic matter content and pollen flux corre- spond to the higher level of carbonate content. The above relations suggest that during 6.7―3.5 ka BP, the productivity and effective precipitation were greatly improved in the lake drainage area, and this would probably strengthen the hydrodynamic conditions, enhancing organic matter, pollen and carbonate inputs from terrestrial sources. Such processes would account for the enrichment of both organic matter and carbonate in the sediments. While during 9.0―6.7 ka BP, the lower level of or- ganic matter, pollen flux but high carbonate content show depressed productivity and declined vege- tation coverage. The higher carbonate content at this stage would have probably resulted from the higher evaporation ratio of the lake water under relatively drier climate conditions. Therefore, it is in- ferred that during 6.7―3.5 ka BP, the climate was more humid with abundant rainfalls and vegetation was more flourishing in the Lake Daihai area. This can be seen as Holocene Climate Optimum (HCO). As a result, this has evident discrepancies with the traditional notion that the HCO occurs at Early Holocene or early Mid

关键词： Lake Daihai, Mid-Holocene, lacustrine sediments, environmental characteristics.

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Variations of δ^(18)O in precipitation from the Muztagata Glacier, East Pamirs

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Science China earth sciences 2006年第1期49卷 36-42页

作者： LI Zhen1, YAO Tandong1,2. TIAN Lide1,2. XU Baiqing1,2.& Wu Guangjian2.1. Key Laboratory of Cryosphere and environment, Jointly Established by Cold and Arid Regions environmental and Engi-neering Research {2. and {2. of Tibetan Plateau Research, chinese academy of sciences and chinese academy of Meteorological sciences, China Meteorological Administration, CAS, Lanzhou 730000, China 2. Laboratory of environment and Process on Tibetan Plateau, {2. of Tibetan Plateau Research, chinese academy of sciences, Beijing 100085, China Key Laboratory of Cryosphere and environment Jointly Established by Cold and Arid Regions Environmental and Engineering Research Institute and Institute of Tibetan Plateau Research Chinese Academy of Sciences and Chinese Academy of Meteorological Sciences China Meteorological Administration Lanzhou China Laboratory of environment and Process on Tibetan Plateau Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing China

Expeditions to Muztagata (in the eastern Pamirs) during the summer seasons of2.02.and 2.03 collected precipitation samples and measured their oxygen isotopes. The δ^(18)O inprecipitation displays a wide range, varying from -17.40per thousand to +1.33per thousand inJune—September 2.02.and from -2..31per thousand to +4.59per thousand in May—August 2.03. Theδ^(18)O in precipitation correlates with the initial temperature of precipitation during theobserving periods. The positive correlation between δ^(18)O and temperature suggests that δ^(18)Ocan be used as an indicator of temperature in this region. The δ^(18)O values in fresh-snow samplescollected from two snow events at different elevations on the Muztagata Glacier show a strong''altitude effect'', with a ratio of nearly -0.40per thousand per 100 m from 5500 m to 7450 m.

关键词： Muztagata, δ18O, temperature, altitude effect.

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Vermiform trace fossils from the Precambrian Ruyang Group, western Henan

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chinese Science Bulletin 1997年第3期42卷 251-254页

作者： HU Jianmin, MENG Qingren and LI Wenhou1 xi’ an College of Geology, xi’an 710054, China 2. {2. of Geophysics,{2., Beijing 100101, China 3 Department of Geology, Northwest University, xi’an 710069, China xi’an College of Geology Xi’an China institute of Geophysics Chinese Academy of Sciences Beijing China Department of Geology Northwest University Xi’an China

THE origin and evolution of Precambrian lives has been a long-standing controversial problem. It is now generally accepted by most paleontologists that the origin of metazoa can be traced back to more than 1000 Ma, because the Ediacara and latest pre-Ediacara fauna, such as the Huainan fauna, are featured by their diversification of forms, complicated structures

关键词： Precambrian trace fossil Ruyang Group.

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Physical mechanisms of plant roots affecting weathering and leaching of loess soil

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Science China earth sciences 2006年第9期49卷 1002-1008页

作者： LI Yong1,2. ZHANG Qingwen1,2. WAN Guojiang3, HUANG Ronggui3, PIAO Hechun3, BAI Lingyu2.& LI Lu2.1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, institute of Soil and Water Conservation, chinese academy of sciences, Yangling 712.00, China 2. institute of Agro-environment and Sustainable Development, chinese academy of Agricultural sciences, Beijing 100081, China 3. institute of Geochemistry, chinese academy of sciences, Guiyang 550002. China State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Institute of Soil and Water Conservation Chinese Academy of Sciences Yangling China institute of Agro-environment and Sustainable Development Chinese Academy of Agricultural Sciences Beijing China institute of Geochemistry Chinese Academy of Sciences Guiyang China

Plant roots have potential impacts on soil mineral weathering and *** objective is to understand the physical mechanisms of plant roots affecting weathering andleaching of loess soil. Root densities were measured through the method of a large-size dug profile,and transport fluxes of soil elements were determined using an undisturbed monolith soilinfiltration device on the hilly and gully regions of the chinese Loess Plateau. The results showthat the improvement effects of soil environment by plant roots are mainly controlled by the densityand weight of the fibrous roots with the diameters less than 1 mm. Plant roots have the strongereffects on soil physical properties than chemical properties. The principal components analysis(PCA) indicates that soil physical properties by plant roots account for 56.7% of variations in soilenvironment whereas soil chemical properties and pH contribute about 2..2. of the soil *** roles of plant roots in controlling soil weathering and leaching increased in the followingorder: infiltration enhancement > increase of bio-active substance > stabilization of soilstructure. The effects of plant roots on soil mineral weathering and leaching can be quantifiedusing the multiple regression models with the high prediction accuracies developed in this study.

关键词： plant roots, soil weathering and leaching rates, soil environment field, principal components analysis (PCA), chinese Loess Plateau.

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中国经济发展的机遇与挑战——学习中央经济工作会议精神座谈会综述

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中国工业经济 2024年第1期 5-16页

作者：中国社会科学院工业经济研究所课题组史丹不详中国社会科学院工业经济研究所

2.2.年12.11—12.,中央经济工作会议在北京举行。习近平总书记出席会议并发表重要讲话,全面总结2.2.年经济工作,深刻分析当前经济形势,系统部署2.2.年经济工作。会议要求,2.2.年要坚持稳中求进、以进促稳、先立后破,多出有利于稳预期... 详细信息

2.2.年12.11—12.,中央经济工作会议在北京举行。习近平总书记出席会议并发表重要讲话,全面总结2.2.年经济工作,深刻分析当前经济形势,系统部署2.2.年经济工作。会议要求,2.2.年要坚持稳中求进、以进促稳、先立后破,多出有利于稳预期、稳增长、稳就业的政策,在转方式、调结构、提质量、增效益上积极进取,不断巩固稳中向好的基础。要强化宏观政策逆周期和跨周期调节,继续实施积极的财政政策和稳健的货币政策,加强政策工具创新和协调配合。为深入解读2.2.年中央经济工作会议精神,中国社会科学院工业经济研究所“我国发展的新战略机遇与风险挑战研究”课题组邀请7位专家学者交流学习体会,立足当前经济走势,回应当下经济热点问题,为推动高质量发展建言献策。

关键词：高质量发展宏观政策科技创新城乡融合绿色低碳

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Paleoenvironments indicated by the fossil mammalian assemblages from red clay-loess sequence in the chinese Loess Plateau since 8.0 Ma B.P.

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Science China earth sciences 2006年第5期49卷 518-530页

作者： XUE xiangxu1,2. ZHANG Yunxiang1,2.& YUE Leping1,2.1. State Key Laboratory of Continent Dynamics (Northwest University), {2. of Cenozoic Geology and environment, De- partment of Geology, Northwest University, xi’an 710069, China 2. {2., State Key Laboratory of Loess and Quaternary Geology, chinese academy of sciences, xi’an 710075, China State Key Laboratory of Continent Dynamics (Northwest University) Institute of Cenozoic Geology and Environment Department of Geology Northwest University Xi’an China institute of earth environment State Key Laboratory of Loess and Quaternary Geology Chinese Academy of Sciences Xi’an China

Information from eleven profiles of eolian earthy red silty clay and loess of the middle of the Late Miocene to Holocene age have been studied and correlated. A complete summary profile with projected isotopic ages and fossil-bearing beds has been assembled. The profile is subdivided into 12.stratigraphic units proceeding from the lower (older) to the upper (younger) one. The character of mammalian assemblages contained in each unit was analyzed and the corresponding pa- leo-climatic environments were deduced. The environmental character of each period and the change from the middle of the Late Miocene at about 8.0 Ma B.P. up to the Holocene progressed from the hot semiarid and semi-moist, warmer-moist, warm-moister of the Late Miocene. To slightly less warm moist, cool-dry, slight-warmer-moister of the Pliocene; later the cool to cold dry periods alternated frequently with the mild semiarid and semi-moist periods of the Quaternary. Vegetation progressed from the grasslands with sparse woods, wooded shrub-grasslands and subtropical forest-grasslands of the Late Miocene age to sparse grasslands and dry grasslands of the Pliocene; and to sparse grasslands, dry grasslands and tundras of the Quaternary. The climate changes in the Neogene were of low-amplitute in a generally warm-humid background. Those of the Quaternary were of higher am- plitude with a longer phase. Cool or cold dry and slightly warm semiarid and semi-moist climates al- ternated on a generally cool-dry background. The tendency since the start of the Quaternary was the change to more northern and western shift in the Loess Plateau, with progressively cooler and dryer conditions. The dramatic uplift of the Qinghai-xizang (Tibet) Plateau and the forming and expansion of the Arctic ice sheet might be the main reasons of the more pronounced changes in the Quaternary.

关键词： paleoenvironment, mammalian fossils, eolian red clay-loess sequence, Loess Plateau.

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