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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 {2., chinese academy of Sciences, xi’an 710075, china 2. Guangzhou institute of Geochemistry, chinese academy of Sciences, Guangzhou 510640, china 1. chinese academy of Sciences SKLLQG Institute of Earth Environment 710075 Xi’an China 2. chinese academy of Sciences Guangzhou Institute of Geochemistry 510640 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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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), institute of Cenozoic Geology and environment, De- partment of Geology, Northwest University, xi’an 710069, {2. 2. institute of earth environment, State Key Laboratory of Loess and Quaternary Geology, chinese academy of Sciences, xi’an 710075, {2. 1. State Key Laboratory of Continent Dynamics (Northwest University) Institute of Cenozoic Geology and Environment Department of Geology Northwest University Xi’an 710069 China 2. institute of earth {2. State Key Laboratory of Loess and Quaternary Geology Chinese Academy of Sciences Xi’an 710075 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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environmental characteristics of Mid-Holocene recorded by lacustrine sediments from Lake Daihai, north environment sensitive zone, {2.

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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, institute of earth {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 1. State Key Lab of Loess and Quaternary Geology Institute of Earth Environment 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 210008 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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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 {2. of Sciences, Beijing 10002., china 2. institute of earth environment, chinese {2. of Sciences, xi’an 710075, china 3. institute of Geomechanics, chinese {2. of Geological Sciences, Beijing 100081, china 1. institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China 3. institute of Geomechanics Chinese Academy of Geological Sciences Beijing 100081 China 2. institute of earth {2. Chinese Academy of Sciences Xi’an 710075 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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The microtine distribution and its environmental significance since the Middle Pleistocene in Zhangping Caves of the Qinling Mountains

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Science china earth Sciences 2008年第2期51卷 294-299页

作者： LI Yongxiang1 & XUE xiangXu1,2.1 State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, institute of Cenozoic Geology and environment, xi’an 710069, {2. 2.institute of earth environment, State Key Laboratory of Loess and Quaternary Geology, chinese academy of Sciences, xi’an 710075, {2. 1. State Key Laboratory of Continental Dynamics Department of Geology Northwest University Institute of Cenozoic Geology and Environment Xi’an 710069 China 2. institute of earth {2. State Key Laboratory of Loess and Quaternary Geology Chinese Academy of Sciences Xi’an 710075 China

Three microtine species are recovered from the Zhangping Caves of the Qingling Mountains, namely Microtus oeconomus, Caryomys inez and Caryomys eva. They are climate-sensitive ones with different ecological habits, therefore their distribution well corresponds to environmental variations. Statistical comparison of the distribution of fossil microtines and their counterparts nowadays displays that the climate variation of the studied area and its contiguity since the middle Pleistocene are: warm and humid at 493 ka ago, cool and humid at 2.9 ka ago―cold and humid at 2.5 ka ago―cool and humid at 2. ka ago, and warm and dry at present.

关键词： environmental variation since Middle Pleistocene microtine fossils Zhangping Caves of the Qinling Mountains

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The characteristic spectral lines of target atoms in the impact of^(40)Ar^(q+)ions on metal surfaces

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Science china(Physics,Mechanics & Astronomy) 2004年第6期47卷 729-736页

作者： ZHANG xiao’an1,2.ZHAO Yongtao1,2.LI Fuli1,YANG Zhihu2.xiAO Guoqing2.& ZHAN Wenlong2.1.Department of Applied Physics,xi’an Jiaotong University,xi’an 710049,china 2.institute of Modern Physics,{2. academy of Sciences,Lanzhou 730000,china Department of Applied Physics Xi'an Jiaotong University Xi'an 710049 China institute of Modern Physics Chinese Academy of Sciences Lanzhou 730000 China

We report the measured results of the 2.0 nm—1000 nm characteristic spectral lines of target atoms when highly charged ions40Ar q+(6≤q≤14) with the same kinetic energy and40Ar6+ with different kinetic energies are incident upon Al, Ti, Ni, Ta and Au surfaces, respectively. The results for12.Xe6+,12.Xe10+ and12.Xe15+ with the same kinetic energy (150 keV) incident upon a Ta surface are also reported. These results show that when the projectile and target are properly selected (40Ar12. impinges on Al,12.Xe6+ impinges on Ta), the spectral intensity of characteristic spectral lines of the target atom is effectively enhanced, and is not strongly dependent on the kinetic energy of the incident ions.

关键词： highly charged ion, hollow atom, characteristic spectrum, spectral intensity.

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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 {2. of Sciences, Wuhan 430077, china 2. xi’an Research institute of Surveying and Mapping, xi’an 710054, china 1. institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China 2. xi’an Research institute of Surveying and Mapping Xi’an 710054 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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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 1. 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 730000 China 2. Laboratory of environment and Process on Tibetan Plateau Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 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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Comparison of eastern paleo-Tethyan ophiolites and its geodynamic significance--Evidence from Dur'ngoi ophiolite

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Science china earth Sciences 2004年第4期47卷 378-384页

作者： CHEN Liang1,2. SUN Yong1,2. PEI xianzhi2. Feng Tao2.& Zhang Guowei2.1. Open Laboratory of Continental Dynamics, Ministry of Education, Northwest University, xi抋n 710069, china 2. institute of Geology and Geophysics, {2. academy of Sciences, Beijing 10002., china Open Laboratory of Continental Dynamics Ministry of Education Northwest University Xi’an 710069 China institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China

Nd-Pb isotopic geochemistry of metabasalt from Dur抧goi ophiolite, Qinghai Prov-ince, NW china reveals the presence of DMM mixing with EMII components in its upper mantle source, which is comparable with present Indian MORB. Comparisons indicate that the geo-chemistry, chronology and source characteristics of Dur抧goi ophiolite coincide with Pa-leo-tethyan ophiolites from 揝anjiang?area. Together with evidences from regional geology in adjacent areas, this study proves that independent paleo-tethyan basins evolved contemporarily, the dynamics of which is attributed to the interaction of mantle plume with over-riding lithosphere.

关键词： ophiolite, Paleo-Tethys, DUPAL anomaly, Indosinian movement.

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Digital image analysis of palaeoenvironmental records and applications

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chinese Science Bulletin 2002年第23期47卷 1957-1963,2025-2026页

作者： SUN Donghuai1,2. LIU Yu2.& TAN Ming31. South china Sea institute of Oceanology, {2. academy of Sciences. Guangzhou 510301, china 2. State Key Laboratory of Loess and Quaternary Geology, earth environmental institute, {2. academy of Sciences, xi’an 710075, china 3. institute of Geology and Geophysics, {2. academy of Sciences, Beijing 10002., china South china Sea institute of Oceanology Chinese Academy of Sciences Guangzhou China State Key Laboratory of Loess and Quaternary Geology Earth Environmental Institute Chinese Academy of Sciences Xi’an China institute of Geology and Geophysics Chinese Academy of Sciences Beijing China

environmental change signals in geological or biological records are commonly reflected on their reflecting or transmitting images. These environmental signals can be extracted through digital image analysis. The analysis principle involves section line selection, color value reading and calculating environmental proxy index along the section lines, layer identification, auto-chronology and investigation of structure evolution of growth bands. On detailed illustrations of the image technique, this note provides image analyzing procedures of coral, tree-ring and stalagmite records. The environmental implications of the proxy index from image analysis are accordingly given through application demonstration of the image technique.

关键词： digital image environmental records.

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