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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 {2. of Continent Dynamics (Northwest University), {2. of Cenozoic geology and Environment, De- partment of geology, Northwest University, xi’an 710069, china 2. {2. of earth Environment, state key {2. of {12. and quaternary geology, Chinese Academy of Sciences, xi’an 710075, china 1. state key {2. of Continent Dynamics (Northwest University) Institute of Cenozoic Geology and Environment Department of Geology Northwest University Xi’an 710069 China 2. institute of earth Environment 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 {2. 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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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 {2. of Continental Dynamics, Department of {2., Northwest University, institute of Cenozoic {2. and Environment, xi’an 710069, china 2.institute of earth Environment, state key {2. of {12. and quaternary {2., Chinese Academy of Sciences, xi’an 710075, china 1. state key {2. of Continental Dynamics Department of Geology Northwest University Institute of Cenozoic Geology and Environment Xi’an 710069 China 2. institute of earth Environment 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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Characterization of MASDs of surface soils in north china and its influence on estimating dust emission

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Chinese Science Bulletin 2004年第20期49卷 2169-2176页

作者： MEI Fanmin1,2. ZHANG xiaoye1, LU Huayu1, SHEN Zhenxing1 & WANG Yaqiang1 1. state key {2. of {2. and quaternary geology, institute of earth Environment, Chinese Academy of Sciences, xian 710075, china 2. xian University of Engineering Science and Technology, xian 710048, china state key {2. of {2. and quaternary geology Institute of Earth Environment Chinese Academy of Sciences Xi''an 710075 China xi''an University of Engineering Science and Technology Xi''an 710048 China

The micro-aggregated size distribution (MASD) of surface soil is an important parameter for modelling dust emission. However, there is no dataset of MASDs of all sur-face soil types in north china. The MASDs are here pre-sented, measured by dry sieving, for typical surface soil sam-ples, including sandy soil, gravelly sand soil, gravelly loam soil, loam soil and silt loam soil, collected from sandy deserts, Gobi deserts, oases, farmlands in steppe regions and steppe areas in north china. The MASDs of various surface soil types exhibit a combination of several log-normal distribu-tions of five separated sizes with mean mass median diame-ters (MMDs) of 90, 2.0, 390, 600 and 980 mm, respectively, and mean standard deviations (SDs) of 1.2., 1.40, 1.2., 1.35 and 1.2. respectively. The log-normal distributions corre-spond to very fine sand, fine sand, medium sand, coarse sand and very coarse sand population. On the basis of characteri-zation of the retrieved MASDs of various surface soil types in north china, dust emission fluxes are modelled by a dust production model (DPM model). It is shown that dust emis-sion has been significantly influenced by MASDs. Fine sand and very fine sand are always associated with the highest dust emission fluxes. Emission fluxes of the medium sand, gravelly sand soil, gravelly loam soil and loam soil are lower than those of very fine sand and fine sand, but larger than those of the coarse sand. The differences in dust emission fluxes vary among the different soil types from 101 to 103 mg·m-2.s-1. Dust emission fluxes from sandy deserts and farmlands covered with sand sheets in north china rang from 101 to 104 mg·m-2.s-1 while those from Gobi deserts, farmlands and steppes with gravelly desertification range from 101 to 102.mg·m-2. s-1. The modelled results indicate that deserts and farmlands with sand are the major dust sources in north china.

关键词：华北地区 MASDs 微块状粒度分布地面土壤粉尘排放壤土大气污染气溶胶

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Preliminary reconstruction of the desert and sandy land distributions in china since the last interglacial period

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Science china earth Sciences 2004年第z1期47卷 89-100页

作者： CHEN Huizhong, SU Zhizhu, YANG Ping & DONG Guangrongkey laboratory of Desert and Desertification, Cold and Arid Regions {2. and Engineering Research {2., Chinese Academy of Sciences, Lanzhou 730000, china state key laboratory of loess quaternary geology, {2. of {12. Environment, Chinese Academy of Sciences, xi’an 710075, china {2. of loess Plateau, Shanxi University, Taiyuan 030006, china 1. key laboratory of Desert and Desertification Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences 730000 Lanzhou China 2. state key {2. of {2. quaternary geology Institute of Earth Environment Chinese Academy of Sciences 710075 Xi’an China 3. institute of loess Plateau Shanxi University 030006 Taiyuan China

The desert and sandy land are the products of arid climate. The spatial distribution of modern deserts and sandy land in china and their relation to climate show following characteristics: arid and hyper-arid desert zones, at isohyet of less than 2.0 mm, are dominated by mobile dunes; semi-arid steppe and arid desert steppe with the precipitation between 2.0?00 mm, are dominated by semi-fixed and fixed sand dunes; the precipitation of sub-humid forest grassland and humid forest zones with scattered fixed sand land is higher than 400 mm. With this as reference, in combination with considerable amount of paleoclimatic data in desert regions and adjacent regions, the distributions of desert and sandy land in china during the last intergla-cial period, the last glacial maximum (LGM), and the Holocene megathermal, were preliminarily reconstructed. The results compared with that of today show that the distribution of desert and sandy land in china was greatly dwindled during last interglacial period, and the mobile dune area was about two-thirds of that of today's, but greatly expanded during LGM. However, the dwindling area of desert and sandy land in the Holocene megathermal was smaller than that in the last interglacial period. The forcing mechanism was mainly related to the changes of East Asian winter and summer monsoon, south-northward swing of the westerlies and the variations of the Qinghai-Tibet Plateau monsoon intensity caused by global climate changes during the cold and warm intervals since the last interglacial period.

关键词： the glacial-interglacial period, desert, sandy land, spatial distribution.

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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, Chinese Academy of Sciences. Guangzhou 510301, china 2. state key laboratory of loess and quaternary geology, earth environmental institute, Chinese Academy of Sciences, xi’an 710075, china 3. institute of geology and Geophysics, Chinese Academy of Sciences, Beijing 10002., china South china Sea institute of Oceanology Chinese Academy of Sciences Guangzhou China state key {2. of {2. 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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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 {2. and {2. 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 2.0008, china 1. state key Lab of {2. and {2. 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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Constraints of authigenic carbonates on trace elements (Sr,Mg) of lacustrine ostracod shells in paleoenviron-ment reconstruction and its mechanism

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Science china earth Sciences 2008年第5期51卷 654-664页

作者： HU Guang1,2. JIN ZhangDong1 & ZHANG Fei3 1 state key {2. of {2. and quaternary geology, institute of earth Environment, Chinese Academy of Sciences, xi’an 710075, china 2.Graduate University of the Chinese Academy of Sciences, Beijing 100049, china 3 College of Resources and environmental Science, Nanjing Agricultural University, Nanjing 2.0095, china state key {2. of {2. and quaternary geology Institute of Earth Environment Chinese Academy of Sciences Xi’an 710075 China Graduate University of the Chinese Academy of Sciences Beijing 100049 China College of Resources and Env

Molar ratios of Mg/Ca and Sr/Ca were measured in two species of ostracod shells preserved in the upper core (15–55 m) of the Hequing Basin in Yunnan Province, southwest china. By correlating the molar ratios between Mg/Ca and Sr/Ca and comparing them with Sr concentrations of the sediments, we suggested that: (1) the molar Mg/Ca and Sr/Ca ratio variations in respective ostracod primo reflected the changes in its ambient water composition and ecology; (2. the molar Sr/Ca ratios responded better to the salinity change linearly than Mg/Ca without aragonite precipitation in the system, and otherwise there was no linear relation between them; and (3) the molar Sr/Ca ratios were mainly controlled by salinity and authigenic carbonate precipitation, whereas the molar Mg/Ca ratios were related to both salinity and temperature. In fact, the rate of ostracod growth owing to temperature controls the fluctuation of Mg/Ca in shells. Here, more attentions should be paid to the constraint of authigenic mineral precipitation processes on the trace elements in ostracod shells and to the correlation between these trace elements in biogenic carbonates and compositions of the sediments in systems and in future in vitro experiments.

关键词： ostracod shell molar Sr/Ca ratio molar Mg/Ca ratio environmental response Heqing Basin

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Boron isotopic fractionation in laboratory inorganic carbonate precipitation:Evidence for the incorpora-tion of B(OH)_3 into carbonate

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Science china earth Sciences 2008年第12期51卷 1776-1785页

作者： xiAO YingKai1,2. LI HuaLing1,3, LIU WeiGuo4, WANG xiuFang1 & JIANG ShaoYong5 1 Qinghai institute of Salt Lakes, Chinese Academy of Sciences, xining 810008, china 2.{2. key laboratory of environmental Geochemistry, institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002. china 3 Nanjing institute of geology and Mineral Resources, Nanjing 2.0016, china 4 {2. key laboratory of loess and quaternary geology, institute of earth Environment, Chinese Academy of Sciences, xi’an 710075, china 5 {2. key laboratory for Mineral Deposits Research, Department of earth Sciences, Nanjing University, Nanjing 2.0093, china 1. Qinghai institute of Salt Lakes Chinese Academy of Sciences Xining 810008 China 2. state key {2. of {2. Geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China 3. Nanjing institute of geology and Mineral Resources 210016 Nanjing China 4. state key {2. of {2. and quaternary geology Institute of Earth Environment Chinese Academy of Sciences Xi’an 710075 China 5. state key {2. for Mineral Deposits Research Department of Earth Sciences Nanjing University Nanjing 210093 China

A laboratory inorganic carbonate precipitation experiment at high pH of 8.96 to 9.34 was conducted, and the boron isotopic fractionations of the precipitated carbonate were measured. The data show that boron isotopic fractionation factors (αcarb-3) between carbonate and B(OH)3 in seawater range 0.937 and 0.965, with an average value of 0.953. Our results together with those reported by Sanyal and collabo-rators show that the αcarb-3 values between carbonate and B(OH)3 in solution are not constant but are negatively correlated with the pH of seawater. The measured boron isotopic compositions of carbonate precipitation (δ11Bcarb) do not exactly lie on the best-fit theoretical δ 11B4-pH curves and neither do they exactly parallel any theoretical δ 11B4-pH curves. Therefore, it is reasonable to argue that a changeable proportion of B(OH)3 with pH of seawater should also be incorporated into carbonate except for the dominant incorporation of B(OH)4- in carbonate . Hence, in the reconstruction of the paleo-pH of sea-water from boron isotopes in marine biogenic carbonates, the use of theoretical boron isotopic frac-tionation factor (α4-3) between B(OH)4- and B(OH)3 is not suitable. Instead, an empirical equation should be established.

关键词： boron isotopic fractionation biogenic carbonate B(OH)3 incorporation

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An unusual isotopic fractionation of boron in synthetic calcium carbonate precipitated from seawater and saline water

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Science china Chemistry 2006年第5期49卷 454-465页

作者： xiAO Yingkai1,2.LI Shizhen1,WEI Haizhen1,SUN Aide1,ZHOU Weijian2.& LIU Weiguo2.1. Qinghai institute of Salt Lakes,Chinese Academy of Sciences,xining 810008,china {2.,institute of earth Environment,Chinese Academy of Sciences,xi’an 710075,china 1. Qinghai institute of Salt Lakes Chinese Academy of Sciences Xining 810008 China 2. state key laboratory of loess and quaternary geology Institute of Earth Environment Chinese Academy of Sciences Xi’an 710075 China

Inorganic calcium carbonate precipitation from natural seawater and salinewater at various pH values was carried out experimentally. The results show the clear positiverelationships between boron concentration and δ^(11)B of inorganic calcium carbonate with the pH ofnatural seawater and saline water. However, the variations of boron isotopic fractionation betweeninorganic calcite and seawater/saline water with pH are inconsistent with the hypothesis thatB(OH)_4^- is the dominant species incorporated into the biogenic calcite structure. The isotopicfractionation factors a between synthetic calcium carbonate precipitate and parent solutionsincrease systematically as pH increases, from 0.9884 at pH 7.60 to 1.0072.at pH 8.60 for seawaterand from 0.982. at pH 7.60 to 1.0178 at pH 8.75 for saline water. An unusual boron isotopicfractionation factor of larger than 1 in synthetic calcium carbonate precipitated fromseawater/saline water at higher pH is observed, which implies that a substantial amount of theisotopically heavier B(OH)_3 species must be incorporated preferentially into synthetic inorganiccarbonate. The results propose that the incorporation of B(OH)_3 is attributed to the formation ofMg(OH)_2.at higher pH of calcifying microenvironment during the synthetic calcium carbonateprecipitation. The preliminary experiment of Mg(OH)_2.precipitated from artificial seawater showsthat heavier ^(11)B is enriched in Mg(OH)_2.precipitation, which suggests that isotopically heavierB(OH)_3 species incorporated preferentially into Mg(OH)_2.precipitation. This result cannot beapplied to explain the boron isotopic fractionation of marine bio-carbonate because of thepossibility that the unusual environment in this study appears in formation of marine bio-carbonateis infinitesimal. We, however, must pay more attention to this phenomenon observed in this study,which accidentally appears in especially natural environment.

关键词： boron, isotopic fractionation, calcium carbonate precipitate, seawater, saline water.

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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, Chinese Academy of Sciences,{2., 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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