Aeolian Facies Belts in the Taklimakan Desert1

At least at the beginning of the last glacial epoch, the facies belts of dune sand, sandy loam and loess formed by winds had existed in the Taklimakan desert and areas south of it. There were no appreciable changes in the NE and NW wind systems and their wind forces that deposited dune sand, sandy loam and loess in the global cold stage since the last glacial epoch; accordingly no marked shifts of the boundaries of these aeolian facies belts took place. In the global warm stage since then, the climate in the Taklimakan desert and areas south of it became warm and dry, resulting in ablation of substantial volumes of ice and snow in their surrounding mountains and thus forming alluvial and diluvial deposits in the region. The alluvial-diluvial actions, however, failed to change the general framework of aeolian facies belts.     

塔克拉玛干沙漠及其以南风成相带划分和认识

至少在末次冰期初，塔克拉玛干沙漠及其以南就已存在风成的砂丘砂、亚砂土和黄土岩相带。末次冰期以来的全球冷期中，造成砂丘砂、亚砂土和黄土沉积的ＮＥ和ＮＷ风系及其影响下的风力未有显著变化，因此，这几个风成相带沉积界线亦没有明显移动。自那时以来的全球暖期，塔克拉玛干和其南部，气候暖干，导致四周山地冰雪大量消融，于本区形成冲积，洪积。然而，冲洪积作用并未能改变风成相带分布的基本格局。     

Environmental conditions leading to the formation of Holocene soil layers in the Northern Taklimakan Desert,Tarim Basin,Northwest China

Radiocarbon‐dated palaeontological remains and bedding features suggests that climatic changes in the northern Taklimakan Desert since the beginning of the Holocene can be divided into four stages: (i) 12 000–10 000 BP, a cool–to temperate–dry climate resulting in apparent alluvial–fluvial and weak aeolian activities; (ii) 10 000–8000 BP, a dry cold climate, resulting in large‐scale sand dune activity under regional desert expansion; (iii) 8000–3000 BP dry, warm climate, with a decreased area of shifting sand and the fixation of many sand dunes; (iv) 3000 BP to present, rising aeolian activity resulting in sandstorms, under the combined influence of climatic warming and excessive exploitation of land and water resources. Holocene deposits from profiles in the Northern Taklimakan Desert consist mainly of fine‐grained aeolian sand and silty clay. The fine aeolian sand was formed from re‐sorting of aeolian sand during the cold period of the Holocene, while the silty clay was formed by flood deposition in the Holocene warm period. The desert and desert steppe arboreal species and high CaCO₃ content of the warm period strata suggest that the Holocene climate in the area, although generally dry, varied between warm/dry and cold/dry, and, especially in recent times, has become increasingly dry. Copyright © 2004 John Wiley & Sons, Ltd.     

塔克拉玛干沙漠石英氧同位素与粒级关系的研究

沙漠与黄土的物源联系是黄土研究关注的问题之一。石英氧同位素可示踪物源,粒度被用以分析沉积环境,但在沙漠物源研究中将二者结合应用的报道尚不多。本文测定了塔克拉玛干沙漠沙丘沙和沙丘剖面中河湖相沉积物的粒度及不同粒级的石英氧同位素,结果显示:1沙丘沙以极细砂和细砂为主,粉砂和黏土含量很低;河湖相沉积物以粉砂和黏土为主,砂含量低于5%。2各粒级石英δ~(18)OSMOW值介于13.8‰~19.7‰,其中沙丘沙为13.8‰~19.7‰,河湖相沉积物为15.6‰~17.6‰;沙丘沙石英δ~(18)O值随粒级增大未呈现减小趋势,同一粒级石英的δ~(18)O值存在一定变异。3经比较,塔克拉玛干沙漠砂和粉砂粒级的石英δ~(18)O值均高于中国其他沙漠,且20μm的石英δ~(18)O值与黄土高原的马兰黄土、洛川黄土—古土壤序列20μm的石英δ~(18)O值并无显著性差异。     

北京西山末次冰期旋回次生黄土初步研究

北京西山是中国末次冰期旋回风成黄土与古气候研究的经典地区。除风成黄土外 ,该区各种次生黄土也十分发育 ,由于后者的堆积速率较大 ,其环境变化的分辨率更高。次生黄土中S1古土壤由 3层古土壤夹两层黄土构成 ,L1中的古土壤由两层古土壤夹 1层黄土组成。经年代测定和古气候分析 ,S1中的 3层古土壤分别可与深海氧同位素 5阶段中的 3个暖期对比 ,S1中的两层黄土可与5阶段中的两个次阶段对比。     

塔克拉玛干沙漠输电线塔装配式基础试验研究

为研究新疆塔克拉玛干沙漠地区输电线路工程中的组合装配式杆塔基础承载特性,开展了2种尺寸规格共4个基础在上拔与水平力组合作用下的现场试验,得到了基础顶部和基础底板的荷载-位移曲线、基础底板土压力变化规律。结果表明：上拔与水平力组合作用下,基础顶部上拔荷载-位移曲线为缓变型、水平荷载-位移曲线近似为直线;由混凝土底板和角钢支架所构成的组合装配式基础因自重轻、基础底板上覆沙体结构松散,使得基础的抗倾覆承载能力低。由混凝土底板和角钢支架组成的装配式基础各部件具有良好的协同工作性能,但水平荷载对装配式基础的承载性能影响大。根据基础上拔极限承载力试验值,采用柱式破裂面力学计算模型得到风加沙柱面平均摩擦阻力为2.6 kPa     

塔里木盆地南缘新生代沉积:对青藏高原北缘隆升和塔克拉玛干沙漠演化的指示

塔里木盆地南缘新生代沉积地层厚达万米以上。研究的叶城和阿尔塔什两个剖面分别厚4500m和7000m,基本代表了塔里木南部的新生代沉积。叶城剖面的底界年龄根据磁性地层测定约为8Ma。阿尔塔什剖面的底界年龄根据海相碳酸盐岩87Sr/86Sr的比值与全球Sr同位素曲线对比,约为30～35Ma。从岩性地层分析,剖面的下部为中新统乌恰群,主要由泥岩和粉砂岩组成,沉积相为低能环境的辫状河和曲流河。剖面的中部是上新统阿图什组,由红色泥岩、砂岩夹薄层砾岩以及埋藏风成黄土构成,沉积环境为冲-洪积扇的中远端。剖面的上部是上新统—下更新统西域组,由中粗砾岩夹块状粉砂岩透镜体(埋藏风成黄土)组成,主要是近源洪积扇沉积和风成沉积,以上地层层序可以进行很好的区域对比。塔里木盆地南缘新生代沉积由新近纪红层向上变化为逆粒序砾岩和碎屑流沉积,记录了青藏高原北缘隆升造成的沉积环境的变化,尤其是干旱化气候的阶段性演化。在约8Ma时,叶城和阿尔塔什两个剖面都发育了风成沙丘沉积。而在阿尔塔什剖面,沙丘沉积之下还发育了一套厚层的膏盐沉积,指示了塔里木盆地南缘在此前后已经相当干旱,只是仅凭这些证据还难以判断沙漠发育的规模。而上新世—更新世阿图什组和西域组中发育的埋藏风成黄土沉积,则指示了塔克拉玛干沙漠在此时已经发育到了相当规模,极度干旱的气候条件(可能类似于现在)已经形成。     

毛乌素沙地东南部边缘不同地质成因类型土地沙漠化粒度特征及其地质意义

首次对毛乌素沙地东南部边缘沙漠—黄土地带的土地沙漠化进行系统的地质学分类,提出了沙地内部就地起沙型沙漠化、河流谷地就地起沙型沙漠化、风化残积就地起沙型沙漠化和风沙侵入型沙漠化等四种土地沙漠化类型。通过深入分析不同地质成因类型土地沙漠化的粒度特征,探讨了不同地质作用对土地沙漠化的贡献及其对土地沙漠化防治方面的重要意义。研究表明,研究区的土地沙漠化以就地起沙型为主,河流的水力搬运是沙漠化物质搬运的主要途径,风力作用则是对河流湖泊沉积物的进一步分选和再沉积。最后,提出了不同类型的土地沙漠化防治对策建议。     

Positive Ion Contained in Tamarix Cone Sedimentary Veins and Climatic and Environmental Change in Southern Region of Taklimakan Desert

Based on the research on Tamarix cone sedimentary veins in three different places which are Andier Ancient City, Andier Meadow, and Damagou Township in the southern region of the Taklimakan Desert, the relationship between the characteristics of the positive ion content in Tamarix fallen leaves and climatic change during the past 400 years is systematically analyzed. The results show: the order of four kinds of positive ion content’s change range in three sampling sites is Ca²⁺> K⁺> Mg²⁺> Na⁺. The correlation coefficient between Ca²⁺ content and the total positive ion content is higher, which indicates that Ca²⁺ content or the total positive ion content can reflect the change trends. There is an inverse correlation between positive ion content in Tamarix fallen leaves and the local temperature. According to the change of positive ion content, the climate in the southern region of the Taklimakan Desert can be divided into cold and warm periods during the past 400 years, among which the period of 1590-1691 is warm period, of 1692-1896 is cold period (warm fluctuations are 1799-1808,1825-1829,1878-1881,1887-1891), of 1897-2010 is warm period (cold fluctuations are 1939-1941,1992-1998); Precipitation has a poor correlation with the positive ion content; There is a better correspondence between the changes of positive ion content and the regional flood events. This research provides a kind of research method for the environmental evolution in the southern region of the Taklimakan Desert,and it is of great help to environmental change research of the arid desert regions. It has further perfected the feasibility of using positive ion content in Tamarix cone sedimentary veins to reveal the environmental change, and fills up the blank of high resolution climatic change during the past 400 years in the southern region of the Taklimakan Desert.     

A Late Quaternary Climate Record Based on Multi-Proxies Analysis from the Jiaochang Loess Section in the Eastern Tibetan Plateau, China

We compared the stable carbon isotopic records from a loess transect of the Jiaochang in the eastern Tibetan Plateau, spanning the last ~21,000 years, with multiproxy data for pedogenesis, including magnetic susceptibility, clay fraction, Fed/Fet ratio, carbonate and total organic carbon content, in order to probe the mechanisms of δ13C values of organic matter and Late Quaternary climate variations in the eastern Tibetan Plateau. Our results indicate that there is no simple relationship between δ13C of organic matter and summer monsoon variations. The change in δ13C values of organic matter (in accordance with the ratios of C3 to C4 plants) results from the interaction among temperature, aridity and atmospheric pCO2 level. Drier climate and lower atmospheric pCO2 level contribute to positive carbon isotopic excursion, while negative carbon isotopic excursion is the result of lower temperature and increased atmospheric pCO2 level. Additionally, our results imply that the Tibetan monsoon may play an important role in climate system in the eastern Tibet Plateau, which specifically reflects frequently changing climate in that area. The results provide new insights into the forcing mechanisms on both the δ13C values of organic matter and the local climate system.     

中原末次冰期间冰阶以来的古季风气候变迁

中原邙山黄土地层以巨厚的马兰黄土为特色。本文研究了末次冰期间冰阶以来邙山黄土－古土壤序列的粗颗粒含量和磁化率值曲线反映的冬夏季风变迁及其相互关系,发现在万年尺度上夏季风增强对应于冬季风减弱,冬季风增强对应于夏季风减弱,但在千年尺度上冬季风变化比夏季风强烈得多,而且末次间冰段开始时冬季风减弱明显早于夏季风增强。通过中原黄土记录与深海及冰芯Ｏ同位素记录的对比,发现短时间尺度气候变化阶段明显具有很大的区域性特征,它们不能简单地进行等时性全球对比,而应该通过各自独立的时间标尺来建立古气候变化的远距离联系。     

风积沙漠地区三维地震勘探资料处理中Q补偿应用实例

在有效波组为低频、低噪且地质任务以小构造解释为目标的地区,采用Q补偿技术有利于提高有效波组的主频,达到提高纵向分辨率的目的。以鄂尔多斯某勘探区为例,采用Q值补偿技术,以克服该区沙漠地貌明显的吸收衰减滤波效应问题,提高其地震资料的中、高频成分。通过对Q补偿参数进行测试,发现Q值为50时有效波响应明显。应用结果表明,经Q补偿后,地震时间剖面有效波主频明显提高,DF7、DF8断层在补偿后的地震时间剖面上较补偿前断点更清晰、位置解释误差更少。     

海陆交互相下粘性土的性状研究

长江口北侧海陆交互相沉积粘性土具有粘粒与粉粒交替形成的互层层理结构特征及粉粒含量高的粒度成分特征。且表现出物理性质指标与力学性质指标互不吻合的工程特性。运用多元统计理论中主成分分析原理,分析了海陆交互相沉积粘性土常规物理性质指标反映其工程特性的能力。研究结果表明：将亚砂土隶属于粘性土范畴是不科学的,同时运用液性指数判别其物理稠度状态及推断其工程特性的方法存在不尽合理之处。     

鄂尔多斯盆地白垩系沙漠相沉积特征及其水文地质意义

白垩纪鄂尔多斯盆地在燕山期抬升-沉降及气候演变的背景条件下,受水力、风力等地质作用,经历了早白垩世宜君-洛河期→环河期与罗汉洞期→泾川期两个沙漠沉积演化阶段。其中,洛河期和罗汉洞期是沙漠发育的两个主要时期,形成了旱谷、沙丘、丘间及沙漠湖等多类型沙漠亚相碎屑岩沉积。沙丘沉积砂岩作为白垩系沙漠相最主要的沉积岩石,具有分布稳定、厚度巨大、含盐量低、孔隙空间发育、储水性和透水性强等特点,不但具有良好的地下水赋存和循环条件,而且一般赋存着水质较好的地下水。     

毛乌素沙地沉积物粒度特征与土地沙漠化

为了研究毛乌素沙地沉积物的粒度特征与土地沙漠化的地质成因类型,通过系统研究沙地及相邻地区晚更新世以来在沙地内部、覆沙黄土区、黄土高原和河流谷地与湖泊等不同地质构造地貌条件下所形成的沉积物粒度特征,指出不同地质成因类型的沉积物是这些地区土地沙漠化的物质基础,区分不同类型的沉积物也是构成不同地质成因类型土地沙漠化分类的理论基础,探讨了不同地质作用对土地沙漠化的贡献及其对土地沙漠化防治方面的意义。研究表明,研究区的土地沙漠化是以各种类型的就地起沙为主要特征,地表径流的水力搬运是沙漠化物质搬运的重要途径。现代毛乌素沙地及其邻区的土地沙漠化是对地质历史时期形成的各种沉积物的进一步搬运、分选和再沉积过程,具有相对复杂的粒度特征。     

最后4个冰期旋回中国黄土记录的东亚冬季风变化

开展高分辨率的黄土记录研究, 是揭示过去气候变迁和变率的主要途径.选择黄土高原中部的灵台和赵家川剖面, 对L5以上的黄土-古土壤序列进行了石英颗粒的提取和粒度分析.结果表明, 石英粗颗粒(> 43μm) 体积分数变化揭示了最后4个冰期旋回东亚冬季风存有的快速变化特征, 并同深海氧同位素记录具有良好的对应关系; 然而, 在每一个冰期时段, 石英粗颗粒体积分数的变化幅度和频率存有较大差异, 可能意味着对应的冰期下垫面状况和气候系统内部的非线性响应机制并不相同.值得注意的是由石英粗颗粒体积分数反映的东亚冬季风变化, 在某些时段不仅同磁化率记录的夏季风变化不协调, 而且同深海氧同位素记录存有明显差异.深入研究这种由不同代用指标反映的古气候变化间的差异, 对理解黄土记录的全球性意义显得尤为重要.      

Last glacial maximum ecology and climate from terrestrial gastropod assemblages in Peoria loess,western Kentucky

The Rocks loess section, in unglaciated western Kentucky, provides a high-resolution environmental record during the last glacial maximum onset. The Peoria Silt (9 m thick) contains 26 terrestrial gastropod species, with up to 15 species within a single 5 cm interval. Thirteen radiocarbon ages, using shells or charcoal, range between 30 and 24.5 cal ka; younger loess has been leached or eroded. Stratigraphic shifts in gastropod assemblages imply significant cooling, particularly ~27 cal ka, as solar insolation was decreasing and the southern Laurentide Ice Sheet rapidly advancing. Midwestern to southern species (e.g. Anguispira kochi, Gastrocopta pentodon, Hawaii miniscula, Helicodiscus parallelus, Vallonia perspectiva) occur only in the lowermost Peoria Silt (~30–27 cal ka). In contrast, cold-tolerant species (Columella alticola, Vertigo modesta, Vallonia gracilicosta) occur only in full glacial Peoria Silt (27–24.5 cal ka). Inferred mean July temperatures, from mutual climatic range methods, range from ~23 °C at 30 cal ka, cooling to ~18 °C by 26 cal ka; about 3–8 °C cooler than today (~26 °C). Superimposed on this cooling trend are multi-centennial variations in detrital carbonate, fossil shell concentrations, palaeotemperature estimates, and oxygen isotope values (Vertigo, Discus, Helicodiscus). The finer-scale variations imply relatively synchronous fluctuations in glacial sediment supply, loess sedimentation, and climate.     

中更新世全球最大冰期与中国沙漠扩张

位于青藏高原和西北干旱区交界带的沙沟黄土剖面, 详细记录了0.8 Ma BP以来东亚季风系统和沙漠演化的历史. L6黄土层中, 中值粒径和砂粒含量表明当时冬季风极端强盛, 沙漠大规模扩张, 其范围仅次于末次冰期最盛期. 在0.6～0.7 Ma BP以前(即深海氧同位素MIS16阶段), 北半球高纬度大陆冰盖大规模扩展, 全球冰量达到最大, 并且西伯利亚冰盖的扩展, 还使得西伯利亚高压增强; 同时, 青藏高原上也发育了最大规模的冰川, 从而强化了西风和东亚冬季风. 其结果造成了中国季风边缘区的沙漠扩张. 虽然全球冰量和青藏高原是影响沙漠演化的重要因素, 但在不同的时段其机制可能有所不同, 也不能忽略其它因素的影响.     

上扬子地台南缘不同沉积相区上泥盆统和下石炭统沉积层序之对比

层序的空间分布是否具有全球性,地史时期海平面变化是否具有全球等时一致性,是层序地层学的根本问题。上扬子地台南缘不同沉积相区上泥盆统和下石炭统沉积层序研究表明,不同级别的层序具有特定的空间分布和对比范围,虽然形成各种级别层序的海平面变化基本上是全球性的。本文把空间分布,特别是在不同沉积相区的分布作为定义和识别各种级别层序的一个标准。正层序（ 三级层序） 的分布可能是全球性的,至少可以在同一大陆边缘的不同相区辨认,并能进行远距离对比,有些甚至可以进行全球对比。一般来说,亚层序（ 四级层序,时间间隔0.5 M a～ 1.5 M a） 在不同的沉积相区对比比较困难,虽然有些亚层序的空间分布也可以是全球性的。亚层序至少应当在一个沉积相带内可以普遍识别和对比。更高级的层序,包括副层序（ 五级层序,即Wang 和 Shi 1996 年使用的亚层序） 和小层序（ 六级层序） 的分布是区域性的或地区性的,它们可能分别反映米兰柯维奇旋回的长周期和短周期。正层序和亚层序一般可在不同沉积相区识别,而副层序和小层序一般仅能在浅海相区识别,在斜坡和盆地相区则不易辨认。     

东北地区末次冰期以来气候地貌的若干特征

末次冰期,长白山天池周围有冰斗发育,高2200m左右,东北的广大地区为冰缘环境。许多冰缘形态至今控制着地貌景观。冰后期,长白山的冰川地貌受到冰缘环境的控制,广大地区的冰缘地貌则受到温暖环境的改造。作为气候地貌界限的冰雪线,由末次冰期的44—45°N移至今日的51°N附近。末次冰期以来,气候地貌带表现出沿经度和纬度平行移动的特点