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南海西部54万年以来元素地球化学记录及其反映的古环境演变 总被引：3，自引：1，他引：2
通过对南海西部上升流区MD05-2899孔开展高分辨率碳酸盐地层学和XRF岩芯扫描元素地球化学分析,重建了晚第四纪54万来以来东亚夏季风的演化历史,探讨海平面升降对南海西部陆源碎屑供应量的影响。研究选用了ln(Ba/Al)作为该海区古生产力的指标,ln(Br/Al)作为有机物的指标,ln(Ti/Al)作为陆源碎屑供应量的指标。研究结果显示,东亚夏季风在过去54万年以来强度不断增强,具有明显的冰期—间冰期旋回特征,在间冰期强盛和冰期减弱,是控制该海区有机物含量变化的主要因素。东亚夏季风不断强盛可能直接导致了南海周边陆地降雨增强,河流径流量加大,使得南海西部上升流区域的陆源碎屑供应量在间冰期明显高于冰期。研究发现,当相对海平面低于-60 m的时候,大面积暴露的巽他陆架可能向南海西部深水区输入大量陆源碎屑物质,造成研究站位的陆源碎屑供应量在冰盛期出现高值。因此,晚第四纪的东亚夏季风演化和海平面升降共同控制了南海西部上升流区陆源碎屑物质供应量的变化。 相似文献
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本文通过对IODP 363航次于澳大利亚西北岸外陆架上钻取的U1483站岩芯进行沉积物粒度、镁同位素以及主量元素成分等分析,重建200 ka以来帝汶海西南部沉积物输入演化及其指示的源区风化和侵蚀历史,探讨海洋沉积物中细粒硅质碎屑组分镁同位素的古环境指示意义。U1483站陆源碎屑组分主要由黏土质粉砂组成,其δ26Mg变化范围超过0.25‰。通过计算化学蚀变指数(chemical index of alteration, CIA)和两种物理侵蚀指标(包括陆源物质堆积速率和Ti/Ca比值),结果显示200 ka以来δ26Mg指标与CIA具有非常一致的曲线形态。本文推测陆源碎屑组分的Mg同位素组成主要反映物源区大陆硅酸盐风化强度的变化,而受矿物学分选、岩性和早期成岩作用的影响较小。结合区域古气候记录,我们发现本研究中的风化和侵蚀记录与同一个站位已发表的澳洲夏季风降水和表层海水温度变化具有较好的耦合关系,而与赤道太平洋海平面变化的相关程度较低,反映了轨道时间尺度上沉积物所记录的物源区风化和侵蚀演化主要受控于澳洲古季风系统,表现为气候驱动型风化模式。本研... 相似文献
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沉积物微量金属元素在重建水体环境变化中的意义 总被引：7，自引：0，他引：7
沉积物所记录的微量金属含量与形态的变化是指示人类活动影响下水体环境变化的有效指标,主要用于指示沉积物重金属污染、水体初级生产力变化和氧化还原条件等方面的水体环境状况。总体而言,沉积物中微量金属含量在近一个世纪以来显著上升,反映了采矿、冶金、污水排放、化肥使用、煤炭和石油燃烧等各种人类活动造成水体和沉积物重金属污染的记录作为浮游植物微量营养元素,Cu、Zn、Ni、Ba、Cd等在沉积物中的记录可以指示水体初级生产力水平。U、Mo、V、Cu、Cd、Mn等氧化还原敏感元素在沉积物中的富集或贫化,及其比值(如Re/Mo、Cd/U、Th/U和V/Sc)的变化,是指示水体和沉积物氧化还原环境的有效指标。但需要指出的是,在受人类活动影响的水体中,这些生产力和氧化还原指标很少能指示水体生产力或氧化还原状况,可能主要与人类活动同时造成这些金属元素大量污染输入而掩盖了其自生来源和内在变化的沉积记录有关。所以,对沉积物中微量金属元素来源的判别(陆源碎屑输入、人为输入和水体自生来源)是重建水体环境变化的重要前提。本文总结了多种化学和统计学方法(包括同位素示踪法、化学提取法、富集因子法和主成分分析法等)在沉积物金属来源判别中的应用另外,成岩作用等多种因素会干扰沉积物金属记录对环境变化的指示作用,所以构建多元素指标来综合判断沉积物记录所反映的环境信息是今后的研究所必须关注的 相似文献
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对贵州关岭晚三叠统法郎组瓦窑段底部的毛凹剖面系统地采集了105个岩石样品，测定了样品中的36种化学元素含量。作者对它们进行元素富集因子（EF）分析、R型聚类分析、R型因子分析、元素和氧化物的含量与Al2O3的含量比值以及δCe在剖面中垂向变化的分析，讨论了元素含量变化的制约因素、沉积物的来源、古海洋氧化还原条件的变化、关岭动物群的埋藏环境。结果表明：研究的5.2 ~17.7 m段剖面地层以陆源碎屑和生物碎屑混合沉积为主，沉积物来源于陆壳，而不是火山和热液的来源，其沉积的氧化还原条件多次反复变化；元素的含量变化主要受陆源物质、氧化还原条件、生物碎屑以及成岩作用控制；从元素地层学角度将所研究的剖面段从下到上可划分为4层，第1层至第4层元素对比值曲线呈现出平缓波动-频繁波动-平缓波动的周期性变化特征；该段偏还原的环境对海百合及海生爬行动物化石的保存和埋藏起了良好的作用。 相似文献
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为研究神农架后山坪地区古城组碳酸盐岩的地球化学特征及其成因和沉积环境,系统采集了该组样品并进行主、微量元素地球化学分析。结果显示,样品的TiO_2与SiO_2、Al_2O_3呈一定程度的正相关,与CaO、MgO呈负相关,说明古城组的沉积物来源可能为陆源沉积物和化学沉积物,主要为陆源沉积物;古城组沉积岩为水成沉积岩,非热水来源沉积,沉积物富火山碎屑或经历过钾交代变质作用;古城组沉积时为寒冷干燥、化学风化作用弱的古海洋氧化环境,地球化学参数指示,古城组沉积时期的氧化程度较比中元古代古海洋环境强,这与该时期所发育的冰期(古城冰期)有良好对应。 相似文献
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长江口及其邻近海域表层沉积物中氧化还原敏感性微量元素的环境指示意义 总被引：5，自引：2，他引：3
对长江口及其邻近海域表层沉积物和底层悬浮体中氧化还原敏感元素分布规律和富集特征进行了分析与研究。结果表明氧化还原敏感元素在研究区具有明显的“离岸富集”特征,去除粒度效应、陆源碎屑来源组分和有机质的吸附作用等因素的影响之后,氧化还原敏感元素仍显示出在缺氧区的富集。通过同一站位底层悬浮体和沉积物中氧化还原敏感元素含量的分析比较,发现底层水缺氧是导致氧化还原敏感元素Mo、Cd、V等在沉积物中富集的主要原因。Mo、Cd、V等元素的不同富集程度可用来反映缺氧区的缺氧程度。因此,Mo, Cd, V等RSE在长江口外缺氧区及其邻近海域具有氧化还原环境指示意义,可以指示长江口外缺氧区的存在与大体范围,并可在一定程度上用来衡量缺氧区的缺氧程度。U理论上虽然也对环境的氧化还原条件敏感,但由于受陆源碎屑来源组分的影响较大,在长江口外缺氧区的富集并不明显,因此U在研究区不具有氧化还原环境指示意义。 相似文献
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对太平洋1787站柱状沉积物进行了碎屑组分分布和来源的研究,并根据碎屑组分的分布特征对火山活动和南极底流活动状况进行探讨.结果表明,沉积物中的碎屑组分主要是生物来源、海洋自生来源和火山源,并推测本柱芯沉积期曾有11次火山活动期和9次南极底流入侵.在火山活动期,沉积物中火山来源矿物含量显著增加;在南极底流活动期,沉积物中褐铁矿和微结核等形成于氧化环境的矿物含量较高,生物扰动构造发育.所推测的底流活动期在氧同位素曲线上均有明显反映,并与古地磁资料得出的沉积间断基本吻合,表明沉积物的碎屑组分分布特征能间接指示古海洋事件. 相似文献
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Heinrich事件和末次冰期气候的不稳定性 总被引：10，自引：0，他引：10
对北大西洋深海沉积物的研究表明：末次冰期北大西洋沉积物记录中有多次洋面温度降低、有孔虫含量减少、盐度降低和粗颗粒的碳酸盐碎屑快速堆积的现象，这些时间跨度上千年或几百年的气候快速波动被称为Heinrich事件［１－４］，很难用古气候的米兰科维奇理论来解释。最近对末次冰期中国马兰黄土堆积的调查发现，在末次冰期之中东亚冬季风也有多次加强，它与北大西洋沉积物中的Heinrich事件对应很好，暗示着东亚季风的变迁更直接受控于北半球冰量的变化，而不是过去人们认为的东亚古季风气候变化与地球轨道变化引起太阳辐射变化直接相关。 相似文献
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《物探化探计算技术》2015,(4)
对南海北部湾东部海域61个站位表层沉积物的常量元素分析结果表明,研究区沉积物中的常量元素以SiO2、Al2O3和CaO含量最高,平均含量分别为61.83%、11.18%和5.32%,其中SiO2、Al2O3代表了陆源碎屑组分,CaO代表了生物碎屑组分。沉积物中常量元素的含量与沉积物类型密切相关,表明元素的丰度受沉积物粒度控制明显;而元素较低的富集系数,指示沉积物中的碎屑物质主要为地壳来源。元素相关分析和R型因子分析表明,沉积作用、粒度效应、海洋生物作用和自生作用等,对沉积物中常量元素的分布起着主要控制作用。在因子分析基础上,应用Q型聚类法并综合元素空间分布规律和富集特征,把研究区分为六个地球化学分区:Ⅰ区沉积物主要来源于北部湾北部的河流输砂和近岸侵蚀物;Ⅱ区为琼州海峡东侧来砂、昌化江以及红河等其他河流输砂以及北部湾周边近岸侵蚀物的混合沉积;Ⅲ区主要为红河输砂;Ⅳ区沉积物主要来源于海南岛西部和南部近岸侵蚀物,另外海洋生物活动和自生作用也是该区沉积物的重要物质来源;Ⅴ区和Ⅵ区为北部湾湾内沉积物与外海沉积物共同作用下的混合沉积,其中Ⅵ区部分海域的沉积物受到自生作用影响。 相似文献
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Guboglo M. N. 《GeoJournal》1980,4(1):53-58
International unity is becoming ever stronger in this country owing to an increasing similarity in the development of the cultural environment. This comprises the provision of all the country's republics with a sufficient number of schools, theatres, and other institutions and cultural information media in accordance with the needs of the population. An important part is played by the rise in ‘the general educational level, as well as the level of professional qualifications and skills. Among all the Soviet nations and nationalities, this rise being more rapid among formerly backward peoples. Prominent among the factors of internationalization is the progressive development of the nationalities’ cultural resources, while professional culture is being increasingly brought within the reach of the masses.The implementation of the nationalities policy promotes the all-round development of all Soviet nations and nationalities, their drawing together, the upsurge of the individual capabilities of every Soviet citizen. 相似文献
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Deviation of the major axis of the inertia ellipsoid of the Moon from the direction toward the Earth
B. P. Kondratyev 《Astronomy Reports》2017,61(8):709-714
It is known from observations that the center of mass of the Moon does not coincide with the geometric center of its figure, and the line connecting these two centers is not aligned with the direction toward the center of the Earth, instead deviating toward the Southeast. This stationary deviation of the axis of the inertia ellipsoid of the Moon to the South of the direction toward the Earth is analyzed. A system of five linear differential equations describing the physical libration of the Moon in latitude is considered, and these equations are derived using a new vector method taking into account perturbations from the Earth and partly from the Sun. The characteristic equation of this system is obtained, and all five oscillation frequencies are found. Special attention is paid to the fifth (zero) frequency, for which the solution of the latitude libration equations are stationary and represents a previously unknown additional motion of the rotational axis of theMoon in a cone with a small opening angle. In contrast to the astronomical precession of the Earth, the rotation of the angular-velocity vector is in the positive direction (counter-clockwise), with the period T 3 = 27.32 days. On this basis, this phenomenon has been named “quasi-precession.” This quasi-precession leads to a stationary inclination of the major axis of the inertia ellipsoid of theMoon to the South (for an observer on Earth), making it possible to explain one component of the observed deviation of the center of mass of the Moon from the direction toward the Earth. The opening angle of the quasiprecession cone is approximately 0.834″. 相似文献
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Chronological analyses of correlations between certain global repeating events (mass extinctions of marine organisms, meteorite impacts, and flashes in the frequency of geomagnetic reversals) during the Phanerozoic Eon and the motion of the solar system in the Galaxy are presented for five rotationally symmetrical models for the regular Galactic gravitational field. Thirteen of sixteen mass-extinction events can be described by a repetition interval of 183±3 million years. This is in agreement with the anomalistic period (interval between two subsequent passages of the Sun through the apocenter of its Galactic orbit) in the model of Allen and Martos. The positions of the minima and maxima in Gaussian functions approximating the frequency distribution for geomagnetic reversals also agree with the times of passage of the Sun through the apocenter and pericenter, respectively, of its Galactic orbit in this model. The maximum in the distribution of the deviations of the dates of mass extinctions from the nearest dates of impacts of large, crater-forming bodies is close to zero, providing evidence that many such events are correlated. As a rule, extinctions follow impact events. The impacts of large bodies have occurred most often when the solar system passes through the Galactic plane, while mass extinctions occur more often at some distance from the Galactic plane (about 40 pc). As a rule, intervals of increases in the frequency of geomagnetic reversals coincide with dates of impacts of large bodies. At the same time, these intervals do not show a clear correlation with the dates of mass extinctions. The intensity of mass extinctions, like the energy released by impacts, is consistently higher in periods when the Sun is moving from the apocenter toward the pericenter of its orbit, than when it is moving from the pericenter toward the apocenter. Thus, there is evidence for a variety of relationships between repeating global events in the Phanerozoic and the motion of the Sun in the Galaxy. Long-period variations in the frequency of geomagnetic reversals are correlated with the orbital motion of the Sun, and increases in the frequency of geomagnetic reversals are correlated with impacts. Mass extinctions are correlated with the impacts of large bodies, whose motions may have been perturbed by clouds of interstellar material concentrated toward the Galactic plane and by the shock front associated with the Perseus spiral arm, through which the solar system passes. The velocity of the Sun relative to the spiral pattern is estimated. 相似文献
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摩擦桩基桩土间极限摩阻力取值问题探讨 总被引：1，自引：0，他引：1
通过对广珠东线高速公路横沥大桥的试桩及土体的工程地质条件分析,总结出影响摩擦桩基桩土间极限摩阻力取值的一般问题以及解决问题的方法和措施。 相似文献
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位于华北和扬子两板块碰撞带中的苏鲁榴辉岩形成的温压条件不但是超高压，而且是高温。榴辉岩的PTt轨迹表明其为陆-陆磁撞俯冲带的产物。榴辉岩的区域性围岩花岗质片麻岩为新元古代同碰撞期花岗岩，榴辉岩及其他直接围岩皆呈包体存在于其中，并见新元古代花岗岩呈脉状侵入榴辉岩包体中。区域性围岩新元古代花岗岩的锆石中发现有柯石英、绿辉石等包裹体，表明新元古代花岗岩的组成物质也经受过超高压变质作用，且榴辉岩与围岩新元古代花岗岩的锆石U-Pb体系同位素年龄基本相同。但新元古代花岗岩所记录的变质作用和变形作用期次（或阶段）却少于榴辉岩。椐上述可得如下推断：超高压榴辉岩与新元古代花岗岩岩浆是同时在碰撞带底部（俯冲板块前部）形成的；榴辉岩的第一折返阶段是由新元古代花岗岩岩浆携带上升的，其第二折返阶段是和新元古代花岗岩一起由逆冲及区域性隆起而上升，遭受剥蚀。 相似文献
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某高速公路下伏煤矿采空区稳定性分析 总被引：10，自引：0，他引：10
在论述某高速公路下伏砦脖煤矿采空区地质、采矿和工程地质特征的基础上, 进行了稳定性数值模拟分析, 定性与定量地分析与评价了该煤矿采空区的地表变形特征及稳定性。研究结果表明: 该煤矿采空区的变形尚未完成, 对拟建的高速公路将产生很大的危害, 必须采取相应的工程治理措施。 相似文献
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The Importance of the Precipitation and the Susceptibility of the Slopes for the Triggering of Landslides Along the Roads 总被引：3，自引：1，他引：2
Clemente Irigaray Francisco Lamas Rachid El Hamdouni Tomás Fernández José Chacón 《Natural Hazards》2000,21(1):65-81
In order to characterise the influence of the heavyrains on the observed landslides during the 1996–1997hydrological cycle, rainfall records for the last 100years are analysed from 104 stations in easternAndalusia. Regarding the amounts of rain recordedbetween October 1996 and March 1997 in the 104stations studied, 31 presented new all-time records;15 presented values that were 80–100% of thepre-1995 record; 49 stations, 80–50%; and 9stations, < 50%. A map has been devised of thesusceptibility of the materials through which thesouth-eastern Andalusian road network crosses,together with an inventory of the damage caused byinstability phenomena on banks and cuttings of theroad network during the winter of 1996–1997. Therelationships between the rainfall during the studyperiod, the damage caused to the road network and thesusceptibility of the materials affected are analysed.The results indicate that there is a clearcorrespondence between the rainfall recorded and thesusceptibility of the materials with the inventorieddamage. It is concluded that the widespread seriousdamage caused in early 1997 to the roads andsurrounding areas in the Alpujarra region and thecoast of the Province of Granada was mainly caused bythe extraordinarily heavy rains. However, considerablyless damage was observed where the susceptibility ofthe terrain is low, thus highlighting the extremeusefulness of terrain-susceptibility maps for riskprevention and territorial planning. 相似文献
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The structure of the eastern Pyrenees consists mainly of south-directed thrusts involving basement and cover rocks. An antiformal stack developed by the piling up of basement thrust sheets which outcrop in the Axial zone. These structures account for a thin-skinned thrust model rather than a vertical fault model in which the Axial zone would be essentially autochthonous, and the North-Pyrenean fault the axial plane of a fan thrust system. New data from the Eastern Pyrenees and the thin-skinned model suggest that(1) the structure east of the Pedraforca nappe is similar to that of the Central Pyrenees; (2) the cover rocks of the South-Pyrenean units and of the Axial zone-after restoration—built up a northwards-thickening prism consistent with the existence of a unique Pyrenean sedimentary basin during Mesozoic time; (3) the Axial zone is only a complex antiformal stack developed as a part of South-Pyrenean system related to the Paleogene thrusting-tectonics. The Axial zone palaeogeographic area had no special meaning during Mesozoic time. 相似文献