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31.
黄土中稀土元素的初步探讨 总被引：10，自引：0，他引：10
REE oxides in loess are estimated to amount to about 200 ppm. The REE distribution patterns in loess and its clay fraction are characterized by the enrichment of rare earth elements of Ce family. The REE distribution patterns of loess in the middle Huanghe (Yellow River) Valley are consistent with those of sands from the Tengeli desert, probably indicating the consistency of their material sources. The REE distribution patterns are similar to each other in the elay fractions of Malan loess everywhere in the middle Huanghe Valley, indicating the homogeneity in their composition. Close to the average value of the earth‘s crust, the REE distribution patterns in loees and its clay fraction are similar to that of sedimentary rocks (e.g., North American shales), but different from that of chrondrites. It seems to show that large amounts of loessic material were transported from the provenance by moving water into sedimentarysy stems after it had been separated from its precursor, and then transported by wind to where it is now distributed. 相似文献
32.
黄土剖面中氧化物的比值和相对淋溶、积聚值在地质上的意义 总被引：9，自引：1，他引：9
As have been determined, the ratios of oxides and the contents of CaCO3 show a tendency to increase from bottom to top in Luochuan loess section, whereas an opposite tendency is observed for the relative values of weathering leaching or accumulation of loess, Moreover, the limits of oxide ratios from less to greater than the average value coincide with the boundary between Wucheng and Lishi loess strata, as well as with the boundary of magnetic polarity reversal. The ratios of oxides and the variations of relative weathering-leaching or accumulation extents are synchronous with the fluctuation of CaCO3 contents. From this investigation, it is shown that the ratios of oxides in the superimposed loees and paleosols from the loess profile are found rhythmically varied. These Characteristics might be explained by the hypothesis of repeated climatic fluctuation from dry (loess) to humid (paleosol) during the Quaternary period. 相似文献
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The F/Cl ratio for loess and palcosol has been studied based on the difference in the geochemical behaviour of fluorine and chlorine under hypergene conditions. The variation of F/Cl ratio in the loess section indicates a paleoclimatic evolution from humid to arid since loess accumulation. The maximum F/Cl ratio is found .in the fifth paleosol layer, reflecting an optimum climatic period for pedogenesis. The variation of F/Cl ratio is synchronous with the climatic fluctuation from warm-humid to arid-cold. 相似文献
35.
末次间冰期以来渭南黄土剖面地球化学指标所反映的古气候变化 总被引：15，自引：6，他引：15
渭南剖面由全新世土壤Ｓ０，末次冰期黄土Ｌ１及末次间期古土壤Ｓ１和组成。其中，Ｌ１可以进一步划分为三层黄土和两层弱发育的土壤；Ｓ１由三层土壤组成。碳酸盐，游离铁及有机质含旺在渭南剖面上的变化表明上述化学成分可以用作缺气候的替代性指标，并能反映古气候的变化。 相似文献
36.
根据地质环境背景资料和近350个地质灾害点和数十个水土流失区的数据库对广东沿海陆地表层地质灾害进行了综合分析和统计分析。结果表明，地质灾害的主要控制因素可分为三大类：地质环境因素、气候气象因素和人类活动因素，其中地质环境因素又可分为构造不稳定因素、斜坡不稳定因素和地面不稳定因素。指出，在广东沿海地区，除了地震灾害外，陆地表层地质灾害的主控因素是气候气象因素和人类活动因素，这是与山区以地质环境因素(尤其是内动力作用)为主是不相同的。降雨强度和时间、台风雨和风暴潮以及人类活动等对边坡和植被的改造是在沿海地区现有的地质环境背景下地质灾害多发的主要动力源。 相似文献
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The contents and distributions of CaCO3,Fe2O3.FeO and free Fe2O3 in the Weinan loess section of Shaanxi Province of China were investigated through dense sampling.The results show that the contents of CaCO3 and the ration of Fe2O3/FeO may be chosen as proxy in dices for the precipitation and temperature changes in the formation time of the strata,respectively.According to these geochemical indices,six stages of plaeoclimate evolution are proposed in this region since 142 ka B.P.,and secondary climate changes are discussed as well based on the curves of geochemical indices. 相似文献
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第四纪沉积地球化学是研究第四纪时期化学元素及其同位素在地壳中的分布与演化规律的科学。它着重研究元素及其同位素在不同成因类型的第四纪沉积物中分市、分配、迁移和富集的规律。距今2—3Ma以来的第四纪是地球历史的最新篇章。第四纪沉积物作为第四纪地质过程在特定的地质环境中所形成的产物,留下了许多自然环境变迁的遗迹,含有它们形 相似文献
39.
黄河中游地区马兰黄土微量元素分布图 总被引：3，自引：0，他引：3
应用黄河中游地区约340块马兰黄土(和有关沉积物)样品中Zn、Cu、Mn、Co、Ni、Mo六个微量元素的分析资料，编制了该区黄土微量元素分布图。分布模式图清楚表明，各元素的含量均自西北向东南逐渐增加，并明显地呈带状分布。这分布规律除受黄土粒度成分的控制外，并与区域的矿物成分和黄土堆积时生物气候环境的差异有关。黄土微量元素分布图对黄土区农业利用和人类生存环境评价有重要参考价值。 相似文献