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911.
Quantitative measurements on the paleo-weathering intensity of the loess-soil sequences and implication on paleomonsoon 总被引:2,自引:0,他引:2
The loess-soil sequences in northern China provide a near continuous record of Quaternary paleoclimate. The pedogenetic intensity
of the sequences is closely linked with the variations of the East Asian summer monsoon. In this study, 2181 samples from
the Changwu and Xifeng loess sections are analyzed and two high-resolution paleo-weathering timeseries of the last 1.2 Ma
are generated, using the ratio of CBD extractable free Fe2O3 (FeD) versus the total iron (FeT). This new index is compared with micromorphological features, low-frequency magnetic susceptibility,
frequency-dependent magnetic susceptibility, and the Rb/Sr ratio[5,6]. The results suggest that the FeD/FeT ratio is able to better reflect the degree of soil development. Since the chemical
weathering of loess in the Loess Plateau region mainly depends upon the summer precipitation and temperature under modern
climate condition, which are closely associated with strength of summer monsoon, and the chemical weathering intensity of
loess primarily reflects the variations of the summer monsoon circulation. 相似文献
912.
913.
914.
苏南地区地热资源研究 总被引:2,自引:0,他引:2
在充分收集区域地质,水文于质,物化探及地热资料的基础上,分析了苏南地区地下热水的形成和赋存的背景,条件,规律及特征,并进行地下热水的划分与预测,为进一步的研究,勘察,开发提供的依据。 相似文献
915.
东南极伊利莎白公主地LGB65点的雪层密度与剖面特征 总被引:5,自引:8,他引:5
对东南极冰盖伊利莎白公主地LGB65点的50m雪芯及雪坑进行了雪层密度与剖面分析。结果表明,该处雪的密实化过程属冷型落实化类型,第一和第二临界密度深度分别为10.4m和60.4m深霜不育,雪层中为数不多的雏形深霜层厚度仅几厘米,多分布在冰壳层的上、下两侧,16.0m以上,发芯透光性的变化不明显,之下,透光性逐渐表现出韵律变化,雪层中辐射壳和风壳频繁出现,其中辐射壳可作为划分年层的重要依据,综合雪层内的各种层位特征,初步划分出LGB65雪芯的年层约为243a,总的年平均积累率为131.9mm,20世纪60年代年积累率低于平均水平,70年代中期以后,;积累率出现大幅度增加,进250a来该处的年积累率呈增大趋势。 相似文献
916.
东太平洋中国开辟区沉积物中热水活动的矿物学及地球化学证据 总被引:5,自引:0,他引:5
通过对东太平洋多金属结核中国开辟区表层沉积物和短柱状沉积物的系统观察和分析,首次根据矿物学和地球化学两方面的证据,发现中国开辟区沉积物中热水活动及其产物的存在。X射线衍射分析表明,沉积物样品中普遍含有重晶石,部分样品中含量高达10%以上,扫描电镜观察发现,重晶石均为完整自形晶,并与同为自形的石英及钠长石共生。根据本区重晶石的地质背景及结晶形态,可以认为它的形成环境与加利福尼亚湾瓜伊马斯盆地(Guaymas)相似,属热水成因,伴生的石英和钠长石亦为常见的热水矿物,。这一共生组合的形成温度不低于70℃。地球化学研究发现,在柱状沉积物剖面上,Ba的垂向分布有两种类型,一种为平稳型,在一定深度范围内无明显变化。另一种为跃升型,并伴有其他活泼组分的同步变化,跃升型可视为热水活动在沉积历史上的记录,迄今为止,热水矿物组合主要见于东区的表层沉积物,而在西区,Ba在沉积物中的富集主要见于10cm以下层位,根据沉积速率推算,在中国开辟区西区的热水化活动记录比东区至少早0.1Ma。 相似文献
917.
Down-core variation in planktonic foraminifera (PF) at Site 1143 (ODP 184) has disclosed the evolution of upper water-column
structure over the last 12 Ma in the southern South China Sea. In the early Late Miocene (∽10.6–7.8 Ma), there existed a lower
percentage of total deep-dwelling species, reflecting a water thermocline deeper than that in the Middle Miocene, which resulted
from the closure of Indonesian seaway and relevant intensification of the equatorial warm current. After the increase in deep-dwelling
PF and the rising of thermocline during the late Late Miocene (7.6–6.4 Ma), the total deep-dwelling species decreased gradually
from late Late Miocene (6.4 Ma) to the Pliocene, implying the deepening of water thermocline. The evolution of thermocline
depth in the southern South China Sea reflected by the PF at Site 1143 might be a good indicator of the change of west Pacific
“warm pool”. 相似文献
918.
Variations in chemical compositions of the eolian dust in Chinese Loess Plateau over the past 2.5 Ma and chemical weathering in the Asian inland 总被引:5,自引:0,他引:5
Major and trace elements as well as strontium isotopic composition have been analyzed on the acid-insoluble (AI) phase of
the loess-paleosol sequence from Luochuan, Shaanxi Province, China. Results show that the chemical composition of AI phase
of loess and paleosols is distinctive to the average composition of upper continental crust (UCC), characterized by depletion
of mobile elements Na, Ca and Sr. The distribution pattern of elements in AI phase reveals that initial dust, derived from
a vast area of Asian inland, has suffered from Na- and Ca-removed chemical weathering compared to UCC. Some geochemical parameters
(such as CIA values, Na/K, Rb/Sr and87Sr/86Sr ratios) display a regular variation and evolution, reflecting that the chemical weathering in the source region of loess
deposits has decreased gradually since 2.5 Ma with the general increase of global ice volume. This coincidence reflects that
the aridity of Asian inland since the Quaternary is a possible regional response to the global climate change. 相似文献
919.
Anisotropy of the apparent resistivity variation rate near the epicentral region for strong earthquakes 总被引:1,自引:0,他引:1
IntroductionThe geo-electrical anisotropy before earthquake is of special significance for the prediction of earthquake location and for the research on crustal stress status near the epicentral region. The anisotropy has been studied from various aspects (CHEN, et al, 1983; QIAN, et al, 1985, 1996; LU, et al, 1990a; MAO, et al, 1995; RUAN, et al, 1999). But the anisotropic phenomena presented by geo-electrical data are not practically satisfactory and not clear as compared with the res… 相似文献
920.
Fabrizio Eva 《GeoJournal》2001,52(4):295-301
Discussion of the future of Europe continues to be a marginal political issue, partly because of the resistance of states, on both the practical (bureaucratic) and conceptual levels, created by the government leaders and heads of state. In turn, the nation-states are challenged from within by independent and separatist movements that have laid bare the fundamental hypocrisy of rhetorical discussions of the principle regarding the self-determination of peoples; interfering with states (and their borders) has proven to be a taboo for Europe. The growing flexibility of the globalised economy should be paralleled by a growing flexibility in the conception of the division and political organisation of territory, but this is not the case. Further inflexibility stems from the socio-economic inequity that we accept in our daily lives as normal, in particular as regards inequality in the use and division of territory. Equality, or better egaliberté (equality and liberty), is a sufficiently dynamic and flexible concept to be taken as a point of reference in envisaging the society, Europe, and world of tomorrow. It is only through the concept of egaliberté that we can imagine a Europe based on relations between regions that are conceived and organised on multiple scales and not as region-nations conceived on the basis of ethnicity or in the name of supposed cultural homogeneity. 相似文献