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John Stamatakos Rob Van Der Voo Ben Van Der Pluijm Stephen Potts Trond Torsvik 《Geophysical Journal International》1994,119(3):1009-1013
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Li ChuanXin Guo ZhaoJie Meng ZiFang Li HaiYan Zhang ZhiCheng Wu ChaoDong 《中国科学D辑(英文版)》2007,50(4):544-554
Analyses of rock-magnetic properties of Neogene sediments of the Taxihe section, northern Tianshan Mountains, show that the section can be classified into three categories including lacustrine facies, fluvial facies and alluvial facies, which correspond to the lower, middle and upper of the Taxihe section respectively. The magnetic minerals of the lacustrine facies may be affected by the process of weath- ering, lithogenesis and biolithogenesis besides the source of the sediments. The natural remanence intensities are between 10-3 A/m and 10-2 A/m. The minerals are dominated by magnetite and the high coercive magnetic mineral may be goethite. The magnetic grains are the mixture of PSD SD or SD SP. The natural remanence intensities of the strata of fluvial facies are between 10-2 A/m and 10-1 A/m, about ten times that of the lacustrine facies. The magnetic minerals are mainly magnetite and hematite, and the magnetic grains are mainly PSD. The characteristic remanence (ChRM) carriers are magnetites. In the alluvial facies, the natural remanence intensities are mostly less than 1×10-2 A/m. The magnetic minerals of the series are dominated by magnetite and hematite, almost the same as the fluvial facies. But the difference is that most of the stepwise demagnetization can reveal two components and the ChRM carriers are hematites. The magnetic grains are PSD in terms of the hysteresis parameters. 相似文献
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利用全国660个常规气象站40年(1961-2000年)整编气象资料.采用逆距离权重反比法、样条函数法和普通克立格法等常用的3种插值方法,分析了直接插值法和综合余项法对气温插值的影响,提出了去除气温形成中的确定性部分后,以随机项进行插值可提高气温插值精度。并从空间上、时间上对比眲不同插值方法的误差,最后分析了气象站的空间分布密度对插值方法的敏感性。验证结果表明:除个别月份外,综合余项法的各项平均绝对误差均在1℃以内,比直接插值法减小了0.6～1.6℃,精度提高了38%～85%;且综合余项法的精度不依赖于台站密度的大小、插值方法的不同,具有较高的精确性和稳定性,这说明影响空间插值精度的关键因子并非是气象观测站点密度的提高、空问插值方法的改进。 相似文献
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Palaeomagnetism of the loess/palaeosol sequence in Viatovo (NE Bulgaria) in the Danube basin 总被引：1，自引：0，他引：1
Diana Jordanova Jozef Hus Jordan Evlogiev Raoul Geeraerts 《Physics of the Earth and Planetary Interiors》2008,167(1-2):71-83
The results of a palaeomagnetic investigation of a 27 m thick loess/palaeosol sequence in Viatovo (NE Bulgaria) are presented in this paper. The sequence consists of topsoil S0, seven loess horizons (L1–L7) and six interbedded palaeosols (S1–S6) overlying a red clay (terra rossa) complex. Magnetic viscosity experiments, IRM acquisition, AMS analysis and NRM stepwise alternating and thermal demagnetisation experiments of pilot samples were implemented for precise determination of the characteristic remanence and construction of a reliable magnetostratigraphical scheme. Analysis of IRM acquisition curves using the expectation – maximization algorithm of Heslop et al. [Heslop, D., Dekkers, M., Kruiver, P., van Oorschot, H., 2002. Analysis of isothermal remanent magnetization acquisition curves using the expectation – maximization algorithm. Geophys. J. Int., 148, 58–64] suggests that the best fitting is obtained by three coercivity components. Component 1 corresponds to SD maghemite/magnetite, while component 2 is probably related to the presence of oxidised detrital magnetites. The third component shows varying coercivities depending on the degree of pedogenic alteration of the samples and probably reflects the presence of detrital magnetite grains oxidised at different degree.
The relevance of the Viatovo section as a key representative sequence for the loess cover in the Danube basin is confirmed by the presence of geomagnetic polarity changes in the lower part of the sequence. The youngest one recorded in the seventh loess unit L7 can be identified as corresponding to the Matuyama/Brunhes palaeomagnetic polarity transition. Two normal magnetozones were found in the red clay complex, probably corresponding to the Jaramillo and Olduvai subchronozones of the Matuyama chron. 相似文献
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Marcos A. E. Chaparro Juan M. Lirio Héctor Nuñez Claudia S. G. Gogorza Ana M. Sinito 《Environmental Geology》2005,49(1):30-43
Magnetic properties of lagoon and stream sediments from Chascomús area (Buenos Aires Province) and the relevance of various magnetic parameters as giving pollution status are studied in the present work. This work is focussed on magnetic parameters, such as concentration-dependent (magnetic susceptibility, saturation anhysteric and isothermal remanent magnetisation) and feature-dependent parameters (S-ratio, coercivity of remanence, anhysteric susceptibility/magnetic susceptibility-ratio), as pollution indicators. Firstly and most importantly, different magnetic parameters and chemical measurements were correlated in order to investigate their goodness, obtaining the best results for feature-dependent magnetic parameters. Coercivity of remanence correlate very well with chemical variables, showing correlations at high level of significance up to 0.9094, and the anhysteric susceptibility/magnetic susceptibility-ratio also shows very good correlations (up to 0.8376). Some results and advantages of using a new experimental method in order to discriminate hard and soft magnetic phases are also shown. This method uses alternately backfield isothermal remanent magnetisation and alternating field demagnetisation. From the experimental separation, the presence of hard magnetic phases in some samples was confirmed. 相似文献
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根据江苏省1960—2009年54个气象台站常规气象观测资料,利用Penman-Monteith公式计算了全省各地区50 a的逐日潜在蒸散量,结合逐日降水量,推算出了相对湿润度指数值,并采用国家标准《气象干旱等级》(GB/T20481-2006)中的相对湿润度分级指标对全省干湿状况进行了评估,分析其时空变化特征。研究表明:1)就全年而言,江苏省半干旱区与湿润区各占50%左右的面积,其中淮北、江淮北部、苏北沿海的北部为半干旱区,江淮南部、苏北沿海的南部、沿江、苏南地区为湿润区;2)降水量和潜在蒸散量是影响相对湿润度指数的两个关键因子,降水量的变化对相对湿润度的时空分布起着主导作用,潜在蒸散量起着辅助作用。3)江苏省1 a中冬季的南北气候干湿反差最大、夏季最小,湿润区范围夏季最大、秋季最小,半干旱区范围秋季最大、夏季没有,干旱区范围春季最大、夏季和秋季没有。夏季气候最湿润、春季气候最干燥。4)淮北和苏北沿海地区的相对湿润度指数年变化呈"单峰型",江淮、沿江和苏南地区的年变化呈"双峰型",苏北沿海地区相对湿润度年内变化最大,沿江地区最小。 相似文献
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