西藏羌塘盆地东部中-上侏罗统沉积特征及沉积相划分   总被引：1，自引：2，他引：1  

张玉修  张开均  李勇  李亚林  谢尧武  黎兵 《大地构造与成矿学》2007,31(1):52-62

详细野外剖面测量基础上,对羌塘盆地东部中-上侏罗统剖面主要岩类的宏观特征(颜色和构造)、物质组分、结构及磁化率等特征进行系统研究,研究区碎屑岩主要为砾岩、砂岩、粉砂岩和泥岩等岩类,磁化率值呈现低→高→低→高→低(雀莫错组→布曲组→夏里组→索瓦组→雪山组)的规律性变化。综合沉积特征显示雀莫错组和雪山组主要为河流相-河控三角洲相沉积,布曲组为碳酸盐缓坡相沉积为主,夏里组主要为潮坪-泻湖相沉积,索瓦组主要为混积陆棚-泻湖-潮坪相沉积,中-晚侏罗世羌塘盆地古水深在下降的总趋势中呈现浅→深→浅→深→浅的升降旋回,盆地沉积中心由东向西迁移,区域构造演化和全球海平面变化共同控制了盆地沉积面貌。  相似文献   

Structural and fabric analyses of basal slip zone of the Jin’nosuke-dani landslide, northern central Japan: its application to the slip mechanism of decollement     

Kiichiro Kawamura  Yujiro Ogawa  Norio Oyagi  Tetsuro Kitahara  Ryo Anma 《Landslides》2007,4(4):371-380

We describe in detail the deformation structures and textures of a large-scale landslide body that developed in the Betto-dani Valley in northern central Japan. We studied the shape-preferred orientation of clasts and clay flakes and the development of internal shear planes within the slip zone of the landslide. The slip has an average rate of 5–10 cm/year under the overburden pressure of approximately 1.6 MPa; these values are similar to those of the proto-decollement zone of the Nankai accretionary prism in SW Japan. The anisotropy of magnetic susceptibility of samples obtained from the slip zone reveals that the long axes of clay flakes define an imbricate structure. The slip was due to a long-term periodical creep, which occurs during the thaw seasons with an average slip rate of 0.16–0.32 μm/min. During the creep, the long axes of grains including clay flakes in the slip zone are developed from parallel to perpendicular to the slip direction. The observed textures provide a clue to elucidate the deformation textures and process in the decollement zone of the Nankai prism.  相似文献   

Assessment of regional karstification degree and groundwater sensitivity to pollution using hydrograph analysis in the Velka Fatra Mountains, Slovakia     

Peter Malik 《Environmental Geology》2007,51(5):707-711

Hydrograph analyses of groundwater depletion process in the spring were used for estimation of karstification degree and groundwater sensitivity to pollution in the whole catchment area. Differences of individual depletion hydrographs enable assessment of the anticipated extent of absorption, attenuation and self-purification processes during the groundwater penetration through the rock environment between its infiltration and its outflow in the spring. The method was applied in the SW part of the Velka Fatra Mountains (Slovakia) “Tlsta” hydrogeological structure. In total, 209 individual recession curves from 20 gauged springs were analyzed. Depending on characteristic groundwater depletion hydrographs with independent sub-regimes, categories of groundwater sensitivity to pollution were defined. Finally, resulting sensitivities to pollution were linked to lithostratigraphical units in the area.  相似文献   

Use of variograms for field magnetometry analysis in Upper Silesia Industrial Region     

J. Zawadzki  P. Fabijańczyk 《Studia Geophysica et Geodaetica》2007,51(4):535-550

Measurements of topsoil magnetic susceptibility are often used for quick assessment of soil contamination of anthropogenic origin, with heavy metals or other pollutants. However, because of complicated correlations between low-field magnetic susceptibility (shortened to magnetic susceptibility) of topsoil and soil pollution, the outcome of a field magnetometry survey can not be related directly to soil pollution. For each case study, the results should be interpreted on their own taking into account not only the type of pollution but also pedogenic, biogenic and environmental factors. In practice, it is very difficult to measure and consider all these factors. Here we illustrate the merit of geostatistical methods, which are focused on the spatial variability of a phenomenon, in the interpretation of soil magnetometry results. This article presents the analysis of spatial variability of top soil layers magnetic susceptibility-within the Upper Silesia Industrial Region (USIR)-using semivariance analysis. It also explains how to adjust the sampling density of field magnetometry measurements to spatial variability of the soil pollution as well as to the spatial scale of the investigated area. For this purpose, the values of magnetic susceptibility have been measured by using various sampling densities at areas of different size located within USIR. This enabled to determine the main scales of magnetic susceptibility spatial variability of soils within USIR using semivariance. A few distinct scales of variability were found from the site scale to a more regional scale. Variability ranges of 30 km, 12 km, and 5 km refer to the large regional scale, whereas smaller ranges of few hundreds down to a few tens of meters, can be attributed to the local (site) scale. In addition, the precision of the measuring campaigns, performed within USIR with different sampling densities, was compared through the analysis of the spatial variability of the soil magnetic susceptibility signal by using ordinary kriging. jarek97@yahoo.com, piotr.fabijanczyk@is.pw.edu.pl  相似文献   

酒泉地区香蕉上市量与气象灾害的关系及预警系统     

郭良才  石奋字  岳平  王月琴 《干旱气象》2002,20(2):14-15

文中通过对香蕉运输过程中气象灾害的分析 ,总结出了香蕉运输过程中气象灾害发生的规律 ,据此建立了一套防灾减灾的预警系统 ,并对采用该系统前后的气象灾害进行了对比分析  相似文献   

近12000年以来北京地区地球磁场变化机理探讨   总被引：3，自引：0，他引：3       下载免费PDF全文

朱日祥  刘青松  郭斌 《地球物理学报》2001,44(2):211-218

距今12000年以来北京地区地球磁场长期变化由长周期(大于1000年)和短周期(约500年)两部分组成，长周期和短周期分量分别受控于漂移场和稳定场的变化.与日本地区相比，北京地区地球磁场最显著的特征是在距今(5110-4670)±110年之间曾发生短极性漂移事件，这样的短极性地磁事件可能与地球外核流体运动的异常变化有关.  相似文献   

A Late Pleistocene palaeoclimate record based on mineral magnetic properties of the entrance facies sediments of Kulna Cave, Czech Republic     

P. Sroubek  J. F. Diehl  J. Kadlec  K. Valoch 《Geophysical Journal International》2001,147(2):247-262

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塔里木盆地南缘沉积物磁化率变化与历史时期环境演化   总被引：3，自引：2，他引：3  

钟巍  舒强  熊黑钢  塔西甫拉提·特依 《干旱区地理》2001,24(3):212-216

磁化率作为一种重要的环境指标，在恢复气候环境演变方面得到了较为广泛的应用。本研究表明，塔克拉玛干沙漠南缘沉积物的低频磁化率对于本地区环境的演变反映较为敏感，因此本文以低频磁化率为主导指标，结合其它地质记录，对尼雅地区的古气候环境进行了恢复，研究结果表明：近4000年来尼雅地区的气候环境以干旱化为主，但期间仍有几次相对干湿的波动，共经历了3次相对湿润期和3次相对干旱期。据此恢复出的古气候环境与其它环境指标恢复出的结果具有较好的吻合性，不仅具有鲜明的区域性特征，同时也具全球性的一致性。  相似文献   

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  

郝青振  郭正堂 《中国科学D辑(英文版)》2001,44(6):566-576

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   

Algorithm of Calculation of Lyapounov Coefficients for Analysis of Chemical Autooscillations, as Applied to Calcite Crystallization Model     

N. A. Bryxina  V. S. Sheplev 《Mathematical Geology》2001,33(8):993-1010

The numerical algorithm of calculation of Lyapounov coefficients (L _k) of any order is developed. The apparatus of analytical calculations is not used in this algorithm. The proposed algorithm is of use for usual computer languages and allows us to find the numerical value of L _k for any k and to make complete qualitative analyses of dynamic models on the plane.  相似文献