A multivariate statistical and geostatistical study on the geochemistry of allochtonous karst bauxite deposits in Hungary     

Bárdossy  George  Kovács  Ó. 《Natural Resources Research》1995,4(2):138-153

A geochemical evaluation of the Szc-Halimba-Kisld area, Hungary, covering an area of more than 200 km² is presented using different statistical and geostatistical methods. The study area is a representative example of allochtonous karst bauxite accumulation. The three groups of deposits studied here have been explored and mined since 1950. Several thousand boreholes have been drilled, and bauxite cores were analyzed for the five main chemical components. A total of 80,000 pleces of analytical data were processed, followed by a geological examination of borehole logs and of mining excavations.The quantitative geochemical evaluation of the data set led to both geochemical and practical results: The geochemical behavior of the allochtonous, clastic karst bauxite deposits differs essentially from that of the autochtonous and parautochtonous ones, as well as that of the lateritic bauxite deposits. The deposits of the study area can be split into several subsequent geochemical-sedimentological units, each representing an event of bauxite transport and accumulation. Clear regional patterns can be revealed in the composition of these units. The geostatistically measured chemical variability of the geochemical units is rather different, the lowest units showing the smallest variability. The interrelations of the main chemical components are weaker and more irregular in the studied deposits than in the autochtonous lateritic bauxite deposits. Additional local genetic features, such as transport routes, can be delineated by the methods applied. Within each deposit, local changes of chemical composition and of its variability can be determined more precisely. These results can be used in bauxite prospecting and exploration, because areas of high or low bauxite quality can be predicted.  相似文献   

Analysis on the sources of mercury in soils in the Chengdu Basin, China     

Limin REN Bing QIN Wenchun TANG Zhendong MA Yikeng HU 《中国地球化学学报》2006,25(B08):10-10

Mercury is a pollutant of concern due to its toxic and bioaccumulative properties. Studies on the distribution and hazard of mercury in the environment are mainly focused on its forms, toxicity and the environment standard, and progresses and results have been achieved. But these studies in the past were concentrated on the scales of laboratory or smaller districts merely, such as a small unit of mineral area, vegetable base, paddy field, lake, etc. Multi-target regional geochemical survey carried out by China Geological Survey from the 1990s to now is a fundamental and commonweal geological survey, large-scale and systematical inquisition and research were conducted in 19 provinces （or municipalities directly under the Central Government） in the eastern overlay region of China, and the purpose is to provide the basic geochemical data for national economic construction, adjustment of industrial and agricultural structures and sustainable social development. Geochemical studies aim at investigating soils in these regions and 52 elements have been tested, producing a great amount of data at the same time. Methods： based on the data from 3061 samples of surface soil and 832 samples of deep soil from the project of multi-purpose geochemical survey in the Chengdu Basin, Sichuan, China, this paper describes the correlation relationship between Hg and other 48 elements and their spatial distribution in surface and deep soils of these areas by applying the method of linear regression and factor analysis.  相似文献   

Présence d'une mangrove à Avicennia au Miocène moyen dans la région de Digne (Alpes-de-Haute-Provence,France) : implications stratigraphiques et paléoclimatiques     

Jean-Jacques Châteauneuf  Hugues Bauer  Isabelle Cojan 《Comptes Rendus Geoscience》2006,338(3):197-205

Avicennia pollen grains have been discovered in marine facies from the Middle Miocene deltaic series of Châteauredon (southeastern France). Based on the local stratigraphy, an age between 15.8 and 16.5 Ma is proposed for these grains. The age and the transgressive context of the Avicennia bearing-levels are in agreement with the maximum extension of the mangrove known in the western Mediterranean during interval N8–NN4 pro parte, in relation with the Langhian highstand. This mangrove occurrence at 42°N latitude during Middle Miocene is a more northern witness of the mangrove sites known in Languedoc and Provence areas. It also implies a lower climatic gradient than today. To cite this article: J.-J. Châteauneuf et al., C. R. Geoscience 338 (2006).  相似文献   

Relations between climatic variability and hydrologic time series from four alluvial basins across the southwestern United States   总被引：1，自引：3，他引：1  

R. T. Hanson  M. D. Dettinger  M. W. Newhouse 《Hydrogeology Journal》2006,14(7):1122-1146

Hydrologic time series of groundwater levels, streamflow, precipitation, and tree-ring indices from four alluvial basins in the southwestern United States were spectrally analyzed, and then frequency components were reconstructed to isolate variability due to climatic variations on four time scales. Reconstructed components (RCs), from each time series, were compared to climatic indices like the Pacific Decadal Oscillation (PDO), North American Monsoon (NAM), and El Niño-Southern Oscillation (ENSO), to reveal that as much as 80% of RC variation can be correlated with climate variations on corresponding time scales. In most cases, the hydrologic RCs lag behind the climate indices by 1–36 months. In all four basins, PDO-like components were the largest contributors to cyclic hydrologic variability. Generally, California time series have more variation associated with PDO and ENSO than the Arizona series, and Arizona basins have more variation associated with NAM. ENSO cycles were present in all four basins but were the largest relative contributors in southeastern Arizona. Groundwater levels show a wide range of climate responses that can be correlated from well to well in the various basins, with climate responses found in unconfined and confined aquifers from pumping centers to mountain fronts.  相似文献   

Impacts of Holocene climatic variations on alluvial fan activity below snowpatches in subarctic Québec     

Violaine Lafortune  Louise Filion  Bernard Htu 《Geomorphology》2006,76(3-4):375-391

In the Lake Guillaume-Delisle area of subarctic Québec, storm-generated alluvial fans have been active sporadically throughout the Holocene. In this study, we propose that the persistence of late-lying snowpatches in fan catchments during Holocene cold episodes promoted alluvial fan activity by lowering the precipitation threshold required to trigger a torrential event. This hypothesis was tested by characterizing the depositional processes responsible for alluvial fan formation below snowpatches, and by reconstructing the Holocene alluvial fan activity. Stratigraphic and sedimentary analyses conducted on seven alluvial fans revealed that they were deposited by torrential activity leading to waterlaid, transient, or hyperconcentrated deposition. The chronology of the storm-generated alluvial fans — based on 22 radiocarbon dates — indicates that torrential activity was enhanced during the cooler Late Holocene (i.e., after ca. 3500 cal. yr BP). Snowier winters and cooler summers were beneficial to nival activity, allowing the persistence of larger snowpatches throughout the summer and fall seasons. Rainfall-induced thaw of such snowpatches during rainstorm events is inferred to have contributed to alluvial fan activity by increasing water availability. Three peaks of alluvial activity occurred during the Late Holocene (2950–2750, 1900–1400, and 800–300 cal. yr BP) and are indicative of increased storminess resulting in higher fan activity. Increased fan activity during cooler episodes was concurrent with increased runoff activity in the immediate pronival area. This stresses the importance of nivation below snowpatches and pinpoints the role of nivation in enhancing geomorphological activity during period of cooler and more humid climate in subarctic environments.  相似文献   

On global forces of nature driving the Earth’s climate. Are humans involved?     

L. F. Khilyuk  G. V. Chilingar 《Environmental Geology》2006,50(6):899-910

The authors identify and describe the following global forces of nature driving the Earth’s climate: (1) solar radiation as a dominant external energy supplier to the Earth, (2) outgassing as a major supplier of gases to the World Ocean and the atmosphere, and, possibly, (3) microbial activities generating and consuming atmospheric gases at the interface of lithosphere and atmosphere. The writers provide quantitative estimates of the scope and extent of their corresponding effects on the Earth’s climate. Quantitative comparison of the scope and extent of the forces of nature and anthropogenic influences on the Earth’s climate is especially important at the time of broad-scale public debates on current global warming. The writers show that the human-induced climatic changes are negligible.  相似文献   

水环境容量的影响因素及分析研究     

孙秀喜  冯耀奇 《地下水》2005,27(5):389-391

本文采用流量级频率分析和统计分析方法,对黄河下游流量及泥沙含量对水环境容量的影响进行了研究分析.分析结果:河流在平滩流量时不仅输沙能力最大[8],而且输运污染物能力也最大,黄河下游水环境容量萎缩是平滩流量降低的必然结果.  相似文献   

新疆塔里木河流域平原区土地利用覆盖变化及其对生态环境影响分析   总被引：1，自引：0，他引：1  

郭健 《地下水》2005,27(6):493-496

分析了塔里木河流域平原区近十余年土地利用覆盖变化和用水量的变化情况,对两者间的关系进行了研究,提出了为防止生态环境进一步恶化应采取的对策.  相似文献   

克拉玛依夏季日最高气温与08时 850hPa温度的关系   总被引：2，自引：0，他引：2  

冀新琪 《沙漠与绿洲气象(新疆气象)》2005,28(4):12-13

根据克拉玛依40年气温观测资料,分析克拉玛依夏季日最高气温与08时850hPa温度的关系,寻找预报夏季日最高气温关键因子.  相似文献   

时间序列转折突变点检测的线性函数方法   总被引：6，自引：2，他引：6  

曹杰  陶云  田永丽 《高原气象》2002,21(5):518-521

根据转折突变的定义，在引入线性半截多项式的前提下，提出检测时间序列转折突变点的一种新方法。此方法不仅能找出时间序列中存在的多个转折突变点，而且使得检测到的突变点通过统计显著性检验。应用此方法对北半球1851—1990年年平均气温距平及其11年滑动平均序列，1901—1999年昆明5月降水及其11年滑动平均的降水序列分别进行了检测。发现北半球年平均气温距平在1879、1889、1939和1973年附近出现了年际转折突变，在1878、1888和1941年以及1972年出现了年代际尺度的转折突变；昆明5月雨量不存在年际转折突变点，但昆明5月雨量在1918、1966以及1978年附近出现了年代际尺度转折突变。  相似文献