Vent area and depositional mechanisms of the Upper Member of the Neapolitan Yellow Tuff (Campi Flegrei, Italy): new insights from directional fabric through image analysis     

Laura Valentini  Bruno Capaccioni  Piermaria Luigi Rossi  Roberto Scandone  Damiano Sarocchi 《Bulletin of Volcanology》2008,70(9):1087-1101

In order to provide new information about the source area and depositional mechanisms of the Upper Member of the Neapolitan Yellow Tuff (NYT), a prominent pyroclastic deposit of the Campi Flegrei Volcanic District (southern Italy), statistics on directional fabric, by means of computer-assisted image analysis on 32 rock samples, were compiled. Seventeen samples were collected along vertical direction on two selected exposures and fifteen were taken from outcrops widely distributed all around the Campi Flegrei Volcanic District. Fabric measurements within the investigated successions reveal a vertically homogeneous direction of the mean particle iso-orientation, with considerable variability in the strength of particle iso-orientation even at cm-scale. The existence of particle iso-orientation can be related to continuous sedimentation from a concentrated bedload region beneath suspension currents, producing massive or inversely graded beds by traction carpet sedimentation. The considerable vertical variability in the strength of iso-orientation is the result of very unstable flow regimes, up to the extreme condition of discrete depositional events, with a variable combination of traction carpet and/or direct suspension sedimentation. The vertical homogeneity in the mean orientation values, found in the investigated sections, may derive from the sequential deposition of laminae to thin beds, whose relatively flat upper surfaces were unable to significantly deflect the depositional system of the following currents. According to the observed homogeneous mean particle orientation values along the investigated vertical profiles, samples collected through areal distribution are considered representative of the local paleo-flow directions of the whole deposit. The mean directions of the samples collected areally show two different coherent patterns which point to the existence of two different source areas. The first, which includes all samples from the northern outcrops, appears to converge in a narrow area about 2 km NE of the town of Pozzuoli, largely in coincidence with the inferred area on the basis of the pumice fall distribution. The second, which includes samples from Capo Miseno and Posillipo areas, points to the central part of the Pozzuoli Bay, about 4 km offshore the town of Pozzuoli.  相似文献   

Identification of fuel samples from the Prestige wreckage by pattern recognition methods   总被引：1，自引：0，他引：1  

Fernández-Varela R  Andrade JM  Muniategui S  Prada D  Ramírez-Villalobos F 《Marine pollution bulletin》2008,56(2):335-347

A set of 34 worldwide crude oils, 12 distilled products (kerosene, gas oils, and fuel oils) and 45 oil samples taken from several Galician beaches (NW Spain) after the wreckage of the Prestige tanker off the Galician coast was studied. Gas chromatography with flame ionization detection was combined with chemometric multivariate pattern recognition methods (principal components analysis, cluster analysis and Kohonen neural networks) to differentiate and characterize the Prestige fuel oil. All multivariate studies differentiated between several groups of crude oils, fuel oils, distilled products, and samples belonging to the Prestige's wreck and samples from other illegal discharges. In addition, a reduced set of 13 n-alkanes out of 36, were statistically selected by Procrustes Rotation to cope with the main patterns in the datasets. These variables retained the most important characteristics of the data set and lead to a fast and cheap analytical screening methodology.  相似文献   

一类西太平洋副热带高压双脊线过程维持机制初探   总被引：2，自引：1，他引：1       下载免费PDF全文

祁莉  张祖强  何金海  陈桦 《地球物理学报》2008,51(3):682-691

本文通过对1979~2005年5~10月发生在西太平洋地区的156个副热带高压双脊线过程进行统计分析,发现87.82%的双脊线过程的出现是因为南侧新生一脊线,而且有明显的“季节锁相”,即其发生频数在7月中旬至9月中旬有两个峰值.历年过程中最典型的“南生南存型”双脊线过程的合成分析表明该类双脊线过程形成、维持和消失与副高南侧外围东风波系统自东南向西北传播发展密切相关.500 hPa距平环流演变显示北侧脊线的减弱消失符合气候规律,东风波槽前的异常气旋仅影响副高北侧脊线位置;而东风波槽后的异常反气旋性环流有利于南侧脊线异常发展与维持,造成该类双脊线过程结束后副高异常偏南.进一步分析发现,东风波和西太平洋副热带高压的相互作用改变了副高区域垂直运动分布.这一方面改变了经向风的分布,使500 hPa副高南侧脊线区域地转涡度平流项发展;另一方面引起非绝热加热垂直分布不均匀,在两脊线之间诱生一异常气旋性环流,在南侧脊线区生成异常反气旋环流.因此,东风波与西太平洋副热带高压的相互作用可能会造成副高的不连续南退,这对副高预报有一定预示作用.  相似文献   

河南省区域暴雨的客观分型   总被引：3，自引：0，他引：3  

布亚林  郑世林 《气象与环境科学》2000,(1):8-9

从多层聚类分析入手,利用微机对１９８０～１９９５ 年河南省２１３ 场区域暴雨过程的５００ ｈＰａ 高度场进行客观分型,得出了４ 类天气形势及其与暴雨落区的对应关系。  相似文献   

数字地面模型在土地整治中的应用研究     

王云帆  王庆 《国土资源信息化》2011,(5):46-48,31

DTM作为地理空间定位的数字数据的集合,在GIS空间数据库中,能够反映地理基础、社会经济、资源与环境和地形等多方面的信息。本文在综述数字地面模型的建立方法的基础上,应用DTM进行坡度分级和区域设计模型叠加模式,探讨了三维地表模型在土地整治中应用。  相似文献   

全球铜矿资源储量格局   总被引：1，自引：0，他引：1  

王威 《国土资源情报》2014,(6):38-41

本文通过对铜矿资源国的储量的整理和分析,得到全球铜矿资源储量格局,利用储采比进行铜矿资源保障程度论证,并结合矿产资源勘查特点,对不同资源储量国提出不同的工作重点,从而有针对性地开展铜矿资源的境外合作。  相似文献   

中高纬度大气遥相关动力学及其对东亚冬季气候影响的研究进展   总被引：6，自引：1，他引：5       下载免费PDF全文

TAN Benkui  CHEN Wen 《Acta Meteorologica Sinica》2014,28(5):780-802

北半球热带外大气存在多种形态的大气遥相关。按其空间结构,可以分为两类：（1）异常中心为南北分布的偶极子型（例如北大西洋涛动、北太平洋涛动）;（2）异常中心呈波列型（例如北太平洋/北美型遥相关、欧亚型遥相关）。这些遥相关活动及其变异,不仅对遥相关控制的地区,而且对与遥相关相距很远的地区的天气和气候也产生影响。研究大气遥相关的形成机理及其天气气候影响,是进行短期气候预测的基础。近十多年来北半球中高纬度的大气遥相关动力学研究取得很大进展,在此对一些主要进展进行总结,特别关注影响中国天气、气候的大气遥相关及其影响机理方面的研究进展。  相似文献   

Seasonal patterns of tidepool macroalgal assemblages in the North of Portugal. Consistence between species and functional group approaches     

M. Rubal  P. Veiga  R. Vieira  I. Sousa-Pinto 《Journal of Sea Research》2011,66(3):187-194

Macroalgae are useful organisms to monitor the environmental quality and to detect impacts due to anthropogenic activities. However, it is very important to identify the scales of variation in natural assemblages, particularly for the detection of environmental impacts. Otherwise, changes due to anthropogenic impacts may be confused with differences due to natural temporal variability. Another important task is to determine the appropriate level of taxonomical effort needed to detect changes in the assemblage structure. Many taxonomical surrogates, at higher taxonomic levels than that of species, have been proposed but, the consistence in space and time of the results produced by surrogates with those obtained at specific level should be tested. The objectives of this study are to identify the seasonal patterns of tidepool macroalgal communities using objective procedures and to test the consistence between the patterns obtained considering data at the species level and functional groups. Results showed that the seasonal pattern obtained using functional groups and species was consistent. Tidepool macroalgal assemblages showed a seasonal pattern with significant differences between spring–summer and autumn–winter. This pattern can be explained by changes in environmental variables and the seasonal development of the dominating species. Ulva spp. and the non-indigenous species Grateloupia turuturu were the species responsible for this pattern due to their high seasonality in terms of biomass. Finally, the abundance and species diversity within the corticated functional group was proposed as indicator of environmental impacts due to its relatively constant abundance and its sensitivity to environmental impacts.  相似文献   

未来气候变化对7种荒漠植物分布的潜在影响   总被引：1，自引：0，他引：1  

吴建国 《干旱区地理》2011,34(1):70-85

利用CART(classification and regression tree,分类和回归树)模型,采用A2和B2气候情景,分析了气候变化对百花蒿、红砂、灌木亚菊、灌木小甘菊、戈壁藜、瓣鳞花和白梭梭分布范围及空间格局的影响.结果显示:气候变化下,就目前适宜分布范围,这些植物都呈现缩小趋势;就新适宜及总适宜分布范围,...  相似文献   

滨海湿地生态补偿机制建设初探   总被引：2，自引：1，他引：1  

王艳霞  张素娟  张义文 《湿地科学与管理》2011,7(4):56-58

初步探讨了我国滨海湿地生态补偿机制框架,确定了生态补偿的范围为生态地位重要、生态环境脆弱的滨海湿地,补偿主体为政府和湿地开发利用者,补偿客体为滨海湿地管理者和保护者;提出了补偿标准测算应注意的问题和可供选择的方法;从资金补偿和项目补偿两个方面探索了补偿方式和途径;并提出了完善滨海湿地监测和管理系统、明晰滨海湿地产权、推进生态补偿市场化运作、完善生态产业等生态补偿实施对策措施。  相似文献