共查询到20条相似文献，搜索用时 31 毫秒
1.
Oluwole Ameyan 《Applied geography (Sevenoaks, England)》1985,5(4):309-323
In an attempt to elucidate the spatial variability of soils as a preliminary to detailed mapping, 100 sites within a single parent material stratum were sampled along a grid of parallel traverses. The data collected have been subjected to statistical analyses, notably determination of coefficient of variation (CV) and principal component analysis (PCA). These analyses indicate that the soils of the area of study display marked variability which does not correspond to the variability in parent material, that the spatial variations of soil chemical properties are mainly due to variations in both the clay and organic matter contents of the soils, and that textural characteristics may be used as differentiators to produce groups with precise edaphological meanings in this environment. Such groupings must, however, take cognizance of the considerable local variations due to anthropogenic factors. 相似文献
2.
The Albian to Santonian Colorado Group in the heavy oil area of Cold Lake, east-central Alberta represents a relatively condensed
section of shale-dominated sedimentation within the Western Interior Sea. These shales form the cap rock to the underlying
Clearwater and Grand Rapids formations that are exploited for bitumen extraction. Two cores covering the entire Colorado Group
provide a unique opportunity for establishment of a stratigraphic reference in an area that has received attention only for
its heavy oil-bearing Mannville Group. Based on sedimentology, geochemistry, micropaleontology, nannofossils, and wireline
log data, the Colorado Group was subdivided into the Joli Fou, Viking, Westgate, Fish Scales, Belle Fourche, Second White
Specks, and Niobrara formations. The Niobrara Formation was subdivided further into the Verger Member, informal Cold Lake
member, and First White Specks Member. Because of this region’s small accommodation space and distance to sources of coarse
clastic sediment, disconformities are indicated lithologically by bioclastic layers and missing biozones. Foraminiferal subzones
revealed two erosional boundaries associated with the Viking Formation. Faunal and floral evidence coupled with wireline log
correlations suggest that the Middle to Upper Turonian Carlile Formation, as described from southeastern Alberta, is missing.
That extends the Middle Turonian to Coniacian unconformity, as recognized in central Saskatchewan, westwards into Alberta. 相似文献
3.
J. Thibal A. Etchecopar J.-P. Pozzi V. Barthès & J. Pocachard 《Geophysical Journal International》1999,137(3):839-846
Precise time and facies correlations between drilled holes are fundamental for a better understanding of the geological evolution of sedimentary basins. A downhole magnetic measurement device called the geological high-sensitivity magnetic tool (GHMT) has been run within two wells drilled by Gaz de France in the Landes oil-field (southwest France) as part of a gas storage exploration program. The method of interpretation of downhole magnetic measurements yielded a magnetostratigraphy within each well, allowing absolute dating and time correlations between the wells.
Magnetic susceptibility and natural gamma ray intensity are useful parameters for establishing high-resolution lithological correlations at a basin scale. We present a correlation parameter established from a simultaneous analysis of the susceptibility and the gamma ray logs within each well. The correlation parameter appears to provide a new tool for delineating lithological elements when local lithological changes are too subtle to show clear well-to-well correlations either from susceptibility logs or from gamma ray logs. This new approach is interpreted as a sensitive way to detect relative variations between the detrital and clay content of the penetrated sediment. 相似文献
Magnetic susceptibility and natural gamma ray intensity are useful parameters for establishing high-resolution lithological correlations at a basin scale. We present a correlation parameter established from a simultaneous analysis of the susceptibility and the gamma ray logs within each well. The correlation parameter appears to provide a new tool for delineating lithological elements when local lithological changes are too subtle to show clear well-to-well correlations either from susceptibility logs or from gamma ray logs. This new approach is interpreted as a sensitive way to detect relative variations between the detrital and clay content of the penetrated sediment. 相似文献
4.
应用遥感数据研究中国植被生态系统与气候的关系 总被引：48，自引：2，他引：48
应用1982-1994年NOAA/AVHRR的归一化植被指数（NDVI）资料和587个气象台站的数据对我国不同类型植被生态系统和气候的关系进行研究，首先将我国的植被类型划分为21类，在此基础上分别研究了不同时间尺度下我国不同区域，不同植被类型和气候的关系。结果表明：在多年平均状态下，植被生态系统NDVI水平主要受水分条件的影响；年内变化上，温度对植被生态系统季相变化化起着比降水略大的作用，年降水量造成了植被季相响应的差异，在年际变化上，分别研究了4个季节和整个生长期尺度上的关系，一般情形为温度和降水对植被的年际波动起着大致相反的作用，不同植被类型在不同的生长时期（季节）对气候的变化响应方式也不同，发现在植被的生长期，我国南方和北方的植被生态系统对温度和降水的响应方式相反；同时存在2个植被-气候敏感区，分别为我国北方的典型草原到森林的过渡区和云南中部部分区域。 相似文献
5.
YU-LONG XIE JI-HONG WANG YI-ZENG LIANG LI-XIAN SUN XIN-HUA SONG RU-QIN YU Department of Chemistry Chemical Engineering Hunan University Changsh People''s Republic of China 《地理学报(英文版)》1993,(6)
Principal component analysis (PCA) is a widely used technique in chemometrics.The classical PCAmethod is,unfortunately,non-robust,since the variance is adopted as the objective function.In thispaper,projection pursuit (PP) is used to carry out PCA with a criterion which is more robust than thevariance.In addition,the generalized simulated annealing (GSA) algorithm is introduced as anoptimization procedure in the process of PP calculation to guarantee the global optimum.The resultsfor simulated data sets show that PCA via PP is resistant to the deviation of the error distribution fromthe normal one.The method is especially recommended for use in cases with possible outlier(s) existingin the data. 相似文献
6.
RICHARD ASPINALL 《International journal of geographical information science》2013,27(2):105-121
Abstract This paper describes an inductive modelling procedure integrated with a geographical information system for analysis of pattern within spatial data. The aim of the modelling procedure is to predict the distribution within one data set by combining a number of other data sets. Data set combination is carried out using Bayes’ theorem. Inputs to the theorem, in the form of conditional probabilities, are derived from an inductive learning process in which attributes of the data set to be modelled are compared with attributes of a variety of predictor data sets. This process is carried out on random subsets of the data to generate error bounds on inputs for analysis of error propagation associated with the use of Bayes’ theorem to combine data sets in the GIS. The statistical significance of model inputs is calculated as part of the inductive learning process. Use of the modelling procedure is illustrated through the analysis of the winter habitat relationships of red deer in Grampian Region, north-east Scotland. The distribution of red deer in Deer Management Group areas in Gordon and in Kincardine and Deeside Districts is used to develop a model which predicts the distribution throughout Grampian Region; this is tested against red deer distribution in Moray District. Habitat data sets used for constructing the model are accumulated frost and altitude, obtained from maps, and land cover, derived from satellite imagery. Errors resulting from the use of Bayes’ theorem to combine data sets within the GIS and introduced in generalizing output from 50 m pixel to 1 km grid squares resolution are analysed and presented in a series of maps. This analysis of error trains is an integral part of the implemented analytical procedure and provides support to the interpretation of the results of modelling. Potential applications of the modelling procedure are discussed. 相似文献
7.
New expressions are derived for the standard errors in the eigenvalues of a cross-product matrix by themethod of error propagation.Cross-product matrices frequently arise in multivariate data analysis,especially in principal component analysis (PCA).The derived standard errors account for the variabilityin the data as a result of measurement noise and are therefore essentially different from the standarderrors developed in multivariate statistics.Those standard errors were derived in order to account for thefinite number of observations on a fixed number of variables,the so-called sampling error.They can beused for making inferences about the population eigenvalues.Making inferences about the populationeigenvalues is often not the purposes of PCA in physical sciences,This is particularly true if themeasurements are performed on an analytical instrument that produces two-dimensional arrays for onechemical sample:the rows and columns of such a data matrix cannot be identified with observations onvariables at all.However,PCA can still be used as a general data reduction technique,but now the effectof measurement noise on the standard errors in the eigenvalues has to be considered.The consequencesfor significance testing of the eigenvalues as well as the usefulness for error estimates for scores andloadings of PCA,multiple linear regression (MLR) and the generalized rank annihilation method(GRAM) are discussed.The adequacy of the derived expressions is tested by Monte Carlo simulations. 相似文献
8.
Long-period geomagnetic data can resolve large-scale 3-D mantle electrical conductivity heterogeneities which are indicators of physiochemical variations found in the Earth's dynamic mantle. A prerequisite for mapping such heterogeneity is the ability to model accurately electromagnetic induction in a heterogeneous sphere. A previously developed finite element method solution to the geomagnetic induction problem is validated against an analytic solution for a fully 3-D geometry: an off-axis spherical inclusion embedded in a uniform sphere. Geomagnetic induction is then modelled in a uniform spherical mantle overlain by a realistic distribution of oceanic and continental conductances. Our results indicate that the contrast in electrical conductivity between oceans and continents is not primarily responsible for the observed geographic variability of long-period geomagnetic data. In the absence of persistent high-wavenumber magnetospheric disturbances, this argues strongly for the existence of large-scale, high-contrast electrical conductivity heterogeneities in the mid-mantle. Lastly, for several periods the geomagnetic anomaly associated with a mid-mantle spherical inclusion is calculated. A high-contrast inclusion can be readily detected beneath the outer shell of oceans and continents. A comparison between observed and computed c responses suggests that the mid-mantle contains more than one order of magnitude of lateral variability in electrical conductivity, while the upper mantle contains at least two orders of magnitude of lateral variability in electrical conductivity. 相似文献
9.
Piret Plink-Björklund 《Basin Research》2020,32(2):251-262
Utilizing two outcrop data sets with dip direction exposures of shallow-water (tens of meters) deltaic clinoforms, this paper quantifies sedimentary facies proportions and clinoform lengths and gradients, and links process regimes to delta clinoform dimensions. Both data sets are from foreland basins, the Cretaceous Chimney Rock Sandstone of the Rock Springs Formation from the US Western Interior, and the Eocene Brogniartfjellet Clinoform Complex 8 of the Battfjellet Formation from the Central Basin of Spitsbergen. Sedimentary facies indicate presence of both river- and wave-dominated clinothems in each data set. Facies characteristics and distribution implies that river-dominated clinothem progradation was primarily driven by deposition from weak hyperpycnal flow turbidity currents across the clinoforms, and minor slumps. Wave-dominated clinothems were constructed by wave processes rather than alongshore currents, and are also progradational subaerial clinoforms, with one exception, where the formation of a compound subaqueous clinoform set indicates erosion and sediment bypass above the wave base. Sediment distribution and lithological heterogeneity in the river-dominated clinothems is controlled by individual hyperpycnal flow events or mouth-bar collapse events, and thus by self-organization and minimal reworking that results in a heterogeneity that is difficult to predict (high entropy). The efficient reworking of river-derived sediments in wave-dominated clinothems results in predictable lithological sediment partitioning (low entropy). Clinoform dimension analyses show that although of similar sediment caliber, river-dominated clinoforms in both data sets are on average 3–4 times steeper and 3–4 times shorter than the wave-dominated clinoforms, with mean gradients of ca 4 degrees and ca 1 degree, respectively, and mean lengths of 150–230 m and 640–760 m. These results require corroboration from additional data sets, but do suggest that river- and wave-dominated delta clinoforms are likely to have distinct downdip extents (lengths) and gradients for given clinoform heights. Clinoform shape can thus be a method for differentiating ancient river- vs. wave-dominated deltaic clinoforms, in addition to their sedimentary facies, biogenic features and sandstone maturity, and helpful when incorporated into reservoir models. 相似文献
10.
de Quadros Telmo F. P. Koppe Jair C. Strieder Adelir J. Costa João Felipe C. L. 《Natural Resources Research》2003,12(1):57-65
A large number of mineral deposits are associated with hydrothermal processes, especially auriferous deposits. In such processes, studies on percolating fluids may indicate the presence of potash (K), among other elements. In this study, aerogammaspectrometric data-processing methodologies are evaluated, especially those methods based on the suppression of the primary contribution of potassium, the result of lithological and soil variations, and to environmental conditions. Resulting maps point out the contribution of hydrothermal K. This processing procedure was used because of the association of hydrothermal K and auriferous mineralizations according to the deposit model defined for the studied region. Intensity maps locate the areas with great influence of hydrothermal K. Data integration required to improve a change in the gammaspectrometric data processing in order to positively correlate hydrothermalised areas. Data integration could distinguish high and medium favorable targets for mineral exploration of lode-Au deposits in the studied region. 相似文献
11.
12.
Hendrik Vogel Bernd Wagner Giovanni Zanchetta Roberto Sulpizio Peter Rosén 《Journal of Paleolimnology》2010,44(1):295-310
Lake Ohrid is probably of Pliocene age, and the oldest extant lake in Europe. In this study climatic and environmental changes
during the last glacial-interglacial cycle are reconstructed using lithological, sedimentological, geochemical and physical
proxy analysis of a 15-m-long sediment succession from Lake Ohrid. A chronological framework is derived from tephrochronology
and radiocarbon dating, which yields a basal age of ca. 136 ka. The succession is not continuous, however, with a hiatus between
ca. 97.6 and 81.7 ka. Sediment accumulation in course of the last climatic cycle is controlled by the complex interaction
of a variety of climate-controlled parameters and their impact on catchment dynamics, limnology, and hydrology of the lake.
Warm interglacial and cold glacial climate conditions can be clearly distinguished from organic matter, calcite, clastic detritus
and lithostratigraphic data. During interglacial periods, short-term fluctuations are recorded by abrupt variations in organic
matter and calcite content, indicating climatically-induced changes in lake productivity and hydrology. During glacial periods,
high variability in the contents of coarse silt to fine sand sized clastic matter is probably a function of climatically-induced
changes in catchment dynamics and wind activity. In some instances tephra layers provide potential stratigraphic markers for
short-lived climate perturbations. Given their widespread distribution in sites across the region, tephra analysis has the
potential to provide insight into variation in the impact of climate and environmental change across the Mediterranean. 相似文献
13.
Variations in the stone covers on desert surfaces have implications for the operation of hydrological processes. Some recent attention has been given to the difficulties of identifying and quantifying relevant characteristics of stone covers. Investigation of how such characteristics vary in relation to geological and topographical controls are limited. Results are presented of a field study of the characteristics of stone covers on four lithologies in the late Tertiary to Quaternary basalt plateau of northeast Jordan. Marked variations occur in clast dimensions and the characteristics of sorting between lithologies which are likely to affect hydrological response. A more subtle control, relating to slope conditions, is superimposed on the lithological differences. R- and Q-mode factor analysis identifies groupings within the data, which demonstrate the distinctiveness of different lithologies. Characteristics of the stone covers on sites affected by human occupation are markedly different from undisturbed sites on the same lithology. 相似文献
14.
Javier Roca-Pardiñas Tomás R. Cotos-Yáñez Rubén Pérez-Álvarez 《International journal of geographical information science》2017,31(4):676-693
We propose a method to evaluate the existence of spatial variability in the covariance structure in a geographically weighted principal components analysis (GWPCA). The method, that is extensive to locally weighted principal components analysis, is based on performing a statistical hypothesis test using the eigenvectors of the PCA scores covariance matrix. The application of the method to simulated data shows that it has a greater statistical power than the current statistical test that uses the eigenvalues of the raw data covariance matrix. Finally, the method was applied to a real problem whose objective is to find spatial distribution patterns in a set of soil pollutants. The results show the utility of GWPCA versus PCA. 相似文献
15.
Annual growth rings are well-defined in some shrubby species distributed along the Patagonian steppe and provide useful information to identify the environmental factors that influence the radial growth of shrubs in the region. However, little is known about variations in ring width from these species and their relationships with local environment. In this paper we present 18 growth ring width chronologies covering the last 2–3 decades from the shrub Anarthrophyllum rigidum (Fabaceae) encompassing most of its natural range of distribution in Argentina. Interannual variations in growth were first analyzed collectively to identify common regional patterns. In addition, shrub growth at each site was compared with local climate records and site-specific characteristics. Based on a principal component analysis (PCA), sites were joined in four major groups related to the site proximity to the Andes (foothills versus Patagonian plateau) and latitude (north versus south Patagonia). The relatively similar percentage of PCA variance associated with each group reflects environmental differences among sites. Consistent with this observation, we noted large variability in the responses of the A. rigidum woody growth to regional climatic fluctuations. At most sites, this species is favored by abundant winter precipitation, warmer spring and autumn temperatures (controlling the duration of the growing season), cool summers, or a combination of these factors. However, deviations from these patterns are also recorded. Our study represents the first large-scale dendroclimatological analysis of a shrubby species in southern South America. The results presented here provide information on the main patterns and factors affecting the growth of A. rigidum in Patagonia, and may be useful for determining well-suited practices for management and conservation of this ubiquitous species. 相似文献
16.
本文利用主成分分析法提取了川西高原北部5个样点反映气温变化的树轮宽度年表的主成分年表,其中第一主成分年表(PC1)的方差贡献率为59.52%,能够较好地代表川西高原北部地区树轮宽度变化的共同特征。在器测时段内(1961-2010年),PC1年表、6-7月区域平均气温观测序列与东亚气温场的相关分布较为一致,均与中国的西北-青藏高原一带以及西伯利亚东部呈现显著的正相关(r > 0.443,p < 0.001),表明PC1年表能够反映较大空间范围的气温变化特征。器测时期,PC1年表和观测序列与全球海温场的相关分析表明,两者均与西太平洋、印度洋及北大西洋海域显著正相关,反映了在海气相互作用过程中多个海区海表温度变化可能对研究区气温变化有一定影响;而利用PC1年表在更长时间尺度(1854-2010年)及分阶段分析则发现不同阶段对区域气温起主导作用的海区有比较明显的差异,甚至在比较大的空间范围内在不同阶段出现相反的分布型,且由相关系数反映出的海气相互作用强度也具有显著的差异,气温波动较大时,海气相互作用也比较强烈。异常年分析则反映出西北太平洋和北大西洋海温异常对研究区气温异常具有持续稳定的影响。 相似文献
17.
Wilson M. Khaemba Alfred Stein 《International journal of geographical information science》2013,27(8):833-853
This paper applies generalised linear statistical techniques in a GIS to analyse wildlife data from a Kenyan wildlife reserve and its surrounding areas. Attention focuses on the spatial distribution of elephant during nine successive surveys, analysing their temporal and spatial relationship to 12 environmental covariates. A principal component analysis identifies five major determining factors, thereby reducing dimensionality in the data, while a simple spatial analysis procedure, suitable for wildlife data obtained from airborne surveys, quantfies clustering for different animal species. The number of explanatory variables appearing in abundance models is found to be subject to large variations during successive surveys with a minimum and maximum of four and eight variables, respectively. Species from highly clustered populations are found to have over 20 times more observations within short distances compared to the rest. The study concludes that a combination of generalised linear modelling and GIS gives deeper insight into the dynamics of wildlife species in and around well-defined nature reserves. 相似文献
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19.
Climate change and human activity can cause remarkable hydrological variation.Traits of hydrological series such as runoff before and after the change points could be sig-nificantly different,so the calculation of instream ecological water requirements (EWRs) is confronted with more challenges.Taking the Xitiaoxi River (XTXR) in the upper reach of the Taihu Lake Basin as an example,this paper investigates the calculation of EWRs using the range of variability approach (RVA) under changing environment.The change point diagnosis of the natural and observed runoff series are conducted for XTXR.Then,differences in the hydrological alternation indicators and instream EWRs processes obtained from various daily runoff series are compared.It was found that the natural and observed annual runoff series in XTXR from 1957 to 2018 both show significant variations,and the change points are in 2007 and 1999 respectively.If runoff data before the change points or all runoff data are used,the instream EWRs obtained from natural runoff are significantly lower than those obtained from the observed runoff.At the monthly time step,EWRs differences within a year mainly oc-curred from May to August.Also,calculation results of the instream EWRs are strongly re-lated to the selected period of runoff series.The EWRs obtained using runoff series after the change points have rather acute fluctuation within a year.Therefore,when the RVA method is used under changing environment,the instream EWRs should be prudently determined by comparing different calculation results on the basis of river runoff restoration and variability analysis.To a certain extent,this paper enriches our understanding about the hydrological method for EWRs estimation,and proposes new ideas for future research on EWRs. 相似文献
20.
地形具有高度的空间异质性,同一区域不同地形对该区的气候变化有着显著的影响,分析研究地形异质性对气候的影响具有十分重要的意义。基于天山山区DEM栅格图像资料和61个气象站点1961-2014年的气温和降水资料,运用空间分析、反距离权重插值法、偏最小二乘法和统计分析等方法,对该区域的地形异质性及其对气候的影响进行了相关研究。结果表明：（1）天山山区整体坡度大,其中中部与西南部的地形异质性指标值较高,其它地区的地形异质性值偏低。（2）从气候的空间分布来看,天山中部的气温较低,降水量丰富,其他区域的气温较高,降水量较少。（3）在地形异质性对气候影响方面,坡度对研究区气候的影响贡献最大,而地表粗糙度对研究区气候的影响最弱。 相似文献