Borehole and surface-based hydrogeophysics     

Roger Guérin 《Hydrogeology Journal》2005,13(1):251-254

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Karst database development in Minnesota: design and data assembly   总被引：1，自引：0，他引：1  

Y. Gao  E. C. Alexander Jr  R. G. Tipping 《Environmental Geology》2005,47(8):1072-1082

The Karst Feature Database (KFD) of Minnesota is a relational GIS-based Database Management System (DBMS). Previous karst feature datasets used inconsistent attributes to describe karst features in different areas of Minnesota. Existing metadata were modified and standardized to represent a comprehensive metadata for all the karst features in Minnesota. Microsoft Access 2000 and ArcView 3.2 were used to develop this working database. Existing county and sub-county karst feature datasets have been assembled into the KFD, which is capable of visualizing and analyzing the entire data set. By November 17 2002, 11,682 karst features were stored in the KFD of Minnesota. Data tables are stored in a Microsoft Access 2000 DBMS and linked to corresponding ArcView applications. The current KFD of Minnesota has been moved from a Windows NT server to a Windows 2000 Citrix server accessible to researchers and planners through networked interfaces.  相似文献   

应用遥感方法研究黄河三角洲地表蒸发及其与下垫面关系   总被引：10，自引：1，他引：10  

崔亚莉  徐映雪  邵景力  张长春 《地学前缘》2005,12(Z1):159-165

文中主要应用遥感方法计算了黄河三角洲地表蒸发量及其地表特征参数。地表特征参数及其合理组合揭示出黄河三角洲下垫面的基本特征:农田植被指数和天然植被的植被指数有不同的变化规律,下垫面覆盖度低,裸地较多,地表较湿润,蒸发量较大。蒸发量时空分布主要受下垫面条件控制,滨海裸地和受人类活动影响较大的农田等地蒸发量较大,年际平均蒸发量在570~860 mm之间。  相似文献   

玄武岩浆起源和演化的一些基本概念以及对中国东部中-新生代基性火山岩成因的新思路   总被引：44，自引：3，他引：44  

牛耀龄 《高校地质学报》2005,11(1):9-46

以全球大地构造为背景讨论了玄武岩浆起源和演化的一些基本概念.这些概念的正确理解有助于合理解释各种环境中火成岩的形成机制,也有助于依据野外岩石组合来判别古构造环境.在此基础上结合已有资料和观察,对中国东部中生代岩石圈减薄及中-新生代基性火山岩成因提出了一些新解释.这些解释与地质观察相吻合,且符合基本的物理学原理.虽然中国东部基性火山活动可称为"板内"火山活动,但它实际上是板块构造的特殊产物.中国东部中生代岩石圈减薄是其下部被改造为软流层的缘故.这种改造是加水"软化"所致.水则源于中国东部地幔过渡带(410～660 km)内古太平洋(或其前身)俯冲板块脱水作用.其将岩石圈底部改造为软流层的过程,实际上就是岩石圈减薄的过程.因为软流层是地幔对流的重要部分,而大陆岩石圈则不直接参与地幔对流.中生代玄武岩具有εNd＜0的特征,说明其源于新近改造而成的软流层,亦即原古老岩石圈之底部.中国大陆北北东-南南西向的海拔梯度突变界线与东-西部重力异常,陆壳厚度变化,以及地幔地震波速变化梯度吻合.因此可将北北东-南南西向梯度线称为"东-西梯度界".该界东-西海拔高差(西部高原与东部丘陵平原),陆壳厚度差异(西部厚而东部薄)和100～150 km的深度范围地幔地震波速差异(西部快而东部慢),均受控于上地幔重力均衡原理.这表明西部高原岩石圈厚度＞150～200 km,而东部丘陵平原岩石圈厚度＜80km."遥远"的西太平洋俯冲带具有自然的地幔楔吸引作用.此吸引作用可引起中国东部"新生"软流层东流.软流层东流必将引起西部高原底部软流层的东向补给(流动).这一过程必然导致东移软流层的减压,即从西部的深源(岩石圈深度＞150～200 km处)到东部的浅源(岩石圈深度～80km处).东移软流层的减压分熔可合理解释具有软流圈地球化学特征(εNd＞0)的新生代中国东部基性火山活动及玄武岩的成因.这些对中国东部中-新生代地质过程的解释,将为更加细致的,以岩石学和地球化学为主的讨论所验证.  相似文献   

Whole-rock and mineralogical composition of Phanerozoic ooidal ironstones: Comparison and differentiation of types and subtypes   总被引：2，自引：0，他引：2  

Arno Mücke  Farhad Farshad 《Ore Geology Reviews》2005,26(3-4):227-262

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Amphibole Ar/Ar Geochronology from the Okcheon Metamorphic Belt, South Korea and its Tectonic Implications     

Sung Won Kim   《Gondwana Research》2005,8(3):385-402

An understanding of the Okcheon Metamorphic Belt (OMB) in South Korea is central to unraveling the tectono-metamorphic evolution of East Asia. Amphibole-bearing rocks in the OMB occur as calcsilicate layers and lenses in psammitic rocks, in the psammitic rocks themselves, and in the mafic volcanic layers and intrusives. Most amphiboles fail to show ⁴⁰Ar/³⁹Ar plateau ages; those that do have ages ranging from 132 to 975 Ma. The disturbed age pattern and wide variation in ⁴⁰Ar/³⁹Ar ages can be related to metamorphic grade, retrograde chemical reactions, excess Ar and amphibole composition. The oldest age (975 Ma) can be interpreted either as an old igneous or metamorphic age predating sedimentation or a false age caused by excess Ar. The youngest age of 132 Ma and the disturbed age pattern found in amphiboles from rocks located close to Jurassic granitoids are the result of retrograde thermal metamorphic effects accompanying intrusion of the granitoids. Some medium- or coarse-grained amphiboles in the calcsilicates are aggregates of fine-grained crystals. As a result, they are heterogeneous and prove to be readily affected by excess Ar. A disturbed age pattern in amphiboles from the calcsilicates occurring in the high-grade metamorphic zone may also be the product of excess Ar. On the other hand, the disturbed pattern of amphiboles present in the calcsilicates from the low-grade metamorphic zone could arise from both excess Ar and mixed ages. However, amphiboles from psammitic rocks and some calcsilicates in the high-grade metamorphic zone and in intrusive metabasites display real plateau ages of 237 to 261 Ma. The temperature conditions in the high-grade metamorphic zone were higher than the argon closing temperature for amphibole, and the amphiboles in this zone give plateau ages only when they are homogeneous in composition, lack excess Ar, and have not been thermally affected by intrusion of the granitoids. The unmodified ⁴⁰Ar/³⁹Ar ages prove rather younger than the age of the Late Paleozoic metamorphic event of 280 to 300 Ma, but they are close to muscovite K-Ar ages of 263 to 277 Ma. These ⁴⁰Ar/³⁹Ar amphibole ages are interpreted as the time of cooling that followed the main regional, intermediate-P/T metamorphic climax. The results demonstrate that interpretation of ⁴⁰Ar/³⁹Ar amphibole ages in an area subjected to several metamorphic events can be accomplished only by undertaking a thorough tectono-metamorphic study, accompanied by detailed chemical analysis of the amphiboles.  相似文献   

Diet and habitat of toxodont megaherbivores (Mammalia, Notoungulata) from the late Quaternary of South and Central America     

Bruce J. MacFadden 《Quaternary Research》2005,64(2):113-124

The toxodont megaherbivores Toxodon and Mixotoxodon were endemic to South and Central America during the late Quaternary. Isotopic signatures of 47 toxodont teeth were analyzed to reconstruct diet and ancient habitat. Tooth enamel carbon isotope data from six regions of South and Central America indicate significant differences in toxodont diet and local vegetation during the late Quaternary. Toxodonts ranged ecologically from C₃ forest browsers in the Amazon (mean δ¹³C = −13.4‰), to mixed C₃ grazers and/or browsers living either in C₃ grasslands, or mixed C₃ forested and grassland habitats in Honduras (mean δ¹³C = −9.3‰), Buenos Aires province, Argentina (δ¹³C = −8.7‰), and Bahia, Brazil (mean δ¹³C = −8.6‰), to predominantly C₄ grazers in northern Argentina (δ¹³C = −4.4‰), to specialized C₄ grazers in the Chaco of Bolivia (δ¹³C = −0.1‰). Although these toxodonts had very high-crowned teeth classically interpreted for grazing, the isotopic data indicate that these megaherbivores had the evolutionary capacity to feed on a variety of dominant local vegetation. In the ancient Amazon region, carbon isotope data for the toxodonts indicate a C₃-based tropical rainforest habitat with no evidence for grasslands as would be predicted from the Neotropical forest refugia hypothesis.  相似文献   

Structure de socle,sismostratigraphie et héritage structural au cours du rifting au niveau de la marge d'Ifni/Tan-Tan (Maroc sud-occidental)     

Naïma AbouAli  Mohamad Hafid  El Hassane Chellaï  Mohamed Nahim  Mahmoud Zizi 《Comptes Rendus Geoscience》2005,337(14):1267-1276

Seismic reflection profiles from the Ifni/Tan-Tan Atlantic margin of southern Morocco, interpreted in the light of well data and field geology from the Western Anti-Atlas, allowed us to establish the seismostratigraphic framework of the syn-rift series and to reveal (i) a compressional structural style in the pre-Triassic basement similar to that established in the adjacent outcropping onshore basement but with an opposed western vergence, (ii) the importance of inherited anterior structures in the formation of Triassic-Liassic rift structures and (iii) an east–west propagation of these rift structures. To cite this article: N. AbouAli et al., C. R. Geoscience 337 (2005).  相似文献   

Using CRD method for quantification of groundwater recharge in the Gaza Strip, Palestine   总被引：1，自引：0，他引：1  

Husam Baalousha 《Environmental Geology》2005,48(7):889-900

Rainfall is the main source of groundwater recharge in the Gaza Strip area in Palestine. The area is located in the semi-arid zone and there is no source of recharge other than rainfall. Estimation of groundwater recharge from rainfall is not an easy task since it depends on many uncertain parameters. The cumulative rainfall departure (CRD) method, which depends on the water balance principle, was used in this study to estimate the net groundwater recharge from rainfall. This method does not require much data as is the case with other classical recharge estimation methods. The CRD method was carried out using optimisation approach to minimise the root mean square error (RMSE) between the measured and the simulated groundwater head. The results of this method were compared with the results of other recharge estimation methods from literature. It was found that the results of the CRD method are very close to the results of the other methods, but with less data requirements and greater ease of application. Based on the CRD method, the annual amount of groundwater recharge from rainfall in the Gaza Strip is about 43 million m³. An erratum to this article can be found at  相似文献   

Quantitative assessment on the influence of heavy rainfall on the crystalline schist landslide by monitoring system -case study on Zentoku landslide, Japan   总被引：2，自引：1，他引：2  

Yong Hong  Hiromasa Hiura  Kazuo Shino  Kyoji Sassa  Hiroshi Fukuoka 《Landslides》2005,2(1):31-41

On Shikoku Island, which is one of the four main islands of Japan, a large number of large-scale crystalline schist landslides have been revealed and are being monitored by an observation system. Seasonal heavy rainfall is the most active meteorological factor that can threaten the stability of this kind of site-specific landslide. In this paper, on the basis of the study of the rainfall-related behavior of a typical crystalline schist landslide, the Zentoku landslide, by analyzing the precisely and continuously observed piezometric and movement data, a method was developed to quantitatively assess the effect of heavy rainfall on a large-scale landslide. The results indicated that heavy rainfall-induced landslide displacement shows good correlation with the variation of groundwater levels. Variations of groundwater level have been simulated with the use of a tank model. The simulation using this model permits the change in water levels for future rainfall events to be predicted. By combining the predicted results with the empirical relation between displacements and water levels, rainfall-induced landslide movement during extreme rainfall events can be estimated in advance. The effect of heavy rainfall on sliding behavior can be quantified in terms of the change in displacement. Thus warning information or advisories for the local residents can be provided.  相似文献