Review: Hydrogeology of weathered crystalline/hard-rock aquifers—guidelines for the operational survey and management of their groundwater resources     

Lachassagne  Patrick  Dewandel  Benoît  Wyns  Robert 《Hydrogeology Journal》2021,29(8):2561-2594

Hard rocks or crystalline rocks (i.e., plutonic and metamorphic rocks) constitute the basement of all continents, and are particularly exposed at the surface in the large shields of Africa, India, North and South America, Australia and Europe. They were, and are still in some cases, exposed to deep weathering processes. The storativity and hydraulic conductivity of hard rocks, and thus their groundwater resources, are controlled by these weathering processes, which created weathering profiles. Hard-rock aquifers then develop mainly within the first 100 m below ground surface, within these weathering profiles. Where partially or noneroded, these weathering profiles comprise: (1) a capacitive but generally low-permeability unconsolidated layer (the saprolite), located immediately above (2) the permeable stratiform fractured layer (SFL). The development of the SFL’s fracture network is the consequence of the stress induced by the swelling of some minerals, notably biotite. To a much lesser extent, further weathering, and thus hydraulic conductivity, also develops deeper below the SFL, at the periphery of or within preexisting geological discontinuities (joints, dykes, veins, lithological contacts, etc.). The demonstration and recognition of this conceptual model have enabled understanding of the functioning of such aquifers. Moreover, this conceptual model has facilitated a comprehensive corpus of applied methodologies in hydrogeology and geology, which are described in this review paper such as water-well siting, mapping hydrogeological potentialities from local to country scale, quantitative management, hydrodynamical modeling, protection of hard-rock groundwater resources (even in thermal and mineral aquifers), computing the drainage discharge of tunnels, quarrying, etc.

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Investigation of potential debris flows above the Koroška Bela settlement,NW Slovenia,from hydro-technical and conceptual design perspectives     

Bezak  Nejc  Sodnik  Jošt  Maček  Matej  Jurček  Timotej  Jež  Jernej  Peternel  Tina  Mikoš  Matjaž 《Landslides》2021,18(12):3891-3906

Debris flows are one of the natural disasters that can occur in the alpine environment, cause large economic damage, and endanger human lives. This study presents an overview of recent research done in relation to the debris flow hazard assessment and conceptual mitigation at the Koro?ka Bela area in Slovenia. This includes fieldwork, lab experiments, modelling, and a conceptual design of hydro-technical measures to reduce the risk. The results indicate that multiple debris flows occurred in the past in the area but a relatively long period of more than 100 years without an extreme event led to urbanization and development of the area. Magnitudes of the most extreme events as the worst-case scenarios were estimated to be in the range between 100,000 and 400,000 m³, using debris flow modelling and geological information from research trenches. Based on the landslide volumes, such events could also potentially occur in the future in extreme conditions. Additionally, torrential floods could mobilize more than 15,000 m³ of material located along the stream network that can be regarded as potentially unstable. The existing check dam system does not have the capacity to capture this material. Thus, a new check dam and three flexible net barriers could help to reduce the risk due to torrential outbursts or debris flows.

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Formation and shock impact history of the Csatalja ordinary chondrite     

Ildiko Gyollai  Ákos Kereszturi  Elias Chatzitheodoridis  Zsolt Kereszty  Máté Szabó  Csilla Király  Zoltan Szalai 《Meteoritics & planetary science》2023,58(1):2-24

The analysis of the Csatalja H4 chondrite (which was found in August 2012) suggests shock-related textures and spatial inhomogeneities, indicating a complex geological history. In the most heavily fractured and sheared units, small opaque grains and older fractures have locally enhanced the shock effect, producing melt. While the impact textures were evident in most units of the meteorite, mechanical shearing is apparent in only two units, suggesting that these units might have been present at somewhat different locations inside the parent body. Shearing also occurred at the border of the so-called xenolith unit, confirming its mechanical mixing with the other units. Besides fragmentation and melting, chemical changes due to impact have also been identified, producing compositional homogenization of olivines in 30% of the investigated area of the sample's thin section (23 mm²), and moderate accumulation of Fe, Ca, and Na in the strongly shocked zones, initiating crystallization of feldspar in veins with a specific spatial distribution (feldspar glass with metal–sulfide globules). Analyzing the high P–T minerals, the peak shock pressure and temperature values differed substantially in the various units, ranging between 2 and 17 GPa, 100 and >1200 °C. The xenolith unit crystallized more slowly after the impact event and does not show shock impact alterations, suggesting that it was formed in a deeper region of the parent body. This was later shifted to its current surroundings and was lithified (fixed) to the rest of the sample. This “randomly selected” Csatalja sample provides information on the range of the formation temperatures, pressures, and processes that contributed to the heterogeneity of meteorites at the mm spatial scale, in general. The identified heterogeneity is a result not purely of the shock effects but also of the different pre-shock structural characteristics. The shock also mixed fragments mechanically that have been formed at different environments, with at least several dozens or even 100 m depth in the parent body.  相似文献   

Long-term variability of temperature and precipitation in the Czech Lands: an attribution analysis     

Jiří Mikšovský  Rudolf Brázdil  Petr Štĕpánek  Pavel Zahradníček  Petr Pišoft 《Climatic change》2014,125(2):253-264

Among the key problems associated with the study of climate variability and its evolution are identification of the factors responsible for observed changes and quantification of their effects. Here, correlation and regression analysis are employed to detect the imprints of selected natural forcings (solar and volcanic activity) and anthropogenic influences (amounts of greenhouse gases—GHGs—and atmospheric aerosols), as well as prominent climatic oscillations (Southern Oscillation—SO, North Atlantic Oscillation—NAO, Atlantic Multidecadal Oscillation—AMO) in the Czech annual and monthly temperature and precipitation series for the 1866–2010 period. We show that the long-term evolution of Czech temperature change is dominated by the influence of an increasing concentration of anthropogenic GHGs (explaining most of the observed warming), combined with substantially lower, and generally statistically insignificant, contributions from the sulphate aerosols (mild cooling) and variations in solar activity (mild warming), but with no distinct imprint from major volcanic eruptions. A significant portion of the observed short-term temperature variability can be linked to the influence of NAO. The contributions from SO and AMO are substantially weaker in magnitude. Aside from NAO, no major influence from the explanatory variables was found in the precipitation series. Nonlinear forms of regression were used to test for nonlinear interactions between the predictors and temperature/precipitation; the nonlinearities disclosed were, however, very weak, or not detectable at all. In addition to the outcomes of the attribution analysis for the Czech series, results for European and global land temperatures are also shown and discussed.  相似文献   

Timescales associated with climate change and their relevance in adaptation strategies   总被引：2，自引：1，他引：1  

Ramón de Elía  Sébastien Biner  Anne Frigon  Hélène Côté 《Climatic change》2014,126(1-2):93-106

Anthropogenic greenhouse gas emissions that induce changes in the Earth’s climate affect particular variables and locations differently. A key part of this difference is the timescale at which this change takes place, which will eventually have important consequences for adaptation requirements. This idea of timescale associated with climate change has been used several times in the past to estimate the urgency of adaptation in particular regions. The definition of climate-change timescale is, however, not unique. For example, we can think of it in terms of an expected trend (e.g. in temperature) reaching a given threshold, or think of it in terms of the time it may take this trend to become statistically significant. We may also wonder about the validity of this speculation given that, due to natural variability, the expected trend may in fact not be realized. In this article we explore alternative ways of defining the timescale of climate-change, compare their properties, and illustrate them with an example for the case of projected surface temperature over North America. It is shown that these timescales are analytically related but may differ substantially in magnitude under certain conditions. In particular, it is shown that climate change impact on vulnerable systems may arrive before statistical detection of the variable’s trend takes place. This fact may have implications on how climate change impacts are seen by those with diverging interests.  相似文献   

Geophysical Images of the North Anatolian Fault Zone in the Erzincan Basin, Eastern Turkey, and their Tectonic Implications     

Ümİt Avşar  Erşan Türkoğlu  Martyn Unsworth  İlyas Çağlar  Bülent Kaypak 《Pure and Applied Geophysics》2013,170(3):409-431

The collision between the Arabian and Eurasian plates in eastern Turkey causes the Anatolian block to move westward. The North Anatolian Fault (NAF) is a major strike-slip fault that forms the northern boundary of the Anatolian block, and the Erzincan Basin is the largest sedimentary basin on the NAF. In the last century, two large earthquakes have ruptured the NAF within the Erzincan Basin and caused major damage (M _s = 8.0 in 1939 and M _s = 6.8 in 1992). The seismic hazard in Erzincan from future earthquakes on the NAF is significant because the unconsolidated sedimentary basin can amplify the ground motion during an earthquake. The amount of amplification depends on the thickness and geometry of the basin. Geophysical constraints can be used to image basin depth and predict the amount of seismic amplification. In this study, the basin geometry and fault zone structure were investigated using broadband magnetotelluric (MT) data collected on two profiles crossing the Erzincan Basin. A total of 24 broadband MT stations were acquired with 1–2 km spacing in 2005. Inversion of the MT data with 1D, 2D and 3D algorithms showed that the maximum thickness of the unconsolidated sediments is ~3 km in the Erzincan Basin. The MT resistivity models show that the northern flanks of the basin have a steeper dip than the southern flanks, and the basin deepens towards the east where it has a depth of 3.5 km. The MT models also show that the structure of the NAF may vary from east to west along the Erzincan Basin.  相似文献   

In situ X-ray diffraction measurements of the <Emphasis Type="Italic">fcc</Emphasis>–<Emphasis Type="Italic">hcp</Emphasis> phase transition boundary of an Fe–Ni alloy in an internally heated diamond anvil cell     

Tetsuya?KomabayashiEmail author  Kei?Hirose  Yasuo?Ohishi 《Physics and Chemistry of Minerals》2012,39(4):329-338

The phase transition boundary between the face-centered cubic (fcc) structure and hexagonal close-packed (hcp) structure in an Fe–Ni alloy was determined at pressures from 25 to 107 GPa by using an internally resistive-heated diamond anvil cell (DAC), combined with in situ synchrotron X-ray diffraction measurements. The fcc–hcp phase transition boundary in Fe–9.7 wt% Ni is located at slightly lower temperatures than that in pure Fe, confirming the previous understanding that the addition of Ni expands the stability field of the fcc phase. The dP/dT slope of the boundary was determined to be 0.0426 GPa/K, which is slightly larger than that of pure Fe. The pressure interval of the two-phase region is about 6 GPa at a constant temperature, implying that the previous estimates by laser-heated DAC experiments of 10–20 GPa were overestimated. The two-phase region of fcc + hcp would be limited to a pressure of about 120 GPa even in Fe–15 wt%Ni, excluding the possibility of the existence of the fcc phase in the inner core if the simple linear extrapolation of the two-phase region is applied. The pressure and temperature dependences of the c/a axial ratio of the hcp phase in Fe–9.7 wt% Ni are generally consistent with those in pure Fe, suggesting that Ni has minor effects on the c/a ratio.  相似文献   

侏罗纪末至白垩纪非海相介形类生物地层学:回顾与展望     

Benjamin SAMES  David J.HORNE 《地层学杂志》2012,(2):266-288

以非海相介形类为依据而建立的侏罗纪末至白垩纪的生物地层学,尤其是欧洲所谓"Purbeck-Wealden层段"(提塘阶顶部至巴列姆阶/阿普特阶底部)和全球同期沉积层的生物地层学建立已久,但这一生物地层学存有很多问题与局限性。本文对中生代晚期(聚焦于早白垩世)的非海相介形类生物地层学的基本原理、历史、目前进展、存在问题和前景进行了综述。因为介形类的繁殖、扩散与成种机制已有比较成熟的研究,所以介形类的生物地层学的应用潜力被认识已久。然而,全球不同地区中生代晚期的非海相介形类众多的研究积累已构成了一个丰富但常常混乱和矛盾的文献库。这些问题不仅存在于介形类的分类鉴定中,也见于关于古环境和系统发育的解释中。虽然地区性的盆地内的介形类生物地层学研究已产生了好结果,并可能能够用于局部地区的高精度对比。但是在进行地区间(盆地间至全球)的对比时,其实用性广遭怀疑。在过去的二十年间,许多学者采用了将今论古的古生物学研究方法,努力修订和更新中生代晚期的非海相介形类的生物地层学与古环境意义,从而促进了地区间生物地层学研究和对比的发展。古生物学家认识到,对于许多非海相介形类动物来讲,它们的分布和扩散不仅仅局限于单个的水系或较小的地理区域,而是和现生的非海相介形类一样,晚侏罗世至白垩纪的非海相介形类动物和它们的卵可被较大的动物或风长距离搬运,跨越迁移的屏障,进行扩散。鉴于以上事实,地区间的对比必须涉及两大内容:分类学的应用与古环境背景。缺乏适用于地区—全球的稳定和一致的分类学系统是进行正确对比的重要障碍。由于大量地方性分类命名、地方性特有动物的假设、与壳体特征相关的分类和生态型认识的混乱,以及对种内变异尺度的统一认识的缺乏,导致了对生物分异度的过高或过低的估量。非海相白垩纪介形类的地层记录受到诸多因素的影响:分类单元的演化与灭绝、扩散事件、当地的环境变化和地区性至全球的气候变迁。在生物地层学的应用中,我们可以通过不同手段去把握同时代的Cytheroidea,特别是Cypridoidea中具重要地层意义的Cypridea属及其亲近者(即CypridoideaMartin,1940)的分类单元的形态变异度。解释种内变异时需要格外谨慎。区分生物自生(内因)导致的变异(遗传的和形态的变异)和环境(外因)导致的变异(生态表型)是一大难题。比较保守的分类学观念(分类单元很少,但变异极大(分类单元中包含了多种生态表型))有助于不同古环境间的(生物地层)对比。另一方法是运用随着时间的古环境变化及其对介形类组合的组成的影响来进行(生物地层)对比。古生物工作者已在利用受环境控制的周期性介形类组合变化建立对比关系方面进行了大量有意义的尝试,但这些工作仍处在争议中。建立全球生物地层学方法,建立统一而持久的分类概念这一目标可以达到,但不可能在短期内实现。用现代的思想(概念)理解和研究非海相介形类的古生物学和古生物地理学及新资料将有助于修订工作的进展。尽管我们对中生代的非海相介形类的演化和分布的认识还很不全面,但目前我们已取得了可喜的进展。盆地间至大陆间的对比是否可行,早已不是问题。目前和未来的指导原则无疑是发展以介形类为基础,并与其他的年代地层学和地质年代学资料及方案相结合的从地区至全球范围的地层对比系统。因为我们正在迈向一个非海相晚中生代介形类生物地层学的重新解释和应用的新时代,我们必须承认我们还有许多东西需要学习。  相似文献   

Risk occurrences of damaging frosts during the growing season of vegetables in the Elbe River lowland,the Czech Republic     

Vera Potop  Pavel Zahraniček  Luboš Türkott  Petr Štěpánek  Josef Soukup 《Natural Hazards》2014,71(1):1-19

This study has, for the first time, analysed in detail the risk occurrences of the last spring frost, first fall frost and the length of the frost-free period during the growing season of vegetable crops at a high horizontal resolution of 10 km in the Elbe River lowland in the Czech Republic. The daily minimum air temperature from 116 grid points throughout the studied area for the period 1961–2011 was used. The daily values of minimum air temperature ranges of 0 to ?1.1 °C, ?1.2 to ?2.2 °C and below ?2.2 °C were considered to constitute mild, moderate and severe frost intensities, respectively. Firstly, the spatiotemporal variability of the date of the last spring frost, the date of the first fall frost and the length of the frost-free period in the Elbe River lowland is provided. Secondly, the estimation of the probability of a later date in the spring and an earlier date in the fall for various severe frost events and the length of the frost-free period is determined. Third, the changes in the timing of the last and first frosts of the three severities, as well as the length of the frost-free period, are evaluated. From 1961 to 2011, the Elbe River lowland has experienced a decrease in the number of frost days, while the length of the frost-free period between the last spring frost and the first fall frost has increased. The temporal evolution of the frost-free period anomalies displays two distinct periods: a shortening of the frost-free period in the 1960s and an intensified lengthening of the frost-free period since the 1980s. Whereas the latest spring frost has ended on an earlier date across the Elbe River lowland, the first frost date in the fall has generally been delayed to a later date. The dates of the last spring frost have advanced by ?0.21 days per year on average. The fall dates are delayed up to 0.18 days per year, whereas the frost-free period is lengthening by up to 0.39 days per year on average. However, regional frost series suggests that the frost-free period exhibits a large amount of inter-annual variability. In terms of the growth of field vegetables, a late spring frost remains a risk factor, but the degree of risk has decreased. There is a 25 % chance of the occurrence of dangerous spring frosts during the planting of field vegetables after 3rd May, but after 15th May, the risk is only 10 %.  相似文献   

Dehydration of dioctahedral aluminous phyllosilicates: thermodynamic modelling and implications for thermobarometric estimates   总被引：1，自引：1，他引：0  

Benoît Dubacq  Olivier Vidal  Vincent De Andrade 《Contributions to Mineralogy and Petrology》2010,159(2):159-174

We propose a solid-solution model for dioctahedral aluminous phyllosilicates accounting for the main compositional variations, including hydration, observed in natural smectites, interlayered illite/smectite, illites, and phengites from diagenetic to high-grade metamorphic conditions. The suggested formalism involves dehydrated micas and hydrated pyrophyllite-like thermodynamic end-members. With these end-members, the equilibrium conditions of quartz + water + K-bearing mica-like phyllosilicates of fixed 2:1 composition are represented by a line in P–T space along which the interlayer water content varies. The relevant thermodynamic properties required for the calculation of equilibrium conditions were derived using a set of 250 natural data of known maximal temperature and pressure conditions, which covers a range between 25°C and few MPa to 800°C and 5 GPa. The temperatures calculated at fixed pressure with our model are in fair agreement with those reported in the literature for the 250 natural data. At low temperature and pressure, the amount of interlayer water in K-deficient phengite and illite is predicted to reach 100% of the apparent vacancies, which is consistent with previous values reported in the literature. Although the amount of interlayer water is predicted to decrease with pressure and temperature, it is calculated to be significant in K-deficient phengite from LT–HP pelites metamorphosed at about 350°C, 10 kbar. The presence of molecular water in the interlayer site of such phengites has been confirmed by FTIR mapping. Its implications for P–T estimates are discussed.  相似文献