Hydrogeology and groundwater flow in a basalt-capped Mesozoic sedimentary series of the Ethiopian highlands     

Ine Vandecasteele  Jan Nyssen  Wim Clymans  Jan Moeyersons  Kristine Martens  Marc Van Camp  Tesfamichael Gebreyohannes  Florimond Desmedt  Jozef Deckers  Kristine Walraevens 《Hydrogeology Journal》2011,19(3):641-650

A hydrogeological study was undertaken in the Zenako-Argaka catchment, near Hagere Selam in Tigray, northern Ethiopia, during the rainy season of 2006. A geological map was produced through geophysical measurements and field observations, and a fracture zone identified in the north west of the catchment. A perched water table was found within the Trap Basalt series above the laterized upper Aram Aradam Sandstones. A map of this water table was compiled. Water-level variation during the measurement period was at least 4.5?m. Variation in basal flow for the whole catchment for the measurement period was between 12 and 276?m³/day. A groundwater flow model was produced using Visual MODFLOW, indicating the general direction of flow to be towards the south, and illustrating that the waterways have only a limited influence on groundwater flow. The soil water budget was calculated for the period 1995?C2006, which showed the important influence of the distribution of rainfall in time. Although Hagere Selam received some 724?mm of rainfall per year over this period, the strong seasonal variation in rainfall meant there was a water deficit for on average 10?months per year.  相似文献   

Ordovician and Cretaceous tectonothermal history of the Southern Gemericum Unit from microprobe monazite geochronology (Western Carpathians,Slovakia)     

Anna Vozárová  Patrik Konečný  Katarína Šarinová  Jozef Vozár 《International Journal of Earth Sciences》2014,103(4):1005-1022

The Southern Gemericum basement in the Inner Western Carpathians experienced a polyphase regional deformation. Differences in the pre-Alpine and Alpine events have been constantly discussed. To address this, monazites from metapelites and acid metavolcanic rocks were dated using the Th–U–Pb electron microprobe method. Three monazite generations, such as Precambrian, Early Paleozoic, and Alpine, have been recognized in the greenschist facies pelites and acid metavolcanic rocks of the Southern Gemericum basement. Both inherited magmatic monazite grains in metavolcanites and rare relics of detrital monazites within the polyphase monazite grains in metapelites yielded the Precambrian age in the time span of 550–660 Ma. They prove the provenance and derivation from deeper crustal Cadomian fragments. High-Y magmatic monazites of Early Paleozoic age (444 ± 13 and 477 ± 7 Ma) have been recorded in the acid metavolcanites and their metavolcaniclastics. These ages roughly fit within the previously published magmatic zircon age determinations (at 494 ± 1.7 and 464 ± 1.7 Ma) that clearly indicate two-phase volcanic activity in the Early Paleozoic Southern Gemericum basin. The Early Paleozoic magmatic monazites were partly overprinted by the low-Y Alpine monazites (133 ± 5 and 184 ± 16 Ma) at their rims. In Al-rich metapelites, the newly formed low-Y monazites of Alpine age commonly occur, reflecting the polystage compression geodynamic evolution with three distinct peaks at 100 ± 8, 133 ± 5, and 190 ± 16 Ma, respectively. No data as the evidence of the pre-Alpine metamorphic events were observed in metapelites. Only some monazites yield the age indications for the Permian extensional thermal re-heating (260–290 Ma). The monazite age data from the Southern Gemericum basement indicate the strong overprinting due to the polyphase Alpine deformation at least in the greenschist facies conditions.  相似文献   

Arsenic mobility from anthropogenic impoundment sediments – Consequences of contamination to biota, water and sediments, Poša, Eastern Slovakia     

Edgar Hiller  L&#x;ubomír Jurkovi   Jozef Kordík  Igor Slaninka  Michal Jankulr  Juraj Majzlan  Jrg Gttlicher  Ralph Steininger 《Applied Geochemistry》2009,24(11):2175-2185

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Regional groundwater flow modeling of the Geba basin,northern Ethiopia     

Gebreyohannes  Tesfamichael  De Smedt  Florimond  Walraevens  Kristine  Gebresilassie  Solomon  Hussien  Abdelwassie  Hagos  Miruts  Amare  Kassa  Deckers  Jozef  Gebrehiwot  Kindeya 《Hydrogeology Journal》2017,25(3):639-655

Hydrogeology Journal - The Geba basin is one of the most food-insecure areas of the Tigray regional state in northern Ethiopia due to recurrent drought resulting from erratic distribution of...  相似文献   

Archaeomagnetic investigation of two mediaeval brick constructions in north Belgium and the magnetic anisotropy of bricks     

Jozef Hus  Souad Ech‐Chakrouni  Diana Jordanova  Raoul Geeraerts 《Geoarchaeology》2003,18(2):225-253

Archaeomagnetic dates derived from geomagnetic field direction records in baked materials are proposed for a mediaeval brick kiln (from inclination I and declination D) and for bricks from a brick wall (from I only) in northern Belgium. They are used to verify whether a brick chronology based on the format of bricks is feasible in Flanders. The brick kiln yielded a highly reliable average magnetization direction corresponding to an archaeomagnetic date around A.D. 1650, using the British and French geomagnetic field secular variation curves as a reference, at least half a century younger than expected from historical data. The fidelity of the geomagnetic records was controlled by measuring the magnetic anisotropy of the bricks. Anisotropy of magnetic susceptibility (AMS) measurements demonstrate that the bricks have a shape related magnetic fabric, which is induced during the molding process. A test to control whether AMS can substitute for the anisotropy of thermo‐remanent magnetization (ATRM) failed because of induced changes during laboratory heating. © 2003 Wiley Periodicals, Inc.  相似文献   

The stability of stars with potential-dependent masses     

Vladimír Majerník  Jozef Gembarovič 《Astrophysics and Space Science》1990,172(1):147-153

We calculate the effective mass of a spherical star-like object under the assumption that the mass of an object represents a function of the gravitational potential in which it occurs. We show that due to this mass-dependence on the gravitational potential, it is not possible that a star of a larger mass than that of a neutron star shrinks to a point singularity. We present the value of the upper limits to the mass of spherical mass bodies as a function of their radii in a large range of their mass densities.  相似文献   

Solar wind and spin of small interplanetary particles     

Jozef Klačka 《Earth, Moon, and Planets》1994,66(2):213-216

The action of the solar corpuscular radiation on the rotational properties of small interplanetary dust particles is investigated. It is shown that the solar wind increases the angular momentum (spin) of the particle. Analytic solutions are presented for dominant terms in which quantities of the orders (v/u) ⁿ ,n 1, are neglected (v is the orbital velocity of dust particle around the Sun andu is the speed of the solar wind particles).  相似文献   

The stratigraphic and paleoenvironmental setting of Aptian OAE black shale deposits in the Pieniny Klippen Belt, Slovak Western Carpathians     

Jozef Michalík  Jn Sotk  Otília Lintnerov  Eva Halsov  Marta B&#x;k  Petr Skupien  Daniela Boorov 《Cretaceous Research》2008,29(5-6):871

During the Jurassic and Cretaceous, the Pieniny Klippen Belt units of the Outer Western Carpathians were situated on the edge of the Paleoeuropean shelf rimming the northermost margin of the Mediterranean Tethys. During the late early Aptian humid event, Lower Cretaceous pelagic carbonate (Maiolica) sedimentation was interrupted by terrigenous input as a consequence of the first major mid-Cretaceous climate perturbations. The fluctuation of radiolarian abundance indicated an expansion of the oxygen-minimum zone due to upwelling conditions and salinity changes. Foraminifera, radiolarians, non-calcareous dinocysts, and calcareous nannofossils encountered in the West Carpathian Rochovica section enable a comparison of the black shales of the upper lower Aptian Koňhora Formation with the well-known Selli Event. Subsequent anoxia patterns (depositional, productive, and stagnant) have taken part in the depositional regime. Early Aptian climate perturbations both in the Outer Western Carpathians, Swiss Prealps (situated in a similar position on the distal southern edge of the former Paleoeuropean shelf) and/or in other parts of the world are traceable with sedimentological, biological, and chemical proxies.  相似文献   

Study on seismic behavior of nonplastic silt by means of ring-shear apparatus     

Jozef Jurko  Kyoji Sassa  Hiroshi Fukuoka 《Landslides》2008,5(2):189-201

The influence of static shear stress on undrained cyclic behavior of nonplastic and low-plasticity silts has been studied by means of undrained cyclic torque-controlled ring-shear tests. The cyclic and post-cyclic behavior of silty soils assumed on sliding surface were investigated to assess the liquefaction potential and cyclically induced deformation of silty slopes. Six different initial static shear stresses corresponding to slope angles from 0° to 25° were examined. To better understand undrained cyclic behavior of silt governed by a change in clay content, three different mixtures were achieved by mixing of nonplastic silt with 0%, 10%, and 20% of commercially available clay. These tests were conducted to simulate field conditions prior to earthquake with initial static shear stresses corresponding to slopes and those with no initial static shear stresses of level grounds. The gradual loss of mobilized undrained cyclic shear resistance after failure and pore water buildup in relation to a number of cycles was observed. The undrained response of the soil to cyclic shear stress loading with the constant amplitude revealed the significant effect of the initial static shear stress on the excess pore water pressure generation and post-failure shear resistance. Test results showed that an increase in the initial static shear stress at the given initial effective normal stress is associated with an increase of mobilized shear resistance at its peak state; however, the actual resistance to liquefaction diminished for both nonplastic and low-plasticity silts. During both cyclic and post-cyclic stages of loading, distinctly different types of shear deformation were identified. In order to evaluate mobility of landslides, a modified conventional brittleness index for seismic loading, , was proposed and used to characterize unlimited deformation of silts.  相似文献   

Mineralogy,petrography, geochemistry,and classification of the Košice meteorite          下载免费PDF全文

Daniel Ozdín  Jozef Plavčan  Michaela Horňáčková  Pavel Uher  Vladimír Porubčan  Pavel Veis  Jozef Rakovský  Juraj Tóth  Patrik Konečný  Ján Svoreň 《Meteoritics & planetary science》2015,50(5):864-879

The Ko?ice meteorite was observed to fall on 28 February 2010 at 23:25 UT near the city of Ko?ice in eastern Slovakia and its mineralogy, petrology, and geochemistry are described. The characteristic features of the meteorite fragments are fan‐like, mosaic, lamellar, and granular chondrules, which were up to 1.2 mm in diameter. The fusion crust has a black‐gray color with a thickness up to 0.6 mm. The matrix of the meteorite is formed mainly by forsterite (Fo_80.6); diopside; enstatite (Fs_16.7); albite; troilite; Fe‐Ni metals such as iron and taenite; and some augite, chlorapatite, merrillite, chromite, and tetrataenite. Plagioclase‐like glass was also identified. Relative uniform chemical composition of basic silicates, partially brecciated textures, as well as skeletal taenite crystals into troilite veinlets suggest monomict breccia formed at conditions of rapid cooling. The Ko?ice meteorite is classified as ordinary chondrite of the H5 type which has been slightly weathered, and only short veinlets of Fe hydroxides are present. The textural relationships indicate an S3 degree of shock metamorphism and W0 weathering grade. Some fragments of the meteorite Ko?ice are formed by monomict breccia of the petrological type H5. On the basis of REE content, we suggest the Ko?ice chondrite is probably from the same parent body as H5 chondrite Morávka from Czech Republic. Electron‐microprobe analysis (EMPA) with focused and defocused electron beam, whole‐rock analysis (WRA), inductively coupled plasma mass and optical emission spectroscopy (ICP MS, ICP OES), and calibration‐free laser induced breakdown spectroscopy (CF‐LIBS) were used to characterize the Ko?ice fragments. The results provide further evidence that whole‐rock analysis gives the most accurate analyses, but this method is completely destructive. Two other proposed methods are partially destructive (EMPA) or nondestructive (CF‐LIBS), but only major and minor elements can be evaluated due to the significantly lower sample consumption.  相似文献