Evolution of geochemistry and depositional settings of Early Palaeozoic siliciclastics of the Barrandian (Teplá-Barrandian Unit,Bohemian Massif,Czech Republic)     

Franti?ek?Pato?ka  Petr??torchEmail author 《International Journal of Earth Sciences》2004,93(5):728-741

Cambrian and Ordovician-Middle Devonian sequences of two successive Early Palaeozoic basins of the Barrandian unconformably overlie Cadomian basement in the Bohemian Massif NW interior (Teplá-Barrandian unit) which is the easternmost peri-Gondwanan remnant within the Variscides. Correlation of stratigraphy and geochemistry of the Early Palaeozoic siliciclastic rocks elucidated sediment provenances. Sandstones of the Middle Cambrian Píbram-Jince Basin were derived from a Cadomian Neoproterozoic island arc. The source area of the Ordovician shallow-marine siliciclastics of the successor Prague Basin is a dissected Cadomian orogen. Late Cambrian acid volcanics of the Barrandian and Cambrian (meta)granitoids emplaced in the W part of the Teplá-Barrandian Cadomian basement are also discernible in these sediments. Old sedimentary component increased during the Ordovician. Early Llandovery siliciclastic rocks show characteristics of an abruptly weakened supply of terrigenous material and an elevated proportion of synsedimentary basic volcanics as a result of Silurian transgression. Emsian siliciclastics (intercalated in the Late Silurian to Early Devonian limestone suite) presumably comprise an addition of coeval basic/ultrabasic volcaniclastics. Middle Devonian flysch-like siliciclastics indicate reappearance of Cadomian source near the Barrandian during early Variscan convergences of Armorican microplates that preceeded accretion of the Teplá-Barrandian unit within the Bohemian Massif terrane mosaic.Dr. Patoka deceased in July 2004.  相似文献   

Detection and quantification of local anthropogenic and regional climatic transient signals in temperature logs from Czechia and Slovenia     

Petr Děde?ek  Jan ?afanda  Du?an Rajver 《Climatic change》2012,113(3-4):787-801

The paper reports on detection and quantification of the impact of local anthropogenic structures and regional climatic changes on subsurface temperature field. The analyzed temperature records were obtained by temperature monitoring in a borehole in Prague-Spo?ilov (Czechia) and by repeated logging of a borehole in ?empeter (Slovenia). The observed data were compared with temperatures yielded by mathematical 3D time-variable geothermal models of the boreholes’ sites with the aim to decompose the observed transient component of the subsurface temperature into the part affected by construction of new buildings and other anthropogenic structures in surroundings of the boreholes and into the part affected by the ground surface temperature warming due to the surface air temperature rise. A direct human impact on the subsurface temperature warming was proved and contributions of individual anthropogenic structures to this change were evaluated. In the case of Spo?ilov, where the mean annual warming rate reached 0.034°C per year at the depth of 38.3?m during the period 1993–2008, it turned out that about half of the observed warming can be attributed to the air (ground) surface temperature change and half to the human activity on the surface in the immediate vicinity of the borehole. The situation is similar in ?empeter, where the effect of the recently built surface anthropogenic structures is detectable down to the depth of 80?m and the share of the anthropogenic signal on the non-stationary component of the observed subsurface temperature amounts to 30% at the depth of 50?m.  相似文献   

Performance of ENSEMBLES regional climate models over Central Europe using various metrics   总被引：1，自引：1，他引：0  

Eva Holtanová  Ji?í Mik?ovsky  Jaroslava Kalvová  Petr Pi?oft  Martin Motl 《Theoretical and Applied Climatology》2012,108(3-4):463-470

We show the evaluation of ENSEMBLES regional climate models (RCMs) driven by reanalysis ERA40 over a region centered at the Czech Republic. Attention is paid especially to the model ALADIN-CLIMATE/CZ, being used as the basis of the new climate change scenarios simulation for the Czech Republic. The validation criteria used here are based on monthly or seasonal mean air temperature and precipitation. We concentrate not only on spatiotemporal mean values but also on temporal standard deviation, inter-annual variability, the mean annual cycle, and the skill of the models to represent the observed spatial patterns of these quantities. Model ALADIN-CLIMATE/CZ performs quite well in comparison to the other RCMs; we find its performance satisfactory for further use for impact studies. However, it is also shown that the results of evaluation of the RCMs’ skill in simulating observed climate strongly depend on the criteria incorporated for the evaluation.  相似文献   

Use of a soil moisture network for drought monitoring in the Czech Republic   总被引：1，自引：0，他引：1  

Martin Mozny  Mirek Trnka  Zdenek Zalud  Petr Hlavinka  Jiri Nekovar  Vera Potop  Michal Virag 《Theoretical and Applied Climatology》2012,107(1-2):99-111

Since 2000, the network of stations that make up the Czech Hydrometeorological Institute (CHMI) has measured the soil moisture content at the 0- to 0.9-m layer using sensors placed within the natural soil profile under closely cropped grass cover. Using information from 8?years of continuous observation at seven stations throughout the Czech Republic, we verified the usefulness of the Soil Moisture Index (SMI). The SMI is a potentially useful index for calculating the water deficit in the Czech Republic and Central Europe. During this period, a statistically significant decrease in moisture content was detected, and negative SMI values predominated. There were frequent occurrences of flash drought, defined as a very rapid decline in soil moisture during a 3-week period. The CHMI can use SMI values below ?3 in the Integrated Warning Service System. The routine calculation of SMI values can alert agricultural producers to the development of flash drought conditions and provide them with information regarding the effectiveness of recent rainfall events. An increase in soil moisture, in contrast, could serve as a warning sign for hydrology because it creates the preconditions for flooding. The complex study of soil humidity regimes is becoming more significant in connection with current global climatic change warnings in hydrological cycles.  相似文献   

European floods during the winter 1783/1784: scenarios of an extreme event during the ‘Little Ice Age’   总被引：1，自引：0，他引：1  

Rudolf Brázdil  Gaston R. Demarée  Mathias Deutsch  Emmanuel Garnier  Andrea Kiss  Jürg Luterbacher  Neil Macdonald  Christian Rohr  Petr Dobrovolný  Petr Kolář  Kateřina Chromá 《Theoretical and Applied Climatology》2010,100(1-2):163-189

The Lakagígar eruption in Iceland during 1783 was followed by the severe winter of 1783/1784, which was characterised by low temperatures, frozen soils, ice-bound watercourses and high rates of snow accumulation across much of Europe. Sudden warming coupled with rainfall led to rapid snowmelt, resulting in a series of flooding phases across much of Europe. The first phase of flooding occurred in late December 1783–early January 1784 in England, France, the Low Countries and historical Hungary. The second phase at the turn of February–March 1784 was of greater extent, generated by the melting of an unusually large accumulation of snow and river ice, affecting catchments across France and Central Europe (where it is still considered as one of the most disastrous known floods), throughout the Danube catchment and in southeast Central Europe. The third and final phase of flooding occurred mainly in historical Hungary during late March and early April 1784. The different impacts and consequences of the above floods on both local and regional scales were reflected in the economic and societal responses, material damage and human losses. The winter of 1783/1784 can be considered as typical, if severe, for the Little Ice Age period across much of Europe.  相似文献   

The Mammoth Peak sheeted complex,Tuolumne batholith,Sierra Nevada,California: a record of initial growth or late thermal contraction in a magma chamber?     

Jiří Žák  Scott R. Paterson  Vojtěch Janoušek  Petr Kabele 《Contributions to Mineralogy and Petrology》2009,158(4):447-470

The Mammoth Peak sheeted intrusive complex formed in the interior of a ~7–10 km deep magma chamber, specifically in the Half Dome granodiorite of the Tuolumne batholith, central Sierra Nevada, CA (USA). The sheets consist of fractionated melts with accumulated hornblende, biotite, magnetite, titanite, apatite, and zircon. The accumulation, especially of titanite, had a profound effect on minor and trace elements (Nb, Ta, Ti, REE, U, Th, P, Zr, Hf, etc.), increasing their contents up to five to six times. Our thermal–mechanical modeling using the finite element method shows that cooling-generated tensile stresses resulted in the inward propagation of two perpendicular sets of dilational cracks in the host granodiorite. We interpret the sheeted complex to have formed by a crack-seal mechanism in a high strength, crystal-rich mush, whereby outward younging pulses of fractionated magma were injected into these syn-magmatic cracks at the margin of an active magma chamber. Thermal–mechanical instabilities developed after the assembly of the sheeted complex, which was then overprinted by late ~NW–SE magmatic foliation. This case example provides a cautionary note regarding the interpretation that sheeted zones in large granitoid plutons imply a diking mechanism of growth because the sheeted/dike complexes in plutons (1) may display inverse growth directions from the growth of the overall intrusive sequence; (2) need not record initial chamber construction and instead may reflect late pulsing of magma within an already constructed magma chamber; (3) have an overprinting magmatic fabric indicating the continued presence of melt after construction of sheeted complexes and thus a prolonged thermal history as compared to dikes; and (4) because the scale of the observed sheeted complexes may be small (<1%) in comparison to large homogenous parts of plutons, in which there is no evidence for sheeting or diking. Thus, where extensive dike complexes in plutons are absent, such as in much of the Tuolumne batholith, the application of an incremental diking model to explain chamber construction is at best speculative.  相似文献   

Book Reviews: Automatic Extraction of Man-Made Objects from Aerial And Space Images (II). Edited By A. Gruen, E.P. Baltsavias and O. Henricsson. Birkhäuser-Vlg., Basel - Boston - Berlin, 1997,245 figs., 24 tabs., ix + 393 pp., hard cover.     

Petr Holota 《Studia Geophysica et Geodaetica》1999,43(2):228-228

  相似文献   

Hydraulic characteristics of the Maastrichtian sedimentary rocks of the southeastern Bida Basin, central Nigeria     

Petr Vrbka  Olusola Johnson Ojo  Holler Gebhardt   《Journal of African Earth Sciences》1999,29(4):935

A set of outcrop samples from the Lokoja and Patti Formations of the southern Bida Basin (Nigeria) was examined for grain size distribution, sedimentary and hydraulic characteristics. Most of the samples are well-sorted with an uniformity coefficient (U) ranging between 1.3 and 6.3. The mean effective grain diameter (d₁₀) is in the order of 0.11 mm, the mean value of d₉₀ was determined as 0.66 mm (both geometric mean) and the median grain size (d₅₀) as 0.23 mm. Based on these values, the sedimentary sequence can be described as ‘fine to medium sized sand’, having minor amounts of either silt, or coarse sand and some gravel. The total porosity of the samples was determined by laboratory methods to be in the range of 9–29%. The hydraulic conductivity (K) was determined according to Hazen.and Beyer, and by Shepherd's formula, the last resulting in a geometric mean of 3.3 m d⁻¹ or 3.3 darcy. The results are used to estimate local groundwater potential. The entire pore space (potential groundwater reservoir) for the area under study is estimated to be in the order of 290–430 km³. Because of higher hydraulic conductivities, it is recommended that the Lokoja Formation is concentrated on as a target for groundwater exploration.  相似文献   

Prevailing-frequency approximation of the coupling ray theory along the SH and SV reference rays in a heterogeneous generally anisotropic medium which is approximately uniaxial     

Petr Bulant  Luděk Klimeš 《Studia Geophysica et Geodaetica》2017,61(3):513-540

The behaviour of the actual polarization of an electromagnetic wave or elastic S–wave is described by the coupling ray theory, which represents the generalization of both the zero–order isotropic and anisotropic ray theories and provides continuous transition between them. The coupling ray theory is usually applied to anisotropic common reference rays, but it is more accurate if it is applied to reference rays which are closer to the actual wave paths. In a generally anisotropic or bianisotropic medium, the actual wave paths may be approximated by the anisotropic–ray–theory rays if these rays behave reasonably. In an approximately uniaxial (approximately transversely isotropic) anisotropic medium, we can define and trace the SH (ordinary) and SV (extraordinary) reference rays, and use them as reference rays for the prevailing–frequency approximation of the coupling ray theory. In both cases, i.e. for the anisotropic–ray–theory rays or the SH and SV reference rays, we have two sets of reference rays. We thus obtain two arrivals along each reference ray of the first set and have to select the correct one. Analogously, we obtain two arrivals along each reference ray of the second set and have to select the correct one. In this paper, we suggest the way of selecting the correct arrivals. We then demonstrate the accuracy of the resulting prevailing–frequency approximation of the coupling ray theory using elastic S waves along the SH and SV reference rays in four different approximately uniaxial (approximately transversely isotropic) velocity models.  相似文献   

Geophysical evidence of the Eastern Marginal Fault of the Cheb Basin (Czech Republic)     

Vratislav Blecha  Tomáš Fischer  Petr Tábořík  Jan Vilhem  Radek Klanica  Jan Valenta  Petra Štěpančíková 《Studia Geophysica et Geodaetica》2018,62(4):660-680

The western part of the Bohemian Massif hosts an intersection of two regional fault zones, the SW-NE trending Oh?e/Eger Graben and the NNW-SSE trending Mariánské Lázně Fault, which has been reactivated several times in the geological history and controlled the formation of the Tertiary Cheb Basin. The broader area of the Cheb Basin is also related to permanent seismic activity of M_L 3+ earthquake swarms. The Eastern Marginal Fault of the Cheb Basin (northern segment of the Mariánské Lázně Fault) separates the basin sediments and underlying granites in the SW from the Kru?né Hory/Erzgebirge Mts. crystalline unit in the NE. We describe a detailed geophysical survey targeted to locating the Eastern Marginal Fault and determining its geometry in the depth. The survey was conducted at the Kopanina site near the Nový Kostel focal zone, which shows the strongest seismic activity of the whole Western Bohemia earthquake swarm region. Complex geophysical survey included gravimetry, electrical resistivity tomography, audiomagnetotellurics and seismic refraction. We found that the rocks within the Eastern Marginal Fault show low resistivity, low seismic velocity and density, which indicates their deep fracturing, weathering and higher water content. The dip of the fault in shallow depths is about 60° towards SW. At greater depths, the slope turns to subvertical with dip angle of about 80°. Results of geoelectrical methods show blocky fabric of the Cheb Basin and deep weathering of the granite bedrock, which is consistent with geologic models based on borehole surveys.  相似文献