Institute of Geology of the CAS

Prague, Czech Republic

Institute of Geology of the CAS

Prague, Czech Republic
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Piedrahita V.A.,EAFIT University | Bernet M.,CNRS Institute of Earth Sciences | Chadima M.,AGICO Inc. | Chadima M.,Institute of Geology of the CAS | And 3 more authors.
Sedimentary Geology | Year: 2017

New detrital zircon-fission track (ZFT) and magnetic fabric data are presented to constrain the time of deposition, provenance and deformation of the of Lower and Upper members of the Amagá Formation in the Amagá Basin. The Amagá Basin is located in the northern Andes, between the Western and Central Cordilleras of Colombia. The Amagá Formation was deposited in a transpressive geodynamic context and is allegedly synchronous with tectonic events such as the Andean orogeny and the Panama-Choco Block collision with the northwestern South American Plate. Detrital ZFT data confirm an Oligocene age for the Lower Member and a middle-Miocene age for the Upper Member of the Amagá Formation. In addition to constraining the depositional age, the ZFT data presented in this study also reflect Paleocene-Eocene, late to early Oligocene and late to middle Miocene cooling in sediment source areas mainly located in the Central and Western Cordilleras of Colombia. These ages can be associated with regional exhumation events in the central and northern Andes of South America. Collisional stages of the Panama-Choco Block against northwestern South America, subduction of the Farallon-Nazca Plate and strike-slip reactivation periods of the Cauca-Romeral fault system, caused NW-SE compression and NE-SW simple shear in the Amagá Basin. This deformational regime, identified by magnetic fabric data, induces syn- and post-depositional deformation over the Amagá Formation. © 2017 Elsevier B.V.

Matys Grygar T.,Academy of Sciences of the Czech Republic | Hosek M.,Academy of Sciences of the Czech Republic | Mach K.,North Bohemian Mines | Schnabl P.,Institute of Geology of the CAS | Martinez M.,University of Bremen
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2017

The work investigates the extensive freshwater lacustrine deposits of the Most Formation, which formed in the period between 17.7. Ma and ca. 15.9. Ma, in order to describe climate changes just before the Miocene Climatic Optimum (MCO). The Most Basin, an incipient rift within the European Cenozoic Rift System, exhibited a sedimentary environment that was sufficiently stable to preserve orbital signatures of environmental changes. Changes in the mineral composition of the sediments were characterised in terms of variations in their elemental composition, particularly their Al/Si and K/Ti element ratios and Fe, Sr, and Zr elemental abundances, which were efficiently obtained using X-ray fluorescence spectroscopy with a density of 3-4 samples per metre of core (approximately 15-20 samples per precession cycle). The sediments are distinguished by the presence of distinct and correlated horizons (1-10. cm thick) containing Sr, Ba-rich crandallite, a mineral from the aluminium-phosphate-sulphate (APS) group. Chemo-, magneto-, and cyclostratigraphy were used to correlate eight cores with lengths up to 240. m and to date the sediment; discrepancies at scales of up to two precession cycles (each ca. 20. kyr, typically ~. 4. m per cycle) were observed. The primary age model was based on magnetic polarity analysis (5 reversals) and later refined at the metre scale using cyclostratigraphy. We interpret the onset of the basin-wide lacustrine phase in the Most Basin as being a consequence of the enhanced input of fluvial clastic sediment to the former peat swamps during the high-eccentricity period at 17.7-17.55. Ma, i.e., immediately after the initial decay of the East Antarctic ice sheet according to Levy et al. (2016). The most important environmental change recorded by the lacustrine interval in the Most Basin occurred at 16.44. Ma during an eccentricity maximum and is nearly coeval with further shrinkage of the East Antarctic ice sheet. The second stage of monotonous lacustrine deposition, which exhibited enhanced precession-controlled compositional variability in 16.1-16.0. Ma witnessed the onset of the MCO. Sediments younger than 15.9. Ma are missing due to erosional removal after subsequent basin inversion. The sediments of the Most Formation represent an archive of environmental change in central Europe during the early stages of the MCO and have a temporal resolution ca. 5. kyr. © 2017 Elsevier B.V.

Krmicek L.,Brno University of Technology | Krmicek L.,Institute of Geology of the CAS | Horak V.,Brno University of Technology | Kubouskova S.,Masaryk University | Petruzalek M.,Institute of Geology of the CAS
Procedia Engineering | Year: 2017

Rock massifs traditionally used for the construction of foundations, tunnels or as a source of crushed stone, frequently contain compositionally (texturally, mineralogically, geochemically) contrasting inclusions - xenoliths. The presence of xenoliths is a commonly overlooked fact which may, however, significantly affect the total strength of the massifs. The most frequent xenoliths in igneous massifs are mafic microgranular enclaves occurring as ellipsoidal inclusions with the size varying from centimetre to metre scales in the host rocks. Our pilot experimental study brings a complex assessment of strength properties (e.g., rebound hardness, uniaxial compressive strength, rock tensile strength) of multicomponent geomaterials, i.e., host-rocks and their enclaves, sampled both from quartz-rich (granitoid) and quartz-poor (syenitoid) massifs. © 2017 The Authors.

Kallistova A.,Charles University | Kallistova A.,Institute of Geology of the CAS | Horacek I.,Charles University | Slouf M.,Czech Institute of Macromolecular Chemical | And 3 more authors.
PLoS ONE | Year: 2017

Using the distal molar of a minipig as a model, we studied changes in the microstructural characteristics of apatite crystallites during enamel maturation (16-23 months of postnatal age), and their effects upon the mechanical properties of the enamel coat. The slow rate of tooth development in a pig model enabled us to reveal essential heterochronies in particular components of the maturation process. The maturation changes began along the enameldentine junction (EDJ) of the trigonid, spreading subsequently to the outer layers of the enamel coat to appear at the surface zone with a 2-month delay. Correspondingly, at the distal part of the tooth the timing of maturation processes is delayed by 3-5 month compared to the mesial part of the tooth. The early stage of enamel maturation (16-20 months), when the enamel coat is composed almost exclusively of radial prismatic enamel, is characterized by a gradual increase in crystallite thickness (by a mean monthly increment of 3.8 nm); and an increase in the prism width and thickness of crystals composed of elementary crystallites. The late stage of maturation (the last two months prior to tooth eruption), marked with the rapid appearance of the interprismatic matrix (IPM) during which the crystals densely infill spaces between prisms, is characterized by an abrupt decrease in microstrain and abrupt changes in the micromechanical properties of the enamel: a rapid increase in its ability to resist long-term load and its considerable hardening. The results suggest that in terms of crystallization dynamics the processes characterizing the early and late stage of mammalian enamel maturation represent distinct entities. In regards to common features with enamel formation in the tribosphenic molar we argue that the separation of these processes could be a common apomorphy of mammalian amelogenetic dynamics in general. © 2017 Kallistova et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Bruthans J.,Charles University | Kamas J.,Charles University | Filippi M.,Institute of Geology of the CAS | Zare M.,Shiraz University | Mayo A.L.,Brigham Young University
International Journal of Speleology | Year: 2017

Southern Iran hosts abundant salt karst phenomena in numerous salt diapirs. This paper provides a new insight into the relationships among climate, cap soil and salt karst hydrogeology. Cave systems were documented and mapped. Soil, drip, stream, and flood waters from different environments were studied at several diapirs. It was revealed that the soil water chemistry depends on both the climate and cap soil thickness. In semi-arid climates, a thick cap soil forms (>3 m) and water has very low TDS values (0.15 g/l). In arid climates, a shallow cap soil forms, and soil water is gypsum-saturated with low dissolved halite contents. In both environments, drip waters from salt caves and springs displayed high TDS values (255 to 347 g/l). This is explained by the dissolution of halite and minor anhydrite/gypsum, a K-Mg sulfate and sylvite. Spring water plots on a local meteoric water line, whereas drips in caves have an evaporative signature. The flash flood runoff is dominated by event rain water based on isotopic data, while springs are dominantly supplied by a base flow component. The mean residence time of water on the diapirs is controlled by the cap soil thickness. Water residence times may reach several hundreds of years on a thick cap soil based on an exponential model but <120 years on a thin cap soil. © 2017, University of Teheran. All rights reserved.

Chalupa F.,Charles University | Vilhelm J.,Charles University | Petruzalek M.,Institute of Geology of the CAS | Bukovska Z.,Czech Geological Survey
Acta Montanistica Slovaca | Year: 2017

This article compares static moduli determined using uniaxial tests and dynamic moduli calculated from elastic wave propagation velocities. On the example of limestones, we present the fact that for isotropic and intact rock, static and dynamic moduli correspond to each other over a broad range of frequencies. In damaged rock (cracks, weathering), a difference occurs and static moduli decrease. To include the effect of damage, T-matrix model has been selected. Dynamic moduli, porosity, density changes and information about properties of macroscopic cracks are necessary data for model calculation. These data are provided by other well logging methods such as an acoustic log with full waveform registration, density log, neutron log and acoustic scanner. Using all these data, a T-matrix model can predict static moduli from dynamic moduli. As we are dealing with well log data, we calculated vertical component of the elastic tensor only. This component is represented by Young’s modulus E and Poisson’s ratio ν. The functionality of the model has been verified on real well logging data and corresponding limestone specimens acquired from borehole core. The differences between values of E modulus, originally up to 20 %, decreased to values similar to differences in intact rock, i.e. the order of the first units of percent. In the case of ν values, demonstrable reduction of dynamic values, approaching static values was achieved, the resulting difference being less than 15 %. © 2017, Technical University of Kosice. All rights reserved.

Ludvikova J.,Czech Institute of Chemical Process Fundamentals | Jiratova K.,Czech Institute of Chemical Process Fundamentals | Klempa J.,Czech Institute of Chemical Process Fundamentals | Boehmova V.,Institute of Geology of the CAS | Obalova L.,VSB - Technical University of Ostrava
Catalysis Today | Year: 2012

Catalytic activity of the Co-Mn-Al mixed oxide catalysts (Co:Mn:Al molar ratio of 4:1:1) supported over titania was examined in total oxidation of ethanol. The prepared catalysts were characterized by chemical analysis (AAS), surface area measurements, and temperature programmed techniques (TPR, TPD). In ethanol oxidation, the catalysts activity gradually increased with increasing active phase content. Low concentration of Co-Mn-Al oxides in the catalyst negatively affected formation of reaction byproducts: carbon monoxide production steeply increased when Co + Mn metals concentration were lower than 5 wt.%. On the other hand, formation of the second main reaction intermediate, acetaldehyde was limited, when acidity of the catalyst was not high, i.e. concentration of Co-Mn metals over titania was low. © 2011 Elsevier B.V. All rights reserved.

Zigova A.,Institute of Geology of the CAS | Stastny M.,Institute of Geology of the CAS
Acta Geodynamica et Geomaterialia | Year: 2015

The development of soil cover on loess in regions of Cretaceous sediments and Devonian limestones in the Bohemian Massif was analysed. The study was performed in areas with different land use. Parent material was characterized on the basis of thin section study. Soils were evaluated by macromorphological analysis, particle size distribution, chemical properties, parameters of soil organic matter and mineral composition of clay fraction. The results revealed differences in the formation of soil cover which are predominately connected with geological conditions. The main pedogenetic process for Bohemian Cretaceous Basin is humification. Pedogenetic clay differentiation is relatively slight. Intense pedogenetic clay differentiation, less pronounced processes of litter formation and humification are characteristic for soils in the Devonian limestone areas. The intensity of processes of pedogenetic clay differentiation is influenced by pH values. The quality and quantity of soil organic matter were influenced by the source of biomass, biological activity and type of land use. Petrography of parent material from thin sections shows some differences among features of Ck horizons. The most abundant minerals of clay fraction of the studied soil are quartz, illite and kaolinite. Bt horizons of Albic Luvisols have an elevated content of illite. © 2015 Academy of Sciences of the Czech Republic. All Rights Reserved.

Bella P.,State Nature Conservancy of the Slovak Republic | Bella P.,Catholic University in Ruzomberok | Bosak P.,Institute of Geology of the CAS
Acta Carsologica | Year: 2015

Ceiling channels belong to specific geomorphological forms occurring only in caves. Their origin has been commonly connected with the paragenesis. According to review articles, the terms of ceiling channel and paragenesis were defined by Philippe Renault (1958) for the first time. Nevertheless, Zdeněk Roth in his study of morphology and geomorphological evolu­tion of the Domica Cave (southern Slovakia) published in 1937 (in Czech with long French summary) not only described ceil­ing channels, but he presented also their definition. Roth and other authors used the term later in describing features of sev­eral caves in Slovakia and Hungary. Based on original Roth ob­servations, Josef Kunský defined the term generally in his text­book (1950 in Czech, 1956 in Polish and 1958 in French). The description of paragenetic ceiling channels by Renault (1958) can be considered as the first one only in Western European karstology literature. © 2015 Zalozba Z R C. All rights reserved.

PubMed | CAS Institute of Biophysics, University of Chicago, Martin Luther University of Halle Wittenberg, Institute of Geology of the CAS and 3 more.
Type: Journal Article | Journal: The New phytologist | Year: 2016

Cadmium (Cd) is an important environmental pollutant and is poisonous to most organisms. We aimed to unravel the mechanisms of Cd toxicity in the model water plant Ceratophyllum demersum exposed to low (nM) concentrations of Cd as are present in nature. Experiments were conducted under environmentally relevant conditions, including nature-like light and temperature cycles, and a low biomass to water ratio. We measured chlorophyll (Chl) fluorescence kinetics, oxygen exchange, the concentrations of reactive oxygen species and pigments, metal binding to proteins, and the accumulation of starch and metals. The inhibition threshold concentration for most parameters was 20nM. Below this concentration, hardly any stress symptoms were observed. The first site of inhibition was photosynthetic light reactions (the maximal quantum yield of photosystem II (PSII) reaction centre measured as Fv /Fm , light-acclimated PSII activity PSII , and total Chl). Trimers of the PSII light-harvesting complexes (LHCIIs) decreased more than LHC monomers and detection of Cd in the monomers suggested replacement of magnesium (Mg) by Cd in the Chl molecules. As a consequence of dysfunctional photosynthesis and energy dissipation, reactive oxygen species (superoxide and hydrogen peroxide) appeared. Cadmium had negative effects on macrophytes at much lower concentrations than reported previously, emphasizing the importance of studies applying environmentally relevant conditions. A chain of inhibition events could be established.

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