International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

Volume 67 no. 3 / June 2016

Volume 67 no. 3 / June 2016

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Articles in this issue

  • Gemstone deposits of Serbia

    Abstract: Gemstone minerals in Serbia have never been regarded as an interesting and significant resource. Nevertheless, more than 150 deposits and occurrences have been recorded and some of them preliminarily explored in the last 50 years. The majority of deposits and occurrences are located within the Serbo-Macedonian metallogenic province and the most significant metallogenic units at the existing level of knowledge are the Fruška Gora ore district, Cer ore district, Šumadija metallogenic zone, Kopaonik metallogenic zone and Lece-Halkidiki metallogenic zone. The most important genetic type of deposits is hydrothermal, particularly in case of serpentinite/peridotite as host/parent rock. Placer deposits are also economically important. The dominant gemstones are silica minerals: chalcedony (chrysoprase, carnelian, bluish chalcedony etc.), jasper (picture, landscape, red etc.), common opal (dendritic, green, milky white etc.), silica masses (undivided), and quartz (rock crystal, amethyst etc.). Beside silica minerals significant gemstones in Serbia include also beryl (aquamarine), garnet (almandine and pyrope), tourmaline, fluorite, rhodochrosite, carbonate-silica breccia, carbonate-silica onyx, silicified wood, howlite, serpentinite, marble onyx, and kyanite. This paper aims to present an overview of Serbian gemstone deposits and occurrences and their position based on a simplified gemstone metallogenic map of Serbia, as well as genetic-industrial classification of gemstone deposits and gemstone varieties.
  • Calcareous nannofossils of the Jurassic/Cretaceous boundary strata in the Puerto Escaño section (southern Spain) — biostratigraphy and palaeoecology

    Abstract: We obtained material from the Puerto Escaño section (southern Spain) to study the Jurassic/Cretaceous (J/K) boundary interval. The same samples had already been processed for magnetostratigraphic studies and biostratigraphic zonation based on calpionellids and ammonites (Pruner et al. 2010), but not for calcareous nannofossils. The aim of this study was to process the samples using micropalaeontological analysis and to compare and calibrate results for calcareous nannofossils with existing magnetostratigraphic and other biostratigraphic data. The calcareous nannofossil assemblage was dominated by the genera Watznaueria, Cyclagelosphaera, Nannoconus, Conusphaera and Polycostella. Several nannofossil bioevents were recorded on the basis of the distribution of stratigraphically important taxa, including zonal and subzonal markers. Based on the lowest occurrences (LO) of M. chiastius, N. globulus minor, N. wintereri, N. steinmanii minor, N. steinmannii steinmannii, N. kamptneri minor and N. kampteri kamptneri, two nannofossil subzones (NJT 15b, NJT 17a) and two nannofossil zones (NJT 16, NK-1) were recognized. The paper introduces new palaeoecological data based on geochemical analysis and macrofauna occurrences
  • Upper Cretaceous to Lower Miocene of the Subsilesian Unit (Western Carpathians, Czech Republic): stratotypes of formations revised

    Abstract: Type sections/areas for all four formations distinguished in the sedimentary succession of the Subsilesian Unit on Czech territory were revisited and described. New data on lithology, sedimentology, fossil record, biostratigraphy, heavy-minerals and geochemical proxies are based on observations and analysis of these sections. The historical type section of the Frýdek Formation was destroyed during railway construction in 19th century. Outcrops of Campanian to Maastrichtian marls and sandstones on the southwestern slope of “Castle hill” at Frýdek, are proposed as a new type section. The Ostravice riverbed in Frýdlant nad Ostravicí was originally designated as the type area, not mentioning the particular section. This area, even when supplemented with Sibudov Creek, does not show all typical facies of the formation. The outcrops range from lowermost Eocene to Eocene–Oligocene transition. In the original description of the Menilite Formation Glocker mentioned several localities in the area covering the Ždánice, Subsilesian and Silesian units, not mentioning the principal one. The single sections, each not exceeding a thickness of 2 m, are not sufficient to be a type section. Instead of that, we propose the area between Paršovice and Bystřice pod Hostýnem, covering the historical localities, as the type area. The type locality of the Ženklava Formation is an outcrop in an unnamed creek in Ženklava according to the original definition. It seems to be reasonable to extend the type section to the whole 500 m long section of the creek with the outcrops that better illustrate the lithological variability of the formation. New biostratigraphic data allow assignment to late Egerian (Eggenburgian?)
  • Age and provenance of mica-schist pebbles from the Eocene conglomerates of the Tylicz and Krynica Zone (Magura Nappe, Outer Flysch Carpathians)

    Abstract: During the Late Cretaceous to Palaeogene, the Magura Basin was supplied by clastic material from source areas situated on the northern and southern margins of the basin, which do not outcrop on the surface at present. The northern source area is traditionally connected with the Silesian Ridge, whereas the position of the southern one is still under discussion. A source area situated SE of the Magura Basin supplied the Eocene pebbly para-conglomerates containing partly exotic material. The studied clastic material contains fragments of crystalline rocks, and frequent clasts of Mesozoic to Palaeogene deep and shallow-water limestones. Numerous mica schists, scarce volcanites and granitoids as well as gneisses, quartzites and cataclasites were found in the group of crystalline exotic pebbles. Monazite ages of “exotic” mica-schist pebbles from the Tylicz, Zarzecze and Piwniczna-Mniszek sections document the Variscan 310±10 Ma age of metamorphic processes. The provenance of these exotic rocks could be connected with a remote source area located SE of the Magura Basin, which could be the NW part of the Dacia Mega Unit. The idea is strongly supported by palaeotransport directions from the SE, the absence of material derived from the Pieniny Klippen Belt, the presence of shallow water limestones, typical facies of the Median Dacides belt and metamorphic age distribution proved by monazite dating.
  • A seismic source zone model for the seismic hazard assessment of Slovakia

    Abstract: We present a new seismic source zone model for the seismic hazard assessment of Slovakia based on a new seismotectonic model of the territory of Slovakia and adjacent areas. The seismotectonic model has been developed using a new Slovak earthquake catalogue (SLOVEC 2011), successive division of the large-scale geological structures into tectonic regions, seismogeological domains and seismogenic structures. The main criteria for definitions of regions, domains and structures are the age of the last tectonic consolidation of geological structures, thickness of lithosphere, thickness of crust, geothermal conditions, current tectonic regime and seismic activity. The seismic source zones are presented on a 1:1,000,000 scale map.
  • In-situ ground gamma spectrometry — an effective tool for geological mapping (the Malé Karpaty Mts., Slovakia)

    Abstract: This contribution presents the results of profile in-situ gamma spectrometry measurements that sought to determine the content of natural radionuclides 40K, 238U and 232Th in a near surface horizon of rocks, their weathering cover and soils in the area of the Malé Karpaty Mts. It is widely established that the exploration of radioactivity of bedrocks and cover rocks can be a very effective and useful tool for both geological mapping, for identifying deposits of mineral resources, and even addressing the issues of structural and tectonic geology. This assertion is equally confirmed by the ground gamma spectrometry measurements carried out as part of this case study on larger scales, seeking more detailed geological structure solutions. The results obtained provide a welcome addition to an already existing database, which monitors the content of naturally occurring radionuclides individually for every rock lithotype of the Western Carpathians, by elaborating on the data collected by previous research and by updating this database for any future needs. The presented results confirmed the low to medium radioactivity levels of rocks and soils in the studied area. The highest values were detected in granitoids and metamorfic phyllitic rocks of the Malé Karpaty Mts. core; the lowest values were detected in carbonates, arenaceous sediments and, above all, amphibolite bodies. In this way, the presented results of the interpreted profile (P5) confirm the model of local geological structure as represented on the most up-to-date edition of the geological map of the Malé Karpaty Mts. (Polák et al. 2011).