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Cave formation initiated by dissolution of carbonate cement in qartzose sandstones
Adamovič, Jiří ; Mikuláš, Radek ; Navrátil, Tomáš ; Mertlík, J.
Besides cavities of irregular shape, European sandstones also feature symmetrical cavities of spherical, ellipsoidal or teardrop shapes. Most of them are tens of centimetres across but some reach as much as 2–3 m in diameter and may coalesce into large caves tens of metres in length. Their origin has not been clearly explained yet. Based on the field comparison between such cavities in quartzose sandstones and incompletely developed cavities in carbonate-cemented sandstones, it can be demonstrated that the symmetrical cavities form by carbonate dissolution within the limits of former carbonate concretions. The diagnostic features of post-concretionary cavities include their circular or elliptical cross-section, a uniform orientation of their long axes across the region, and the presence of a set of parallel vertical joints or grooves/ribs on their inner walls. In some sandstone areas (e.g., Petite Suisse area in Luxembourg, Kokořín area in the Czech Republic), a wide variety of transitional forms can be found between the cavities and concretions forming positive relief on a vertical cliff face, depending on the position of the carbonate dissolution front in the present landscape.
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Problematické aspekty ichntaxonomie: tafosérie, "fotosérie" a "grafosérie"
Mikuláš, Radek
The probability of misidentification of trace fossils is extremely high if the authors did not see the original material but used only published photographs. Clearly, it is impracticable to visit all the collections containing the revised material and impossible to visit all type localities, but further caution against the use of photos or drawings must be done here. Photographed material can result in the effect named here “photoseries”: just the method of illumination of the object can make it classifiable as two different ichnotaxa. Diffuse light enables an annulate tunnel to be featured as Rhabdoglyphus, but raking light depicts instead “invaginated segments” of Fustiglyphus of idealized drawings is obviously even more problematic, as shown by nice “graphoseries” if we consider the original specimen, the method of its preparation, and the published figure.
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Guide to the Post-conference excursion Sandstone Landscapes: Diversity, Ecology and Conservation
Mikuláš, Radek ; Adamovič, Jiří ; Cílek, Václav ; Hendrych, J. ; Líčenková, M. ; Mertlík, J. ; Mrkáček, Z. ; Petříček, V. ; Tomášek, O. ; Šoltysová, L. ; Vacková, D. ; Herben, Tomáš ; Kopřivová, L.
The Kokořínsko PLA, Bohemian Paradise PLA and Polická vrchovina Highland represent a high-diversity "sandstone phenomenon". Sandstones of the Bohemian Paradise can be considered as optimum for development of microrelief features influenced by saet erosion and case hardening.
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