New insight into the origin of Ordovician oolitic iron ores from Skalka Deposit near Mníšek pod Brdy (Prague Basin, Barrandian)

The Skalka Deposit near Mníšek pod Brdy currently represents one of the best exposed localities of Ordovician oolitic iron ores in the Barrandian. The studied oolitic iron ores consist mainly of siderite (Fe = 1.47–1.86 apfu) and kaolinite (Si = 7.99–8.06 apfu; VIAl = 7.62–7.67 apfu). This mineral association has been formed as a result of the process of diagenesis and has resulted from the decomposition of chlorite and Fe-(oxo-)hydroxides. Presence of colofane indicates rather low temperatures for this transformation. Paleontological record makes the previous hypothesis, that the iron ore deposit was formed in an isolated depression separated from the Prague Basin by a flat elevation, questionable. The presence of abundant graptolites and agglutinated foraminifers in the shales of the Šárka Formation indicates rather deep-water open-marine conditions. Ferruginous ooids are typically formed on shoals affected by wave action. The presence of these ooids in deep-water shale and existence of oolitic iron ore deposit accompanied by this shale does not need to be explained by sudden shallowing, but more likely by reworking of ooids in gravity flows to sublittoral or bathyal depths. Original position of shoal was most likely situated towards NNW where ore deposit and finally the complete Šárka Formation disappear. The fossil record indicates open-marine realm southeast of the Skalka area.The Skalka Deposit near Mníšek pod Brdy currently represents one of the best exposed localities of Ordovician oolitic iron ores in the Barrandian. The studied oolitic iron ores consist mainly of siderite (Fe = 1.47–1.86 apfu) and kaolinite (Si = 7.99–8.06 apfu; VIAl = 7.62–7.67 apfu). This mineral association has been formed as a result of the process of diagenesis and has resulted from the decomposition of chlorite and Fe-(oxo-)hydroxides. Presence of colofane indicates rather low temperatures for this transformation. Paleontological record makes the previous hypothesis, that the iron ore deposit was formed in an isolated depression separated from the Prague Basin by a flat elevation, questionable. The presence of abundant graptolites and agglutinated foraminifers in the shales of the Šárka Formation indicates rather deep-water open-marine conditions. Ferruginous ooids are typically formed on shoals affected by wave action. The presence of these ooids in deep-water shale and existence of oolitic iron ore deposit accompanied by this shale does not need to be explained by sudden shallowing, but more likely by reworking of ooids in gravity flows to sublittoral or bathyal depths. Original position of shoal was most likely situated towards NNW where ore deposit and finally the complete Šárka Formation disappear. The fossil record indicates open-marine realm southeast of the Skalka area

Carbonate concretions of the Moravsko-Slezské Beskydy Mountains (Czech Republic)

The carbonate concretions up to 1 m in diameter occur in the Cretaceous and Paleogene formations of the Silesian Unit in the Moravskoslezské Beskydy Mountains. Three concretions from three different formations were analyzed (Veřovice and Istebna formations and Albian-Cenomanian of the Kelč Development of the Silesian Unit). The concretions contain mainly siderite (Fe0.56-0.80 Ca0.03-0.07 Mg0.09-0.19 Mn0.01-0.06 CO3) and minor calcite. Accessory crystals and framboids of pyrite are common. Differences among samples are mainly in the grain size of carbonates and in variable proportion of siderite and calcite. Primary lamination composed of fine clastic grains is preserved within the calcite and/or siderite cement. The septaria cracks are filled with calcite and minor siderite.The carbonate concretions up to 1 m in diameter occur in the Cretaceous and Paleogene formations of the Silesian Unit in the Moravskoslezské Beskydy Mountains. Three concretions from three different formations were analyzed (Veřovice and Istebna formations and Albian-Cenomanian of the Kelč Development of the Silesian Unit). The concretions contain mainly siderite (Fe0.56-0.80 Ca0.03-0.07 Mg0.09-0.19 Mn0.01-0.06 CO3) and minor calcite. Accessory crystals and framboids of pyrite are common. Differences among samples are mainly in the grain size of carbonates and in variable proportion of siderite and calcite. Primary lamination composed of fine clastic grains is preserved within the calcite and/or siderite cement. The septaria cracks are filled with calcite and minor siderite

The influence of various sport activities on the degeneration of intervertebral discs

Excessive physical activity is one of the main risk factors in the formation of degenerative changes of the intervertebral discs. Recreational and elite sport also represents a repeated increased physical load, and based on the type of sport, a more intense and sometimes less intense action of direct forces on the intervertebral discs. On the other hand, sport and training is in general regarded as beneficial for our health. Many doctors also regards sport as a form of prevention against back injuries. The authors analyze numerous sporting activities with different types of direct forces acting on the spine, with the goal to inform on realistic scientific facts regarding the impact of these activities on the degeneration of the intervertebral disc. They inform about the available facts, which confirm the positive effects of a certain type of sport load on the degeneration of the intervertebral disc, and its correlation with the clinically manifested back pain

Kenozoické sedimenty v lomu Předklášteří u Tišnova

During the extraction of stone for the production of stone ballast in the multi-level quarry in Předklášteří near Tišnov, unconsolidated sediments with a total width of 400 m and a thickness of up to 30 m have been extensively discovered in recent years. This outcrop extends over the 2 highest levels of the quarry. During the exploration work in 1965, these sediments were not detected, because today's quarry mining area has already exceeded the original considerations about the extent of mining. The quarry mines medium-grained, biotite metagranites of the Svratka Unit of Brunovistulicum.Our research has confirmed the affiliation of exposed sediments to the Pleistocene colluvial deposits. Sediments were found in the lower part of the layered sequence, trapped along the fault of the E–W direction, which were assigned stratigraphically to the Lower Miocene (Ottnangian).We used the following methods to study these sediments: sedimentological, petrographic, mineralogical, geochemical and paleontological research. In our work, we focused mainly on the Lower Miocene part of the outcrop, because the first results from sediments in the Quaternary overlaying did not bring knowledge that would allow the stratigraphical sequence to be classified in age.The altitude of the base of these fluvial to delta sediments 370 to 375 m indicates that they are pre-Quaternary deposits. In the case of Lower Miocene lake, delta or river sediments in the wider surroundings of this locality, the following indications are used for stratigraphic classification: translucent heavy mineral associations; presence of reworked Upper Cretaceous microfauna and lithofacial association. Geochemical analyses of silty clays to claystones were compared with the occurrences of similar sediments from Brno and its surroundings (Kohoutovice, Obřany, Svinošice). These analyses proved that the sediments underwent a short transport of several kilometres and could be derived from weatherings and eluvies of the rocks of the surrounding Brunovistulicum. The lower part of the outcrop can be assessed as a relic of Lower Miocene sediments of one of the northern source areas of the Nesvačilka trough. This partial branch is often referred to in places of continuous occurrence of Ottnangian sediments as the Jinačovice depression