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Influence of the stress field on weathering and erosion of sandstone landforms
Řihošek, Jaroslav ; Bruthans, Jiří (advisor) ; Mikuláš, Radek (referee) ; Válek, Jan (referee)
The influence of mechanical stress on weathering and erosion has been overlooked in works focused on sandstone landforms formation, although stress has been shown to be a key factor in the formation of a number of different sandstone landforms recently. The main goal of the doctoral thesis is to understand the relationship between mechanical stress and weathering or erosion in the formation and development of sandstone landforms. The influence of mechanical stress on the mode of weathering and the rate of disintegration of the material forming historical monuments in Petra, Jordan was investigated on the site and on samples in laboratory. A negative exponential dependence has been proven between the speed of salt weathering and the magnitude of uniaxial compression of Petra sandstone samples. The role of mechanical stress as a mechanism controlling the formation and development of the shape of sandstone forms was further studied in rock overhangs, sandstone arcades and rock gates in the Czech Republic and the USA. The doctoral thesis presents and verifies a method using Střeleč sandstone as a natural analogue in physical models simulating weathering and erosion of cemented sandstone. These physical models usually take the form of a reduced initial shape of a sandstone object created in situ from...
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Petrology and geochemistry of Devonian volcanic rocks in the southern part of the Šternberk-Horní Benešov Belt
Řihošek, Jaroslav ; Kachlík, Václav (advisor) ; Přichystal, Antonín (referee)
Šternberk-Horní Benešov belt (SHB) is built by Devonian and Lower Carboniferous rocks located between Culmian Eastern Jeseníky and Western Jeseníky nappes. As the SHP is located in the Low Jeseníky Mountains , it is a part of Rhenohercynian zone of European Variscides. The southern part of SHB is built by a volcanic complex of intrusive rocks, lavas and volcanoclastic rocks with intercalated beds of Stínava- Chabičov shales. Alkaline volcanism in Rhenohercynian zone was earlier interpreted as a result of extension in back-arc basin. Structural measurements of this study proved, that volcanosedimetary succession (situated north eventually northward) of Šternberk) is a tectonic slice. This slice was dragged out on the base of the Culmian greywacke nappe during the Variscan orogeny. Firstly the slice was thrusted northeastwards over the body of younger Culm greywacke. After that, the stack of nappes (including the Devonian volcanic rocks ) was sheared in dextral transpressional regime. The field works also indicated, that the Devonian vol- canic complex was tectonically separated from its stratigraphic footwall and hanging- wall. Volcanic rocks gradually built an elevation, eventually reaching the sea level. Anal- ysis of volcanic facies proved that the most of volcanoclastic rocks was deposited near...
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