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Mechanisms and time scales of formation of ribbon continents
Syahputra, Reza ; Žák, Jiří (advisor) ; Zulauf, Gernold (referee) ; Hrouda, František (referee)
Investigation into the ribbon continents has started since the 1980s; however, most studies focued on oceanic closure phase, involving the subduction, accretion, and collision. The formation of ribbon continents has received little attention, perhaps because it has less recent examples. This thesis is designed to address several possible scenarios for the formation of ribbon continent by investigating the tectonics, magmatism, and sedimentation of the former Avalonian-Cadomian belt during the break-up of the peri-Gondwana terranes and transition from the active- to passive-margin settings. The data originated from three different locations within the Bohemian Massif, the Czech Republic, which can also be viewed as a Cambro- Ordovician crustal evolution from the lower crust to the surface level: (1) intermediate to felsic of the Kdyně pluton in the Plzeň region, (2) the continental Příbram-Jince basin in the Central Bohemian region, and (3) metagranites and granitic orthogneisses of the Moldanubian zone in Pardubice and Vysočina regions. The methods used involve the integration of structural mapping, microstructural analysis, stratigraphic and sedimentological analysis, and in particular the anisotropy of magnetic susceptibility (AMS) accompanied by an examination of magnetic mineralogy using...
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Paleomagnetic study of Paleozoic rocks from SW Mongolia
Joštová, Daniela ; Lexa, Ondrej (advisor) ; Hrouda, František (referee)
English abstract The aim of this thesis is verification of the theory about evolution of the Mongolian orocline in Permo-Triassic by the paleomagnetic analysis of rocks taken from south-west Mongolia and it is the first step to understand the problematics in bigger detail. Basics of magnetism, geomagnetism, paleomagnetism and geology of the studied part of Mongolia are described in first part of this thesis. Second part is dedicated to methodology and my own research with the thermoremanent magnetizations data. Mongolia is situated between three cratons - Siberia, North China and Tarim and it is part of the Central Asian Orogenic Belt (CAOB), which evolution is not well understood and it is still being studied by a lot of researches. Kröner (2010) says, that the area of Mongolia can be divided to 4 tectonic zones (Lake, Trans-Altai, Gobi-Altai and South Gobi), however Badarch et al. (2002) are dividing the area to 44 terranes, which are separated to two parts - North (Caledonian) and South (Variscan) by the Main Mongolian Lineament. Studied part of the Mongolian area lies eastward from north boarder of China and the samples were taken from three parts - Altay, Edrene and Khovd. Sampling techniques and the whole procedure of analysing the measured data is also mentioned. There is also a comparison of the...
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Brittle tectonics in the NE Bohemian Massif as related to recent tectonic movements indicated by GPS measurement
Nováková, Lucie ; Hrouda, František (advisor) ; Melichar, Rostislav (referee) ; Decker, Kurt (referee)
North-eastern part of the Bohemian Massif is characterised by many NW-SE striking faults. The Sudetic Marginal Fault Zone (SMFZ) and Hronov - Poříčí Fault Zone (HPFZ) represent the major seismoactive dislocations in this area. Field structural investigations, including fault-slip data collection were carried out on a number of natural outcrops and quarries with the aim of establishing a robust and field-constrained model for the local brittle structural evolution of the studied areas. Almost 5000 faults and fractures have been measured and studied in 116 localities. Two principle sets of faults within the SMFZ are oriented in the N-S and W-E directions. The faults are mainly dipping under 80-90ř. The lineations found on the fault planes are mainly trending to the SW and W. The kinematic frequent analysis was performed due to the distribution of the fault types in the orientations. The faults were divided into the different tectonic phases based on their origin or reactivation and their relative age using the calculation of paleostress analysis. The paleostress analysis of the fault-slip data within the SMFZ resulted identification of six tectonic phases from the youngest to the oldest: strike-slip regime with maximum compression σ1 in the NNW-SSE direction, compressional regime with σ1 in the...
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Paleomagnetism and magnetomineralogy of rocks from the Bohemian Massif and Tethyan Realm
Schnabl, Petr ; Pruner, Petr (advisor) ; Hrouda, František (referee) ; Petrovský, Eduard (referee)
Mgr. Petr Schnabl - Dissertation Paleomagnetism and magnetomineralogy of rocks from the Bohemian Massif and Tethyan Realm Abstract The thesis deals with paleomagnetic and rock magnetic properties of Silurian/Devonian and Jurassic/Cretaceous limestones, Paleogene/Neogene basaltic rocks and altered Silurian basalts. The main goal is to determine the history of the Earths' magnetic field from the Silurian to the present. Two lithostratigraphic formations are defined in the Jičín volcanic field on the basis of volcanology, paleomagnetism and radiometric dating. The Trosky Formation (24.6?/18.3 - 15.7 Ma) is composed of several Strombolian-type volcanoes, while the Kozákov Formation (5.2 - 4.6 Ma) is represented by effusive products with a crater vent of a single giant volcano. One Pliocene (4.3-3.3 Ma) and two Pleistocene phases (2.6 -2.1 Ma and 1.8 - 1.1 Ma) of volcanic activity Magnetostratigraphy is a very important tool for the definition of the J/K boundary. The boundary between the Crassicolaria and Calpionella zones is present within geopolarity zone M19n. The boundary between the ammonite zones Jacobi and Durangites also lies close to this point. Paleomagnetic directions of Silurian and Devonian rocks in the Bohemian Massif are very difficult to interpret and have been studied as a challenging problem...
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