National Repository of Grey Literature 52 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Frequency changes in normal and reversed polarities of geomagnetic field
Olšanská, Irena ; Kletetschka, Günther (advisor) ; Pruner, Petr (referee)
This work consits of two parts, literature review and practical section. Literature review covers essential knowledge about magnetic field of Earth in attempt of understanding its inversion events. This section contains thistory of research of geomagnetism, key theories, physical quantities, magnetic properties of the minerals and outlines the knowledge of paleomagnetism. Practical part concerns the analysis of geomagnetic field inversions. It deals with inversions that happened during the last 157, 53 million years (Gee and Kent, 2007) and compares the duration of normal and reversal polarity and both types together. Statistical methods of investigation,namely Gaussian distribution and frequency, were employed. The evaluation of results showed that the average time between two inversions is: 124 000 years for normal, 450 000 years for reversal and 287 000 years for both types. The intervals shortened over last 80 million years. Comparing the frequencies of each period following results were obtained: both types usually lasts about 350 000 years, periods that are shorter than 350 000 years appears more often for normal polarity, but the frequencies of longer periods are similar for both types.
Paleomagnetic record of basaltic lava flows on Nelson Island, Antarctica
Haislová, Radka ; Kletetschka, Günther (advisor) ; Pruner, Petr (referee)
Paleomagnetism is geophysical method for determination of former magnetic field orientation on the Earth using measurement of remanent magnetisation of rocks. Combined with radiomagnetic datingk paleomagnetism enables study of time evolution of the magnetic field on the Earth and/or reconstruction of former positions of litospheric plates. This thesis is elaborates on paleomagnetic record of basalt lava flow on the Nelson's Island in Antarctica and summarizes geological data. In the research part of this thesis theory of magnetism is introduced and the paleomagnetism method is emphasized. Additionaly, I provide a short review of magnetic minerals, that can occur in basalt. These mineral can potentialy hold some information about the character of magnetic field of the geological past. Radiometric dating methods are included as atool for determination of absolute age of solidification of ingenous rocks (lava). Specifically, the K-Ar and Ar-Ar dating methods are emphasized. The regional section of this thesis conntains geological overview about the Antarctica and the Nelson's Island with its surroundings.Included is a section about the laboratory devices for measuring vector magnetisation of oriented rock samples (for example rotational and cryogenic magnetometer). The thesis is concluded with its...
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...
The Silurian-Devonian boundary in the Barrandian (Czech Republic): Sedimentology, magnetic susceptibility and gamma-ray spectrometry stratigraphy
Vacek, František ; Bosák, Pavel (advisor) ; Pruner, Petr (referee) ; Kukal, Zdeněk (referee)
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Magnetomineralogie devonských vápenců z lokality Branžovy : závěrečná zpráva
Čížková, Kristýna ; Elbra, Tiiu ; Pruner, Petr ; Schnabl, Petr
Devonské vápence z lokality Branžovy byly podrobeny měření magnetické susceptibility v závislosti na teplotě, postupnému sycení magnetickým polem a demagnetování střídavým polem za účelem zjištění magnetomineralogických vlastností. Ve vzorcích byly identifikovány minerály s vysokou i nízkou koercivitou. Podařilo se interpretovat kritické teploty některých magnetických minerálů.
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