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Magnetic fabric of loess and paleosols on selected localities in South Moravia
Obersteinová, Tereza ; Kadlec, Jaroslav (advisor) ; Chadima, Martin (referee)
Pleistocene loess-palaeosol sequences provide a unique proxy-record enabling detailed reconstruction of Quaternary palaeoenvironments. Environmental magnetic methods are often used to read the natural archives. The loess-palaeosol sequences exposed in two sections located in southern Moravia and a sequence from central Bohemia were studied in a frame of this Diploma Thesis. Variations of bulk magnetic susceptibility, measured in the sediments, show similar pattern as in the Chinese loess-palaeosol bodies - i.e. palaeosols reveal higher magnetic susceptibility in comparison with loess due to magnetic enhancement. The magnetic enhancement is driven by weathering during pedogenic processes related to the formation of ultra-fine magnetite particles. The magnetite content is controlling the sediment magnetic behavior. The magnetic enhancement rate indicates more intense pedogenic processes in the Moravia in comparison with Bohemia. Magnetic fabric in studied loess, represented by space orientation of anisotropy of magnetic susceptibility ellipsoid, indicates dominating glacial wind palaeocurrents across the southern Moravia blowing from W or SW, respectively. The magnetic fabric in the central Bohemian sequence has revealed a dominant control of running water and re-deposition of the loess material...
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Primary and secondary magnetic fabric as a tool for paleoenvironmental reconstruction
Žatecká, Michaela ; Chadima, Martin (advisor) ; Pruner, Petr (referee)
This diploma thesis deals with the research of primary and secondary magnetic fabric of aeolian loess sediments and paleosols on the cross-section temporary cropping out during the construction work in Prague 6. Magnetic enrichment - and the formation of magnetic nanoparticles in soil horizons - occurs during pedogenesis in warmer interglacials periods. The aim of this work is the interpretation of the paleoenvironment, weathering and pedogenic processes, by measuring the magnetic properties of sediments. Magnetic susceptibility, frequency-dependent magnetic susceptibility, anhysteresis remanent magnetization and natural remanent magnetization are used to detect the increased occurrence of magnetic particles, which indicate these pedogenic processes. The most developed paleosol horizon within the cross-section was the horizon of black soil and subsoil brown soil. Small signs of pedogenesis were revealed in the upper and lower loess part of the section. The magnetic fabric of loess, measured by means of anisotropy of magnetic susceptibility, reflects secondary sedimentary processes. This involves the displacement of clastic particles by flowing water and the redeposition of the material along the slope. The direction of movement of these sediments corresponds to the current geomorphology of the...
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Magnetic fabric of loess and paleosols on selected localities in South Moravia
Obersteinová, Tereza ; Kadlec, Jaroslav (advisor) ; Chadima, Martin (referee)
Pleistocene loess-palaeosol sequences provide a unique proxy-record enabling detailed reconstruction of Quaternary palaeoenvironments. Environmental magnetic methods are often used to read the natural archives. The loess-palaeosol sequences exposed in two sections located in southern Moravia and a sequence from central Bohemia were studied in a frame of this Diploma Thesis. Variations of bulk magnetic susceptibility, measured in the sediments, show similar pattern as in the Chinese loess-palaeosol bodies - i.e. palaeosols reveal higher magnetic susceptibility in comparison with loess due to magnetic enhancement. The magnetic enhancement is driven by weathering during pedogenic processes related to the formation of ultra-fine magnetite particles. The magnetite content is controlling the sediment magnetic behavior. The magnetic enhancement rate indicates more intense pedogenic processes in the Moravia in comparison with Bohemia. Magnetic fabric in studied loess, represented by space orientation of anisotropy of magnetic susceptibility ellipsoid, indicates dominating glacial wind palaeocurrents across the southern Moravia blowing from W or SW, respectively. The magnetic fabric in the central Bohemian sequence has revealed a dominant control of running water and re-deposition of the loess material...
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