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Magnetic polarity in concretions
Smrčinová, Lucie ; Kletetschka, Günther (advisor) ; Adamovič, Jiří (referee)
Terrestrial iron oxides, such as hematite, goethite and magnetite, form specifically cemented concretions in sandstones using an aqueous diagenetic solution. According to the new results, the timeline on which concretions are formed could be much larger than current estimates. The basis for this claim is a magnetic record of the Jurassic Navajo Sandstone in Utah. The record contains fluctuations of remanent magnetization, which could prove the inversion of the Earth's magnetic field. This observation suggests that the time axis of the accumulation of iron concretions is comparable to the time axis of the accumulation of marine iron-manganese nodules, which contain a complex magnetic record. The occurrence of extremely slow changes in iron deposition in sandstones also helps to better understand the origin of concretions. In addition, terrestrial concretions provide an analogy for the "blueberries" found by the Mars rover Opportunity on Mars. These concretions probably underwent similar formation processes and could record inversions of the early magnetic dynamo on Mars.
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Magnetic record of conretions
Smrčinová, Lucie ; Kletetschka, Günther (advisor) ; Adamovič, Jiří (referee)
Abstact The submitted bachelor thesis is focusing on the analysis of emergence of the concretion samples, which were discovered in recent years on the location of Jurassic Navajo Sandstone in Utah, and simultaneously their comparison with concretions found during exploration of Mars on the place Meridiani Planum. The major objective of this study is to compare the condition of origin and to search possible similarities. Terestrical concretions of iron oxid maintain diagenetical record of interaction between underground water flow and sandy material. Based on the input parametres, observed here, numerical and laboratory simulations were performed, leading to explanation of an image about growth of these spherules. Important factors during precipitation of nodules is concentation, flux and time. The experiment with reactions of ferrous sulfate, iron nitrate and potassium hydroxid shows the process of precipitation and maturation of hydrated iron around nucleation center of cencretion. Comparison laboratory results, numerical simulations and found samples helps to understanding to emergence of iron concretionson Mars in a certain chemical and hydrological environment. The importance of this contribution is, that on the basis of knowledge research about concretions, their both magnetical and geochemical...
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