Informace o publikaci
Tectonics of the Lower Paleozoic sedimentary rocks between Vápenný Podol and Heřmanův Městec
| Autoři | |
|---|---|
| Rok publikování | 2024 |
| Druh | Článek ve sborníku |
| Konference | Studentská geologická konference 2024 |
| Fakulta / Pracoviště MU | |
| Citace | |
| Klíčová slova | Seník Formation; Vápenný Podol Syncline; paleostress analysis; shear strain; orientation analysis |
| Popis | The rocks of the Seník Formation (Cambrian) and the Míčov Formation (Ordovician) within the Chrudim Paleozoic between villages Vápenný Podol and Heřmanův Městec exhibit both ductile and brittle deformation. The deformation phases responsible for their present appearance primarily occurred during the Variscan orogeny. Magnitudes of deformation were estimated on selected fossil samples, several deformational phases were interpreted, and the orientation of principal normal stresses of brittle fractures was determined from collected structural data. Deformation of fossils was determined based on changes in angles and length ratios. Breddin's diagram was utilized to quantify this deformation using shear angle. The magnitude of fossil deformation in the Seník Formation near Heřmanův Městec was small. Exact deformation values could not be obtained due to the unclear orientation of the principal normal stress ?1. However, the shear angle was small on all analyzed fossils, with an ellipticity not exceeding 1.4. These resulting deformation values are applicable only to the Palác locality near Heřmanův Městec, where a localized antiform mega-fold exists, representing the only area in the Seník Formation where trilobite fossils have been found. The direction of lineation that corresponds to the stretching direction cannot be visually determined at this locality. Based on these observations, it is assumed that the rocks around the Palác locality near Heřmanův Městec underwent less deformation than other outcrops of the Seník Formation, where potential fossil remains would likely have been destroyed due to greater deformation. In the graphitic shales of the Míčov Formation, two-fold systems (older and younger) were identified. The original orientations of structural elements of the older folds were reoriented during younger deformational phases. This can be observed from the geometry of the dataset's grouping of lineations in the Lambert azimuthal equal-area projection. They exhibited a circular distribution around linear elements corresponding to the ?-pole of schistosity. The schistosity was folded by folds with a WNW-ESE direction, representing the youngest plastic deformation processes. Based on the vergence of folds, it can also be assumed that in younger deformation phases, there was likely thrusting of southern block over the northern one, causing a general convergence of graphitic shales towards the south. The orientation of principal normal stresses was determined using paleostress analysis in the MARK2010 program. In the rocks of the Seník Formation, the results indicated normal fault tectonics. Extension was oriented approximately horizontally in the S-N direction, and the stress ? 2 was in the E-W direction. In the Míčov Formation, the direction of movement on the fault could not be determined, so the only correct solution was for the principal normal stress ? 2 , which is steeply inclined towards the southwest |
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