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Characteristics and origin of deformation structures within lignite seams : a case study from Polish opencast mines

Widera M.

Geological Quarterly

2016

Vol. 60, No. 1

181--191

The present paper discusses the genesis of some deformation structures within Miocene lignite seams in Poland. These meso- to macro-scale deformation structures are the best developed in areas where the thickest lignite seams are exploited, that is, in the Bełchatów, Turów and Lubstów lignite opencast mines. They show a wide variety of structures such as high-angle inclined strata, normal and reverse faults and folds, fractures and clastic dikes. These deformation structures were not analysed in terms of the structural development of the lignite-bearing areas, but rather in the context of their origin. The high-angle inclination of clastic sedimentary strata clearly formed mainly as a result of vertical tectonic movements in the sub-Cenozoic basement, their currently measured dip angle being significantly higher than their natural angle of repose. All the observed normal and reverse faults cutting the Miocene strata are a clear example of syn- and/or post-depositional tectonics. The normal faults clearly indicate tensional tectonics while the reverse faults reflect compressional tectonics. In turn, the majority of folds occurring within the lignite seams are a result of peat/lignite compaction. However, one of the folds studied is predominantly the result of vertical displacements in the sub-Cenozoic basement. The en echelon fracture pattern may additionally indicate the horizontal component of these displacements. Finally, the most spectacular and debatable structures are clastic dikes. In this study the genesis of some of them is linked with the evolution of the graben’s marginal fault.

Dajki klastyczne i brekcje sejsmotektoniczne w utworach permu basenu Nachodu (Sudety Środkowe)

Wojewoda J., Burliga S.

Przegląd Geologiczny

2008

Vol. 56, nr 9

857-862

Clastic dikes have been evidenced in Permian conglomerates occurring near Kudowa Zdrój in the Nachod Basin, the Sudetes, NE Bohemian Massif. The lithology of the dikes is the same as that of the polimictic conglomerate hosting them; they only differ in textural characteristics. The spatial orientation of the dikes points out to their genetic relationship with a nearby fault that, in a map view, separates Permian and Cretaceous formations. The dikes must have intruded after tectonic rotation of conglomerate beds on the fault to a position similar to the present one and they represent record of post-diagenetic seismotectonic events.