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Palynostratigraphy and mineralogy of black shales accompanying teschenite association rocks in the Žermanice quarry


Petr Skupien, Dalibor Matýsek, Jakub Jirásek, Petr Stelmach

Geoscience Research Reports 50, 2017, pages 263–267

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Published online: 31 October 2017

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Stratigraphic studies of samples of black shales collected at an outcrop near the Žermanice quarry brought new data on Lower Cretaceous sediments of the Hradiště Formation accompanying magmatic rocks of the teschenite association of the Silesian Unit (flysch belt, Western Carpathians).
All types of the sedimentary organic matter (SOM) were investigated in the given samples in which spores and pollen grains (23 vol.%) and dinocysts (22 vol. %) constitute the major component of the palynomorphs. Phytoclasts compose 55 vol.% of palynofacies, whereas amorphous organic matter is completely missing. The palynofacies composition from the viewpoint of paleoecology corresponds to a shallow-water oxidized sedimentary environment (shelf). The so-called littoral species (Circulodinium, Muderongia, Systematophora) prevail in the composition of dinoflagelate cysts. The palynomorphs in all samples show signs of thermal transformation (sample Žer-1 is dark brown, while palynomorphs in other two samples are almost black). Considering the state of preservation of organic matter, the cysts of dinoflagellate were studied in detail only in sample Žer-1.
The following dinoflagellate cyst taxa were identified in the studied samples: Circulodinium distinctum, C. vermiculatum, Cleistosphaeridium sp., Cymososphaeridium validum, Endoscrinium campanula, Gonyaulacysta cretacea, Hapsocysta sp., Hystrichodinium pulchrum, Hystrichosphaerina schindewolfii, Lithodinia sp., Muderongia mcwhaei, M. microperforata, M. neocomica, M. staurota, M. tabulata, Occisucysta tentorium, Stiphrosphaeridium sp., Systematophora sp. The dinocyst assemblage of these taxa can be correlated with that of the Hauterivian age which was identified in the Silesian Unit and reported by Skupien and Vašíček (2002) and Skupien and Smaržová (2011).
Mineralogical studies of aleurites and pelites revealed that sediments adjacent to volcanics of the teschenite association are affected by metasomatic processes to much greater extent than is evident from the field observations. Sodium metasomatic processes have also an impact on the black-gray sediments in the contact aureole without any distinct and visible macroscopic changes. Albite content in metasomatized aleurites and pelites of the Hradiště Formation attains as much as 30 vol.%. The mineral assemblage of albite-quartz-illite-mixed IM structures provides a remarkable proof of low-temperature metasomatism of these rocks due to hydrothermal fluids.