Charakterystyka litologiczno-petrograficzna utworów ordowiku z obszaru Myszków-Mrzygłód

Kazimierz Piekarski, Jolanta Markiewicz, Małgorzata Truszel



The surveys aimed at more detailed recognition of tectonic structure of basement of the Mesozoic at NE margin of the Upper Silesian Basin, carried out in the last years by the Geological Institute, supplied some new data on lithology, stratigraphy and petrography of Lower Paleozoic rocks in this region. The paper presents an attempt to reconstruct column of Ordovician rocks encountered in the Myszków - Mrzygłód area and to give their lithological- petrographic characteristics.
Several formations differing in lithological development were distinguished in the rock complex assigned to the Ordovician (Fig. 7). Organic remains are rare here, impeding any more detailed dating of the formation as well as establishment of biostratigraphic units. The following formations were differentiated in the Ordovician column (from the base upwards):
1) Carbonate formation, comprising dark-grey, silicified sparry dolomites and limestones, with intercalations of greywacke mudstones and sandstones at the base. The formation is about 150- 200 m thick and presumably Arenigian or even Llandvirnian? in age.
2) Shaly forrnation, comprising dark-grey or grey- green quartz-chlorite, chlorite-sericite-albite, biotite or actinolite metapelites and metaaleurites with intercalations of skarns and, sometimes, fine-grained greywackes. The formation is about 600 - 800 m thick and presumably Llandeilan-Caradocian? in age.
3) Shaly-greywacke-conglomerate formation, comprising grey and grey-green sericite and sericite-chlorite metapelites and metaaleurites in upper part, and grey-green greywacke metapsammites and metapsephites with intercalations of chlorite-sericite and biotite-quartz metaaleurites in the lower part. The thickness of this formation is estimated at about 400 - 500 m and the age - presumably Lower Ashgillian?
4) Formation of skarn limestones with phosphorites, comprising skarn limestones and marbles at the top, sparry limestones with phosphorite nodules and intercalations in the middle, and silicified micritic limestones at the base. The formation is about 25 m thick and it is dated at the Upper Ashgillian on the basis of the recorded conodont fauna.

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