Key aspects of the stratigraphy of the Upper Silesian middle Keuper, southern Poland

Joachim Szulc, Grzegorz Racki, Karol Jewuła


The stratigraphy of the Upper Silesian Keuper, a continental, mudstone-dominated succession is poorly known, although the already renowned, newly discovered vertebrate localities highlight the growing demand for a more precise intra-regional correlation and an appropriate stratigraphic reference framework. A major lithostrati- graphic unit, preliminarily proposed for the middle Keuper (i.e., above the Schilfsandstein; Stuttgart Formation in “Stratigraphische Tabelle von Deutschland”, 2002) by Szulc and Racki (2015; Przegląd Geologiczny, 63: 103– 113), is described in detail. The redefined Grabowa Variegated Mudstone-Carbonate Formation, the unit pre- viously based on inaccurately presented information, includes the Upper Gypsum Beds and the Steinmergel- keuper in the traditional scheme from Germany (= Weser and Arnstadt formations). Three members are formally defined: the Ozimek (Mudstone-Evaporite) Member, the Patoka (Marly Mudstone-Sandstone) Member and the Woźniki (Limestone) Member. Two significant bone-bearing horizons (Krasiejów and Lisowice) are placed within the Patoka Mbr. The formation thickness in a composite, regional reference section of the Upper Silesian Keuper, based on the new Woźniki K1 and Patoka 1 well profiles, is approximately 215 m thick. The Grabowa Fm generally correlates with the Norian stage, with the base located in the undefined upper Carnian, and is topped by a major, erosive disconformity and sedimentary sequence boundary, near the Norian-Rhaetian boundary. However, hiatuses in the Silesian middle Keuper succession are located and paired with a cannibalistic type of sand-mud flat deposition, largely controlled by Early Cimmerian movements of tectonic blocks associated with the Kraków– Lubliniec shear zone.

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