Osady dolnego tortonu w Brzezówce koło Cieszyna

Stefan Witold Alexandrowicz



The profile of the Miocene sediments at Brzezówka comprises a 700 thick series of grey clays with interbeddings of sands, sandstones and argillaceous gritstones. On the basis of lithological and microfaunistic examinations, 12 beds were distinguished there (Fig. 1), among which the beds 1 to6 represent an older, the beds ,7 to 12 an younger stratigraphical horizon. The older horizon contains an assemblage of foraminifers with Candorbulina universa, Karreriella gaudryinoides, Robulus cultratus, R. echinatus, Planularia dentata, Marginulina hirsuta and Planulina wuellerstorfi. The assemblage is marked by symbol II AB (S. Alexandrowicz 1958), or this is so-called "Cracow assemblage". The upper horizon is characteristic of an impoverishment in microfauna, in which besides planktonic foraminifers also Valvulineria complanata and Bulimina pupoides appear. This is an assemblage marked II C. The assemblages distinguished here allow to correlate the Miocene sediments from Brzezówka with the contemporaneous sediments of·the Ostrava region and the Upper Silesian Basin (Fig. 2). In conclusion the author considers the Miocene clays from Brzezówka to belong to the upper Opolian. However, he ascertained here the absence of the Helvetian and the lower Opolian sediments, i.e. the lower part of the lower Tortonian, as well as the lack. of gypsum horizon arid of the upper Tortonian deposits.

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