Potencialni vyskyt analogie „red beds“
v bohdaleckem souvrstvi (svrchni ordovik Barrandienu,
Ceska Republika): paleontologicka charakteristika

The Bohdalec Formation (Katian Stage) belongs among the most varied units of the Ordovician of the Barrandian area. Apart from the so-called Polyteichus Facies, which itself contains a dozen of lithofacies, reddish clay shales were found in the dump of the underground railway tunnel between Petřiny and Motol stations. It seems improbable that the red colour of these rocks was caused by deep (? pre-Cretaceous) weathering, as the red shales show similar palaeontological characteristics, which is different from the content of grey shales established at the same dump. The fauna is relatively frequent but monotonous; bivalves of the genera Sluha and Myoplusia predominate. Besides, brachiopods Rostricellula ambigena, treptostomate bryozoans, undetermined ostracods and a gastropod Sinuitopsis neglecta are less common; trilobites of the genera Dalmanitina, Calymenella and Sokhretia occur rarely. Small platy remains attributable to ? Anomalocystis sp. were also discovered. The faunal assemblage (in combination with the reddish colour of the rock) points to the oxygenated water and possibly oligotrophic conditions.

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