DIVERSITY OF FOSSILS IN THE SECTIONS OF СHORTKIV SUITE (LOCHKOVIAN) IN PODILLIA

Abstract

The paper deals with a collection of fossils collected by the authors from two outcrops of the Chortkiv Formation of the Lokhkivian stage of the Devonian: on the Dniester River south of Zalishchyky and near the village of Bilche-Zolote on the Seret River (Ternopil region, Ukraine). Although the collection is small, it is represented by a wide variety of fossils from the rock mass of greenishgrey siltstone with interbedded limestone. The section has a thickness of almost 140 m and is rhythmic in nature, with argillites dominating. The systematic composition of the finds testifies to its marine genesis. Cephalopod phragmocones predominate. Their modern representatives live in sea basins with normal salinity. We have no reason to doubt that cephalopods existed in Devonian seas under similar conditions. The remains of pelecypods are second in abundance. The remains of brachiopods, which were also exclusively marine, have been found, but their numbers and diversity have decreased compared to the previous stage. Tentaculites are represented by two species. It is interesting to note that their elongated conical shells are mainly oriented in one direction, in accordance with the hydrodynamics of the environment. The collection contains a number of different ostracods that have not yet been identified. An increase in their number could indicate an abnormal salinity. Finally, the bryozoans are represented by the remains of one species, mostly inlaid with cephalopod shells. All the fossils in our collection are of marine origin, since the modern representatives of the species live in seas with normal salinity. It is planned to use the collection to improve the museum’s Devonian exhibition.