NEW FINDS OF BIVALVE MOLLUSCS IN THE CORE OF THE ROMANIVSKA – 1 WELL (INTERVAL 1685–1695 M) IN THE BILCHE-VOLITSA ZONE OF THE PRECARPATHIAN FOREDEEP

Abstract

The stratigraphy of the Jurassic deposits of the Precarpathian depression, promising in terms of oil and gas, has not yet been developed in sufficient detail due to the extremely rare finds of macrofauna. Until now, there are separate oil-and-gas-bearing strata, the stratigraphic affiliation of which is hotly debated by scientists. In particular, these are deposits of the Kohaniv suite, which is widespread in the Bilche-Volitsa zone of the Precarpathian depression. According to foraminifera, spores and pollen, its age of the Kohaniv suite, is defined as Toar-Batian. While the majority of macrofaunists based on bivalve molluscs determine the age of the Kohaniv suite as Middle Jurassic. New data on finds of bivalve molluscs from the core of the Romanivska – 1 well, which revealed Jurassic deposits in the northwestern part of Precarpathia, are presented. A peculiarity is that the fauna from one interval (int. 1685–1695 m) is with numerous and distinguished by species diversity. Some of the identified species are found here for the first time. A monographic study of the fossil fauna was carried out. A description of six types of bivalve molluscs is given. These are: Cucullaea subdecussata (Goldfuss, 1838); Pinna buchi Koch et Dunker, 1837; Astarte pulla Roemer, 1836; Pholadomya cf. murchisoni Sowerby, 1827; Goniomya recta Pčelincev, 1927; Pleuromya balkhanensis Pčelincev, 1928. One form is assigned to the genus (Goniomya sp.). Based on the study of the bivalve mollusk fauna, the biostratigraphic characterization of the Jurassic deposits was supplemented. This made it possible to reliably substantiate paleontologically the age of the world love of the Outer Zone of the Precarpathian Foredeep as Middle Jurassic.