Junction area between the Western and Eastern Outer Carpathians (Ukraine) as the contact of two accretionary prisms: geological structure, sedimentary features and stratigraphy based on foraminifera

Abstract

At the junction area where the Outer Western Carpathian and Outer Eastern Carpathian accretionary prisms converged, the first was developed ahead of the moving Alсapa Terrane, and the second one ahead of the Tisza-Dacia Terrane. We have compiled a new geological map of the junction area, located in the Latorytsa and Pynya river basins, comprising the Burkut and Svydovets nappes of the Fore-Marmarosh (Fore-Tisza-Dacia) prism and the Dukla Nappe of the Fore-Alcapa prism. The sedimentary formations of these nappes, composed mainly of turbidites and similar deposits, contain foraminifera, which allow us to determine the age of the most of these formations that range from the mid-Cretaceous to the Eocene. Our mapping shows that the Burkut and Svydovets nappes of the Eastern Carpathians plunge to the west under the Dukla Nappe of the Western Carpathian. The thrust boundary between the nappes is deformed and forms gentle antiforms and synforms. In addition, strike-slip faults of sub-Carpathian (NW-SE) direction cut these structures. We mapped broken formations and tectonic mélanges along these faults. The thrusting of the Dukla Nappe of the Fore-Alcapa prism over both Burkut and Svydovets nappes of the Fore-Marmarosh prism was probably caused by the collision of the Alcapa Terrane (upper plate) and Tisza-Dacia Terrane (lower plate) in late Eocene to early Oligocene time. Subsequent movement along NW-SE strike-slip faults may have been caused by the lateral extrusion of the East Carpathian formations towards the Western Carpathians.