Geology of the volcano-sedimentary complex of the Kaminnyi Potik Unit on Chyvchyn Mountain (Ukrainian Carpathians): preliminary results

Abstract

The Kamyanyi (Kaminnyi) Potik Unit (Nappe) is the most internal and structurally-highest unit of the Fore-Marmarosh units, and in many places is directly covered by the Marmarosh Nappes of the Marmarosh Crystalline Massif. Chyvchyn Mount is built of this unit and forms a separate tectonic cap (Chyvchyn Mt. Klippe). It consists of the Upper Jurassic/lowermost Cretaceous Chyvchyn Formation, composed mainly of basic volcanic rocks, and the Tithonian-Early Cretaceous Kamyanyi Potik Formation, represented by calcareous and/or turbiditic deposits containing volcanic material. Geological mapping showed that this complex forms a tectonic klippe, which consists of four small tectonic thrust slices. Structurally, the lowermost one is represented by thin-bedded micritic limestones with cherts, and is interbedded with coarse/fine-grained calcareous pyroclastic turbidites (flysch). The second thrust slice is composed of calcareous-pyroclastic breccia with blocks of limestone, basalt, and chert (radiolarite?), which occur within a pyroclastic matrix and of coral limestones with basalt fragments and pyroclastic intercalations. The third thrust slice is constructed of breccia with a pyroclastic and volcanic matrix and clasts of effusive rocks and limestone. The fourth thrust slice – the highest – is represented by massive basaltic pillow lavas. Sedimentologically, the volcano-sedimentary complex represents a whole spectrum of marine mass-movement deposits, from debris flows through proximal turbidites to distal ones, which were formed during latest Jurassic/earliest Cretaceous time in the Outer Dacide-Severinide part of the Carpathian basins.