TURBIDITES IN THE MIDDLE PALEOCENE VARIEGATED FORMATIONS OF THE SKYBA NAPPE BETWEEN THE RIVERS OPIR AND SVICHA OF THE UKRAINIAN CARPATHIANS

Abstract

The paper presents the results of the study of sections of the Middle Paleocene variegated the Yaremche horizon in the skybas of Parashka, Skolivska, Orivska Skiba tectonic nappe. The work is based on the results of geological observations between the rivers Opir and Svicha and laboratory studies. The Yaremche horizon is characterized by rhythmic-cyclic interlayering of greenish-gray siltpsammitic and siltpelitic turbidites and cherry-red hemipelagites and pelagites. The purpose of the paper is to study the features of horizon sections and to establish the features of paleogeodynamic and paleogeographic modes of their formation. Rhythmostratigraphic study of the Yaremche horizon, allows it to be included in the sequence of the first order, which contains sequences of higher, second and third orders. Terrigenous and carbonate turbidites take part in the construction of sections of the Yaremche horizon. For turbidite sequences, both terrigenous and carbonate composition, are characterized by elements of textures A. Bouma Tdce. However, there are terrigenous layers that have a disordered texture with intervals (bottom up) of dish (plate) structure, which contain fluide escape “pipes”, convoluted limination with gravitational intralayer deformations (in flat top). These layers have an unsorted, multi-grained, pudding structure. The lower contact is erosive, the upper – smooth with hidden traces of erosion. These layers are parallelized by the mechanism of formation with deposits of fluidized (and/or liquefied) flows that occur at the final stage of turbidity currents. The study of petrographic features of petrotypes of turbidite sequences makes it possible to isolate chlidolites (pattums, mixstolites), which belong to greywackes in terms of the material composition of the fragments. The content of cement in them is not less than 10–25 % and indicates the turbulent flow nature of the clay-sand mass from which the deposits were formed. Among the greywackes, a separate group is occupied by fragmentary carbonate rocks – calcarenite-calcillite turbidites (Parashka skyba, Oryava river). They were formed during the redeposition of shelf carbonate material and/or intra-oceanic uplift material to the deep-water sedimentary basin of the continental shelf, which at the time of their accumulation had depths above the CCD. The formation of the Yaremche horizon took place at the foot of the continental slope of the passive outskirts of Eurasia, on the border of the deep-water plain of the External Carpathian flysch paleobasin during the temporary stabilization of the tectonic regime. The continental foothills pulsatingly changed their bathymetric parameters, due to convergent events between Eurasia and the microcontinents of the Tethys Ocean. They controlled the periodic approach and formation of flysch nappe units of accretion prisms on the active continental margin. The scientific results of the study will contribute to a better understanding of the geological structure of the Skiba zone of the Ukrainian Carpathians. The practical results of the study will contribute to the study of geological bodies promising for hydrocarbons.