CONDITIONS OF THE FORMATION OF MIDDLE PALEOCENE FORMATIONS (SKIBOVY AND BORYSLAV-POKUTSK RIVERS, UKRAINIAN CARPATHIANS)

Abstract

The purpose of the study is to reconstruct the formation conditions of the formation of the Middle Paleocene Yaremchan Strocatocolor horizon in the Outer Carpathian Paleobasin based on the results of sedimentological, paleontological, and material studies. The work methods included sedimentological analysis and layer-by-layer description of petrotypes of horizon sections in natural outcrops in accordance with modern methods. Selected rock samples were diagnosed by visual, optical and material (X-ray structural, petrochemical, spectral) examination. The results of the research, started by the predecessors, contributed to the detailing and study of lithodynamic (sedimentological) rock types of the Middle Paleocene Yaremchan horizon. Background and gravity event lithodynamic types are distinguished. Background formations are represented by hemipelagites (greenish-gray mudstones) and pelagites (cherry-red mudstones). Gravitites are mainly characterized by fine-grained turbidites. The study of petrographic features of the petrotypes of turbidite sequences makes it possible to identify chlidolites (pattums, mixtolites), which, according to the material composition of the fragments, belong to gravels and indicates the turbulent flow nature of the clay-sand mass from which the deposition took place. In the background formations of the Yaremchan horizon, petrochemical studies have confirmed a significant content of montmorillonite and chlorite, which may indicate the contribution of a magmatic component to the petrofund of the sedimentary basin. According to geochemical parameters, the deposits of the horizon have an increased content of elements of the association (Mn, Fe), Co, Ni, Cu, Zn, Ag, which are concentrated in ore formations of iron, manganese, and sulfide mineralization and are controlled by the systems of subcarpathian and anticarpathian discontinuities. Lithodynamic types of the Yaremcha horizon alternate rhythmically and cyclically, which makes it possible to distinguish cyclites of different orders. The structural-textural and material features of the lithodynamic types of the Yaremchan horizon and the ratio of hemipelagites and fine-grained turbidites in its sections demonstrate that the formations were formed in the lower fen of deep-sea cones of the removal of terrigenous material in the zone of the continental foot on the border with the abyssal plain. The bathymetric parameters of the sedimentation basin are reliably determined by the micropaleontological works of modern researchers as being characterized by bathyal-abyssal depths close to and below the level (CCD). The identified features of rock sections of the Yaremcha horizon were formed on the northeastern edge of the Outer Carpathian residual water area of the Tethys Ocean in the conditions of the Middle Paleocene tectonic lull during the subduction of the base of the Carpathian flysch basin under Tissia-Dacia.