Facial features of the Paleocene-Eocene deposits of advanced units of the Skyba zone of Ukrainian Carpathians

Abstract

There three main types of facies of Paleocene-Eocene complexes: sandy, siltstone and argillite distinguished within the study area by the nature of the distribution of the strata of the forming components were highlighted. Тhey accumulated avalanche at the foot of the continental slope and formed various facial parts of the foehn (Upper, Middle and Lower foehn). In the upper part of the Foehn was accumulated coarse-grained sediments (clusters of deep boulders and other psephyto-psammitic material containing edaphogenic rocks). Under the action of geostrophic and bottom currents, silt streams of pelitic and psammitic material moved in the direction to the south and south-east of the Carpathian sedimentation basin, forming sandy-clay and clay facies (Middle and Lower foehn). During the turbidite movement of a large amount of sediment from the first (shelf) to the second (foot of the continental slope) level of avalanche sedimentation, sorting and distribution of sediments on the continental slope took place. Based on the analysis of the material composition of Paleocene-Eocene sediments of the study area by such criteria as the size of the fragment, sedimentary textures and the ratio of different rocks, 7 facies were identified, which were deposited as gravitational flows down on the continental slope. Reconstructions of Paleocene-Eocene age flysch deposits showed that terrigene material in the studied sedimentation basin came from two sources – one of which was northwest of the study area and was characterized by a predominance of coarse-grained sandy sediments, while the source wear, which was in the central part of the studied basin was characterized by a predominance of clay silt and fine-grained psammitic material. This nature of the distribution of terrigenous material had a decisive influence on the further formation of Paleocene end Eocene sedimentary strata in the process of sedimentogenesis and post-sedimentary transformations of sediments, and on the formation of reservoir rocks and rocks with potential reservoir properties for hydrocarbon exploration. It has been established that the composition of the Psamitolites of the flysch formation of the Paleocene and Eocene ages of the Carpathians was formed on the passive continental margin or in the inland and boundary seas, and their genesis mostly corresponds only to the platform source of material wear.