Reconstruction of cenozoic paleostress fields in the flysch complex of the Opir river valley (Skyba nappe, Ukrainian Carpathians)

: pp. 68-77
Subbotin Institute of geophysics of National Academy of Sciences of Ukraine
Lviv Polytechnic National University

Purpose. Reconstruction of paleostress fields, as evidence of many publications of different parts of the Carpathians, can carried out through research the most common brittle and semibrittle structure – joints, slickensides, faults, regional and local folds, or complex research of joints and slickensides. The purpose of this paper is to reconstruct the paleostress fields and deformation regimes of flysch deposits in Opir River Valley using complex analysis of joints and slickensides. To select the main tectonic regimes, deformation phases and to establish the evolution of Cenozoic stress fields along the intersection of the Ukrainian Carpathians. Methodology. Paleostress fields was determined by joints and slickensides using complex of structural paragenetic and kinematic methods. Analysis and interpretation of results reconstruction of parameters for regional and local paleostress fields (σ1, σ3) made with using structural computer software packages: Stereonett, Tensor. Results. Analysis more than 4 000 joints of different types in 41 observation points and other mesostructures (slickensides) was carried out in outcrops of six thrusts of Skyba nappe (Orivska, Skolivska, Parashka, Zelemyanky, Rozhanky, Slavska) except the Beregova and Malmanstanska ones. In each stratigraphic complex of flysch rocks was established evolution of the stress fields from ancient to modern. Reconstructed paleostress fields are place in chronological order according to the main stages of tectonic evolution of the orogen, the relative age of main deformation events and the relative age of the study mesostructures. Originality. Detailed field tectonophysical research and using of complex structural paragenetic and kinematic analysis help to determine the chronological order of the stress fields and identify the main deformation phases and subphases of Skyba nappe. Three main tectonic deformation regimes and ten phases and subphases indicate the dominant processes of compression, tension, shear etc. Parameters and orientation of axes paleostress fields (σ1, σ3) show the changes directions of maximum compression and extension from Oligocene to Miocene. Practical significance. Tectonic regimes and deformation phases indicate the stress-and-strain state and geodynamics of study region during Cenozoic time in remote thrusts of Skyba nappe. The most of perpendicular joints formed before the main compression of fold-thrust process.

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