The Late Paleozoic structural evolution of the Magnitogorsk Megazone in the southern Urals

Abstract

Various models of the evolution of the southern Urals at the stage of the Late Paleozoic collision of the East European and Kazakhstan continents have been proposed [3‐5, 7, and others]. The diversity of geodynamic models is caused by poor knowledge of regional tectonics in terms of structural geology. The results of regional structural and tectonophysical studies in the Magnitogorsk Megazone allowed us to recognize and characterize two stages of the Late Paleozoic (postDevonian) tectonic deformations: (1) thrusting in the Middle Carboniferous and (2) strike-slip faulting in the left-lateral transpression regime in the Middle Carboniferous‐Permian. Middle Carboniferous thrusting. The most intense tectonic deformations were confined to the flanks of the megazone within the Main Ural and East Magnitogorsk boundary fault zones, where the high-amplitude counter-dipping listric thrust faults were formed at a depth of 25‐30 km (Figs. 1, 2). The Late Paleozoic thrust structure of the Main Ural Fault Zone is characterized by nappes of higher orders deformed into NNEstriking antiforms and synforms. The westward verging reverse and thrust faults of the second generation are conjugated with the folds. The identification of these structural elements is difficult because of the distortion of the East Magnitogorsk Fault Zone by late strike-slip faults. They are represented by fragments of bivergent imbricate reverse and thrust faults retained in shear slices. The inner sectors of the Magnitogorsk Megazone are characterized by thin submeridional thrust and reverse faults with an amplitude of a few kilometers, which are accompanied by subordinate transfer faults and folds of mainly the open type (Figs. 1‐3a). The transfer faults bound the thrust and reverse fault zones, as well as imbricate packets therein, and serve as