Carpathian Shear Corridor – A strike-slip boundary of an extruded crustal segment

The Carpathian Shear Corridor (CSC), a morphostructurally distinctive ENE-WSW brittle shear zone, is a prominent dynamic interface of crustal fragments shifted during an oblique collision process combined with lateral extrusions in the Late stages of the Western Carpathians tectonic evolution. This tectonics was due to convection in the upper mantle, driven mainly by slab-pull forces related to a subductional process in front of prograding Carpathians. The CSC separates the marginal segment of the Western Carpathians, already firmly attached to the European plate, from the southern still eastwardly moving block. This process led to structural transpositions, anomalous rotation of small blocks and tilting and uplift/subsidence events, resulting in a tectonic style of horst and intramountaine basin alternations within the corridor. Preliminary paleomagnetic data indicate anomalous CCW block rotations within this corridor, and AFT ages indicate Early and Late Miocene (ca 24–22 Ma and ca 10–7 Ma) fault controlled exhumation events triggered by increased shear zone activity. Deep seismic sections, magnetotelluric and gravity data show that CSC follows a frontal ramp of the Western Carpathians thrust over the foreland. The CSC remains an active strike-slip shear zone, and therefore the most important earthquake risk-zone in the Slovakian portion of the Western Carpathians. It presents a lateral ramp transform boundary of eastwardly extruding crustal segment during the Miocene and up to the recent time

Physical properties of Hradište border fault (Turiec Basin, Western Carpathians, Slovakia) inferred by multidisciplinary geophysical approach

International audienceThe Hradište border fault zone has played an important role in the development of the tectonic contact of the Cenozoic sediments of the Turiec Basin with the Malá Fatra Mountains crystalline basement. Seismic, geoelectric, radiometric, gravimetric, magnetometric and ground penetrating radar measurements were used to study the physical properties and determine the exact position and inclination of this fault zone down to a depth of up to 40 m. The Hradište border fault zone represents an almost vertical physical boundary characterized by decreasing seismic velocity (from 3.0 km.s−1 to 2.2 km.s−1) and decreasing electrical resistivity (500 to 150 Ω.m) when passing from the basement west of the fault to sediments to its east. It corresponds also to a compact segment of the lowest volume activity of radon 222Rn values in soil air (8 kBq.m−3 on average) and maximum horizontal gravity gradient (−0.0076 mGal.m−1). The discovery of this anomalous zone also helps us to distinguish two different anomalous blocks. The block west of the fault represents the orthogneisses of the Tatric crystalline complex belonging to the Malá Fatra Mountains. The eastern block is built-up by the Bystrička Member Pliocene sediments of the Turiec Basin. Our study serves as a case study for geophysical research on faults in different tectonic units of the Western Carpathians and other similar orogens