International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

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Geological and tectonic interpretation of the new Bouguer gravity anomaly map of Slovakia

Published: Apr 2023

Pages: 109 - 122

DOI: https://doi.org/10.31577/GeolCarp.2023.08

Authors: VLADIMÍR BEZÁK, MIROSLAV BIELIK, FRANTIŠEK MARKO, PAVOL ZAHOREC, ROMAN PAŠTEKA, JÁN VOZÁR, JURAJ PAPČO

Abstract: This paper analyzes the latest complete Bouguer gravity anomaly map of Slovakia in relation to geological architecture. The observed gravity field consists of regional and local gravity anomalies, as well as marked horizontal gravity gradients. The most remarkable regional feature on this map is the large field with low-density masses in the northern part of Central Slovakia (the so-called Western Carpathian gravity low), which is divided into two gravity sub-lows: the Outer and Inner Western Carpathian gravity low. The source of the first sub-low is the sediments of the Outer Western Carpathian flysch units, and the second one is a crust with prevailing granites and orthogneisses. It is suggested that this field is only the torso of the original one, which stretched along the entire length of Slovakia from the SW to the NE. However, in the youngest stages of tectonic development, the negative gravity anomalous field in the territory of West and East Slovakia changed to a positive one due to the thinning of the lithosphere and crust by the influence of asthenolithic masses from the mantle. The higher density masses in Central Slovakia south of the Carpathian gravity low are not caused only by asthenolithic action. The different tectonic segment with a predominance of metamorphic complexes and a higher average density, in comparison to the low-density granitized complexes in the north, also contributes to its manifestation. The boundary between these two segments in Central Slovakia is a linear and sharp tectonic zone and coincides with the extensive Pohorelá shear zone. Several local anomalies also occur on the complete Bouguer anomaly map, and they were also subjected to geological analysis. These include local areas with a predominance of heavier crust, such as the core mountains in western Slovakia, subvolcanic intrusions, metabasic complexes, and the Cadomian basements. Prominent horizontal gravity gradients reflect the tectonic interfaces (faults, shear zones) that originated mainly during the youngest period of the Western Carpathian tectonic development and were also interpreted. The faults shown in the complete Bouguer anomaly map were active mainly during the transpressional and extensional stage of the Neo-Alpine tectonic development.

Keywords: Slovakia, Western Carpathians, complete Bouguer gravity anomalies, geology, tectonics

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