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

A review of geophysical studies of the lithosphere in the Carpathian–Pannonian region

Published: Dec 2022

Pages: 499 - 516



Abstract: Here, we revisit the most prominent features of the complete Bouguer anomaly map and their interpretation, along with the current knowledge of the lithospheric thickness in the Carpathian–Pannonian region. The stripped gravity map, i.e., the sediment-stripped complete Bouguer anomaly map, was used to interpret the most prominent highs and lows of the gravity field. The complete Bouguer anomaly data were used in structural density modelling and integrated geophysical modelling to determine or revise the previously known sources of the most pronounced gravity features of the region. The Carpathian gravity low was divided into three sub-lows: the Western, Eastern, and Southern. The Western Carpathian gravity low consists of the clearly distinguishable External and Internal lows, which are due to different causes. The source of the External Western Carpathian gravity low reflects the low-density sediments of the External Western Carpathians (2.49–2.59 g cm–3) and the Foredeep (~2.43 g cm–3), while the Internal Western Carpathian gravity low is explained by the upper crustal deficit mass, which is formed by the rocks of the Alpine Tatric and Veporic units. These tectonic units are built mainly from granites and crystalline schists, of which the average density (~2.70 g cm–3) is lower than the average density of the lower crust of the Internal Western Carpathians (~2.90 g cm–3). The main sources of the Eastern and Southern Carpathian gravity lows are the gravity effects of the crustal roots created by continental collision, the Foredeep, and the surface sediments of the External Carpathians. The Pannonian gravity high is caused by the expressive Moho elevation (24–26 km). Since the Pannonian Basin upper mantle, which is built by high-density peridotites or dunites, is located several kilometres closer to the surface, this rock material represents a great excess mass (high-density ­anomalous bodies). Based on the calculated stripped gravity map, several local gravity highs (˃ +50 mGal) have been recognised, and they are all located in the Danube Basin, the Transcarpathian Basin, the Békés Basin, as well as the Makó trough. Their sources are high-density crustal bodies (Eo-Alpine metamorphic complexes), whose apical parts reach depths of only 7 to 12 km. Finally, the expressive different depths of the lithosphere-asthenosphere boundary in the Western and Eastern Carpathians were explained by the different Neo-Alpine development of both orogens. The mantle lithospheric root (~240 km) in the Eastern Carpathians is results from the sinking of the upper part of the broken slab during the frontal continental collision. On the contrary, no thickening of the mantle lithosphere was observed in the junction zone of the Western Carpathians and the Bohemian Massif. The typical thickness of the continental lithosphere (~100 km) in this zone was explained by the oblique continental collision. The Pannonian Basin system is characterised by one of the thinnest continental crusts (~25 km) and lithospheres (~75 km) in the world.

Keywords: complete Bouguer anomaly, stripped gravity map, integrated geophysical modelling, lithosphere, gravimetric interpretation, Carpathian–Pannonian region

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