The Balkan Fold-Thrust Belt: an overview of the main features

Abstract

The Balkan Fold-Thrust Belt is a part of the northern branch of the Alpine-Himalayan orogen in the Balkan Peninsula and represents a Tertiary structure developed along the southern margin of the Moesian Platform. The thrust belt displays of two clearly distinct parts: an eastern one dominated exclusively by thin-skinned thrusting and a western part showing ubiquitous basement involvement. A wide transitional zone is locked between both parts where the structural style is dominantly thin-skinned, but with significant pre-Mesozoic basement involvement in the more internal parts. For the western thick-skinned part the poorly developed syn-orogenic flysch is a characteristic feature that along with the very restricted development of foreland basin suggests a rather limited orogenic shortening compared to the eastern part of the belt. The Tertiary Balkan Fold-Thrust Belt originated mainly through a basement-driven shortening and this is explained by the occurrence of compatibly oriented reactivated basement weak zones of pre-Carboniferous, Jurassic and Early Cretaceous ages. The proposed re-definition of the Balkan thrusts system and internal structure of the allochthons also call for significant re-assessment of the existing schemes of tectonic subdivision.

Strain partitioning during formation of oroclines and indentation

“…The CMFS postdates the Paleocene -Eocene orogen parallel extension recorded by the exhumation of the Danubian units and the coeval thrusting in the Balkanides (Fügenschuh and Schmid, 2005;Matenco and Schmid, 1999;Schmid et al, 1998Schmid et al, , 2020Vangelov et al, 2013). This extensional exhumation is an effect of the same general rotation and translation of the Dacia mega-unit, which was significantly rotated around the Moesian Platform already by the end of Eocene, as shown by large-scale tectonic reconstructions (e.g., Fügenschuh and Schmid, 2005;van Hinsbergen et al, 2020).…”

“…4.1b, 4.2;Fügenschuh and Schmid, 2005;Matenco and Schmid, 1999;Moser et al, 2005;Schmid et al, 1998). During the late extensional exhumation of the Danubian nappes, the main Eocene nappe stacking of the Balkanides took place, which truncated or partly reactivated the late Early Cretaceous thrusts and was followed likely by renewed thrusting in the West Balkans unit (Burchfiel and Nakov, 2015;Schmid et al, 2020;Vangelov et al, 2013). The orogen-parallel extension was followed by the formation of late Oligocene -early middle Miocene high offset curved strike-slip dextral Cerna and Timok faults (Figs.…”

“…Many previous studies have focused on the structure, kinematics and timing of deformations and rotations observed in the South Carpathians and Balkanides (e.g., Ratschbacher et al, 1993;Pătraşcu et al, 1994;Bojar et al, 1998;Schmid et al, 1998;Matenco and Schmid 1999;Willingshofer et al, 1999;Matenco et al, 2003;Dupont-Nivet et al, 2005;van Hinsbergen et al, 2008;Kounov et al, 2010Kounov et al, , 2011Kounov et al, , 2018Panaiotu and Panaiotu, 2010;de Leeuw et al, 2013;Krézsek et al, 2013, Neubauer andBojar, 2013;Vangelov et al, 2013;Burchfiel and Nakov, 2015, among others). A number of large-scale tectonic reconstructions have inferred the general large-scale Topography is based on SRTM data (Farr et al, 2007) rotations and translations of large continental units (e.g., Csontos and Vörös, 2004;Fügenschuh and Schmid, 2005;Ustaszewski et al, 2008;van Hinsbergen et al, 2020).…”

“…4.3e, f). Part of this overall Getic and West Balkan deformation must be late Early Cretaceous in age by the correlation with the Danubian nappes, which is constrained by post-tectonic Upper Cretaceous sediments covering thrust contacts in the vicinity of the basal (frontal) Getic thrusting (Ivanov, 1988;Vangelov et al, 2013;Schmid et al, 2020). However, such overprinting relations are unclear elsewhere in the West Balkan and Forebalkan units.…”

“…4.1). At the Balkanides scale, the late Early Cretaceous and Eocene structuration can be demonstrated only for the Getic/Sredna Gora and Forebalkan thrusting, respectively, outside the area of the West Balkan unit (see also Schmid et al, 2020;Vangelov et al, 2013). Therefore, it is likely that the West Balkan unit was emplaced during the CMFS formation by partly transferring the Timok-Cerna dextral offset to thrusting (Fig.…”