Abstract
Fault-related folds and hanging-wall structures reflect the geometry of the main thrusts in foldthrust belts. The results of the structural analysis of the Supragetic Unit metamorphic basement in eastern Serbia at map-, outcrop- and thin-section scale, and its importance for the late Early Cretaceous nappe-stacking are presented in this paper. The Supragetic Unit metamorphic basement includes various volcano-sedimentary rocks of Ordovician-Silurian protolith age. They were metamorphosed to the low greenschist facies with temperatures reaching 300-350?C and pressure reaching 0.3-0.5 GPa. The microscale studies show that quartz and albite demonstrate dominantly bulging and locally subgrain rotation recrystallisation, while chlorite, sericite and muscovite define spaced to continuous foliation recognised both at the outcrop- and the thin-section-scale. The statistical analysis based on the available map data shows low- to high-angle west-dipping foliation which is interpreted as an indicator of flat-ramp geometry of the Supragetic thrust, rather than east-vergent tight to isoclinal folding. At the thin-section scale ductile to semi-ductile C?-S structures indicate top to ESE thrusting. Subsequent kinking, recognised both at the outcrop- and the thin-section-scale, deform the older foliation. Those kink bands are the result of WNW-ESE to NW-SE compression and could represent the later stage of a continuous deformation event during which C?-S structures were formed. The youngest, brittle deformation is represented by subvertical joints with no offset recognised in thin-sections. The structural characteristics of the Supragetic Unit low-grade metamorphic basement in the studied areas, combined with tectonothermal events recognised elsewhere in Dacia mega-unit, could imply a possible initiation of the late Early Cretaceous nappe-stacking in the ductile to semi-ductile/semi-brittle domain.
Highlights
The highly curved Carpatho-Balkan orogenic system was formed during the polyphase Alpine tectonic evolution
The aim of this study is to constrain the internal structure of the Supragetic Unit basement of Serbian Carpathians (Caras group of IANCU et al, 2005b; Caras terrane of BALINTONI et al, 2009 and BALINTONI et al, 2014) and to estimate its significance for the late Early Cretaceous nappe-stacking in terms of the geometry of the regional thrusts and crustal levels in which the thrusting occurred
Both of these interpretations, as well as the mineral assemblage and the termochronological data (BOJAR et al, 1998; KOUNOV et al, 2010; GRÖGER et al, 2013; ANTIĆ et al, 2016, REISER et al, 2017) indicate that the Supragetic Unit basement was deformed in ductile domain during the late Early Cretaceous
Summary
The highly curved Carpatho-Balkan orogenic system was formed during the polyphase Alpine tectonic evolution. A lot of studies about the kinematics of brittle structures postdating the formation of regional nappe system of Carpatho-Balkanides (i.e. Late Creteceous to recent times) were published (LINZER et al, 1998; ZWEIGEL et al, 1998; MATENCO & SCHMID, 1999; MATENCO & BERTOTTI, 2000; GIBSON, 2001; KOUNOV et al, 2011; MLADENOVIĆ et al, 2014). The aim of this study is to constrain the internal structure of the Supragetic Unit basement of Serbian Carpathians (Caras group of IANCU et al, 2005b; Caras terrane of BALINTONI et al, 2009 and BALINTONI et al, 2014) and to estimate its significance for the late Early Cretaceous nappe-stacking in terms of the geometry of the regional thrusts and crustal levels in which the thrusting occurred
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