From nappe stacking to extensional detachments at the contact between the Carpathians and Dinarides – The Jastrebac Mountains of Central Serbia


Erak, Dalibor
Matenco, Liviu
Toljić, Marinko
Stojadinović, Uroš
Andriessen, Paul A.M.; Willingshofer, Ernst; Ducea, Mihai N.

Reactivation of inherited nappe contacts is a common process in orogenic areas affected by back-arc extension. The amount of back-arc extension is often variable along the orogenic strike, owing to the evolution of arcuated mountain chains during stages of rapid slab retreat. This evolution creates low rates of extension near rotation poles, where kinematics and interplay with the pre-existing orogenic structure are less understood. The amount ofMiocene extension recorded by the Pannonian Basin of Central Europe decreases SE-wards along the inherited Cretaceous – Paleogene contact between the Dinarides and CarpathianMountains. Our study combines kinematic data obtained from field and micro-structural observations assisted with fission track thermochronological analysis and U-Pb zircon dating to demonstrate a complex poly-phase evolution in the key area of the Jastrebac Mountains of Serbia. A first event of Late Cretaceous exhumation was followed by latest Cretaceous – Eocene thrusting and magmatism related to a continental collision that sutured the accretionary wedge containing contractional trench turbidites. The suture zone was subsequently reactivated and exhumed by a newly observed Miocene extensional detachment that lasted longer in the Jastrebac Mountains when compared with similar structures situated elsewhere in the same structural position. Such extensional zones situated near the pole of extensional-driven rotation favour late stage truncations and migration of extension in a hanging-wall direction, while directions of tectonic transport show significant differences in short distances across the strike of major structures.

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Fig. 1. a) Tectonic map of the Alps - Carpathians - Dinarides orogenic system with the extent of the Pannonian - Transylvanian back-arc basins (simplified fromSchmid et al., 2008). The grey box indicates the location of the map in panel b, the thick blue line indicates the location of the cross section in panel c; The grey arcuated lines and arrows sketch the kinematics of extension in the Pannonian basin with a pole of rotation located in the southern part of the Morava corridor (adapted from Matenco and Radivojević, 2012). Grey arrows illustrate the directions of slab retreat thatwas larger in the Carpathians. b) Detailed tectonicmap of the connecting area between the Dinarides and Carpathians Mountains (modified from Schmid et al., 2008). Note that the extent of the overlying Miocene-Quaternary basins is marked with white line, their structure and composition being ignored. The grey box is the location of the Jastrebac geological maps in Figs. 2 and 9. Thick blue lines are locations of the cross sections in Figs. 1c and 11. TF = Timok Fault; CF = Cerna Fault; c) Regional tectonic cross section with the structure of the Jastrebac Mountains in the overall context of the Dinarides and Carpathians (modified from Matenco and Radivojević, 2012). Location of the cross-section is displayed in panel b. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

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Tectonophysics (2016),