Structural and geochronological constraints from the Drina-Ivanjica thrust sheet (Western Serbia): implications for the Cretaceous\u2013Paleogene tectonics of the Internal Dinarides

Kristóf Porkoláb,Gábor H Héja,Zsolt Benkó,Melinda Fialowski,Balázs Soós,Szilvia Kövér,László Fodor,Nevenka Đerić,Nataša Gerzina Spajić

doi:10.1007/s00015-018-0327-2

Abstract

We have investigated successive episodes of ocean-continent and continent–continent convergence in Western Serbia (Drina-Ivanjica thrust sheet). The coupled application of structural and petrological analyses with Illite Crystallinity measurements and K/Ar dating has revealed the timing and structural characteristics of multiple regional deformation phases, and allowed us to revise the origin of the different Triassic units outcropping in the study area. D1 tectonic burial was characterized by anchizonal metamorphism, dominantly WNW-verging isoclinal folding (F1), and related axial planar cleavage (S1) formation in the Paleozoic basement and the stratigraphic cover of the Drina-Ivanjica thrust sheet exposed along the northern rim of this thrust sheet. The timing of D1 deformation is constrained by K/Ar ages suggesting 135–150 Ma tectonic burial for the Drina-Ivanjica thrust sheet. D1 deformation and metamorphism is correlated with the closure of the Vardar ocean by top-W to NW ophiolite obduction and the underthrusting of the Adriatic distal passive margin below the oceanic upper plate. Since D1 structures are lacking in the southern occurrences of Triassic rocks within the study area it is proposed that this Triassic is may not be the original sedimentary cover of the Drina-Ivanjica Paleozoic basement. We propose that this southern Triassic originated from a more external Dinaridic thrust sheet and was transported to its present-day position by a top-NE backthrust presumably during late Early Cretaceous–Paleogene times. Map-scale, NW–SE striking D2 thrust faults and abundant NW–SE trending F2 folds observed in all units correspond to the general trend of the Dinaridic orogen and are attributed to the latest Cretaceous–Paleogene collision between Adria and Europe. Regional Latest Cretaceous–Paleogene shortening was followed by strike-slip tectonics (N–S shortening and perpendicular extension) and subsequent Miocene normal faulting in both orogen-parallel and orogen-perpendicular directions driven by slab rollback processes of the Carpathian-Dinaridic realm.

Highlights

Emplacement of oceanic crust on top of continental margins has been an object of particular interest since the observation of the large volumes of ophiolitic complexes exposed in Eurasia (Goffeet al. 1988; Robertson 2004)
How can we trace the record of tectonic burial in the underthrust continental margin? How can we distinguish between the geological record of underthrusting below the ophiolite and a following continental collision phase? How does deformation propagate from the subducting oceanic plate towards the extended passive margin? A suitable place to investigate these questions is the area of Internal Dinarides, where the former Adriatic continental margin—that structurally underlies the ophiolitic nappe of the former Vardar ocean—is exposed in tectonic windows (Bernoulli and Laubscher, 1972; Schmid et al 2008)
Intra-oceanic subduction was followed by obduction onto the continental margin which resulted in regional deformation and locally metamorphism in the Internal Dinarides (e.g. Borojevic et al 2012; Schefer 2012)

Summary

Introduction

Emplacement of oceanic crust on top of continental margins has been an object of particular interest since the observation of the large volumes of ophiolitic complexes exposed in Eurasia (Goffeet al. 1988; Robertson 2004). A suitable place to investigate these questions is the area of Internal Dinarides, where the former Adriatic continental margin—that structurally underlies the ophiolitic nappe of the former Vardar ocean—is exposed in tectonic windows (Bernoulli and Laubscher, 1972; Schmid et al 2008). The Internal Dinaric structural units like the Studenica or Kopaonik witnessed strong metamorphic overprint due to the Maastrichtian-earliest Paleogene collision between Adria and Europe (Ustaszewski et al 2009; Schefer 2012) which substantially obliterated the traces of Late Jurassic– Early Cretaceous tectonometamorphic events. The geological record of Late Jurassic–Early Cretaceous tectonometamorphic events are, presumably, less obliterated than in other Internal Dinaric units (Milovanovic 1984; Chiari et al 2011)

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Conclusion