Upper Cretaceous volcano-sedimentary formation of the Internal Dinarides: Another piece of evidence for Adria - Europe oblique convergence

The Dinarides constitute an orogenic belt produced by convergence between the Adriatic microplate and Europe following the latest Jurassic-earliest Cretaceous closure of the Neotethys. Concurrently, the area between the Adriatic microplate and the European margin were dominated by the development of sedimentary basin(s), that accommodated increased erosion due to progressive convergence between the two continents and nappe stacking of the internal Dinaric units during the latest Cretaceous - Early Paleogene.  

One of such basins is located at the very contact between the two most internal units of the Dinarides: Jadar - Kopaonik and Drina - Ivanjica units. The remnants of this basin are now exposed as a narrow but continuous imbricated belt of volcano-sedimentary rocks, previously termed as the Upper Cretaceous “olistostrome mélange”. Position of this sedimentary unit is closely related to the existence of Zvornik fault, one of the major strike-slip fault structures in the Dinarides, representing the major tectonic contact between the Jadar - Kopaonik and the Drina - Ivanjica units.

In this contribution, we focus on several areas along the Zvornik fault where this volcano-sedimentary formation is exposed (from NW - SE: Rujevac-Zvornik, Debelo brdo, Jelica Mts., Kopaonik Mts. and Klepa Mts). We study basement rocks, sedimentary units, magmatic rocks and deformation structures, in order to investigate the complex convergent processes between Adria and Europe during the Late Cretaceous. The studied formation comprises a heterogeneous succession dominated by basaltic breccia embedded in a high-density debris-flow matrix, intercalated with coarse-grained mass-transport deposits and minor fine-grained intervals, and deposited within a strongly asymmetric basin linked to activity on the principal Jadar-Kopaonik thrust. Syndepositional deformation, growth strata, and kinematic indicators record basin subsidence coeval with contraction and transcurrent motion.

Our results indicate significant dextral slip along the Zvornik fault already by the Late Cretaceous. Given the fault’s orogen-scale role, its motion likely localized limited extensional domains within the evolving wedge, facilitating partial melting and basalt generation. We interpret Upper Cretaceous sedimentation to have occurred in a wedge-top basin developed atop the advancing Jadar-Kopaonik thrust during Adria-Europe collision, providing new constraints on the timing and kinematics of thrust-sheet stacking, strike-slip partitioning, and magma generation within the internal Dinarides.