Tectono-thermal evolution of the eastern Balkan: constraints from low-temperature thermochronometry

This paper presents the first low-temperature thermochronologic data [fission track and (U-Th-Sm)/He analyses on apatite] on the eastern Balkan, an intraplate fold-and-thrust belt marking the boundary between the Moesian Platform to the north and a series of accreted lithospheric terranes to the south. This boundary has undergone a complex evolution, with multiple reactivations and contrasting kinematics. The analytical dataset and its statistical inverse modelling point to the shallow burial (~2–2.5 km) of syn-orogenic sediments in the frontal portion of the orogenic wedge followed by cooling/exhumation starting in the middle Eocene coeval with orogenic collapse; it also suggests Late Cretaceous unroofing of the Srednogorie Zone to the south. To the north, the flexed and partly deformed lower (Moesian) plate and the associated foredeep sediments have remained thermally unreset, retaining the Late Cretaceous provenance signature of the eroded hinterland. These findings imply relatively limited Cenozoic shortening/exhumation across the eastern Balkan. They are consistent with a significant amount of documented strike-slip deformation focused along inherited structural discontinuities related to a buried Triassic–Jurassic rift system. We propose a causative link between strike-slip deformation in the eastern Balkan and far-field stress transmission related to the oblique closure of the Vardar Ocean to the west.