The North Dobrogea Orogen revisited: Late Miocene structural reactivation along the Trans-European Suture Zone

Abstract

The Northern Dobrogea Orogen is the onshore segment of the southeastern termination of the Trans-European Suture Zone, the most prominent tectonic boundary of Europe, and was affected by multiple superposed deformation episodes in the Paleozoic and Mesozoic. Contrary to the widely held notion that the North Dobrogea Orogen has experienced only very mild and local deformation since the mid-Cretaceous, our (U-Th)/He analyses on apatites from Precambrian, Paleozoic, and Triassic basement and cover rocks indicate a well-defined and widespread episode of cooling/exhumation starting in the late Miocene. The high level of data coherence and the fact that all tectonic units of North Dobrogea have been affected by such episode warrants a geological explanation of supra-regional extent. Miocene cooling/exhumation in Dobrogea can be placed in a larger framework of coeval intraplate compressional deformation affecting a wide area ranging from the Greater Caucasus to the Romanian sector of the Black Sea continental shelf. We propose that the structural inversion of inherited structures in the study area is a distant echo of the Arabia-Eurasia hard collision, which started in the mid-Miocene some 1200 km away to the southeast. Low-temperature thermochronologic data for the area north of the Bitlis-Pütürge suture zone of SE Anatolia indicate that the tectonic stresses related to the Arabian collision were transmitted efficiently in the Eurasian hinterland over large distances, focusing preferentially at rheological discontinuities located as far as the northern shores of the Black Sea. Late Miocene far-field deformation in the hinterland of the Arabia-Eurasia collision zone decreases gradually westward from the rapidly exhuming Greater Caucasus, located in front of the area of maximum indentation, through Crimea, to the Odessa shelf and Dobrogea, where deformation has been significantly less and therefore remained underestimated until now.