International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

POST-OROGENIC UPLIFT-INDUCED EXTENSION: A KINEMATIC MODEL FOR THE PLIOCENE TO RECENT TECTONIC EVOLUTION OF THE EASTERN CARPATHIANS (ROMANIA)

Pages: 315 - 327

Authors: RADU GIRBACEA, WOLFGANG FRISCH, HANS-GERT LINZER

Abstract: We propose a new tectonic model for the Pliocene to recent tectonic evolution of the Eastern Carpathians, especially for the formation of the Brasov-Gheorghieni basin system in the hinterland and for the shortening in the foreland during the "Valachian Phase" of deformation. Kinematic analysis of fault-slip data indicates the formation of the Brasov-Gheorghieni basins due to NW-SE oriented extension, but with joints displaying varying orientations suggesting regional uplift as the source of extension. The trend of regional folds in the foreland indicates NW-SE oriented shortening. The sedimentation rate of coarse material in the foreland basin reflects a high post-Miocene rate of uplift, very accelerated during Pliocene-Quaternary time. The seismological data show active offset along two strike-slip faults (the Trotus and Intramoesian faults), which border both the region of extension in the hinterland and the area of shortening in the foreland. A third strike-slip fault (the Sinaia Fault) is constrained south of the Brasov-Gheorghieni basins by kinematic and seismological data. All these observations have been combined in the following new tectonic model: succeeding the continental collision in Miocene, a very high rate of uplift occurred in the Eastern Carpathians during Pliocene-Quaternary time. The uplift induced gravitational mass transfer from the uplifted area, which had a high potential energy, towards the surrounding areas with low potential energy. The mass transfer took place through the southeastward motion of a crustal block between the Trotus sinistral and the Sinaia dextral strike-slip faults above an older, reactivated detachment horizon of the Eastern Carpathians fold-and-thrust belt. The motion of this crustal block resulted in extension in the hinterland and the formation of the Brasov-Gheorghieni basin system; the extension was accommodated by shortening in the foreland.

Keywords: Pliocene, recent, Eastern Carpathians, Brasov-Gheorghieni basins, post-orogenic uplift, extension, shortening

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