ABSTRACT

The foreland fold and thrust belt of the Carpathians extends from Austria through the Carpathians to the south Carpathian bend in Romania where most structural units plunge beneath younger Pliocene-Pleistocene cover. Folds continue westward until all surface expression disappears before reaching Danube River. The belt is flanked by elements of the European, Russian, and Moesian cratonal areas which are overlain by foredeep deposits that are themselves involved within the external fold and thrust belt and overridden by it. Within the fold and thrust belt are older parts of the Carpathian orogene formed on continental crust with evolutionary differences between the western and eastern Carpathians.

The foreland fold and thrust belt consists of an inner flysch and an outer molasse cut into thrust sheets verging cratonward. Oldest flysch units are Middle Jurassic in the U.S.S.R., Upper Jurassic in Romania, and Upper Cretaceous in C.S.S.R. Oceanic crust may have underlain the flysch, and continental crust the molasse. Timing of thrusting is constrained locally, but suggests deformation in the western Carpathians developed during Oligocene to Miocene time progressively outward. Deformation in the eastern Carpathians began in the Albian or early Cenomanian internally and proceeded to late Miocene deformation externally.

The convex east loop of the Carpathian foreland fold and thrust belt resulted from subduction beneath inner Carpathian continental elements fragmented during collision within the European alpine system and driven or pulled eastward, molding the rocks of the fold and thrust belt against a recess in the craton. A Miocene volcanic arc lies internal to the fold and thrust belt, suggesting subduction of a few hundred kilometers of lithosphere.

Basins developed contemporaneous with thrusting within the Carpathian loop. Two types of basins occur: (1) peripheral (Vienna, Transcarpathian, and Transylvanian), showing fast initial subsidence followed by slower linear subsidence, and (2) central intra-Carpathian (Pannonian), showing only fast linear subsidence. Structural and thermal models indicate the peripheral basins formed by twofold stretching and some dike intrusion, whereas the Pannonian basin formed by either twofold stretching accompanied by subcrustal attenuation or by attenuation and erosion of the subcrustal lithosphere.

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