Mechanism of Formation of Fold Belts: The Alpine-Carpathian Region

Abstract

The development history of the Alpine-Carpathian segment of the Alpine belt is considered. Since the Triassic numerous deep basins on continental crust have been formed there by rapid subsidence without significant stretching or thrust loading. They originated from the destruction of the lower crust under the asthenospheric upwelling. Two oceanic basins were produced by sea-floor spreading in the Jurassic. Deep basins on oceanic and attenuated continental crust were underlain by a thin lithosphere. From the Late Jurassic and until the Pliocene time they were intensely compressed, which formed the Alps, Carpathians and Dinarides. Compression began in the deepest basins and then covered the basins of a moderate depth. No compression occurred in adjacent cratonic regions with a thick lithosphere. The present fold belts follow the boundary between the past deep basins and the surrounding stable regions. Compression of the crust in each region ceased after the crustal surface emerged by several hundreds of meters above sea level. This permits estimating the force that produces the compression. High mountains in the folded regions were formed long after the termination of compression. They could have been produced by upwelling of a hot asthenosphere and phase transformations in the lower crust.