GRAVITY CONSTRAINTS ON THE CRUSTAL STRUCTURE AND SLAB EVOLUTION ALONGA TRANSCARPATHIAN TRANSECT

A new, unified Bouguer anomaly map of the Carpathian are and the Panno nian basin has been compiled from previously prepared and recently pub lished gravity maps. In order to constrain the crustal structure and t he tectonic evolution of the area, a two-dimensional gravity model is presented along a Western Carpathians-Pannonian basin-Southern Carpath ians transect. The model is based on deep seismic lines, where availab le, and on detailed geological sections. The results confirm that the extensional crustal structure of the Pannonian basin revealed by deep seismic surveys agrees with the gravity data. Furthermore, they sugges t that the Western and Southern Carpathians are at different stages of their evolution: the subducted oceanic slab under the Western Carpath ians has already been assimilated to the asthenosphere, while a crusta l slab is still present under the Southern Carpathians. These findings are compatible with the observation that the last major phase of crus tal shortening terminated at the early Middle Miocene in the Western C arpathians, but continued throughout the Pliocene in the Southern Carp athians.