On Late Oligocene to Pliocene depocentre migrations and the evolution of the Carpathian-Pannonian system

Abstract

The Late Oligocene to Pliocene evolution of foredeep basins of the Eastern Alps-Carpathians fold and thrust belt is marked by pronounced internal to external and lateral depocentre shifts. The latter shifts, covering a present along-arc distance of 1700 km, portray accelerating rates of foredeep depocentre migration, particularly so in the late Early and in the Middle Miocene, from about 7 to about 45 cm/yr. Lateral depocentre migration came to a close at the beginning of the Late Miocene; the subsequent Late Miocene to Pliocene foredeep infill history was characterized by exponentially increasing accumulation rates in the intersection area of the East European (Ukrainian) and Moesian platforms. Successive steps in the evolution of the foredeep basins had pronounced counterparts in the intra-Carpathian area. The beginning of acceleration of foredeep depocentre migration in latest Early Miocene times was coeval with the inception of intra-Carpathian extensional tectonics. The extremely rapid Middle Miocene depocentre shift, coupled with a change in direction of foredeep depocentre migration, corresponded with maximum extension in the intra-Carpathian area. The ensuing end of foredeep depocentre migration around the Middle-Late Miocene transition was coeval with the end of extension of the intra-Carpathian area, which, in turn, was followed by the inception of overall, thermal subsidence at about 11.5 Ma. The timing of and spatial relationships between discrete, coeval events in arc and intra-arc evolution put unambiguous geological constraints on geodynamic modelling of the evolution of the Carpathian-Pannonian system. It is speculated that the geological observations may best be understood in terms of the surficial effects of lateral migration of slab detachment. Such effects would mirror the dominant role of a concentrating slab pull, taken to result in, e.g., a time-progressive acceleration of foredeep depocentre migration.