Geomorphological and structural modification of the Serbomacedonian massif during the neotectonic stage

Abstract

The Serbomacedonian massif is an old geotectonic zone strongly modified during the Neogene and the Quaternary. This modification resulted from intensive tectonic activity. Two main sets of faults crossed almost at right angles and contributed to the breakage of the pre-Alpidic crust of the massif, while the subsequent vertical movements of the broken blocks contributed to its morphostructural differentiation. Geomorphological and structural features reveal the formation of three distinct morphotectonic units in the continental part of this zone: - The Northern Unit is dominated by the Morava basin. - The Central Unit forms a mountainous asymmetric ridge. - The Southern Unit forms a complex area of horst and graben structures. The Central and the Southern Units are bounded by the Struma-Strymon basin and the Vardar-Axios basin. In terms of global tectonics, the Northern Unit was affected by a Miocene extension in the Pannonian basin. It continued after the Miocene as a long-term slow process, as indicated by the present low seismicity. The Central Unit bears evidence of compression almost transverse to the long axis of the zone. The tectonic processes are still active as is indicated by high seismicity in the Struma basin and recent uplift of the crust in the area of the ridge. The Southern Unit was affected by an early Miocene extension and a late strong Quaternary extension in the Aegean region. The high seismicity and mobility of this unit indicate, that very active tectonic processes are still continuing.