Conflicting drainage patterns in the Matera Horst Area, southern Italy

The Matera Horst (“ Murgia materana”) is included in the Apulian plateau, basically formed by Mesozoic shallow-water carbonates. The zone is located in a present-day temperate belt and form a flat-topped morphostructural large element inside the foreland area of the southern Apennines. This horst is bordered by high-angle faults and surrounded by downthrown blocks covered by Plio-Quaternary marine and alluvial sediments. The structural high experienced several morphological cycles from Miocene to Quaternary. In particular, three evolutionary stages can be recognized at least. The first stage is currently represented by relics of a flat erosional landscape at the top of the relieves. The second one is testified by gentle slopes with wide glacis at the foothills, locally covered by coarse waste deposits. During the third stage a series of marine terraces formed and a drainage system developed creating both bland valleys and well-defined channels and gorges. The latter streams deeply carve the Cretaceous limestone of the Matera Horst for they represent the morphological response to the tectonic uplift of the area and clearly post-date the former features. Since the fluvial net took place on Pleistocene covers, later widely eroded, it is possible to conclude that the major part of the Matera Horst drainage system represents a good example of superimposition. However, low order streams and segments of major rivers appear to be structurally controlled, as suggested by comparison with the fracture system. Further, also open synclines and gently steeped flexures may locally exert a driving control on minor streams. These apparently conflicting genetic hypotheses can be explained by the role of exhumation of inherited structures of the bedrock in add to a constant interplay between tectonics, erosion and drainage evolution during Quaternary times.