LONG TERM DENUDATION AND UPLIFT RATES IN THE SOUTHEASTERN APENNINES CHAIN (ITALY)

We present in this paper preliminary results of a study focused on the long term denudation and the uplift of the Southern Apennines outer belt, carried out through a geomorphological approach. The Southern Apennines outer belt is part of an arc-shaped accretionary wedge converging towards the east, whose phase of thrusting occurred from late Miocene to early Pleistocene. The more recent deformed marine units are plio-pleistocene in age. The age and the distribution of such units is consistent with the hypothesis of a diachronous deformation of the chain front. In particular, two different segments can be distinguished: the northern one, emerged since Middle Pliocene time, and the southern one, emerged since Early Pleistocene time. On the higher portions of the mountains and hills of this chain stand palaeosurfaces, which are uplifted up to 1200 m a.s.l. with an estimated mean rate of 0.6 mm/y. In order to evaluate the long term denudation and the uplift rates of this chain, a database of the palaeosurfaces attributes has been built with ArcView GIS. Data have been processed to reconstruct the palaeotopography of the main phases of palaeosurfaces modeling and calculate the rock volumes lacking between each couple of them. In particular, a DTM, obtained by interpolating the elevation data of the palaeosurfaces relics, restores a simplified shape of the palaeocatchements belonging to four main geomorphological stages, whose inferred ages are middle Pliocene and middle Pleistocene in the northern sector, and early Pleistocene and middle Pleistocene in the southern one. Finally, the erosion occurred between the youngest palaeosurfaces and the modern topography is calculated by overlapping the obtained DTM and a large scale DEM of the study area. Furthermore, a number of morphometric analysis on the longitudinal profile of the main rivers, coupled with the cross profiles of their valleys, allowed us to distinguish different styles of denudation, which cannot be simply explained with lithologic and climatic controls.