Radiocarbon dating of active faulting in the Agri high valley, southern Italy

Abstract The high valley of the Agri River is a wide intermontane basin located in the Lucanian Apennine, southern Italy. This basin was formed during Quaternary times in the hinterland of the Neogene fold-and-thrust belt. Tectonics has strongly controlled shape, morphology and sedimentary evolution of the basin up to the present. The Agri Valley, in fact, has been hit by recurrent and large earthquakes such as the 1857 Basilicata earthquake. Pleistocene extensional tectonics is commonly envisaged as responsible for the basin evolution. On the grounds of new structural studies, indeed, the valley appears to be a more complex structure than a simple extensional graben, as traditionally assumed in the literature, or than a pull-apart basin, as suggested by some workers. The basin floor is filled by middle Pleistocene faulted alluvial deposits. A new survey has shown evidence of deformation also in younger sediments. At Viggiano, located along the eastern flank of the basin, recent slope deposits still attached to their source area display fault-controlled sedimentation. In this area, different climate-sedimentary cycles represented by coarse breccia talus alternated with palaeosoils are involved in the recent deformation. At Pergola, located a few kilometres northwest of the Agri high valley, the most recent fan deposits found at the foot of a major slope, including evenly bedded breccia and intercalated palaeosoils, are strongly faulted and tilted. In order to establish precise chronological constraints, palaeosoils have been sampled in several sites and at different stratigraphic levels. Radiocarbon dating supports the field evidence of very recent deformation associated to relevant displacements, yielding ages between 40 and 20 ka.