Morphological evidence of Late Quaternary thrusting in the Bradanic Foredeep

We investigated the western coastal sector of the Bradanic Foredeep by analysing marine and fluvial terraces south of the Cavone River (Basilicata, Southern Italy) and focusing on the low Agri Valley.The integrated analysis of both marine and fluvial terraces enables us to directly and physically correlate three orders of fluvial terraces with the three youngest marine terraces. The occurrence of such linked terraces confirms, firstly, the crucial role played by eustatism in both the morphogenic coastal and fluvial processes and, secondly, that we are dealing with different orders of marine terraces. As a consequence, the suggested hypothesis of an array of normal faults, parallel to the present coastline, that vertically displaced an old, single marine terrace can be definitely discarded along with the occurrence of a prevailing extensional regime affecting the region. Following a new approach, the chronology of the terraces has been constrained. The method is based on the sums of residuals between measured elevations of palaeoshorelines and theoretical elevations obtained by deforming the eustatic curve with a constant uplift rate. The best fits obtained for different transects perpendicular to the coast line, allow correlating the palaeoshorelines with OIS 3.1 (40 ka) to 7.5 (240 ka). Accordingly, the estimated uplift rate varies from 1.5 to 1.7 mm/a, in the northern and southern sectors, respectively. From a tectonic point of view, right underneath the investigated area at some km depth, the leading and more recent segment of the blind frontal thrust is characterised by marked variations in dip angle (ramp-flat geometry). This tectonic structure mainly propagated during Quaternary and due to its geometrical setting, the frontal part of the hanging-wall block necessarily generated a typical large-scale ramp anticline. The differential uplift rates inferred in the present research and the associated NNE-wards tilting of the Middle-Late Quaternary terraces observed in the investigated area document the effects at the surface of this deep-seated structure as well as its recent activity