Chronological constraints on a Holocene landslide in an intermontane basin of the southern Apennines, Italy: Morphological evolution and palaeoclimate implications

In this work a detailed geomorphological study aimed to reconstruct the Holocene evolution of a slope largely affected by landsliding is presented. The study area is located in the lower valley of the Tanagro River, flowing in the Auletta basin, a Pliocene to Quaternary tectonic depression located along the elongation axis of southern Apennines. In order to investigate the relationships between landscape evolution and triggering factors, and to better constrain the Holocene palaeoclimate scenario in which the mass movements occurred, geomorphological data have been integrated with those deriving by the stratigraphic, chronological, and minero-geochemical analyses of the deposits genetically related to the landslide events. The investigated landslide shows a complex style of activity, with compound rotational and translational slide in the upper part of the slope evolving into flow in the lower part. The chronological evolution of the landslide activity has been constrained through radiocarbon dating of palustrine deposits, genetically related to the landslide, and of interbedded paleosols. On the basis of the presented data, the main landslide event can be placed at the beginning of the Holocene and it is followed by a period of scarse landslide activity, as demonstrated by the sedimentation of palustrine deposits within an endorheic pond. As the small basin was created by a counterslope rotation related to the main landslide phenomenon, its deposits post-date the age of the landslide. The geomorphological features related to the main gravitative event are strongly modified by reactivations occurred at the beginnings of Sub-Boreal period, which represent, in southern Europe, the warmest and wettest stage of the Holocene. As confirmed by mineralogical and geochemical data, intense and/or prolonged precipitation might have played a major role as triggering factor in reactivating the slope movement.