Dating and explanation of Late Glacial – Holocene landslides: a case study from the Southern Alps

Landslide chronologies are essential both for understanding the causes of mass movements and for the assessment of landslide hazards. The Fadalto landslide (Venetian Prealps, Italy) studied in this paper has been active, as shown by morphological and stratigraphical data, for several thousands years since the Late Glacial. The chronology of this large and complex landslide was significantly improved through identification and radiocarbon and dendrochronological dating of several mass movements which occurred during the Holocene: one in the late Atlantic (5375 ± 95 years BP) and others in historical times (within the last 14 centuries). Understanding the specific causes of these landslides, and establishing a relationship between landslides and climate (or earthquakes) in particular turned out to be a difficult task (mainly due to the imprecision of radiocarbon dating). It can not be ruled out that the landslides occurred under colder and more changeable climate or during a transition between climatic spells with different characteristics. Dendrochronological analyses, on the other hand, show no relationship between one of these historical landslides and climate (or earthquakes). Reactivations of movements involved both the main scarp and the accumulation zone; besides, it was recognised that the landslide can be reactivated through a rock avalanche, a type of complex landsliding not uncommon in the southern Alps.