Spatial distribution patterns of dated landslide events in the Northern Apennines in response to Holocene regional climatic changes

In this work we examine the spatial and temporal distribution of radiocarbon dates from landslides on the NE-facing side of the Northern Apennines during the Holocene, focusing on the region's associated vegetation and climatic changes. We also propose a method for identifying areas and landslides that may contain very old organic materials for future research in the region. This analysis was based on a principal component analysis (PCA) on 5255 grid cells measuring 1 km2 each, overlaid on the study area. These grid cells incorporated variables derived from the terrain characteristics, including underlying lithologies and topographic features. Our findings reveal that, during the upper Holocene, the last dated events of recurrent and single-event landslides occurred first closer to the coldest and wettest territories once occupied by the glacier termina during the Last Glacial Maximum (LGMgt). Subsequently the last dated events occurred at distances greater than 30 km from the LGMgt, towards the mountain chain's margin. Conversely, at the beginning of the Holocene, an opposite pattern emerged, with landslide events occurring towards the chain interior. These spatial patterns were consistently observed when considering also the entire dataset of 87 dates for landslide events. During the middle Holocene, we observed that the recurrent landslides were primarily concentrated within a narrow belt 8.5 km from the LGMgt. Furthermore, higher rates of landslide activity were associated with the 4.2 ka BP event and persisted until approximately 2.0 ka BP, indicating a correlation with wet and cool periods. In conclusion, these spatial patterns in landslide events can be linked to changes in precipitation patterns and dominant atmospheric circulation in the mountain belt occurred since the beginning of the Holocene.