Holocene glacial landscape of the Apennine Mountains

The Holocene glacial landscape in the Apennine Mountains can only be found in the central part of the chain (Gran Sasso Massif) where, after its complete disappearance at the beginning of the Holocene, the Calderone Glacier regenerated at ~4.5 ca ka BP. The frontal oscillations of the Calderone Glacier formed glacial deposits and moraine ridges on the threshold of the glacial cirque. It cannot be ruled out a priori that other mountainous sectors (e.g. Maiella Massif) may have hosted small glaciers during the Holocene, but there is no geomorphological or sedimentological evidence to support this hypothesis. The regeneration of the Calderone Glacier took place in phase with important changes in climatic conditions at the Mid to Late Holocene transition, recorded by various natural terrestrial and marine archives. Collectively, these archives point to climate instability, with alternating cold/arid (e.g. 4.2 ka event) and milder periods. This alternation promoted phases of intense periglacial/slope processes followed by the modest geomorphological activity, with consequent formation of soils. The morphostratigraphic relationships between the deposits linked to climate-driven geomorphological process, dated buried palaeosols and tephra layers made it possible to identify the sequence of cold events that affected the Apennines in the Late Holocene. This morphostratigraphic approach led to the reconstruction of the Holocene expansion phases of the Calderone Glacier, which included a first ‘Neoglacial’ expansion (~4.5 ka) and three subsequent oscillations (2.855–2.755 cal ka BP, 1.410–1.290 cal ka BP and 0.640–0.580 cal ka BP). The last glacial expansion corresponds to the LIA and was the most important, overriding the glacial deposits of the previous Holocene phases.