Geomorphological map of the Montelago area (North Marche Apennines, central Italy): constrains for two relict lakes

The hamlet of Montelago (‘Mountain of the Lake’) lies within the northern Marche Apennines close to the watershed of Fosso del Lago (‘Stream of the Lake’): both Italian toponyms clearly suggest the presence of a paleolake. Official geological maps reported lacustrine sediments within the upper basin of the Fosso del Lago stream, where outcrops of lacustrine sediments have also been noted for about five decades. The nineteenth-century Gregorian cadastral map also reports water ponds roughly in the area where lacustrine sediments were found: nonetheless, their position is clearly shifted upstream with respect to the reported lacustrine sediments. In this context, we have recently performed a targeted geomorphological survey addressed at unravelling such apparent discrepancy. Our study confirms the occurrence of lacustrine sediments spanning from Atlantic up to Sub-Boreal exactly in the place reported by previous geological works. The detailed geomorphological map created for the area allowed us to adequately locate previously published subsurface prospecting both highlighting landslide damming as the process responsible for lake formation and providing information for an adequate morphoevolutive reconstruction of the area. Geomorphological mapping also resolved the problem of the different position of the ponds mapped by the Gregorian Cadastre, stating that these had no direct relationships with the former lake but rather consisted of a small man-made reservoir directly connected by broad channels to springs which are currently dried-out.