Segnalazione di superfici pianeggianti lungo i versanti della Valle Fontanabuona (Liguria orientale, Appennino settentrionale) riconducibili a terrazzamenti del torrente Lavagna: nota preliminare

Flat surfaces on the sides of the Fontanabuona Valley (Eastern Liguria, Northern Apennines) explainable as terraces of the Lavagna torrent. A preliminary note

Abstract

Different series of terrace surfaces occur along a large valley tract of the Lavagna Torrent (Fontanabuona Valley). Their morphology is due to both erosive and depositional phases of the river, which have taken place from the base of the Upper Pleistocene to the beginning of the Holocene. The existence of these terracements on both slopes of the Lavagna Torrent valley is particularly significant near Gallinaria (municipality of Moconesi). Here they are connected with river sediments which perfectly correspond on both sides. Transverse and longitudinal altimetric correlation to the valley line allows the reconstruction of four sets of terraces on both sides. Each set, representing an ancient riverbed, gives evidence of great base-level variations over time. The correlation of such surfaces allows the reconstruction of the ancient beds of the Lavagna Torrent, giving evidence of remarkable pulsations which are due to base-level variations. Morphological evidence along the watershed, showing capture phenomena, truncated valleys in the hydrographic basin, and abandoned riverbeds at different altitudes provide support for the hypothesis of a tectonic origin for the Fontanabuona Valley. Additional data on the evolutionary stages of the Ligurian side of the hydrographic network of the Northern Apennines are thereby made available.