Alluvioni pedemontane terrazzate fra Cagli e Frontone (Appennino marchigiano): un esempio di conoidi alluvionali confinate

Piedmont terrace alluvium between Cagli and Frontone (Marchean Apennines): an example of confined alluvial fans

Abstract

Some minor basins on the left side of the Burano R. valley, draining the NE flank of the calcareous Umbria-Marche Ridge, have built up wide pebbly alluvial coalescent depositional bodies which cover the piedmont areas adiacent to the Ridge. The morphostructural context of the area did not permit the development of fan shapes, even if the recognized sedimentary structures allow us to refer the alluvium to models of «wet alluvial fans». Three different depositional phases have been recognized; among them, only the intermediate phase (by far the most extensive) and the upper one have been supplied by limestones of the Ridge; the lower phase, on the contrary has been supplied from SE, by the marlycalcareous terrains of the adiacent synclinorium. The piedmont deposits rest above the 3rd-order terrace fluvial alluvium of the Burano R. and is würmian in age.