Diverging drainage in the Marche Apennines (central Italy)

In the Marche Apennines diverging drainage developed on the surface of mid-Pleistocene fanglomerates or, at places, on correlated erosional glacis. In mountain areas, diverging nets correspond with wide glacis shaped in severe cold climates at the end of the middle Pleistocene. Glacis were formed by deposition of coalescing alluvial fans and concurrent shaping of smooth erosional surfaces along and near their margins. In the coastal zone, wide fans and related fluvial plains were constructed in Crotonian times close to the mouth of trunk streams crossing a just emerged piedmont area. Both the control of the "cone shaped" topography on post-aggradational flow patterns and the entrenching of primitive distributary channels are conceivable in developing the diverging drainage of the study area. Four case studies, from areas differing both in age and in geological and structural settings, attest to the recurrence of this drainage in composing, together with other patterns, the grain of larger nets. Moreover, the diverging drainage of the coast area allows us to infer that superposition is an effective mechanism of net development on Plio-Pleistocene terrains of the Marche Apennine piedmont at the time when they became emergent. © 2002 Elsevier Science Ltd and INQUA. All rights reserved.