Evoluzione geomomorfologica delle piane alluvionali delle Marche Centro-Meridionali

Geomorphological evolution of the alluvial plain of the central-southern Marche region

Abstract

The present paper describes the Pleistocene-Holocene geomorphological evolution of the alluvial plains of the southerncentral area of the Marche. The oldest among the continental deposits examined (Sicilian-Crotonian) consistin of fluvialdeltaic gravel and sand, are preserved at different elevations on hilltops near the Adriatic Sea. Four orders of strictly alluvial deposits at progressive elevations on the valley floor, following the former, characterize the fluvial basins considered. The differences in elevation among the terraced deposits show the intercalation, with the depositional phases, of erosional phases which are characterized by a different rate of subsidence during the Quater-nary tectonic uplift. The most important among these, enclosed between Sicilian-Crotonian and Mid-Pleistocene deposits, coincides with an important stage of Pleistocene tectonic uplifting. Of particular significance for the Quaternary sedimentary tectonic evolution is the transverse tectonics which produced a topography characterized by undulations crosswise to the Apennines. In the most depressed zones, deposits of fan-delta type for the coastal belt (Sicilian-Crotonian deposits) and of alluvial fans (first order terraces) produced the tickest and most extensive deposits.