Facies di conoide alluvionale nei depositi Pleistocenici del bacino di S. Arcangelo (alta valle del F. Sinni)

Recognition of alluvial fan in the Pleistocenic deposits of St. Arcangelo Basin (upper F. Sinni valley)

Abstract

Preliminary results of sedimentological researches carried out on Plio-Pleistocenic deposits of the Sant’Arcangelo basin are reported. Alluvial fan deposits are recognized in the western area. Three facies are distinguished: facies A, due to debris flow, reveals a fanhead in the western sector; facies B, due to stream flood and sheet-flood, and facies C, as channeled deposits, show an evolution to water-laid deposits. A dispersal pattern, inferred from pebble imbrication, reveals north-western provenance of detrites in the western outcrops, and some eastward coalescing alluvial fans. The relationships between setting, thickness and distribution of coarse-grained facies and the deltaic facies of the eastern part of the basin, suggest the existence of a basin affected by a general uplift, more remarkable along its eastern margin that could limited the axial development of alluvial fans. The western and southern margin were represented by fault escarpments.