CARATTERIZZAZIONE MINERALOGICO-PETROGRAFICA ED INQUADRAMENTO STRATIGRAFICO PRELIMINARE DI ALCUNI DEPOSITI VULCANOCLASTICI DELL'AREA REATINA

Abstract

Fine-grained volcanoclastic deposits occur in the Rieti Basin, interbedded with debris, colluvium and lacustrine deposits of Middle-Upper Pleistocene. Three outcrops along the Velino River valley are reported: Poggio Bustone, Ca­sale Giannantoni and Caporio. The volcanic material is main­ly made up of subrnillimetre- sized sanidine, clinopyroxene and biotite crystals; sometimes pumice fragments are also found. Crystal-chernical features point out to dose relation­ships with the rock-types of the volcanic districts of the potas­sic Roman Comagmatic Region, and to significant differences with the near small eruptive centres of the Umbria-Rieti area. The volcanoclastic products of the Rieti Basin are interpret­ed as distal pyroclastic fall deposits, related to plinian-type eruptive phases or to pyroclastic flows ("co-ignimbrite ash fall deposits") of the Roman Province volcanoes (0.6-0. l Ma).