ASSETTO STRATIGRAFICO-STRUTTURALE DEL M.SUBASIO E DELLE CIRCOSTANTI SUCCESSIONI SILICO-CLASTICHE MIOCENICHE (UMBRIA)

Abstract

A stratigraphic and structural analysis of M. Subasio is presented (SE of Perugia, Umbria). Detailed biostratigraph­ic analysis (over than 300 samples) has permitted to define two new tectonic elements with respect to the previous lmowledges: a more internal thrust system, which carries Jurassic carbonatic structural high of M. Subasio over "centro-umbra" silici-dastic sequence (Burdigalian - Serraval­lian p.p.); a more extemal thrust system which carries "centro-umbra" silici-clastic sequence over the "eugubina" one (Langhianp.p. - Serravallianp.p. ). This pattern is com­plicated by backthrusts ancll younger-on-older geometries. Structural analysis has been achieved in key-areas, in order to define geometries and, where possible, kinematics of deformed elements at various scale. Combination of struc­tural and biostratigraphic studies can be useful to put together more constraints in the evolution of Neogene compression. Results seem to be in agreement with a double stages evo­lution of M. Subasio asimmetrie anticline. Unfortunately, time definition of these two stages is an open problem: in just one tectonic phase (post-Middle Tortonian) or in two tec­tonic phases. In this second case, a compressional reactiva­tion in inner zones of the chain would be documented.