This paper is companion to a 1:15,000 scale geological map of the southern sector of the Narni
Range in Central Italy. This sector of the Apenninic Chain was affected by the western Tethyan
rifting stage during the Early Jurassic, and the inherited architectural setting in turn influenced
the Mesozoic stratigraphy and the Neogene-Quaternary tectonic evolution of the area. Based on
stratigraphic and structural field evidence, a Jurassic structural high has been identified in the
Mt. Cosce sector, flanked northward and westward by deeper basins. The basin that had to exist
to the east, as well as the top of the horst-block, cannot be observed due to recent erosion and
orogenic deformation. The western margin of the Mt. Cosce High was rejuvenated during an
extensional tectonic phase which took place in the late Early Cretaceous. This synsedimentary
faulting is reported in this area for the first time, and is documented by a
sedimentary breccia (Mt. Cosce Breccia) resting unconformably on the Jurassic footwall-block
