Abstract
We carried out geomorphologic and geological investigations in a south-eastern tributary valley of the Tiber River in Rome, the Grottaperfetta valley, aimed to reconstruct its buried geometry. Since results of the geomorphologic study evidenced anomalies of the stream beds, we performed geoelectric and boreholes prospecting to check whether recent faulting, rather than an inherited structural control, possibly contributed to the evolution of the alluvial valley. Vertical offsets of the stratigraphic horizons across adjacent boreholes were evidenced within the Late Pleistocene-Holocene alluvium and its substratum. In order to rule out the effects of irregular geometry of the alluvial deposits, we focussed on sectors where vertical offsets affected all the stratigraphic horizons (alluvium and pre-Holocene substratum), showing an increasing displacement with depth. We identified a site where repeated displacements occur coupled with a lateral variation of soil resistivity, and we drilled an oblique borehole aimed to cross and sample the possible fault zone affecting the terrain. A 7 cm thick granular layer, inclined 50°÷70° on the horizontal, was recovered 5 m b.g., and it was interpreted as the filling material of a fracture. The convergence of the reported features with independent evidence from geoelectric and geomorphologic investigations leads to hypothesize the presence of a faulting zone within the Holocene alluvial terrains and to propose the excavation of a trench to verify this hypothesis.
Highlights
Dealing with active tectonics in highly urbanized areas is always a delicate task, since it has several strong direct and indirect implications
Since lateral discontinuities commonly occur within fluvial sediments, we focused our attention just on those sectors where the vertical offsets affect all the stratigraphic limits, both the alluvial sediments and the underlying preHolocene substratum
A multidisciplinary study including geomorphological investigations, geoelectric and closely-spaced borehole surveys of a portion of the Grottaperfetta alluvial valley in Rome was carried on to verify the hypothesis that faulting processes may affect the Late PleistoceneHolocene alluvial sequence in that area
Summary
Dealing with active tectonics in highly urbanized areas is always a delicate task, since it has several strong direct and indirect implications. 8 and 6, the valleys were excavated deeper than during the previous ones, and the subsequent sea-level rises associated to the high-stands could account only for partial filling of the incisions originated during the erosive phases These marked features of the fluvial incisions are partially obliterated in the urban area, where more than 2,000 years-long anthropic activity strongly modified the original morphology. The Grottaperfetta valley, like most of the Tiber River’s hydrographic network, originated since the times of upwelling and continentalization of the area of Rome, and was deepened during each glacial epoch until the last one (Würm, 18-20 ka). Within this sedimentary body it is frequent the intercalation of organic material such as carbonized plants and peat horizons
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
