Prospezione ed analisi gravimetrica della Piana di Rieti

Abstract

A gravity survey was carried out to identify the geological and structural features of the Rieti Basin, an intermontane depression in the central Apennines (northeastern Latium). Gravity anomalies have been analysed and used for the construction of bathymetric surfaces in order to obtain a 3D model of the area: the topographic surface, the top of the "Umbria-Sabina" units (a pelagic succession of carbonate-siliceous-marly sediments) and the bed of the "viliafranchian" continental deposits are the adopted surfaces. Gravity data - elaborated using a computer program which considers gravity anomalies of bodies delimited by ground surface and one of the above mentioned bathymetric surfaces - have been used for the construction of the maps of Bouguer and residual anomalies. These data, together with geological surface data, allow a first hypothesis to be developed on the structural pattern of the basin, and on the contact between the meso-cenozoic substratum (limestone and marly limestone of the pelagic series) and the deposits filling the basin in particular. According to the model, normal faults cut the "Umbria-Sabina" units along the basin eastern and southern margins, lowering them toward the centre of the basin. The thickness of quaternary deposits in this area is not less than 500 m from ground surface. The lowest gravity anomaly values are measured in the eastern side of the basin below the Cantalice alluvial fan deposits suggesting the presence of a low density body underneath the "viliafranchian" deposits. On the basis of geological data this body could also have been formed by alluvial deposits.