Estudio del subsuelo de la Ciudad Autónoma de Melilla mediante prospección geofísica y modelización geológica 3D

Abstract

The Autonomous City of Melilla is located at the Neogene-Quaternary basin of Melilla-Nador, at the NE part of the Rif. Its sedimentary infill is constituted by bioclastic limestones and detritic levels. The most important reliefs that limit the basin are ancient volcanoes with Neo-Quaternary activity, Tres Forcas Cape at its northern end and the Mount Gourougou at its southern part. The rocks emitted in the various eruptions are constituted by subaerial volcanic flows and pyroclastic levels that have been sequentially interlayered in the sedimentary infill of the basin but whose lateral extension is unknown. The basement of the basin does not crop out in the territory of Melilla although a deep borehole reveals the existence of Paleozoic rocks (marbles and metapelites) more than 560 meters deep. A gravimetric survey was carried out with stations distributed in a mesh which covers the entire territory of Melilla. The aim of the survey was to establish the geometry of the basement and the lateral extension, geometry and thickness of the sedimentary infill and the different volcanic levels. Finally, a 3D geolo- gical model has been built through the integration of surface geological observations, previous subsurface data (boreholes and vertical electric soundings) and the 3D inversion of gravity data.