Late-orogenic vertical movements within the arc of the SW Alps and Ligurian Alps

Abstract

Mainly on the basis of seismic data, we reconstruct magnitude and timing of Miocene to Present vertical movements in the region of the Savigliano basin, an up to 4 km thick succession of Neogene to Quaternary sediments accumulated inside the Alpine arc at the western termination of the Po Plain. We focus, in particular, on the margins of the basin which are the link between the mountain range and the subsiding basin. Seismic data from these regions allow for the definition of upward and downward vertical movements (uplift-exhumation and subsidence) with a spatial and temporal resolution which cannot be attained by other methods. The eastern, southern and western margins of the Savigliano basin display very different geometries of the sedimentary bodies and, therefore, document different vertical movements during Miocene to Present times. The eastern part of the Savigliano basin, and the regions to the E, experienced subsidence followed by exhumation. The southern margin of the basin, in the Cuneo area, was much more stable with Miocene to present formations all pinching-out close to the present day outcropping position of the basement-sedimentary cover contact. In the W, seismic sections record a stage of tilting until the Burdigalian, followed by generalized subsidence which affected also the adjacent regions of the SW Alps. The overall pattern of vertical movements is essentially controlled by the NW-ward migration of a syncline–anticline couple with the synclinal axis presently located in the center of the Savigliano basin. The width of the folds is in the order of 30–60 km (1/2 wavelength). In map view, the trace of the fold axes changes from N–S in the Savigliano basin to E–W in the Alessandria basin.