THE INVOLVING OF THE PLIOCENE-PLEISTOCENE SUCCESSION IN THE T. TRAVERSOLA DEFORMATION ZONE (NW ITALY)

Abstract

The N-S trending T. Traversola Deformation Zone (TTDZ), developing on the western edge of the Asti Reliefs, represents one of the most relevant geological features of the Piedmont hilly area, in northwestern Italy. Morphologically this deformation zone corresponds to an evident scarp with, a rectilinear trend in map view, an height up to a hundred meters and a length of about 30 km, delimiting a hilly area (Asti Reliefs) from a plain area (Poirino Plateau) developed at averagely higher altitudes. In the western side of the Asti Reliefs some local differences between the “villafranchian succession” (Pliocene-Pleistocene) occur across the scarp, together with soft sediment deformations. Close to TTDZ the sediments (Piacenzian and Calabrian) are also widely fractured and locally show cataclastic structure. New morphological, stratigraphic, micro-palontological, structural and geophysical data reported in this study better highlight how the TTDZ is structurally organized in several N-S trending, sub-vertical right faults with horizontal displacement. In the southern slope of the Turin Hill the deformation zone probably continues in the Moncucco Torinese quarry area where it strongly deforms the Messinian sediments. The TTDZ represents the shallow evidence of a deep right structure that separates the Poirino Plateau, showing a significant northward shift, from the Asti Reliefs, where such a shift is less evident. This structure exhibits different deformation magnitude in sediments of different age, suggesting that the tectonic activity took place throughout a long time during post-Messinian periods. The TTDZ could be also interpreted as part of a structural context related to north-thrusting of the Piedmont Hills over the Po foreland basin.