Structural Setting of Western Monferrato (Alps‐Apennines Junction Zone, NW Italy)

New data on the structural setting of the Torino Hill and Western Monferrato domains provide a clearer picture of the kinematic evolution of the Alps‐Apennines junction zone. In the Alps‐Apennines junction, left‐lateral underthrusting of Ligurian units below Alpine crust has often been invoked to explain the underthrusting of the Insubric domain and the NW‐ward movement of the Adriatic indenter. A transpressive fault system (Rio Freddo Fault Zone) developed in the Monferrato epi‐Ligurian succession is here understood as the surficial expression of a deep‐seated thrust along which the Alpine metamorphic basement of the Torino Hill has overridden the Apenninic Ligurian nappes since the Paleogene up to Burdigalian. In the Western Monferrato the regional sinistral transpression differentiated separated crustal blocks during the Oligocene‐early Miocene, and kilometer‐thick successions were steepened by NNW‐SSE faults that acted as reverse and/or left‐lateral faults. Double‐vergent (SE‐NW) low‐angle shear zones then cut the Rio Freddo Fault Zone in post‐Langhian times. They have been here related with the eastward tectonic transport of the Torino Hill and relative Alpine crust toward the Monferrato domain, which occurred before the seismic line scale middle Miocene unconformity was established. This poses the problem of the exact age of this regional unconformity, which in our case should be at least Serravallian. Finally, the Monferrato and Torino Hill domains were coupled, and both were NW‐ward translated by the Padan Thrust Front in the Pliocene. The youngest strike‐slip and reverse faults of the Western Monferrato may be tear or compartmental faults that partitioned the Padan Thrust motion, whose propagation could be controlled by pre‐middle‐Miocene tectonic structures. The structural complexity of the study area is here understood as the inheritance of deep crosscutting regional structures that forced the convergent structural units of the Alpine and Insubric domains to follow different tectonic transport directions since the Oligocene.