**6.1 Closure of the Piemonte-Liguria Ocean and Alpine orogeny**

The Alpine orogen, upon subduction initiation at ~85–100 Ma [30, 141, 142], shows no evidence of magmatic activity during subduction initiation combined with a ~ 50 Ma hiatus in magmatism, or "arc gap" [29]. The orogen contains fragments of the Piemont-Liguria Ocean, which was not a Penrose-type oceanic crust. The Piemont-Liguria Ocean was formed in the Jurassic period when the paleocontinents Laurasia (to the north, with Europe) and Gondwana (to the south, with Africa) started to move away from each other [143]. The Piemont-Liguria Ocean contained
