A first comparison between the onshore and offshore informations leads to a tectonic sketch of the South North-Sea and the Detroit du Pas-de-Calais (Strait of Dover): The more striking feature is that significant structures (North Hinder and Gravelines structures) seem to extend offshore the transverse faults known in the Paleozoic beds of Pas-de-Calais and Boulonnais. This set of deformations can be interpreted as reactions of the thick Meso-Cenozoic cover to fractures acting in the Paleozoic basement. Towards the South, between the Zone de Cisaillement Nord-Artois and the Faille de Montreuil-Bassurelle, along the Weald Artois Axis, where the Meso-Cenozoic cover is thinner, the transverse faults, probably dependent upon the same fractures, have a dextral strike-slip character both in Paleozoic basement and in the Cretaceous strata. The size and significance of this assumed deep faults are discussed in the framework of a model of this part of the Southern North-Sea.