Three episodes of Cenozoic tidal shelly sands (‘faluns'), dated to theMiddle Eocene, Middle Miocene, and Plio-Pleistocene, were deposited by transgressions over the Northeast of the Armorican Massif (Cotentin, Normandy, France) during highstand eustatic sea levels. These shelly calcareous sands and gravelswere deposited behind Palaeozoic rocky shoals that separate the Cotentin Basin from the Atlantic Ocean. The morphology of the Cotentin Basin persisted through the Palaeogene and Neogene times with smooth slopes, despite the Cenozoic eustatic sea-level fluctuations and uplifts that affected the ArmoricanMassif and its borders.