Data from deep borings indicate that the Pliocene sedimentary cycle in the lower Rhone region, France, was characterized by an extensive marine transgression which drowned an accentuated topography and formed a fairly deep and stable sea in Oligocene depressions. Fine sediment was deposited under reducing conditions. The cycle terminated with marine deposition under oxidizing conditions, which was followed by lagoonal, then by coarse terrestrial sedimentation. The Pliocene formations have been dislocated by recent movement.