fig. 13 simplified sketches of sea-floor spreading of the British Isles since the end of the Jurassic (a) At the end of the Jurassic, an emerged Precambrian crustal area (the Rockall, R, microcontinent) lay between Ireland and Greenland, Sea-floor spreading began between Iberia and Newfoundland, developing a fracture zone from the Pyrenees to the Labrador Sea. (b) Early to mid-Cretaceous sea-floor spreading separated Rockall from the British shelf but was aborted, leaving the Rockall Through (RT). (c) A triple junction appears off the Bay of Biscay in the early Senonian (80Ma), and Spain begins to rotate. (d) In the Paleocene (60-65 Ma) a new spreading center begins to separate the Rockall microcontinent from Greenland. (cited from Moores, 1997)