This chapter presents summary descriptions of the post-Caledonian (Devonian and younger) tectonostratigraphic framework preserved within the main NAG-TEC study area. For ease of description the study area has been divided into several sub-areas that include: the West Shetland–Hebrides–Northern Rockall margin, the Faroe–Shetland margin, the Møre–mid-Norway–West Barents–Svalbard margin, the East Greenland margin, the Iceland margin, Jan Mayen microcontinent and adjacent oceanic areas, and the Porcupine– Southern Rockall margin (Figures 1.1 and 7.1). The NAG-TEC region has experienced a shared geological development since its amalgamation – the colli- sion of Baltica and Laurentia – during the Late Silurian Scandic phase of the Caledonian orogeny; its subsequent Late Paleozoic incorporation into the Pangaean supercontinent; the prolonged history of extension linked to the Mesozoic breakup of Pangaea; and ultimately the early Cenozoic opening of the North-East Atlantic Ocean.