NEW K-AR AGES, AND A PROVISIONAL CHRONOLOGY, FOR THE OFFSHORE PART OFTHE BRITISH TERTIARY IGNEOUS PROVINCE

New K-Ar whole-rock ages are presented from 13 offshore locations to t he north and west of Scotland. Ten of these locations have yielded age s which are considered to be geologically significant. Together with p reviously published ages, these suggest that the earliest sills of the Faeroe-Shetland Intrusive Complex were intruded at c. 80 Ma (Campania n), although the bulk of the complex was probably emplaced at 55-53 Ma (early Eocene). Lavas on the Hebrides Shelf exhibit a range of ages f rom c. 63-46 Ma (Danian-Lutetian). New K-Ar ages from Rosemary Bank ar e inconclusive but, combined with calcareous nannofossil analysis and the known magnetic polarity of the bank, suggest that it may have form ed during the Late Cretaceous (70-68 Ma or earlier). The new data are incorporated into the chronology of all the major onshore and offshore components of the British Tertiary Igneous Province. Sources for the offshore lavas include the Faeroe Islands, central igneous complexes a nd large fissures such as those beneath the Wyville-Thomson Ridge and the Hebridean Escarpment.