The timing and duration of volcanism within each igneous province of the North Atlantic region during the Tertiary is required to evaluate possible relationships between this magmatism, plate tectonics and continental drift. Published radioisotopic dates from the British Tertiary volcanic province are listed and briefly reviewed in the context of the data available from other North Atlantic areas. New conventional K–Ar and 40Ar/39Ar age spectrum ages of rocks from Mull, Staffa, Arran, Antrim, the Mountains of Mourne, Carlingford, the Cleveland dyke and the North Welsh dyke swarm are reported.
Volcanism began in the British Province around or just before 65–66 m.y. in the latest Cretaceous or earliest Palaeocene. The earliest episode of basalt lava eruption in Northern Ireland may not be represented in the Hebrides. The major plutonic centres are between 60 and 58 m.y. while minor activity continued at various localities until at least 50 m.y. in the Eocene.