Tertiary igneous activity in the Inner Hebrides

Abstract

SynopsisThe magmatism early in the Tertiary period resulted in (1) eruption of extensive plateau lavas (Skye, Small Isles, Mull) and of Central-Group lavas (Mull, central Arran), and (2) emplacement of central intrusion complexes (Skye, Rhum, Mull, Blackstones Bank, Arran), of sill complexes (northern Skye, Shiant Isles, western Mull, southern Arran) and of dyke swarms (almost all of the Inner Hebrides) focused on the central intrusion complexes. Each of these magmatic stages and the rock types formed are described, with particular emphasis on the central intrusion complexes and the fact that the centres about which intrusion occurred shifted with time. Some of the causes of compositional variation among rock types are briefly discussed. Most of the magmatism occurred between 61 and 58 million years ago when rifting and separation of eastern Greenland and north-western Europe was initiated.