Here is a geological map of the islands. The oldest rocks are the 2 billion-year old gneisses of the Rhinns Complex found in the southern Rhinns peninsula. The Dalradian rocks cover the rest of Islay and are approximately 800-600 miilion years old. They are dominated by limestones (blue) in the ‘core’ of the Islay anticline and the Jura Quartzite (yellow) on its flanks which forms most of the island of Jura.
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