Notes on the geology of Raasay

Abstract

General Remarks. The geology of Raasay, although varied, is not of great complexity. The northern end of the island is rugged ground formed of Lewisian Gneiss, but the fundamental rock in the area to the south is the Torridon Sandstone. The Jurassic strata are faulted against this old group of rocks beyond Carn Dearg and South Screapadal on the north; and the red rocks of the Trias are seen to rest on Torridon Sandstone to the south-east of Suisnish Hill, by Eyre Burn, on the south. Macculloch in 18191 gave a capital account of the general structure of the island, noted the true sequence of the main rock-divisions, and recognised the Liassic aspect of some of the fossils. Eight years later, Murchison, who paid a visit to the Hebrides in company with Sedgwick, determined the occurrence of Lias, Inferior Oolite, and Great Oolite.2 Thirty years elapsed before any further attention was given to the subject. Then, in 1857, Sir Archibald Geikie constructed a geological map of Raasay on the scale of about 2⅓ inches to a mile.3 Six divisions of the Jurassic rocks were represented; these included the Lower Lias limestones and overlying Pabba shales, the Middle Lias Scalpa Beds, and three divisions of the higher sandstones and shales of the Oolitic Series. This survey was utilised in the preparation of the “First Sketch of a Geological Map of Scotland” by Murchison and Geikie, published in 1861, and in other maps issued by the latter author. The