Chapter 19 Rudha Na H-Earba outlier [NM 912 555] of supposed Middle Old Red Sandstone Age

Rudha na h-Earba [NM 912 555] is a promontory of the north-west coast of Loch Linnhe. It obviously lies between two branches of the Loch Linnhe or Great Glen Fault. The outlier consists of a considerable patch of breccia and red sandstone, discovered by Grant Wilson. The sediments rest unconformably on the schists and their felspathic veinings and have a gentle dip towards the S.W. The pebbles found in the breccias are composed of the local complex schistose rocks and pink felsite. "Though no fossil evidence to prove their age has been obtained, the rocks of this outlier greatly resemble those of the basement members of the Orcadian Old Red Sandstone of the Moray Firth Basin" (Sum. Prog. 1904, p. 69).

This comparison of the Rudha na h-Earba beds with the Middle or Orcadian Old Red Sandstone is due to Peach. It must be remembered that an elongated outlier of the formation was already well known along the course of the Great Glen at the head of Loch Lochy [NN 230 900] (Sheet 63, Geol.). Strips of similar material, greatly sheared, have since been found by G. S. Johnstone and J. E. Wright bordering the south-east shore of the loch to near its outlet (Sheet 62, Geol.; see Sum. Prog. 1953 b, p. 37). E. B. B.