On a Marine Holocene Fauna in North-Western Scotland

Abstract

THE country mapped by the officers of the Geological Survey of Scotland on Sheet 71 includes a great many examples of raised beaches, and in the Memoir describing that country (Geology of Glenelg, Lochalsh and South-east Skye, 1910), the heights of the raised beaches are given as occurring up to about 100 ft. above the sea. The suggestion is also made (p. 168) that in the neighbourhood of Loch Alsh, a raised beach varying in height from 30 to 40 ft. along the outer coast seemed to rise in altitude when traced up Loch Alsh away from the open sea; the description continues- At a point a few yards above the junction of the Udalain stream with the sea, Mr Clough and Dr Crampton found a deposit of shelly clay which probably represents the sublittoral zone of this This locality is important, because here one might expect to obtain evidence of the relation between the raised beaches and the later stages of glaciation, and the reported occurrence of a marine fauna at this point made further investigation the more desirable. As I was passing along the shores of Loch Alsh on my way to the Outer Hebrides in 1935, I decided to examine this shelly clay, and the results, which are set out in the present paper, are not in the least what I expected. It was not possible in the time available to prove the stratigraphical relation between the shelly clay and any particular raised beach, but the fauna of the clay is entirely recent in character, and as the depth of deposition represented is not more than 2 or 3 fathoms, it is almost certain that this clay is not contemporaneous with a high-level raised beach. This negative result is disappointing, but the fauna of this clay is worthy of description, especially for comparison with that described in this same Survey Memoir from Loch na Dal, in Skye. I am extremely grateful to Dr W. A. Macfadyen for extracting and identifying the Foraminifera, and for his suggestions about the Foraminifera in the clay from Loch na Dal; I also wish to thank Dr F. W. Anderson for advice about the Loch na Dal fauna, and Mr J. R. le B. Tomlin for help in the identification of the Mollusca.