Loch Creran Research Articles

The Ballachulish Fold near the Head of Loch Creran (Argyllshire)

The main features of the tectonics of the Loch Creran district have already been delineated in a paper dealing with a more extended region, and published in 1910 by the Geological Society of London. The results of this earlier work, brought up to date, are epitomized in the map (p. 322), which will serve as an index of the relations of the district to neighbouring portions of Argyllshire and Inverness-shire. The original mapping of lower Glen Creran was carried out by Mr. H. Kynaston and the late Mr. J. S. Grant Wilson. Before preparing the paper just cited, I visited the district on two or three occasions, once accompanying Mr. C. T. Clough, and at another time Mr. H. B. Maufe. Various alterations in the mapping were made as a result of these traverses, and it was found that the more essential structural features were readily determinable in the light of evidence furnished by the country to the north-east. At the same time, it was apparent from the first that anything like detailed knowledge could only be attained as a result of systematic re-examination, involving a considerable expenditure of time. A favourable opportunity for further work arose officially during the past season, when observations were made which seem worthy of record as an illustration of the complexity locally recognizable in the Highland Schists. Two main difficulties are encountered in the field: there are many slides (fold-faults), so many, in fact, that the original stratigraphical sequence has to be accepted from

Recumbent Folds in the Schists of the Scottish Highlands

I. I ntroduction . T he district discussed in this paper includes a considerable portion of two typical Highland counties, Inverness-shire and Argyllshire. It lies in the main between Loch Linnhe, on the north-west, and a chain of granitic intrusions which, on the south-east, connect the Moor of Rannoch with the upper portion of Loch Etive. It extends northwards to the River Spean, and southwards to Appin and Loch Creran. The region thus defined is dissected by an intricate system of deeply cut glens, flanked by some of the loftiest mountains of Great Britain, including the giant Ben Nevis itself, 4406 feet high. The rock exposures on the mountain sides are remarkably clear, owing to the comparative absence of morainic material. The detailed mapping of this district has recently been completed by the Geological Survey, and the results of the work will shortly be published in an official memoir. In the present paper an outline is given of the complicated tectonics of the crystalline schists. Before entering on this description brief reference may be made to the results obtained by other workers along similar lines of enquiry. ( a ) Historical Review. Geologists are now familiar with the researches of James Nicol [l] , who showed that the gneisses, which Sir Roderick Murchison had described as conformably overlying the fossiliferous strata of the North-West Highlands, are in reality separated from the latter by a powerful dislocation. Dr. Callaway was the first, however, to appreciate clearly that this dislocation is of the nature of a gently

On the occurrence of two spherulitic (“variolitic”) basalt dykes in Ardmuchnish, Argyll

The peninsula of Ardmuchnish is situated about five miles north of Oban, between the mouths of Loch Etive and Loch Creran. It formed a small archipelago, whose various members are now united to one another and to the mainland of Argyll by wide stretches of “raised beach” materials in many places overgrown by peat. From its situation, Ardmuchnish might be expected to retain many proofs of igneous activity, for in the Benderloch, immediately to the east, are both lavas and granites of Old Eed Sandstone age, while some eight miles to the west the Tertiary volcanics of Morvern and Mull rise up steeply from the sea. Hence we find on examining the coast sections numerous later dykes of igneous material penetrating the schists of sedimentary origin which constitute the country rock of the peninsula. The great majority of the dykes are basaltic in character and have a general north-westerly trend, so that they are probably of Tertiary age. The two dykes now under consideration probably belong to this group of Tertiary intrusions, and special reasons in favour of this view will be given in the sequel. In connection with this research I wish to acknowledge my great indebtedness to my colleague Dr J. S. Flett, for it was under his constant supervision that the microscopical investigation of the two rocks was undertaken, and also to Mr T. C. Hall, who prepared the micro-photographs which illustrate the paper (Plate XI.), and which belong to the survey collection.

Loch Creran: Notes from the Western Highlands

Loch Creran: Notes from the Western Highlands