﻿Yol. 66.1 SCHISTS OP THE SCOTTISH HIGHLANDS. 609 



The Windows of Etive. — Glen Etive and its tributary 

 valleys afford us a glimpse of the Ballachulish Core in its under- 

 ground extension, midway between Ballachulish and Allt Coire an 

 Easain (PL XLIV, Sections G & H). About 1500 feet of grey 

 phyllites of the Leven Schist group (7) here overlie upwards of 

 100 feet of calc-silicate hornfels, representing the Ballachulish 

 Limestone (6) ; directly beneath the latter comes a comparatively 

 thin series consisting of the banded portion of the Leven Schists (7) 

 — the thick phyllitic portion is entirely absent, — and then in natural 

 sequence appears the Glen Coe Quartzite (8), forming the floor of 

 the valleys where not cut out by granite. 



When it became obvious, from work in the districts lying to the 

 north, that through these Windows of Etive the Glen Coe succession 1 

 was again exposed to view, Mr. Clough and the writer set out for 

 Allt Charnan, to see whether anything in the nature of an actual 

 break could be detected where theory pointed to the existence of 

 the Ballachulish Slide. The exposures are exceptionally good, and 

 it was found, upon minute investigation, that a plane of discordance 

 separates the calc-silicate hornfels from the banded series below. 

 This plane is described by Mr. Clough as being less marked by 

 any appearance of disruption than the well-known thrusts of the 

 North- West Highlands, resembling rather an exaggerated plane of 

 strain-slip cleavage. It runs for the most part parallel to the 

 bedding and foliation-planes of the schists above and below, but 

 sometime* it obviously transgresses these structures at a slight 

 angle. Occasionally, too, small flat isoclinal folds occur, which 

 affect the schists above the plane and not those beneath, and vice 

 versa (see fig. 5, p. 610). At other times, however, there is evidence 

 for the isoclinal folding of the plane itself, which adds materially 

 to the general complication. 



It cannot be claimed that any appearance of excessive shearing 

 characterizes this plane, along which, it will be remembered, a 

 displacement of more than 14 miles is believed to have occurred. 

 There is nothing, so far as we could see, to distinguish it from 

 strain-slip planes elsewhere, which have a displacement at the 

 most of a few inches or yards. 



As has already been mentioned, Mr. Maufe [20] pointed out in 

 ] 906 that the Glen Coe Quartzite of the Etive district not only 

 floors the valleys, but also caps the hills, being repeated in a great 

 recumbent fold. This feature is illustrated in Sections G & H 

 (PI. XLIV), of which Section H is especially interesting, since it 

 shows how in Beinn Ehionnlaiclh the upper layer of quartzite is 

 bent back upon itself and in turn overlain by yet another fold of 

 the Leven Schists. 



The gape of the Ballachulish Fold between Loch 

 Leven and Loch C reran. — The Ballachulish Slide is probably 



1 The band of Ballachulish Slate is absent in Glen Etive, but otherwise the 

 sections are essentially identical. 



