part 2] THE SOUTH- WEST HIGHLANDS OF SCOTLAND. 103 



Structure. — If for the moment the results of secondary folding 

 are set aside, the main structural featm-es of the Iltay Nappe can 

 be stated in a few words (fig. 4). 



In its lower portion the sequence is predominantly normal. 

 Thus, in Islay, the Islay Quartzite overlies the Portaskaig Con- 

 glomerate and Islay Limestone (1917, pi. xii); and, in conformity 

 with this, all the way from Luing to Dalmally the Easdale Slates 

 persistently separate the Islay Quartzite from the overlying Loch- 

 Awe Nappe (pp. 114, 118, & 119). 



At higher levels, recumbent folding sets in, as proved by an 

 extensive inversion of Loch-Tay Limestone, Pitlochry Schists, and 

 Green Beds over the Ben-Ledi Grits. The flat-l3dng geology of 

 the Loch-Tay district, mapped b}'' J. S. Grant Wilson (Sheet 46), 

 has become too familiar to detain us ; all that need be said is that 

 the inversion of the Loch-Tay Limestone is revealed as holding 

 good for some 15 miles measured across the strike. Far less 

 famous, but equally instructive, is a set of exposures at Campbelton 

 in Kintyre, where a restricted subsidence (perhaps of Tertiary date) 

 has led to the preservation of a little coalfield in the axial regions 

 of the Covval Anticline. The Loch-Ta}'^ Limestone and overlying 

 schists are seen to advance their outcrops notably to the east as 

 they come within the sphere of influence of the depression, whether 

 their approach to it be followed from the north or from the south. 

 It was a great pleasure to me, on visiting the ground in 1919, to 

 find how accurately R. G. Symes, with Dr. Peach's assistance, had 

 traced the main exposures of limestone and associated epidiorite 

 (Sheet 12) : it was also delightful to realize on the ground how 

 clearly the Loch-Tay Limestone overlies the Ben-Ledi Grits, etc., 

 which constitute the main part of the peninsula of Kintyre, both 

 north and south of the depression. 



The normal sequence of Islay and the inverted sequence of 

 Loch Tay are seen in conjunction on the slopes of Ben Lui. 

 Together they supply the two limbs of a great recumbent fold 

 (fig. 4) 1 ; the normal sequence furnishes the lower limb, the 

 inverted sequence the upper (p. 124). In such circumstances, as 

 I have already pointed out, it is difficult to regard the Ben-Lui 

 Fold as anything but a syncline, and since it can be seen to close 

 towards the north-west, it has all the appearance of being a product 

 of south-eastward movement (p. 89). 



At still higher levels, the Loch-Tay inversion gives place to a 

 normal sequence once again, this time through the intervention of 

 the Carrick-Castle Fold, which (as might be expected) closes 

 south-eastwards (p. 86). It has already been pointed out that 

 this fold is probably an anticline, because of Clough's reading of 

 the local evidence of south-eastward movement (p. 101) ; of course, 

 if Clough's evidence were not available, the same result would 

 have been arrived at on my reading of the original order of 

 deposition. 



^ See also 1922, Eeport A, par. 5 ; Report B. 



