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'Vol. 66.~] SCHISTS OF THE SCOTTISH HIGHLANDS. 603 



that portion of the outcrop of the latter which lies between the 

 Ballachulish Granite and the southern limit of the map. 



Near the margin of the granite local deflection of the outcrop 

 of the Appin Core, as also intense contact-alteration of the 

 sediments, renders the geologist's task one of unusual difficulty ; 

 but, on passing to the south of Glen Duror, these complications 

 are soon left behind. 



Suppose, then, that we enter the Appin Core somewhere in the 

 vicinity of Glenstockdale House, about 2 miles north-east of Appin 

 Station. After leaving the Leven Schists (7) we first meet with the 

 Ballachulish Limestone (6), and after this with a narrow belt of the 

 Ballachulish Slates (5). So far all is as regular as between Onich 

 and Port William, but progressing farther into the heart of the core 

 we fail to encounter the Striped Transition Beds (4'), and 

 instead step directly on to the massive pebbly Appin Quartzite (4*), 

 or, according to the locality, on to the Appin Limestone (3) or 

 even the Appin Phyllites (2). We have, in fact, passed over an 

 important slide, which has the effect of suddenly deepening the 

 Appin syncline — in this feature agreeing with the Fort William 

 Slide, although the latter occurs on the other side of the fold. It 

 is obvious, then, that the two slides are complementary, and that 

 they combine to give to the Appin Core increased freedom of advance, 

 or relative advance, into the heart of the other sedimentary masses 

 which lie above it, below it, and in front of it in a south-easterly 

 direction. 



Other examples of slides complementary to the Port William 

 Slide will be noticed in the sequel; the Meall a' Bhuirich Slide, 

 (PI. XLIII) is a good example. The Ballachulish Slide is, however, 

 homologous with the Fort William Slide (compare Sections C & H, 

 Pis. XLIII & XLIY). 



(b) The Aonach Beag Core. 



In the district so far examined the Aonach Beag Core consists 

 entirely of a thick limestone which is generally in the condition of 

 a flaggy, greenish-white, caJc-silicate hornfels. The limestone has, 

 however, escaped contact-alteration in some of the sections east of 

 the Cour, and is there found to be very sandy and impure in com- 

 position and anything from pale grey to cream in colour. 



The limestone of the Aonach Beag Core is correlated with the 

 Ballachulish Limestone for the following reasons : — 



(1) It is linked with the Leven Schists through transition beds, and is of 



the same type as that portion of the Ballachulish Limestone which 

 is similarly connected. 



(2) It nowhere intervenes, structurally speaking that is, between an out- 



crop of the Ballachulish Limestone and one of the Glen Coe Quartzite 

 Thus the Leven Schists, in contact with the Ballachulish Limestone 

 of the Appin Core, pass beneath the syncline holding the Aonach Bea* 

 Limestone, and connect directly with the Glen Coe Quartzite beyond 

 (PI. XLIII, Section A). 



Q. J. G. S. No. 264. 2 t 



