112 ME. E. B. BAILEY ON THE STETJCTFjaE OF [vol. Ixxvili, 



The claim that these three lithological belts belong to the 

 Ballappel Foundation is easily vindicated. The limestone (1) is 

 the southern continuation of the Ballachulish Limestone, which, in 

 the upper limb of the Appin Fold, continues north-eastwards beyond 

 the limits of fig. 6 for more than 30 miles. As has been already 

 stated, the exposure of the limestone Avithin the area covered by fig. 6 

 is incomplete ; it is on this account that one cannot point to a purer 

 black portion of the belt, but what is seen is thoroughly typical 

 in character. Its associates on both sides — the gap in the section 

 on the north-west side is not extensive — tell exactly the same tale. 

 Of these associates the phyllite (2) on the south-east is manifestly 

 the southern continuation of the western part of the type-outcrop 

 of Leven Schists. It presents no noteworthy change of character, 

 except a decrease in metamorphism (fig. 3), and this difference 

 traced on the ground is found to make its appearance quite 

 gradually. Finally, the limestone (3) must be regarded as a 

 folded reappearance of the Ballachulish Limestone. It reproduces 

 exactly the characters which are found in the limestone (1) with 

 this addition that, in the southern coast-section (Camas an Fhais), 

 it shows what may be regarded as a beginning of the pure black 

 portion of the group. 



The Thrust. — The heavy black line of fig. 6 stands for a 

 thrust. The local evidence points clearly to a dislocation of first- 

 class importance, and this evidence I shall now consider under two 

 headings : — 



(1) In the first place, the succession of the Ballappel Foundation, as exem- 

 plified close at hand in the core of the Appin Fold or at the head of 

 Loch Creran in the core of the Ballachulish Fold (1914 ; 1916, p. 51), 

 would lead us to expect one of two things on crossing the south-eastern lime- 

 stone belt : either a return to Leven Schists or, failing this, a continuance 

 into the black part of the Ballachulish Limestone followed by Ballachulish 

 Slates. Instead, one steps abruptly on to a quartzite, which in the south is 

 of imposing dimensions. 



(2) Two exposures of the junction of the limestone with the unexpected 

 quartzite can be closely examined. One occurs west of Lochan Dubh,^ the 

 other on the shore at Camas an Fhais. In both cases the ocular evidence of 

 movement is very striking indeed. The junction is definitely transgressive, 

 and the shearing is extreme 



It will be noted that the evidence afforded by (1) is much more 

 serviceable in many waj^s than that derived from (2) : (1) impli- 

 cates the whole line of contact as traced in fig. 6 for half-a-dozen 

 miles ; whereas (2), considered by itself, might be interpreted as 

 of ver}"- local significance. That the dislocation, where well ex- 

 posed, is definitely betrayed by an appearance of excessive shearing 

 is due in large measure, I think, to the very low grade of meta- 

 morphism of this particular district (fig. 3). 



Iltay Nappe south-east of the Thrust. — The series of 



^ See also 1922, Report A, par. 9. 



