120 ME. E. B. BAILEY ON THE STEUCTUEE OF [vol. Ixxviii, 



(3 a) The detailed downward succession from the centre of the Loch- 

 Awe Syncline through the various subdivisions of the Loch- Awe Group 

 to the Ardrishaig Phyllites has already been traced (p. 97). The con- 

 formity of outcrop of the Islay-Easdale Assemblage shows that this 

 assemblage must in its turn underlie the Ardrishaig Phyllites. It has 

 already been pointed out that the general east-and-west outcrop of the 

 Ardrishaig Phyllites near the northern end of Loch Awe is due to pitch. 

 The significance of the sympathetic east-and-west deflection of the Islay- 

 Easdale outcrop is unmistakable. 



(3 h) Local evidence (1917) shows quite as clearly that the Portaskaig 

 Conglomerate, Islay Limestones, MuU-of-Oa Phyllites, and Maol-an- 

 Fhithich Quartzite, as exposed in the Islay Anticline, structurally underlie 

 the Islay-Easdale Assemblage here considered. 



(3 c) Local evidence further shows that, in the Glen-Orchy Anticline, 

 (pp. 118 & 124) a descending structural sequence can be traced which 

 leads from the Islay-Easdale Assemblage right down to the Sub-Eilde 

 Complex as exposed in the Beinn-Udlaidh Fold. 



(4) It follows, then, that the Islay-Easdale Assemblage overlies that part 

 of the Ballappel Foundation Avith which it comes into contact in the Loch- 

 Creran district. 



(5) Accordingly, if for no other reason, the Islay Quartzite cannot be 

 interpreted as a special facies of the Glen-Coe Quartzite in normal contact 

 with the Banded Leven Schists of the Loch-Creran district. The Glen-Coe 

 Quartzite, which is seen in normal contact with the Banded Leven Schists at 

 the head of Loch Creran and in the Windows of Etive, could only reappear 

 in the district of Lower Loch Creran by emergence from below the adjacent 

 Leven Schists. 



(6) The Islay-Easdale Assemblage is also, for two good independent 

 reasons (6 a & 6 b), distinguishable from the Appin Quartzite and Easdale 

 Slates of the Ballachulish Fold : — 



(6 a) The Islay-Easdale Assemblage has been traced into the Ben- 

 Doirean Range 15 miles south-east of the Windows of Etive, whereas 

 the Appin Quartzite and Ballachulish Slates of the Ballachulish Nappe 

 do not reach so far south-eastwards as these Windows (p. 109). 



(6 h) The Islay-Easdale Assemblage overlies what are, with very high 

 probability, regarded as the Leven Schists of the Ballachulish Nappe in 

 the whole of the Glen-Orchy district (pp. 118 & 119). 



(7) It must be admitted that the Islay-Easdale Assemblage is transgressive 

 in its relationships. Otherwise, one would not find it in Ardmucknish resting 

 upon the Appin Nappe, where one would naturally expect to meet with the 

 Ballachulish Nappe (this statement holds substantially, even though the 

 eastern limestone of Ardmucknish be regarded as a remnant of the Balla- 

 chulish Nappe, as it well may be). 



(8) As the transgression obviously does not antedate the movement which 

 gave rise to the Ballachulish Nappe, it seems necessary to regard it as 

 mechanical, not stratigraphical, in origin. 



(9) The conspicuous shear-zone separating the Islay Quartzite and the 

 Ballachulish Limestone in the Ardmixcknish Peninsula has been discussed 

 (p. 112). Another interesting case of special shearing near the base of the 

 quartzite has been noticed in stream-sections entering Glen Orchy from the 

 east. There are intrusions of basic igneous rock in quartzose schist 

 (probably Killiecrankie Group) in this position, and the two have been 

 sheared and rodded in a most remarkable manner, with a resultant inter- 

 banding of films, in certain cases no thicker than tissue-paper. 



(10) The absence of the Portaskaig Conglomerate and Islay Limestone in 

 the mainland exposures can be very readily attributed to the thrust invoked 

 above on other grounds. The non-occurrence of these characteristic zones is, 

 of course, merely local, since they reappear farther north-east in Schiehallion. 



