part 2] THE SOUTH-WEST HIGHLANDS OF SCOTLAND. 



107 



with pebbles of quartz and felspar, and where these are par- 

 ticularly big they are often accompanied by rock-fragments. In 

 the main, these latter are strictly local in origin (slate, limestone, 

 quartzite, and, in the Loch- Awe Nappe, lava) ; but nordmarkite 

 and other foreign boulders have been found by H. Kynaston 

 (1908 Z», p. 31) and Dr. B. N. Peach (1911, p. 71) at two 

 important localities in the Loch- Awe Nappe. 



Dr. J. S. Flett (1911, p. 75) has shown that the foreign boulders 

 of the Loch-na-Cille Conglomerate (Loch- Awe Nappe) agree 

 in type with those occurring in the Portaskaig Conglomerate 

 of the Iltay Nappe. This is a very significant fact, for it 

 emphasizes what most Highland geologists consider a certainty, 

 that much of the quartz and alkali-felspar of the Crinan Quartzite 

 (Loch Awe) came from the same source as the similar material of 

 the Islay Quartzite (Iltay). But the reader is warned against 

 thinking that. the nordmarkite-boulders afford evidence for corre- 

 lating the definitely volcanic conglomerate of Loch-na-Cille with 

 the definitely non-volcanic conglomerate of Portaskaig. The two 

 are distinct, both in character and in associates. The difference 

 of character depends mainly on the circumstance that at least 90 

 per cent, of the fragments included in the Loch-na-Cille Con- 

 glomerate are of lavaform rocks unknown in the Portaskaig 

 Conglomerate. The contrast of associates Avill be understood from 

 the following statement : — The Crinan and Islay Quartzites, viewed 

 broadly, are in each case susceptible of twofold division : one part 

 is fine or relatively fine in texture, the other coarse. The Loch- 

 na-Cille Conglomerate lies on the coarse side of the Crinan 

 Quartzite, in a position marked by constant recurrence of con- 

 spicuous quartz- and felspar-pebbles. The Portaskaig Conglo- 

 merate, on the other hand, lies on the fine-grained side of the Islay 

 Quartzite. 



Without elaborating the subject, I offer below a table of corre- 

 lation. It is important to remember that age-sequences have 

 been fixed by very convincing evidence in the Iltay and Loch-Awe 

 Nappes, and by suggestive relationships in the Ballappel Founda- 

 tion. This in itself adds to the weight of the proposed cor- 

 relations : — 



Loch Aive. 



Tayvallicli Slates, Lime- 

 stones, and Conglome- 

 rates. 



Crinan Quartzite. 



Shira Limestone. 



Ardrishaig Phyllites. 

 Erins Quartzite. 



Titay. 

 Ben-Lui Schists. 

 Ben-Lawers Calc- Schists. 

 Easdale Slates. 

 Transition Zone. 



Islay Quartzite. 

 Portaskaig Conglomerate 

 and Islay Limestone. 



Ballappel. 

 Leven Schists. 

 Ballachulish Limestone. 

 Ballachulish Slates. 

 Striped Series. 



Appin Quartzite. 



Appin Limestone and 

 Phyllites, and Cuil- 

 Bay Slates and (pos- 

 sibly) Lismore Lime- 

 stone. 



Mull-o£-Oa Phyllites. 

 Maol-an-Fhithich Quartzite. 



