98 MR. E. B. BAILEY ON THE STRUCTURE OE [vol. Ixxviii, 



the Loch-AAve Syncline. They show ascending structural succes- 

 sions towards the Loch- Awe country in the adjoining districts of 

 Islay and Glen Orchy (1917, 1912 h)^ and also an upward structural 

 succession from Crinan Quartzite through Tayvallich Slates into 

 Loch-Avich Slates within the limits of the Loch-Awe Nappe (1918 b, 

 pp. 292, 294 ; 1911, pp. 65-68).2 



There is nothing in what has been noted above that suggests 

 bodily transport of the Loch-Awe Nappe. The obvious fan-folding 

 may be taken as a typical example of movement outwards in two 

 directions from a central axis. Such movement would not be 

 expected to belong to a period of advance of the nappe as a whole ; 

 it seems connected rather with the s^mclinal depression which 

 affected the nappe after its mise en place. Anticipating much 

 that has yet to be discussed, one may state that the Loch- Awe 

 Nappe travelled into its present position from the north-west. 

 The evidence relied upon is afforded by the distortion of the 

 underlying rocks, leading, among other results, to the production 

 of the recumbent syncline of Ben Lui (PI. I & fig. 4, p. 102). 



The Iltay Nappe. 



Constitution. — The following succession has been traced in 

 that part of the South- West Highlands which is fashioned out of 

 the Iltay Nappe (PL I) :— 



Leny Grits witli slates (or phyllites) of the Aberfoyle type. 



Aberf oyle (or Dunoon) grey, green-grey, buff- coloured, purple, and 

 black Slates (or Phyllites) with numerous thin limestone- and 

 grit- bands. 



Ben-Ledi (or Beinn-Bheula) Grits, grey phyllites (or mica-schists), 

 and aJbite-schists (or gneisses), with locally important chlorite- 

 epidote-schists (Green Beds). Garnets are common north-east of 

 the albite-zone (fig. 3). Oligoclase-pebbles are often said to be 

 characteristic of the Ben-Ledi Grits ; my experience is that the 

 common felspar-pebbles are albite and more or less perthitic 

 orthoclase. 



Green-Bed Group, in which chlorite-epidote-schist, often gritty, is 

 strongly developed. Hornblende is common north of Cowal. 



Pitlochry (or Glen-Sluan) Schists and Grits. The schists 

 carry albite in Cowal and garnet farther north (fig. 3). 



Loch-Tay light to dark grey crystalline Limastone (or marble), 

 sometimes mottled with black calcite- crystals ; in large part a 

 calcareous schist or quartzite. Almost always invaded by epidiorite- 

 sills. 



Ben-Lui Garnetif erous Mica-Schist with grits and minor Green 

 Beds ; graphite-schists, interbedded with phyllitic garnetiferous 

 mica-schist, mark the edge against the Ben-Lawers Group in the 

 St. Catherine's district of Upper Loch Pyne. Limestone also occurs. 

 In the district of Lower Loch Fyne garnets are but poorly developed. 



Ben-Lawers Calcareous Schists (or phyllites), with some 

 limestone and fine-grained quartzite. The calcareous material is 

 disseminated, and is often only clearly visible in quartzose lenticles. 



Easdale black graphitic Slates (or Schists), with subordinate bands 

 of quartzite and black limestone. 



^ See also 1922, Rep. A, par. 4. ^ Ibid, Eep. A, par. 2. 



