part 2] THE SOUTH-WEST HiaHLANDS OE SCOTLAND. Ill 



Contact of the Ballappel Foundation and the 

 Iltay Nappe at Loch Creran. 



Several workers have attacked the difficult problems o£ Loch 

 Creran at one time or another in the past — Symes, Grant Wilson, 

 Kynaston, Peach, and myself. Looking back at our record of 

 partial success and partial failure, I feel that the difficulties as 

 they at first presented themselves were insurmountable — that, in 

 fact, we were confronted with a geological redoubt that could not 

 be expected to capitulate until the whole surrounding country had 

 been subjugated. In the summer of 1919 I renewed the assault, 

 and remapped on the 6-inch scale the critical portion of the district 

 covered by fig. 6. I then found that the present state of our 

 knowledge of the South- West Highlands afforded a simple solution 

 of much that had been previously inexplicable. 



The thrust shown as a thick black line in fig. 6 divides the 

 district into two dissimilar portions. These will now be considered 

 in some detail from north-west to south-east. First of all, it may " 

 be stated that the dip everj^where tends to be steep, while the 

 more yielding rocks show very obvious corrugations. 



The Ballappel Foundation, north-west of the Thrust. 

 — Three lithological belts have been mapped, succeeding one 

 another from north-west to south-east as follows : — 



(1) Limestone, never fully exposed, owing to limitation on the nortk-west 

 by sea or raised beach. Four good exposures occur : the northernmost on 

 the shore west of Airds Hill ; the next on the eastern shore of Airds Bay ; the 

 next on the western shore of Eriska ; and the southernmost on the shore at 

 Ardentinny. The northernmost exposure is the fullest, and measures some 

 200 yards across the strike. It reads as follows from north-west to south- 

 east : — Dark-grey highly-calcareous slates, mth thin grey limestone- seams ; 

 dark-grey slates ; sandy-grey limestone weathering brown, except that some 

 of the purer bands weather grey ; thick, white, sandy, thinly-bedded limestone 

 weathering brown ; passage to grey phyllite, which at first has white limy 

 streaks. 



(2) Phyllite, constituting a belt rather more than a mile wide, and well 

 seen in coastal and inland exposures. The deposit is predominantly greenish- 

 grey, and is in part laminated, in part homogeneous. As very subordinate 

 characteristics of the belt, one may note the occasional occurrence of slightly 

 calcareous bands, isolated layers of quartzite, and also seams of dark phyllite. 



(3) Limestone. — The best exposures from north to south are : — At the 

 northern edge of fig. 6, beside a hill-track 500 yards south-south-east of 

 Strathappin Farm — ochreous-weathering calcareous phyllites, with a band of 

 sandy white limestone ; 400 yards north-north-west of Ledgrianoch Farm 

 and about 50 yards east of the high road — buff -weathering phyllitic limestone 

 seen for 20 yards across the strike ; beside the path east of Ledgrianoch — 

 ochreous-weathering calcareous phyllites (and here I may say that these 

 three very important exposures north of Loch Creran might very easily have 

 been overlooked, and that we owe their discovery entirely to Grant Wilson). 

 East of the road and west of Lochan Dubh — pale phyllitic limestone ; and, 

 lastly, a series of exposures, a mile and a half long and 100 yards broad, 

 leading to the coast at Camas an Fhais — very calcareous phyllites with white 

 or yellowish limestone-beds, and (on the shore) a few feet of black slate and 

 black limestone on the south-east side of the outcrop. 



