302 Tlie Structure of tlie South- West Highlands. 



3. The coast-section of the Tayvallich Lavas supplies ahnost 

 conclusive evidence that the structural seqaence noted above is not 

 an in version. ■•■ 



4. Examination of the district between Loch Awe and Beinn 

 Udlaidh shows sufficiently clearly that the Ardrishaig-Loch Awe 

 Assemblage (Mr. Bailey's Loch Awe Nappe) structurally overlies 

 the remainder of the South- West Highlands. 



5. Most of us were already familiar with the Ballachulish 

 recumbent fold and slide. ^ We saw further evidence, and we regard 

 these structures as demonstrated. We also found the recumbent 

 folds of Beinn Udlaidh ^ and Ben Lui so well exposed that we do 

 not think either of them open to question. We were impressed with 

 the fact that, at Ben Lui, Mr. Bailey has interpreted, but not altered, 

 the original Survey mapping . 



6. The recumbent fold of Ben Lui furnishes a complete explanation 

 of the failure of the Cowal Schists to reappear north-west of the Loch 

 Awe Syncline. 



7. As regards the thrust which Mr. Bailey invokes at the base 

 of his Loch Awe Nappe, we do not think an alternative interpretation 

 has been advanced which meets the observable facts, in particular,, 

 the three-sided nature of the Ardrishaig-Ben Lawers complex. 



8. We accept the connexion which Mr. Bailey has traced between 

 Perthshire and Islay round the north end of the Loch Awe Syncline 

 in what he calls the Iltay Nappe, though one of us (E. M. A.) thinks 

 that the possibility of a reinterpretation of the supposed Iltay out- 

 crop on Loch Etive should not be lost sight of. 



9. Some of us were strongly impressed by the evidence of marked 

 disruption adduced by Mr. Bailey near the base of his Iltay Nappe 

 in the lov/ly metamorphosed region of Ardmucknish. 



10. Where constructive metamorphism is marked, obvious 

 crushing is characteristically absent from Mr. Bailey's slides. Clough 

 has compared Bailey's non-mylonitic slide-zones with some of pre- 

 Torridonian age in the North-West Highlands.^ In contrasting these 

 particular mylonitic movement-zones of the North- West High- 

 lands with the mylonitic type well represented among the post- 

 Cambrian thrusts of the same district, Teall and Home say : " These 

 two types no doubt correspond to differences of pressure and 

 temperature at the tim,e of deformation."^ 



11. We were unable to test Mr. Bailey's tentative inter-nappe 

 correlations, or his Islay chronological evidence, upon which, in 

 conjunction with the Ben Lui Fold, he bases much of his case for 

 the nappe-movement having proceeded from the north-west. In 

 these and other matters we should like to suspend judgment. 



^ B. N. Peach & E. B. Bailey, "Geology of Knapdale, etc." : Mem. GeoL 

 Surv., 1911, pp. 60, 69. 



2 Q.J.G.S., vol. Ivi, 1910, p. 593. 



3 E. B. Bailey & W. Macgregor, Q.J.G.S., vol. Iviii, 1912, p. 168. 

 * Q.J.G.S., vol. Iviii, 1912, p. 177. 



^ N.W. Highland Memoir, 1907, p. 598. 



