Discussion

Abstract

Dr. N. R ast said that the paper was of particular importance in the interpretation of Highland tectonics. Since Sir Edward Bailey enunciated his theory of nappes as a basis of Dalradian structures, doubts had from time to time been cast on the validity of this conception, in particular on the existence of large-scale recumbent folds in the Highlands, or alternatively of their Caledonoid trend, and on the presence of coeval fabric in the supposed nappes. Dr. Sturt's investigation provided evidence of the essential truth of Bailey's hypothesis. The sedimentary structures of the Loeb Tummel area were spectacular enough to convince the most rigorous critic that the continuity of formations and the axial plunge showed that the great recumbent folds had a Caledonoid trend and that the apparent absence of an early fabric could be explained by its extremely fine grain-size. Dr. Sturt in his paper also showed the relationship between the Tay nappe, with its south-eastward direction of movement, and the recumbent folds of the Schichallion district, with their north-westward direction of movement. The author had shown, from evidence in his area, that there was no real discrepancy between these directions and that recumbent folds diverged from a common Sròn Mhòr syncline. This circumstance was suspected by the speaker some years ago Indeed, it seemed likely that the Sròn Mhòr syncline of Dr. Sturt was of the same structural significance as the Ben Lawers and Loch Awe synclines to the south-west. Professor B. C. K ing said that all the current