On the Progressive Metamorphism of some Dalradian Sediments in the Region of Loch Awe

Abstract

I. I ntroductory R emarks . I n the course of the geological survey of the Loeh Fyne and Loch Awe districts of Argyllshire, a comparatively unaltered series of rocks was discovered by the author, located in a zone of which Loch Awe forms a central axis. So markedly different in condition were they from the ordinary mica-schists of Argyllshire that for some years they were looked upon as considerably later in age than the more crystalline rocks lying to the north and east of them. As the survey of the district progressed, especially in a north-easterly direction, a change of character was detected in them. They assumed a more crystalline condition ; in some areas a gradual, in others a more marked and rapid change of character was observed. In the years 1892 and 1893 it was found that these rocks, as they approached the more mountainous districts of Argyllshire, between Beinn Buidhe and Ben Cruachan, became more highly crystalline, until at last they were traced passing into highly crystalline schists of the normal Central Highland type. The results of these observations were briefly set out in the Annual Report of the Director-General of the Geological Survey for the year 1893. on p. 265 of which the present author's work is referred to as follows :— ‘Not less important in its bearing upon the origin and sequence of the Highland rocks is the recent work of Mr. J. B. Hill in the district of Loeh Awe, to which reference was made last year.