Cole — On Composite Giismes in Boi/lagJi, Went Donegal. 205 



the granite mass. But the general trend of this foliation is al«o that 

 of the strike of the iiptiltcd sedimentary schists. There is no mystery 

 here as to the origin of the schistose scries, which admittedly consists 

 of shales, limestones, and sandstones, invaded by basic igneous rocks, 

 and subsequently metamorphosed by pressui-e. The dynamic action 

 has here and there induced a foliation oblique to the bedding, while 

 thrust-planes have allowed some blocks to move over others ; but in 

 most localities the original bedding is traceable, and there has been no 

 general rolling out of the complex mass into mylonitic schist or 

 gneiss.^ In the promontory, for instance, leading to Loughros Point, 

 west of Ardara, obvious deformations have gone on, with consequent 

 production of garnetiferous mica-schist ; but in many places the 

 stratification of shales and limestones is left perfectly clear, with a 

 puckered foliation running obliquely through the shales. Even where 

 great quartz-veins come up along the surfaces of foliation, the original 

 bedding may still be seen, and the character of phyllites, rather than . 

 of mica-schists, is preserved by the crumpled shales. 



The folded layers, then, of this stratified "Dalradian" series, 

 although inversions and repetitions had already taken place, furnished 

 the important structural surfaces of the district at the time of the 

 upwelling of the granite. West of Glenties, the igneous rock has 

 come up laccolitically along one of these surfaces, forming a low. 

 granite dome north of Ardara. On the south side the dip of the 

 Dalradian series is away from the elongated dome ; but on the west 

 and north it is towards the granite, and the schists are doubtless there 

 prolonged to some distance beneath the igneous rock. Trusklieve, in 

 Ranny, forming the conspicuous mass north of the Gweebarra, with 

 its bare tabular granite overlying schist, and sending off intrusive veins 

 into this sedimentary substratum, is another example of an igneous 

 boss behaving as a laccolite on its margin. (Compare left-hand end 

 of figure on p. 225). 



Along the margin of the granite dome which stretches north from 

 Ardara, foliation appears in patches in the granite. According to an 

 older view, this indicated that the granite had been formed by the, 

 progressive metamorphism of stratified schists. On the dynamo- 

 metamorphic view it indicated, on the other hand, a crushing and 



^ Mr. Kilioe describes the considerable movements and dislocations in this series 

 in the Glenties area (Mem. S. "W. Donegal, pp. 19-23). 1 attribute, however, 

 certain features of the metamorphism described by him to the contact-action and. 

 intrusion of the granite, working on a regional scale. 



S'2 



