On the Crush- Conglomerates of Argyllshire. 579 



series of basic igneous rocks (' green rock ') of coarse texture and 

 probably intrusive origin. The upper division consists of con- 

 glomerates, pebbly grits, dark and white shales, pebbly limestone, 

 and grey shale. The age of the series cannot be definitely ascer- 

 tained, but the lower division is compared with the Arenig cherts, 

 etc. of the Southern Uplands, while the Margie Series is newer than 

 this, but older than the Old Red Sandstone. Both groups have been 

 much deformed, but the sediments contain clastic micas and have 

 undergone practically no recrystallization, and the igneous rocks are 

 never changed into hornblende-schists. The deformation is greatest 

 near the junction with the Highland Schists, giving rise to a deceptive 

 appearance of an upward succession and an apparent transition in 

 crystalline character, but the crushing never extends more than a 

 few yards into the Highland Series. A major thrust separates the 

 Highland Schists from the Jasper and Green-Rock Series, and a 

 minor thrust generally separates the latter from the Margie Series. 

 The position of the major thrust and that of the later great 

 boundary-fault skirting the Old Red Sandstone have been deter- 

 mined by the outer limit of the aureole of crystallization of which 

 the South-Eastern Highlands form a part. The harder crystalline 

 schists to the north-west have snapped off from the softer portions, 

 now covered by newer rocks to the south-east. 



3. ' On the Crush-Conglomerates of Argyllshire/ By J. B. Hill, 

 Esq., R.N. 



While the sedimentary origin of the Highland Boulder-bed is 

 proved by the foreign boulders contained in it, there occur in 

 the Loch-Awe region certain conglomerates, often along definite 

 horizons, which may have been confused with it, but which the 

 author is able to prove have originated by crushing. The sedi- 

 mentary rocks of the area include all the members of the Loch- 

 Awe Series, consisting of grits, slates, and limestones, the latter being 

 mostly gritty in character. Associated with these is an enormous 

 amount of igneous material of Dalradian age, ranging from inter- 

 mediate to basic in composition, together with porphyrite-dykes 

 probably of Old-Red-Sandstone age, and a plexus of Tertiary dykes. 

 The sediments are everywhere folded, the folds being of isoclinal 

 type. The Dalradian igneous material consists of epidiorites ; and 

 evidence is brought forward to prove that these rocks are intrusive, 

 while their great apparent bulk is probably to be accounted for by 

 repetition due to folding. A petrographical description is given of 

 the various types of rocks represented among the epidiorites, the 

 minerals of which include hornblende and felspar, with chlorite, 

 epidote, calcite, quartz, and iron-ores. There is every gradation in 

 texture from a coarse gabbro-like type to the finest schists, and some 

 of the rocks are vesicular. The rocks are frequently foliated. 



The crush-conglomerates have been observed in the limestones, 

 quartzitcs, and epidiorites ; but they are most conspicuously deve- 

 loped at the junction of rocks of dissimilar character, and especially 

 when the limestone and cpidiorite are in juxtaposition. The 

 junction of the two rocks is intricately folded : folded knobs of epi- 

 diorite measuring from a few inches to a foot or more being packed 



