302 me. e. b. bailey on the [June 19 13, 



curving outcrop leading from Glen Shira to Loch Awe, but a visit 

 to the exposures 2 miles east of the loch showed that cream- 

 coloured and blue-grey limestones are both well developed. Nearer 

 the loch, in a stream crossed by the main road, a section is met with 

 consisting largely of blue, compact, thinly-bedded limestone, with 

 bands of grey slate and more siliceous material. The limestones 

 here are very like many in the Tayvallich position, but the asso- 

 ciated slates are never black. The interposition of this exposure 

 between the Ardrishaig Phyllites and the Oman Qnartzite is 

 fortunately quite clear, although the latter division is not very 

 strongly developed. 



The grey facies of the Shira Limestone continues west of Loch 

 Awe. The part of the outcrop which approaches the escarpment 

 of the unconformable lavas of Old Red Sandstone Age needs re- 

 examination : it is possible — as the Crinan Quartzite is not in 

 strong force — that I have locally confused Shira and Tayvallich 

 Limestones, for black slate occurs with the limestone not far east 

 of the lava escarpment. The matter is a subsidiary detail, so far 

 as the present paper is concerned, but is of importance to anyone 

 who attacks the problem of the black schists and pebbly quartzites 

 of the Dalmally neighbourhood. 



The next exposures to be noticed are on the west side of the 

 Loch Awe syncline, a mile east of the head of Loch Melfort. Here 

 the Shira Limestone is in two beds, separated by a thick epidiorite 

 sill and some green phyllite. The lower band, as exposed near 

 a lime-kiln west of a loch known as Loch Pearsan, on the borders 

 of Sheets 36 and 37 of the Geological Survey 1-inch map, is a 

 well-bedded grey limestone, 12 feet thick. It graduates upwards 

 into calcareous quartzite, with small but recognizable pebbles. In 

 this is a layer of fine-grained pebbly limestone containing limestone- 

 fragments. The upper band, as seen on the northern and southern 

 shores of Loch Pearsan, is a grey-banded limestone with some thin 

 seams of black slate. Here, then, is the Shira Limestone exhibiting 

 — in a very feeble manner, it 'is true — the pebbly nature and the 

 association with black slate which are so emphatically characteristic 

 of the Tayvallich Division. 



Southwards for some distance the Shira Limestone has been 

 recognized in places as a belt of cale-silicate-hornfels, resulting 

 from the metamorphism induced by a small granite-boss. Its 

 outcrop is not shown on the geological maps until, south of this 

 granite, at the head of the alluvium deposited by the river leading 

 into Loch Craignish, its position is marked in the field by three 

 prominent bands of dark-grey limestone separated by grey phyllites; 

 the zone extends here for about a quarter of a mile west from 

 the margin of the Crinan Quartzite. 



Beyond this, towards the head of the loch, one observes occasional 

 exposures of dark-grey limestone; but the division is mostly 

 obscured by alluvium, and no attempt has been made to continue 

 its outcrop on the map. I searched such exposures as occur for 

 black slate, but quite in vain. 



