130 
BATHYMETEICAL SURVEY OF 
garnetiferous mica-scliist. On both sides of tbe valley of the Tay at 
Aberfeldy these rocks may be studied, and they appear on the moor- 
land between the Tay and Strath Ardle, and eastwards by Kirkton of 
Glen Isla, either as isolated patches in the form of outliers, or as more 
or less continuous outcrops. Again, towards the south-west, the Green 
Beds reappear at intervals on the heights between Loch Tay and Loch 
Earn till they are abruptly truncated by the Loch Tay fault. 
One of the best-defined zones in the metamorphic series of the 
Eastern Highlands is that of the Loch Tay limestone, with its overlying 
and underlying garnetiferous mica-schists. In the Tay basin the 
members of these groups (5, 6, 7) usually indicate a stage of high 
metamorphism, the beds being easily eroded by surface agencies. Save 
where deflected by powerful faults, their outcrops are traceable almost 
across the basin. From Glen Fernate, at the head of Strath Ardle, the 
Loch Tay limestone has been followed south-westwards, by Pitlochry, 
along the north slope of the Tay valley at Aberfeldy, to the heights 
overlooking Fortingal, where the outcrop has been deflected by the 
Loch Tay fault. West of this line of disruption the limestone reappears, 
about 4 miles further south, on both sides of Loch Tay (see geological 
map), whence it can be traced westwards up Glen Dochart and across 
Strath Filial! almost to the slopes of Ben Lui, at the south-west 
margin of the Tay basin. Owing to folding, the Loch Tay limestone 
and its associated strata reappear to the north of the line of outcrop 
just indicated, as, for instance, in Glen Lyon and in the valley of the 
Lochay north-west of Killin ; and to the south of this line, it is met 
with at Lochearnhead and on the Braes of Balquhidder. An important 
feature connected with this limestone is the frequent occurrence of a 
massive sill of epidiorite in conjunction with it. 
Still further north the sub-divisions just described are succeeded by 
calc-sericite schists, phyllites, and black schists with thin lenticular 
bands of limestone (groups 8, 9), which present lithological characters 
that are, as a rule, readily identified. The trend of the outcrop of these 
zones has been affected by the north-east and south-west faults which 
traverse the basin, and the black schist spreads over a broad area, in 
certain localities, by means of sharp isoclinal folds. Taking first the 
most southerly outcrop of the calc-sericite schist, phyllites, and black 
schist, they are traceable from Ben Vrackie south-west by Faskally on 
the Tay, to the Loch Tay fault north of Fortingal. West of this line 
of disruption, they have been followed from Glen Lyon, by Ben Lawers, 
and across Glen Lochay to the heights above Glen Dochart, where they 
terminate in a synclinal fold of the underlying garnetiferous mica- 
schists associated with the Loch Tay limestone. Still further west they 
reappear and form a broad outcrop stretching from the upper part 
of Glen Lyon in a south-south-west direction towards Tyndrum, where 
they are again interrupted by a north-east and south-west fault (see 
geological map). 
