﻿I860.] 



NICOL N.W. HIGHLANDS. 



97 



quartzite and limestone occur in this region, a few confirmatory 

 facts and sections must be noticed. 



In ascending the road from Skiag Bridge towards Kyle Sku, the 

 fucoid-beds and limestone may be seen resting on the quartzite, 

 almost to the summit of the ridge. Before reaching the foot of 

 Glasven, however, they thin out, and the quartzite of that mountain 

 and of Queenaig form one continuous mass, as shown in the section. 

 That the quartzite of Glasven does not overlie the limestone is 

 further proved by no trace of limestone being seen in the Corry 

 Derg (fig. 7, p. 95), where the syenite brings up the bottom beds, 

 or between the quartzite and gneiss in the noble sections exposed on 

 the north-east side of that mountain, formerly described. 



The same thing is shown by the section from Loch Assynt near 

 the School-house, in a N.N.E. direction across Cnoc-an-drein. 

 Close to the lake the quartzite is seen cropping out below the lime- 

 stone, which forms all the declivity of the hill, and dips to E. 25° to 

 30° N., at angles ranging from 20° to 40° or more. This diversity 

 of dip is caused by the intrusion among the strata of irregular veins, 

 or lenticular-shaped masses of trap, of which I enumerated not 

 fewer than eight or ten. Near the top of the ridge the qnartzite 

 appears to rest on the limestone, but is separated from it by veins of 

 green trap and of dark clove-brown felspar-porphyry. The quartz- 

 ite (Pipe-rock) dips first E. at 25° to 35°, and then higher up on 

 Cnoc-an-drein rises to 75° to 80°, at length becoming vertical, with 

 a N.N.W. strike, having clearly been forced up by the intrusion of 

 the syenite (shown at s in figs. 7 <fc 8). 



The inferiority of the quartzite to the limestone is even more 

 clearly seen in the Poulan-drein Burn, at the south-east end of Cnoc- 

 an-drein ; it may also be seen along the whole valley of the Traligill 

 Biver, almost to the Bealach at the foot of Ben More. Everywhere 

 the limestone, which in the plateau of Stronchrubie on the south 

 side of the stream dips towards these mountains, is found to form 

 a synclinal axis, and on the north side to dip away from the quartz- 

 ite. The only obscurity in the sections arises from the synclinal 

 fold in the limestone being conjoined with a great fault in the quartz- 

 ite, which is thus brought up in enormous crushed masses, so broken 

 that the lines of stratification can hardly be detected*: this is 

 especially seen near the foot of Coniveal ; but in no place have I 

 observed the limestone dipping below the quartzite of these moun- 

 tains. 



In the line of the section no such obscurity exists. Immediately 

 to the east of Loch Maolack-Corry, well known for its Gillaroo trout, 

 the Stronchrubie limestone, continuous throughout, rises up into a 

 hill, and is seen very distinctly dipping at 40°, to W. 40° N., in 



* This peculiar combination of faults with synclinals (or what may be named 

 a " faulted-synclinal ") is very common in Sutherland. It has probably been 

 caused by the refractory nature of the quartzite, which was more easily broken 

 than bent. To the same cause we may ascribe the frequent combination of a 

 crush (or broken and brecciated condition of the rock) with one or both of these 

 faults and synclinals. 



VOL. XVII. PAKT I. H 



