ROCKS OF THE NORTHERN HIGHLANDS, 369 



Dolomite may be brought into contact with or even under the 

 Quartzite by a reversed fault. 



Towards the top of the burn, about 200 yards above the over- 

 thrown fold, the quartzite curves up to the N.E., dipping away from 

 the gneissic ridge of Glasven ; and examining its base, we find an 

 abundance of red felspar bits, just as at the base of the quartzite on 

 Loch Assynt. This quartzite is also penetrated by felsite, apparently 

 in the bedding, as is commonly the case with the admitted " Lower " 

 Quartzite of this district. 



Scarp between Calcla Burn and Poulan-drein. 



Returning to the junction of dolomite and quartzite, we trace it 

 along the escarpment to the south-east for about three quarters of a 

 mile, and there is little to be seen which could suggest a fault ; but 

 the outcrop is along the strike, and there is no visible superposition 

 of quartzite on dolomite. But 200 or 300 yards from Poulan-drein, 

 the actual contact of the two rocks is seen in a large pot-hole, 30 

 feet deep, and forming a gash running east and west. Its northern 

 side is a face of quartzite vertical right down to the base. The 

 bedding is sharply bent up to the south-west. The south side is occu- 

 pied mainly by the dolomite, lying nearly horizontal, and coming 

 almost into contact with the quartzite at each end of the fissure, both 

 rocks being very much broken. Igneous rock is intruded into the 

 quartzite, and along the bottom of the hole. As this fissure is only 

 a few yards wide, it is obvious that, if the dolomite and quartzite are 

 conformable, the former should be seen in the lower part of the 

 quartzite cliff. The evidence of faulting here seems to be nearly 

 conclusive. 



Between the pot-hole and Poulan-drein, the exposures become 

 scanty ; but it is seen that the Dolomite retains its strike, while the 

 strike of the Quartzite turns round through almost a right angle, 

 the strata dipping gently to the S.E. right dowu to Poulan-drein. 



Section on Poulan-drein (fig. 3) . 



The rocks up the stream are clearly exposed ; and the evidence 

 they furnish is decisive. Ascending from the shore of the loch, we 

 pass over Quartzite, Brown Flags, Salter ella- quartzite, and Dark 

 Dolomite, all dipping steadily at about 15° to E.jNT.E. The White 

 Dolomite succeeds, forming a shallow syncline, as seen on the south- 

 east side, about 100 yards from the stream. Beyond this the Dark 

 Dolomite reappears, but with reversed dip, i. e. to the W.S.W., and, 

 after two or three rapid undulations, is sharply bent up, at the 

 foot-bridge standing nearly vertical, and becoming absolutely so a 

 few yards higher. At a little fall, 50 yards above the bridge, the 

 dolomite is conformably underlain by a band of quartzite 10 feet 

 thick, holding the place of the SaltereUa-zone. This quartzite forms 

 the fall. Above it we come immediately to the Brown Flags, 100 

 feet in thickness, in vertical beds, but in places actually bent back 

 so as to dip at 80-85° into the ""idge. The section in the burn above 

 is obscure for some distance ; but in a small cascade which falls down 



