DEVONIAN AND OLD RED SANDSTONE SYSTEM 235 



Just as the northern belt is cut off by the .Highland boundary 

 fault, so the southern tracts are cut off by the boundary fault of 

 the Southern Uplands, which runs from the coast near Ballantrae 

 north-eastwards till it passes beneath the Carboniferous basin 

 of Dalkeith. A small tract of Lower Old Red near Eyemouth in 

 Berwickshire shows that the Caledonian area of deposition was 

 prolonged southward, and there can be little doubt that the 

 Cheviot area was also a part of it. The Cheviot Hills consist 

 mainly of massive andesitic lava-flows with intercalations of tuff 

 and ashy sandstone, and there are some beds of sandstone and 

 conglomerate at the base, but of no great thickness. 



Passing now to the Upper Old Red Sandstone of the Caledonian 

 region we find this everywhere marked off from the Lower Series 

 by a great break and unconformity. It occurs only in isolated 

 tracts, and frequently oversteps the limits of the Lower Series on 

 to the older rocks. The interval of time which elapsed between 

 the two epochs of deposition must have been a long one, for Mr. 

 Hickling finds that in Forfar no less than 8000 feet of material 

 had been removed from the main anticline before the Upper Old 

 Red was deposited ; in other words, the Lower Series was flexured 

 and then denuded to that extent in the interval which is else- 

 where partially filled by the Middle Old Red. 



The Upper Series occupies several more or less extensive tracts 

 in different parts of the region, the largest being that in the 

 south-east, Roxburgh and Berwick, where it extends from the 

 northern borders of the Cheviots by Jedburgh and Earlstou to Lauder 

 and Greenlaw, and then all round the Lammermuir Hills to the 

 coast at Dunbar. A smaller tract is found in the Pentland Hills, 

 and others in Lanark and Ayrshire. On the northern side of the 

 Lowland area two long belts of it lie between the boundary of the 

 Lower Series and the outcrop of the Carboniferous sandstones, the 

 one extending from the Clyde to the Forth near Stirling, the other 

 from Kinross and Loch Leven to Cupar and Leuchars in Fifr. 

 There are also some small tracts in Forfar. 



The following description of the beds composing this Upper Old 

 Red is condensed from the account given by the late J. G. Goodchild, 

 and is applicable to all the more eastern tracts. 



The series is divisible into a lower and upper stage ; the lower 

 consists of a variable set of conglomerates and sandstones, the 

 coarser beds being at and near the base, and the sandstones 

 becoming finer in grain and more interstratified with marls 

 towards the top ; the sandstones also become more and more 

 largely composed of rounded wind -worn grains. The prevalent 

 colour is bright red ; the thickness is variable (from 100 to 500 



