44 



STRATIGRAPHICAL GEOLOGY 



has a border or base containing stones of the size of boulders as 

 well as pebbles. 



The above may be an ascending or descending sequence. 

 Hitherto it has been generally supposed that the rocks of the 

 Central Highlands are younger than those to the north-west of 

 them, but this is an assumption, and the intermediate position of 

 the Moine schists between the unaltered Hebridean area and the 

 Grampian range may be merely a geographical and structural 

 accident. It does not follow that they are of intermediate age, and 

 we shall see in the sequel that the general order of succession in 

 the metamorphic area may have to be read from south-east to 

 north-west. 



We must now return to the north-western area and give some 



Ballachulish 



N.W 



Glen 



Btive S.E. 

 G 



FlO. 4. SECTION FROM LOCH LINNHE TO LOCH ETIVE. 



Copied from Mr. Bailey. Distance about 14 miles. 

 The numbers refer to those in the succession given on p. 43. 



account of the Torridon sandstone, which in that area is the only 

 formation occupying an intermediate position between the Hebridean 

 complex and the Cambrian quartzites. There is, however, a remark- 

 able gap and unconformity between the gneisses and the Torridon 

 sandstones, and this gap must represent a long interval of time. 

 In some places the surface of the gneiss is a gently undulating 

 plain, but elsewhere it had been carved into a series of hills and 

 valleys, the former rising to heights of from a few hundred to more 

 than 2000 feet above the valley-bottoms. 9 



Moreover, the basement beds of the Torridonian are generally 

 in the form of a conglomerate or breccia, the components of which 

 have been mainly derived from the underlying gneisses, but excep t 

 in this conglomerate fragments of gneiss are by no means abundant 

 in the overlying coarse sandstones, and most of the pebbles found 

 in them consist of rocks which differ from any now exposed in 

 Sutherland or Ross. They include many kinds of rocks, both 

 igneous and sedimentary, such as spherulitic felsite, felspar-porphyry 



