43 6 



DONALD C. BARTON 



transportation undergone should not be sufficient to cause marked 

 comminution and loss of the feldspar. The deposits as a whole 

 should be rather massive, but with cut-and-fill stratification rather 

 common, and with considerable intercalation of coarse block debris 

 toward the sides of the valleys. 



An example of this type of deposit is found in the Applecross 

 group of the Torridonian sandstone, a pre-Cambrian formation 

 extensively developed in the Northwest Highlands of Scotland. 

 The ideal section of the Torridonian sandstone is given by the 

 Geological Survey 1 as shown in Table III. The Applecross group 



TABLE III 



is a formation composed of massive arkose of very uniform character 

 (Fig. 3) , marked off by thin intercalations of fine quartzitic and shaly 

 sandstone into persistent layers of rather uniform thickness — in each 

 case three, six, or ten feet or so. Although extremely massive in 

 texture, the arkose shows most irregular stratification and almost 

 invariably is strongly cross-bedded. Walther reports cross-bedding 

 indicative of dune formation, and faceted pebbles. The lithologic 

 character of the arkose maybe seen from the accompanying photomi- 

 crograph. In the finer-grained phases, quartz composes a slightly 

 greater proportion of the whole than in this medium-grained phase 

 (quartz about 60 per cent and feldspar 40 per cent), and the grains 



1 B. N. Peach, J. Home, and others, "The Geologic Structure of the Northwest 

 Highlands of Scotland," Mem. Geol. Surv. Great Britain, 1907. 



