P. Macnair — Altered Clastic Rocks of Scottish Highlands. 211 



IV. — The Altered Clastic Kocks of the Southern Highlands, 

 their Structure and Succession. 



By Peter Macnair. 

 {Continued from the April Number, page 174.) 



VIII. The Upper Arenaceous Zone. 



I HAVE not been able to trace the exact relationships of this zone, 

 with its bands of limestone, to those already given, as underlying it. 

 Certain grits and quart zi tea occurring on the top of the Ben Lawers 

 ridge may possibly belong to it, and it is certain that many of the 

 quartzites and grits of Glenlyon, Blair Athole, and Ben Y Ghloe 

 belong to a horizon higher than the upper argillaceous series just 

 described. Leaving the matter thus in the meantime, until further 

 research shall explain their true relationship, it, is certain that an 

 arenaceous band of grits and quartzites succeeds the sericite and 

 graphite schists of the upper argillaceous zone, thus completing the 

 whole cycle of deposits, though no evidence has yet been forthcoming 

 to show what or where the top of this series may be. 



Fig. 1. — Section across Ben Lawers to Crieff. 



a. Upper Arenaceous Zone. d. Loch Tay Limestone Zone. 



b. Upper Argillaceous Zone. e. Lower Areuaceous Zone, 

 b'. Baud of Graphite Schist. f. Lower Argillaceous Zone. 



c. Middle Arenaceous Zone. 



IX. Section across Ben Lawers to Crieff. 



Passing now to a consideration of these sections seen in Highland 

 Perthshire, from which we have principally been enabled to deter- 

 mine the general succession and chai'acter of the rocks forming the 

 Southern Highlands, the first section we propose to describe is that 

 from the top of Ben Lawers, across Loch Tay, through Meal Na 

 Creig, and down Glen Turret, as given above. This section shows 

 in descending order the whole of the zones described. On the 

 north-west side of Ben Lawers, and beside the footpath which leads 

 over from Loch Tay to Glenlyon, a quarry has been opened in the 

 graphitic schist beds that form the uppermost member of our upper 

 argillaceous zone. The graphitic schist is here highly carbonaceous 

 and finely foliated, having evidently undergone an extreme amount 

 of alteration, and lying at high angles, with a dip towards the 

 north-west. This bed is shown in the section at the top of the 



