18 The Geology of Lochrutton. 



Ice Age. 



The Pliocene Age, Avith its deep river valleys, quiet 

 sluggish streams, and genial climate, gradually gave place 

 to a new order of things, which was of the utmost import- 

 ance to the formation of the Loch. A period of extreme 

 cold (Pleistocene Age) set in, until Arctic conditions ulti- 

 mately prevailed. Large snowfields were formed in the 

 higher regions, and these gave rise to a system of ice rivers 

 moving slowly down to the plains below. The elevated 

 tract around the Merrick and the Kells acted as a large 

 gathering area for the accumulations of snow, and from 

 that centre the glaciers moved to lower levels. During the 

 period of extreme glaciation, when the snowfall was at its 

 maximum, the ice sheet travelled over the Lochrutton area 

 from west to east. The rocks are scratched and grooved 

 in the direction of the glacial flow. These striated rock- 

 surfaces are found on the hill to the east of Riggfoot, at 

 Barlae Hill further north, and at Beltonhill in the Bogrie 

 valley. Towards the close of the Ice Age, when the glaciers 

 were confined chiefly to the valleys, the direction of their 

 flow conformed generally to the valley turnings. 



Glaciation. " 



The Loch problem has been influenced by its glaciation 

 in two distinct ways : — 



1. The eroding character of the Ice flow as it removed 

 all the decayed rock rubbish of the preceding ages, leaving 

 bare a finely polished rock surface. 



2. The accumulation of this rock debris in the form of 

 moraines, either underneath the glacier or along the decay- 

 ing front of the retreating ice. 



The ice erosion would naturally be more powerful in 

 the upper Merkland valley and the lower Bogrie basin, on 

 account of their direction being the same as that of the ice 

 movement — -eastward. Large quantities of moraine heaps 

 have been left in this lower basin, and so obscure the shape of 

 the old hollow, but the Merkland valley has been severely 

 glaciated, especially at its upper end. Between Loaninghead 



