﻿384 ME. G. BAEEOW ON THE [^^g. 1908, 



22. The High-Leyel Platfoems of Bodmin Mook and their 

 Relatiox to the Deposits of Steeam-Tix and Wolfeam. By 

 Geoege Baeeow, E.G.S. (Communicated by permission of the 

 Director of H.M. Geological Survey. Eead March 4th, 1908.) 



[Plates XLV & XLYI.] 



In the south-west of Cornwall the ancient marine platform, of 

 Pliocene age, rises to a height of 430 feet above the sea, and its 

 upper limit is a steep slope, often a bluff. In the same area the 

 uplift of this platform has led to the deepening and cutting-back 

 of the larger valleys, giving rise to a steepening of slopes in the 

 lower part of the banks. This feature becomes less marked as 

 the valleys are ascended, and in the case of the Eiver Camel it 

 disappears altogether at a distance of 22 miles from the sea. 

 Above this point the river-banks and also the ground above them, 

 now much over 430 feet high, retain in the main the same angle of 

 slope as that which they had in Pliocene times, though of course 

 they have been lowered to some extent by denudation. 



The retention of the characters of the older scenery is naturally 

 most marked in the still higher grounds about the watershed of the 

 Eiver Camel, part of which includes Davidstow lloor. This moor 

 also forms the gathering-ground of the Inney (a tributary of the 

 Tamar) : and, if the watershed be crossed and the valley of this river 

 descended, the features just noted will be met with in reverse 

 order, as that area is approached within which the denudation of 

 post-Pliocene times has produced its most characteristic efiPects. 



The Upper Platform. 



Of the older topography thus partly destroyed by post-Pliocene 

 denudation, the most striking feature in the higher part of the 

 area is presented by two well-marked high-level platforms, one 

 at 750 feet above the sea, and the other may be called the 

 1000-foot platform, although it is really a little below this 

 altitude. The latter was first recognized on Davidstow Moor, 

 where, considering its antiquity, it is remarkably well preserved ; 

 but traces of it are to be seen on the surrounding high lands in 

 all directions. That it must once have covered a very large area 

 is evident, and it may possibly have its counterpart in Britanny. 



On entering the higher ground, formed by the granite, near 

 Davidstow Moor, it is at once obvious that all the higher Tors 

 once stood out as islands. This character is well shown in the 

 ground above Trebartha Hall, some miles away in the south-eastern 

 part of the area ; and, when a favourable point of view can be 

 selected, traces of the platform are to be seen over much of the 

 eastern half of the granite-area. 



