W. W. Watts — Ancient Rocks of Charmcood Forest. 485 



III. — Notes on the Ancient Rocks of Charnwood Forest. 1 



By W. W. Watts, M.A., F.G.S. 



(Communicated by permission of the Director-General of the Geological Survey.) 



DURING the re-survey of sheet 155 of the Geological Survey map 

 by Mr. C. Fox Strangways, the writer was instructed to study 

 the ancient rocks where they crop up inside the boundaries of the 

 Trias. The ancient rocks of Charnwood Forest appear in isolated 

 spots, sometimes of considerable size, through the Trias of the 

 Midland Plain. The oldest rock in contact with them is the 

 Carboniferous Limestone of Grace Dieu, which is dolomitized. 

 Evidence as to their exact age cannot, therefore, be obtained from 

 superposition. 



They clearly existed as islands in the Triassic and Carboniferous 

 sea, and most probably stood up as mountains on the land in Old 

 Red Sandstone times. The Trias runs up into the hollows and 

 valleys of the old rocks, and from the small amount of debris which 

 extends beyond the margins of the masses it is obvious that the 

 smaller of these, at any rate, have been uncovered at a time 

 geologically very recent. Their features are not those of the 

 present day, but date back partly to the subaerial denudation of 

 Old Red Sandstone and probably earlier times, and partly to the 

 aqueous denudation of Carboniferous and Triassic times. This is 

 the reason for the peculiar character of the surface features 

 presented by the old rock ; escarpments are practically absent, 

 hard beds are cut off abruptly, the rocks strike across the ridges, 

 and the landscape generally is not of the usual subaerial character. 

 Present-day denudation, by clearing out the Triassic debris, has 

 done little more than expose to-day a pre-Triassic landscape. 



The ancient rocks themselves may be classified as follows, in 

 descending order : — ■ 



Swithlaud and Groby slates ) 



Conglomerate and quartzite > The Brand Series. 



Purple and green beds ) 



The olive hornstones of Bradgate ^ 



Tbe Woodhouse beds 



Slate agglomerate of Eoecliffe y The Maplewell Series. 



Jlnrustones of Beacon Hill 



Felsitic agglomerate J 



Bocks of Blackbrook The Blackbrook Series. 



This general succession corresponds with that made out by Messrs. 

 Hill and Bonney, with whose observations the author is in 

 substantial agreement. 



These divisions sweep round the semi-dome which is exposed ; it 

 is elongated from north-west to south-east, and broken by several 

 longitudinal faults in the same direction. Probably there are some 

 cross faults as well. 



The succession is most easily made out in the eastern side of the 



1 An abstract was read before the British Association, Liverpool, Sept. 1896. 



