A. Strahan's Address to Section C, Geology. 457' 



of ridges of Charnwood Forest, while the intervening space is over- 

 spread by Trias, resting partly on Carboniferous and partly on 

 older strata. The structure of the Carboniferous and older strata 

 is dominated by vv^hat is known as the Charnian movement, which 

 includes disturbances of several ages ranging in a south-easterly 

 direction. That part of the movement which was post-Carboniferous 

 is identifiable b}^ the fact that Coal-nieasures are tilted on either 

 side of the ridges of old rocks. They once overspread both ridges, 

 but were removed by denudation as a consequence of upheaval 

 before the Trias was deposited. It has been found also in working 

 the coal, as I am informed by Mr. Strangways, that there are large 

 faults having the south-eastward or Charnian direction which shift 

 the Coal-measures, but do not break through tlie overlying Trias. 

 The evidence, therefore, of a great Charnian movement having taken 

 place during the period under consideration is conclusive. The 

 disturbance ranges as a whole in the direction of Northampton, 

 where, in fact, borings have reached the Charnwood rocks at no 

 great depth. 



The five great disturbances which I have briefly indicated tend 

 to converge northwards, but their exact connection with the Pennine 

 axis is not known. What may be only a part of that axis trends- 

 for Charnwood through a tract of Lower Carboniferous rocks exposed 

 at Melbourne, between the Yorkshire and Leicestershire Coalfields, 

 but the Triassic channel I have already mentioned intervenes, and 

 the structure of the rocks underlying the red marl is unknowUc 

 The channel itself appears to be of Triassic age, for not only is the 

 depth of marl in it suggestive of its having been a strait in 

 the Triassic waters, but its northern margin has been found by 

 Mr. Gibson to coincide with, and perhaps to have been determined 

 by, faults known to be mainly of pre-Triassic age. One of these, with 

 a downthrow of 400 yards to the south, runs from Trentham through 

 Longton, and south of Cheadle, while another ranges from near- 

 Nottingham to the north of Derby. 



We come now to the south-west of England, where we find 

 striking proofs of a still more energetic movement than any yet 

 mentioned having intervened between the Carboniferous and Triassic 

 periods. .The central part of the Armorican axis, as it has been 

 called, after the ancient name of Brittany, trends nearly east and 

 west, and keeps to the south of our South Coast ; but we have 

 opportunities in Devon and Cornwall of seeing .some of the 

 stupendous effects produced along its northern side. A belt of 

 country measuring some 130 miles in width has been completely 

 buckled up. Slaty cleavage was superimposed upon the intricate 

 folds into which the strata were being thrown, while after or 

 towards the close of these phenomena granite was extruded at 

 several points along the belt of disturbance, a little north, however, 

 of the line along which the oldest rocks were brought up to the 

 surface. In Devon the Culm-measures are fully involved in the 

 movement, but on the other hand the Permian strata, while con- 

 taining fragments of the cleaved and metamorphosed rocks, are 



