CONTORTED STRATA IN THE YOREDALE ROCKS, NEAR ASHOVF.R. 55 



through it ; along the central line of the upper and now flat 

 surface, will be exposed the lowest rim of voussoirs, and on either 

 side the edges of the others, ranged in the order of their 

 super-imposition. A similar state of things obtains in the two 

 areas we are considering ; natural denudation has brought down 

 the larger anticline to almost the level of the surrounding country, 

 and has positively hollowed out the Ashover anticline into a valley. 

 In each, the lowest rock cut into — the Mountain limestone -is 

 exposed along the axis, and on either side are ranged, at first 

 Yoredale shales, then Millstone grits and Coal measures in 

 irregular bands roughly parallel to the axis. It is outside the 

 needs of our subject to discuss the origin of these curvatures ; it 

 is sufficient to observe that they are due to secular rather than 

 local causes, and are vastly older than the contortions we now 

 will consider. 



These Yoredale flexures are to be found in various valleys in 

 our country ; good sections may be seen on the banks of the 

 Ashop and other streams in its neighbourhood, and numerous 

 small ones above Ashover. The latter examples occur near the 

 bottom of the valley, between Kelstedge Dam and Whitefield Lane. 

 They exhibit a continually varying dip (frequently attaining to 40 

 deg.) that falls into two sets, one ranging from E.N.E. to N.E., 

 and the other more uniformly S.S.W. The rapidity with which 

 the dip passes from the one to the other, indicates wave-like 

 flexures having their axes N.W. and S.E., that is, in a direction 

 approximately coincident with the " run " of this part of the 

 valley. It is impossible to say what the width of these flexures 

 (of which there are doubtless many) may be, but I do not think 

 it can exceed 70 feet in those to which the sections belong. 



There are reasons which lead me to think that these Yoredale 

 contortions are not due to the same operation that resulted in the 

 general rock curvature of this f)art of England. If it were so, 

 the gritstone above and the limestone below must have partaken 

 of the same crumpling, for throughout the nortii Midlands these 

 three rocks are conformable one with another, and, in fact, pass 

 into each other by natural transitions. Unfortunately, where I 



