236 DISLOCATIONS. — RIVERS FLOWING THROUGH FRACTURES. 



Dislocations of the Silurian System and adjacent rocks in the district of Ludlow and 



Wenlock. 



Returning to the district in which the rocks of this system have been described and 

 where no trap rocks are visible, the strata of each formation trending from south-west to 

 north-east, succeed each other at low angles, generally inclined towards the south-east. 

 In the parallel of Wenlock Edge, the Ludlow rocks, the Wenlock limestone, and the 

 Caradoc sandstone, present a regularity of stratification and succession rarely, indeed, 

 seen in the secondary or tertiary deposits. Even there, however, we have abun- 

 dant proofs of great dislocation, principally where these rocks are traversed by the 

 rivers Severn, Onny, Teme, and Lugg. Such fractures are usually marked by much 

 local divarication in the strike and inclination of the beds. For example, on approach- 

 ing the Iron Bridge or Coalbrook Dale from the south-west, the Wenlock limestone 

 after various undulations, is found advancing from the Gleedon Hills on the right bank 

 of the river in a remarkable sharp ridge, called Benthall Edge, and trending E.N.E., 

 W.S.W. At the north-eastern termination of that edge the beds dip 18° to the south- 

 east, being there brought into unconformable contact with the coal measures by the 

 great fault of Broseley. (See Map.) On the left bank of the Severn the same beds 

 of limestone are thrown up into another ridge, called Lincoln Hill, which though not 

 so lofty as that of Benthall Edge, is sharper and narrower, the strata striking nearly 

 N.E., S.W., and being inclined at angles of 50° and 60°. Not only does this great dis- 

 crepancy in the angle of inclination mark the existence of a transverse fault, indicated 

 by the deep fissure through which the Severn escapes, but the fault is further proved by 

 the divergence in the direction of the strata on the opposite banks, those upon the left 

 bank having a strike of 15° or 20° different from that of the beds on the right bank. 

 By this derangement, the Wenlock limestone of Lincoln Hill is accidentally brought 

 into conformable apposition to the coal measures ; thus offering a marked exception to 

 the relations usually existing between rocks so widely separated in the epochs of their 

 formation; indeed the same beds of the coal-field wrapping round the escarpment 

 of the Silurian rocks on the sides of Coalbrook Dale, are there placed in nearly 

 horizontal positions upon the edges of the highly inclined strata of the Wenlock shale, 

 distant only two miles from Lincoln Hill. The greater number of these dislocations 

 have taken place subsequent to the deposition of the carboniferous rocks, since the 

 latter have been powerfully affected by many great faults in common with the Silurian 

 rocks on which they repose. 



Without noticing the minor breaks and faults in the upper Silurian rocks, let us pass to the south- 

 western extremity of Wenlock Edge near the gorge of the river Onny, where the strata are again 

 much broken up. At Dinchope, the Aymestry limestone and associated Ludlow rocks are thrown 

 over, dipping to the south-west and north-east, in a short, low ridge, at right angles to the general 

 strike of the strata. The same beds are upcast to a much higher level, forming the bold cliffs of 



