South-western Coal District of England. 299 



pearing along' the boundaries of the several denuded coal-tracts. Between 

 the central coal-tract of Pensford and the southern coal-tract of Nettlebridge 

 they appear in every valley emerging from beneath elevated platforms of lias 

 and oolite, and are here repeatedly pierced by shafts which descend to the 

 coal. The sections afforded under these circumstances are of the highest 

 geological importance, since they clearly display the relation between the 

 newer red sandstone and the coal-measures, and establish with the utmost 

 precision the distinction between the newer red sandstone and the old, which 

 from their simitar colour and ingredients are so very liable to be confounded. 

 The newer red sandstone, exhibiting throughout its whole course an identity 

 of character and composition, is absolutely continuous from the points in this 

 district, where it rests unconformably on the coal-measures, to the plains of 

 Salop, where its relations to the coal-measures have appeared obscure to the 

 most acute geologists. 



The red sandstone and red marl occur intermixed with the conglomerate, 

 along the entire bed of the Severn, from Westbury cliff on the north-east to 

 the mouth of the Usk on the south-west, with the exception of the narrow 

 interval of old red sandstone and transition limestone near Pyrton Passage, 

 and of two or three projecting crags of mountain limestone previously no- 

 ticed. To the south of the Forest of Dean, they form the base of the exten- 

 sive marshy tract, called Caldecot Level, which lies to the south of the high 

 range of Pencamawr, between the mouths of the Wye and the Usk. Here 

 the red marl is seen beneath the lias, in the small hill of Goldcliff, as it is 

 about 3 miles to the north of Goldcliff, on the further side of a marsh, in a 

 low range of hills, about 3 miles long, running through the parish of Llan- 

 wern. The red marl at the northern extremity of this range abuts against 

 the old red sandstone, which forms part of the southern base of Pencamawr. 

 Still further to the south, the red marl constitutes the flats between the Usk 

 and Taaf. The occurrence of the newer red sandstone formation in the 

 southern part of Glamorganshire, has been noticed in the introductory 

 chapter. 



The red marl and sandstone sweep along the banks of the Severn, to the 

 east of the border of the Forest of Dean, and to the east of the ridge of 

 transition rocks which connects May-hill with the Marcle hills. They fill the 

 trough, marked by the Ledbury canal, which divides the Marcle hills from 

 the southern extremity of the Malverns, and occupy the whole valley between 

 the Malverns and the Severn, except in those few spots which are covered 

 by superstrata of lias. 



