

thfc 



V 



\ 







Part of. 



um 





***»*••■ 



tor 



•r Ji 







In?, 











X 



>- 



\w 



$ 





ALTERED SILURIAN ROCKS. 



109 



62. — Altered coal measure shale from another bed in Upper 

 the same quarry as No. 60, about 10 feet thick, lying Galleby ' 

 between two masses of intrusive greenstone. Wall-case 45. 



63. 



No 



These greenstones are the cause of the alteration of 60 

 and 62, in which the ordinary soft shaly character has dis- 

 appeared and the beds have been much hardened by the 

 action of heat. In the quarry there are two masses of 

 greenstone, apparently interbedded like old lava beds ; but 

 the shales both above and below them being equally altered, 

 they are known to have been intruded between the beds. 

 This is the case with the greenstones generally of the War- 

 wickshire coalfield, which run in long lines between Ather- 

 stone and Mars ton Jabet, the longest being about six miles 

 in length. 



64. — Altered old red marl, Brockhill, 3 miles south- 

 west of Abberley. Map 55 N.E. Worcestershire. Pierced 

 by a greenstone dyke. 



Altered Silurian rocks of Wales and Shropshire. 



65. — Wexlock shale, altered. Upper Heblands, near 



Bishops Castle, Shropshire. This rock is very calcareous, 



and is pierced and much broken by a small dyke of green* 

 stone. 



66. — Shale, lingula flag s, with Lingulce, much hardened 



by heat, Mod II " " ~ " " ' m ~ * " 



ifod 



miles north 



Dolgelly, 



Merionethshire. Map 75 S.E. 



The shales of this hill are pierced by numerous small 



>/ 



Rhobell-fawr, & 



67. — Silurian shale or slate, altered and hardened^ 



Pass of 



From a thin 



band of altered slate in the felspathic trap of Snowdon. 

 Both have been pierced by greenstone^ which here, and near 



