CAMBRIAN ROCKS, CAERMARTHENSHIRE. 



359 



the Taaf, the strata are found to be tilted both to the north-east and to the south-west, 

 in which direction the black flags pass under Caracloc grits and sandstones, which in their 

 turn are overlaid by Upper Silurian rocks, and the Old Red Sandstone of Cynic. (See 

 PL 34. f. 10.) The line of fault by which the Llandeilo flags are affected, is parallel to 

 the river Taaf, and on its left bank. This is the last great flexure and snap to which 

 the formation has been subjected before entering Pembrokeshire; for although the 

 whole of the Silurian System has undergone similarly violent convulsions, (see Map), 

 yet as the amount of each dislocation can be marked with the greatest precision by the 

 changed direction of the beds of limestone, attention has been particularly directed to 

 them. 



The preceding notices of the dislocations in Caermarthenshire have been fuller than 

 usual, because in this country, the Silurian System, after its long course from north- 

 east to south-west, is met by a succession of powerful cross and compound fractures, 

 which towards Pembrokeshire become so frequent, as to give it for some distance an 

 east and west direction, although, as will be shown hereafter, the south-westerly 

 strike is resumed before the final disappearance of the system in the coast cliffs of that 

 county. 



CAMBRIAN SYSTEM. 

 ( Caermarthenshire^) 



a. Passage from Lower Siku-ian to Cambrian. b. Dull schists, with imperfect slaty cleavage. 



c d. Stratification marked by undulating quartzose beds ; the mass traversed by lines of slaty cleavage. 



From the hills near Llanwrtyd, whence the view forming the vignette to the last 

 chapter was taken, the rocks of this system range to the south-west through moun- 

 tainous and sterile tracts, their south-eastern frontier passing near Llandovery to Llan- 

 gadock » and trending afterwards by the west of Llandeilo to Caermarthen, they are 

 deflected to the west, in common with the Silurian formations. If these rocks have a 

 tolerably well-defined boundary in that part of their eastern frontier where they have been 

 described as passing into the younger deposits, (Noeth-grug, Llandeilo, and Grongar,) 

 they have no lines of demarcation or division within themselves, and extend over two- 

 thirds of Caermarthenshire, without any material changes in their mineral structure. 

 A detailed examination of this vast area is not within the objects of my work. 



Between Llanwrtyd and Llandovery are dark rotten schists, having a dull surface, the whole oc- 



2 y 2 



