356 LLANDEILO FLAGS (CHARACTERS AND DISLOCATIONS). 



are exposed in a thickness of nearly half a mile in highly inclined strata, (70° to 80°) 

 on the banks of the brook, extending eastward to the waterfall. Many casts of tri- 

 lobites occur in these beds, and also bands of stone sufficiently calcareous to be burnt 

 for lime. 



The prevailing strike is here 30° south of west, whilst at Pentref and Tyr-wyn-fach, only one 

 mile nearer to Llandeilo, beds charged with the same trilobites, are wrenched from the prevailing 

 strike and range, in vertical positions to the west, and even 10° north of west. If we trace the 

 beds to the westward across the valley of the Towy, we again meet with them greatly developed at 

 Llandeilo, but in the very first ledge on the eastern side of the town they recover their south- 

 westerly strike. This direction is however maintained a very short distance, for in the space occu- 

 pied by even the high road, the same beds are broken off and trend on one side to the west, dipping 

 80° to the north, or nearly at right angles to the beds observed upon the other. In most of the 

 quarries in and about Llandeilo, the number of dislocations to which the flags have been subjected 

 is truly surprising, the strata being for the most part in vertical or highly inclined positions. (See 

 Map, and PI. 34. figs. 7 & 80 In one of the chief quarries of Dynevor Park, the beds are thrown so 

 completely out of the prevailing direction, as to strike E.S.E. and W.N.W., dipping 70° N.N.E., 

 whilst in Bird's Hill they bend round from 15° W. of N. to true N.W., S.E., though in the Llan- 

 gathen and Grongar Hills, the old strike of N.E., S.W. is resumed. In fact the beauty of Dynevor 

 Park depends upon these dislocations, by which the surface has been diversified and thrown into 

 separate knolls now wooded to their summits. (See wood-cut at the head of this chapter, Dynevor 

 Park in the foreground, Golden Grove in the distance.) 



The prevailing flagstone, in beds from two to four inches thick, is dark-grey or 

 indigo colour when extracted, but it weathers to a light ashen hue, the surface being 

 in some parts covered with a profusion of casts of the Asaphus Buchii, other organic 

 remains being rare. The calcareous flags are very generally traversed by veins of white 

 calcareous spar, from one-tenth to half an inch wide, which usually divide the beds into 

 rhomboids. These flags occasionally, as at Griig, about three quarters of a mile north- 

 west of Llandeilo, pass down into thicker masses of sub-crystalline, dark, impure lime- 

 stone, having an east and west strike, and a dip of 45° to the north. They contain 

 encrinites, a few casts of shells, Asaphus Buchii and A. tyrannus. The beds have a 

 corrugated surface, due to the mass being composed of small irregular concretions, and 

 this structure is partly occasioned by the unequal dissemination of sand and even of 

 small pebbles in the calcareous matrix. The true flag-like structure of the Llandeilo 

 flags is not discernible in any of these beds. The Grug quarries exhibit the oldest 

 calcareous beds of this formation, as they lie to the west and north-west of the flags, 

 and the same nodular limestones occur in Llangathen and Grongar Hills in similar 

 positions, rising from beneath the younger strata and graduating on their western flanks 

 into the rotten slates and greywacke grits of the inferior or Cambrian System, in which 

 (in this district) all traces of fossils are lost. 



To the south-west and west of Llandeilo the flagstones are found on both banks of the Towy in 

 distorted masses, none of which have a continuous strike for more than a few hundred paces. Below 



