26 PKOE. E. J. OAItWOOD AND MISS E. GOODYEAR [vol. lxxiv, 



angles to these thrusts, and appears to be of the nature of 

 ' tear '-faults, along which blocks of rock have separated and moved 

 forward along the thrust-planes independently. The view that 

 these represent 'tear '-faults is strengthened by the character of 

 the slickensiding seen on the faces of the faults, the stria? running 

 almost horizontally, and also by the fact that the thrust-planes 

 do not cross these faces, but appear to end against them. A good 

 example of one of these ' tear' -faults may be seen in the south- 

 western corner of Strinds Quarry 1 (PI. Y, tig. 2). 



One other direction of movement occurs in the south of the 

 district, namely, along the floor of the valley through which the 

 railway runs past Dolyhir Station. This direction is roughly 

 west-north-west and east-south-east, or exactly at rig-lit angles to 

 the major axis of the inlier. Only one other fault, parallel to this 

 direction, has been observed in the district: namely, that which 

 lets down the limestone south of Hillhouse Farm, and it is possible 

 that this latter fault was once continuous with the railway valley- 

 fault, and has been shifted north-eastwards by the dislocation which 

 follows the Old Kadnor road, already described. 



This fault along the Dolyhir Valley is not actually seen, as the 

 valley-floor is covered by tip-heaps and quarry-debris. There are,, 

 however, several facts which indicate its existence. In the first 

 place, the line of the valley coincides with the direction of an 

 anticlinal axis in the limestone, as shown by the dip of the base- 

 ment conglomerate on each side of the vallev. In the second 

 place, the base of the limestone on the north side of the railway, 

 exposed in the old quarry at the southern end of Yat Wood 

 (Quarry G), is at a distinctly higher level than the outcrop on the 

 south side, when it reappears in the old working in Quarry B. 

 In the third place, the Archaean rocks which crop out on the north 

 side, do not agree with those exposed on the south of the railway r 

 thus the pebble-conglomerate, which forms so conspicuous a feature 

 round the northern edge of Strinds Quarry, is totally unrepresented 

 north of the railway, where we find instead massive green grey- 

 wackes. But the most conclusive evidence for this fault lies in the 

 relative positions of the base of the limestone in Yat-Hill Quarry 

 and in the old quarry below, now occupied by the railway-siding, 

 there being a difference in height between them of some 50 feet. 

 This is evident from the occurrence of portions of the Pre- Cambrian 

 grits exposed in the floor of Yat Quarry, showing that the lime- 

 stone has here been worked down to the base; while, in the railway- 

 siding quarry below, the workings have only reached to the level of 

 the lower bryozoan reef some 20 feet above the base— this would 

 indicate the presence of a south-east and north-west fault running 

 past the entrance to Yat-Hill Quarry, somewhere in the neigh- 

 bourhood of the limekiln, with a downthrow of some 60 feet to 

 the south. 



It is doubtless the line of weakness produced by this fault that 



1 These faults are similar to those described by Suess as ' Blatter.' 



