part 1] THE GEOLOGY OF THE OLD RADNOR DISTRICT. 2-"> 



eastern boundary of this limestone outlier may still be seen where 

 it is faulted against the Pre-Cambrian conglomerates, at the 



eastern margin of the old workings, about 200 yards from the 

 Harp Inn ; and fragments of the basement Woolhope Conglo- 

 merate have been found here turned up against the fault. 



With regard to the southern and western boundaries of the 

 inlier, there is no direct evidence in proof of their faulted character. 

 There is, however, ample evidence of faulting among the rocks of 

 the inlier near its western and north-western margins, as shown in 

 the accompanying ma]) (PL VII). Two main faults have here 

 been traced running in a general east- north -easterly direction. 

 The southernmost of these faults, which skirts the western edge 

 of Yat Wood, trends gradually more and more towards the south 

 as it approaches the western margin of the inlier, as though 

 influenced by a line of movement along that margin ; while a 

 north-and-south fault runs southwards from the boundary at the 

 corner of Stone's Coppice. 



In addition to the two main north-north-east and south-south- 

 west faults described above, several others, having a generally 

 similar trend, traverse the southern portion of the district. These 

 are well seen on the south side of the railway, where they have 

 been exposed by quarrying operations. In all cases the down- 

 throw is to the west, so that the Pre-Cambrian rocks, underlying 

 the limestone, are brought up on the east, and the higher beds 

 of the limestone are absent on this side, owing to denudation 

 (see figs. .1 & 2, p. 24). These fault-planes, therefore, mark the 

 limit to which the limestone can be profitably worked, and conse- 

 quently they form the eastern boundary of several of the quarries. 

 This is the case in the new Dolyhir Quarry (D), in the smaller 

 old quarry (C) to the east of it (PL III), and in Yat-Hill Quarry 

 (F) on the north side of the railway, and also, though to a less 

 extent, in Strinds Quarry (A). In all these cases the downthrow 

 is to the west. 



In addition to these normal faults, a number of other lines of 

 movement traverse the district. These are in general too numerous 

 and too complicated for description ; but, out of the tangle of 

 shear-planes and thrusts, two main directions of movement may be 

 discerned. One of these has a general north-and-south trend, and 

 may be connected with the faults just described. Along this line 

 occur a series of sub-parallel curved thrust-planes hading steeply' 

 westwards and having their concave faces directed eastwards. A 

 group of these are well seen along the northern and western margins 

 of Strinds Quarry. Their general effect has been to pile up slices 

 of the Pre-Cambrian rocks among the limestone, and also to bring 

 fragments of the lower 'layers of the limestone among the upper 

 beds so as to form a confused mass of crush-breccia. The pheno- 

 menon is rendered more conspicuous by the presence here of 

 a quartz-conglomerate in the Pre-Cambrian rocks, pebbles from 

 this conglomerate having been teased out along the thrust-planes. 



The second set of planes of movement runs nearly at right 



