Vol. 60.] IGNEOUS ROCKS OF 1'OXTESFORD HILL. 453 



to the north thin Coal-Measures, consisting largely of blue brick- 

 clays, wrap round the hill ; while on the eastern side, between the 

 hill and Habberley Brook, no bedded rocks are visible, everything 

 being buried up in a thick mantle of screes from the rocks of Pontes- 

 ford Hill. To the north-east around Earlsdale, the tumpy nature 

 of the ground, and the loose, fragmental, and varied character of the 

 rocks, point strongly to the morainic origin of much of this ground. 

 Immediately to the south-west of Pontesford Hill, a narrow wooded 

 ridge, nearly half a mile in length, extends as far south as the 

 village of Habberley, made up of the intrusive amygdaloidal 

 dolerite of Pontesford. and apparently faulted on both sides against 

 the Cambrian shales of the valley. 



The general trend of the hill is north and south, while the 

 average strike of its beds is north 30° E., south 30" W., with a high 

 dip towards the east-south-east. In his account of the hill already 

 referred to, Dr. Callaway states l that the strike of the beds in 

 Pontesford is east and west, and indicates it thus on the map which 

 accompanies his paper, further, he lays stress upon this east-and- 

 west (or south-east and north-west) strike of the ITriconian rocks of 

 Pontesford and elsewhere in Shropshire, as emphasizing a strong 

 discordance between them and the Longmyndian (' Cambrian ') 

 rocks, which strike roughly north and south. As regards Pontes- 

 ford Hill, the dominant strike, as above stated, is not east and 

 west, but nearly north-north-east and south-south-west : practically 

 parallel, indeed, to that of the purple grits and conglomerates of 

 the Longmynd on the eastern side of Habberley Brook. 



Running from north to south through the northern and central 

 part of the hill, there appears to be a fault with probably a smaller 

 branch-fault immediately to the west of it. Although at no point is 

 it possible to prove the existence of either of these faults, the surface- 

 features of the ground, together with the sudden displacement of 

 the edge of the dolerite (see map, PL XXXVIII), seem to demand 

 the existence of the larger of the two : while the sudden change of 

 direction of the banded structure along a definite line in the Xorthern 

 Rhyolite appears to be adequately accounted for by the smaller fault. 

 A small west-north-westerly cross-fault brings down the basic 

 group, at the extreme southern end of the hill, against the andesitic 

 and rhyolitic tuffs and lavas. 



In carefully following single beds in the rhyolite or andesite- 

 group along the strike, say from south-west to north-east, numerous 

 small breaks are encountered, where the bed slightlv but suddenlv 

 changes its strike, generally adopting a more easterly course. 

 Indeed, the rocks as a whole seem to have settled down into a posi- 

 tion of compromise between a northerly and southerly, and north- 

 easterly and south-westerly trend, and the result has been that, 

 while the general or average strike is nearly north-north-east 

 and south-south-west, the beds, owing to the slight jumps referred to, 

 may have a local strike nearly due north and south, or north-east and 



1 Quart. Journ. Geol. Soc. vol. xxxviii (1882) p. 123 & ibid. vol. xlvii (1891) 

 pp. 119-22. 



Q. J. G. S. No. 240. 2 i 



