C. CALLAWAY ON THE QUARTZITES OP SHROPSHIRE. 761 



Rushton ; but, as the igneous rock of the entire district is mainly 

 bedded, it seems impossible that bosses of it could be pushed up 

 through overlying beds without producing faults. The relations of 

 the quartzite to the older igneous series appear to be similar to the 

 above in both the Caer-Caradoc and the Cardington localities, with 

 the possible exception of one spot at the north-east end of Caer 

 Caradoc, where the nucleus of the range consists of syenite. This 

 syenite may be disruptive, but at any rate it does not affect the 

 general strike of the overlying quartzite. 



As the quartzites are limited by faults on the underside, so I 

 conclude that in most cases, probably in all, they are separated by 

 faults from the strata which overlie. In the Wrekin area, the rock 

 in immediate contact with the quartzite on the opposite side from 

 the underlying volcanic strata is the Hollybush Sandstone. Tig. 1 

 shows this relation. I have given reasons in a previous paper * for 

 believing that the Hollybush is separated from the quartzite by a 

 fault in this locality, and shall refer to the subject further on. In 

 the outlying Charlton-Hill district, the only spot in which I have 

 detected the Hollybush is the one to which I have already referred, 

 where the dip is towards the quartzite. Here also there must be a 

 fault. At Caer Caradoc, as shown in fig. 4, the Hollybush appears to 

 succeed the quartzite conformably. At the Sharp Stones, the upper 

 boundary of the quartz-rock is a fault separating it from the 

 Caradoc. The quartzites would thus appear to be bounded both 

 above and below by faults. These dislocations will appear less 

 difficult of belief when we bear in mind the disturbing influence of 

 the Church- Stretton and associated faults. When we find Wenlock 

 rocks wedged in between Lower Cambrian and Precambrian in one 

 spot, and between faulted masses of Caradoc in another, and when, 

 as in the Harnage district, we see the Hoar-Edge Grits lying at a 

 right angle upon the upturned edges of younger strata, we shall be 

 surprised at no hypothesis, however eccentric, which rests upon a 

 reasonable basis of facts. 



3. The Age of the Quartzites. 



The quartzite is certainly older than the Hollybush Sandstone, 

 for, in every observed case, the sandstone rests upon the quartz- 

 rock, or is at least outside of it with regard to the axis of elevation. 

 This is well seen in the Wrekin subarea, and still more distinctly 

 on the south-east flank of Caer Caradoc (fig. 4). 



But the age of the Hollybush Sandstone must first be determined. 

 It is commonly placed upon the horizon of the Ffestiniog group, on 

 the ground that it underlies the Black Olenus Shales of Malvern, 

 which are with great probability correlated with the Dolgelly series. 

 But the relations of the Hollybush and Black Shales are very 

 obscure, and it has not been shown that they succeed each other 

 conformably. Mr. Belt considers the Hollybush to be a shore 

 deposit of the Menevian sea ; but I am willing to accept the former 

 * Quart, Journ. Geol. Soc. vol. xxxiii. p. 662. 



