172 



PEOF. T. T. GROOM OK THE GEOLOGICAL [Feb. I9OO, 



Limestone has by no means the simple character ascribed to it by 

 that author, and its axis would appear generally to have a steep 

 slope to the east. Whatever be the dispos ition of the limestone, it 

 is necessary to assume the existence of one or more faults between 

 the outcrops of this rock and those of the Aymestry Limestone, in 

 order to explain the non-appearance of a third line of outcrop of 

 the latter. Phillips attempted to explain the structure of the 

 district by the assumption of a fault traversing the middle of the 

 shale-series, and passing between the two limestone-masses at the 

 southern end of Penny Hill l ; but the great apparent thickness of the 

 shales in places, as, for instance, immediately south of Woodbury 

 Hill, tells against this simple explanation. In all probability the 

 district is traversed by several faults, which have resulted in 

 bringing shales of different horizons together. The occurrence of 

 overfolds, and the relative positions of the Aymestry and Wenlock 

 Limestones, seem to indicate clearly that at least one of these faults 



is a thrust-plane, the up- 

 Fig. 25. — Section seen at the southern throw of the fault being on 

 end of Wallsgrove Quarry. the eastern side. This view 



E w. is confirmed by the geological 



p p structure of the northern 



- part of Wallsgrove Hill, now 

 to be described. Some of 

 the faults have been tenta- 

 tively represented in figs. 16- 

 24 (pp. 166-169), but I have 

 not ventured to insert them 

 in themap. 



The structure of the 

 northern end of Wallsgrove 

 Hill is very peculiar. Both 

 the eastern and western bands 

 of Aymestry Limestone curve 

 round north-eastward, and 

 appear to terminate ; the 

 former ends abruptly in a 

 small rounded tump ; the 

 latter seems to tail out. In Wallsgrove Quarry the remarkable 

 relations described by Phillips 2 are still to be seen. 



The Aymestry Limestone, dipping 70° or 80° north-westward, is 

 faulted against a reversed series of beds, including not only the Upper 

 Ludlow Shales and Downton Sandstone (into which the former 

 passes), but also a small thickness, perhaps 4 or 5 feet, of purple 

 Ledbury Shale. Phillips (loc. cit.) attempted to explain these rela- 

 tions by assuming the existence of a second overfold faulted down 

 on the east. The facts may be more simply explained, however, 



1 Mem. Geol. Surv. vol. ii (1848) pt. i, p. 152 & pi. ii. 



2 Ibid. pp. 153-154 : see also Proc. Geol. Assoc, vol. xv (1898) fig. 10, 

 p. 356. 



SL = 



DS = Downton Sandstone. 

 AL = Aymestry Limestone. 

 FF= Faults. 



