Yol. 55.] STKITCTUEE OF THE SOTJTHERX ITALVERl^fS. 155 



would suggest that originally the schists and sandstone and the 

 fault separating them dipped eastward, but that movements, a 

 little later than, those which produced this thrust, resulted in the 

 formation of a small overfold towards the east. 



The structure of Midsummer Hill and of the north-western 

 corner of Raggedstone Hill presents points of diiference from that 

 seen in the greater part of the last-named hill. There is an 

 axial thrust-plane, the gneissic and schistose beds above which, 

 at the southern end of HoUybush Hill, dip eastward. Debris of 

 fossiliferous May Hill Sandstone found in the trench at the extreme 

 northern end of the camp, at a height of about 750 feet, may 

 possibly indicate another thrust-plane : but the foliation of the 

 schists and gneisses in general does not appear to show any relation 

 to the axial thrust-plane, nor to the boundaries of the gneissic 

 complex. The hill, indeed, shows in a marked way the structure 

 termed plagioclinal by Dr. Callaway. The dip of the Cambrian 

 beds, moreover, is prevailingly towards the west, no signs of 

 inversion being seen, except in the case of the conglomerate near 

 the northern end of Midsummer Hill (M 366). 



The structure may be explained in much the same way as that 

 of the greater part of Raggedstone Hill, if we suppose the move- 

 -ment not to have been generally great enough on the one hand to 

 produce overfolding on the western side, or, on the other, to induce 

 new planes of foliation on a large scale (see fig. 19). Secondary 

 foliation appears, however, to have taken place at the southern 

 end of Hollybush Hill above the axial thrust-plane. 



The plagioclinal structure seen in Midsummer Hill and in many 

 other parts of the Malvern range is perhaps best explained by the 

 hypotheses of Dr. Callaway,^ who suggests that the Cambrian 

 beds rest unconformably upon the Archaean. The latter series had 

 in pre-Cambrian times undergone an extensive process of folding 

 before being denuded, the axes of the folds crossing the direction 

 of the range obliquely. 



Little need be said about the structure of Chase End Hill. If 

 the explanation given on p. 149 be true, this hill constitutes a case 

 of extensive overthrust, the overridden shales being inverted by 

 the movement, and a new foliation having been probably developed 

 in the Archaean rocks. That such extensive overthrust has occurred 

 in parts of the Malvern range the evidence given on p. 150 is 

 sufficient to show : there , is proof of intense folding, accompanied 

 by the formation of thrust-planes. Fig. 20 (p. 156) is an attempt to 

 explain the structure of the western part of the range at the point 

 at which the section in fig. 17 (p. 150) is drawn. 



To summarize, I would suggest that the Southern Malverns are 

 a portion of an intensely folded and faulted complex of Archaean, 

 Cambrian, and Silurian rocks, showing the characteristic features 

 of a folded mountain-range, with its overfolds and thrust-planes. 



1 Geol. Mag. 1879, pp. 219-221. 



