GKOTJP IK THE MALYEBN HILLS. 537 



the succession in the two areas. In Shropshire undoubted Malyern 

 gneiss and granitoid rock * lies at the base of the Wrekin volcanic 

 series (of which the Lilleshall beds are a part), and is separated 

 from it by a great interval, during which the lower group was 

 metamorphosed, uplifted, and denuded, the worn fragments forraing 

 conglomerates in the younger series. At Malvern the newer group 

 lies against one flank of the gneissic axis, and is clearly separated 

 from it by a great interval of time, since it rests upon the edges of 

 the older beds. In Shropshire the felsitic group is immediately 

 overlain by a band of quartzitef which is absent at the Malverns. 

 Then follow alike in both districts the Holly bush Sandstone and the 

 Dictyonema-shales. During the Ordovician epoch (Lower Silurian 

 of the Survey) both areas were above water and deposits are 

 wanting. In the May-Hill Sandstone period, depression of both 

 the Malvern and Wrekin chains set in : first, shore-deposits (May- 

 Hill conglomerates) fringed the margin of the sinking islands ; and 

 finally marine sediments (Wenlock and Ludlow) entirely covered in 

 the submerged land. In Devonian times reemergence took place, 

 the rising wedges of Precambrian rock in both districts pushed up and 

 sometimes thrust over the Silurian beds, and the old ridges once more 

 became dry land. Submergence, more or less complete, was again 

 resumed in the later part of the Carboniferous epoch, evidenced in 

 both areas by the comparative absence of the Carboniferous Limestone 

 and by the attenuation of the Coal-measures towards the higher 

 summits of the Precambrian land. 



In both districts the chief dislocations were also contempora- 

 neous. I first call attention to the post-Triassic (probably post- 

 Cretaceous) dislocations which threw down newer Palseozoic and 

 Mesozoic strata against the Malvern axis on the east, and against 

 the Wrekin axis on the north-west, while, alike in both districts, 

 the same Cambrian and Silurian deposits were left flanking the 

 respective ridges on the opposite side. These post-Triassic faults 

 acted along preexisting lines of dislocation, some of which were 

 formed in Precambrian times, and the movements were simultane- 

 ously renewed at intervals in both Shropshire and the Malverns. 

 In both areas the volcanic group is faulted against the gneiss, the 

 Longmynd J rocks against the Precambrian, the Hollybush Sand- 

 stone against the Precambrian, the Dictyonema-shales against the 

 Hollybush Sandstone, and the Silurian against the Precambrian. 



Thus the succession of deposits, the history of the elevations and 

 depressions, the contemporaneity of the main dislocations, and the 

 close lithological resemblances between the respective groups, together 

 with the identity of the relations between the older groups and the 

 flanking formations whose contemporaneity is proved by fossils, 

 furnish us with reasonable evidence of the correlation of the Pre- 

 cambrian rocks of Shropshire with those of Malvern, and in parti- 



* Quart. Journ. Geol. Soc. vol. xxxv. p. 652. 

 t Quart. Journ. Geol. Soc. vol. xxxiv. p. 754. 



I Longmynd sandstones and grits are seen south of the Malvern axis at 

 Huntley, east of May Hill. 



