SILURIAN STRATA REVERSED BY TRAPPEAN ERUPTIONS. 



425 



those hills, the summits of which, as in the Abberley and Woodbury Hills, consist ex- 

 clusively of rocks referrible to an igneous origin. If, however, there could be any doubt 

 respecting the agency which produced these remarkable effects, it is instantly dispelled 

 by an examination of the western slopes of the Malverns, where the inverted or over- 

 turned strata are admirably laid open as above represented, close to the overshadowing 

 and bulging mass of the syenitic chain. The submarine volcanic action which raised 

 the Malvern ridge, may easily be supposed to have forced up the contiguous strata ; 

 first to high degrees of inclination, next to verticality, and finally to have bent them 

 backwards upon their axis, into their present positions. (PI. 36, f. 7.) The eruption 

 of the trappean rocks of Abberley and Woodbury has, therefore, doubtless produced a 

 more intense movement of reversal of the strata in those hills. Unlike the beds on the 

 western flanks of the Malverns, which, in proportion as they recede from the edge of 

 the eruptive chain, regain their regularity and gradually resume their regular positions, 

 the older formations dipping away beneath the younger ; the same deposits in the Ab- 

 berley Hills present the ends of their highly inverted strata to a valley composed of the 

 Old Red Sandstone, the younger rock being surmounted by the older strata of the 

 Silurian System! (PL 36, figs. 1, 2 & 3.) 



Such phenomena are of high interest, as pointing out in our own country what has 

 been indicated by geologists who have laboured in Alpine regions, where inversions of 

 the strata are frequent. Professor Sedgwick and myself, as already stated, traced 

 phenomena of this character throughout a long range on the northern flanks of the 

 Austrian Alps, where the younger strata of the green sand appear to plunge under the 

 older Alpine limestone, and these again under the more ancient rocks towards the 

 centre of the chain. (See Geol. Trans., N. S., Vol. iii. p. 203.) This inverted order in 

 the Abberley Hills could never have been established without previous determination of 

 the regular and uniform succession of similar deposits over a large region where they 

 are ^disturbed ; while all the accompanying phenomena are so clearly explained upon 

 the western flanks of the Malvern Hills, that there is no longer any possibility of 

 avoiding the inference, that the volcanic agency, which threw up this line of trap rocks, 

 was directly the cause by which the strata were forced up and folded back. 



That one great eruption of the Malvern rocks took place after the accumulation of the 

 coal-measures, is proved by various dislocated carboniferous patches at the Abberley Hills. 

 Further, from the highly inclined position of the beds of New Red Sandstone near Great 

 Malvern, it is almost certain that this chain was also partially raised " en masse," after 

 the deposition of that formation. (PI. 36. f. 7.) Whether the movement which affected 

 the Red Sandstone was the same as that which broke up the coal-measures is not easily 

 determined, though we have no difficulty in affirming, that upon this same line of fissure, 

 volcanic action had been in play during the accumulation of the Silurian System, and 

 that the strata then in existence were thrown up by outbursts anterior to the forma- 

 tion of the coal beds, which rest unconformably upon the edges of these older rocks. 



