THE WREKIN — (TRAP AND ALTERED ROCKS OF). 



233 



Wrekin, properly so called, consists of flesh and brick red, compact felspar. This red felspar rock 

 is particularly well displayed in the gnarled points, called the " Raven's Bowl" and the " Bladder," 

 the south-eastern summits of the ridge. One of the varieties of this rock has been described by 

 Mr. Aikin 1 as a cellular claystone, the cavities in which have been so compressed as to give the 

 rock a waved and striped appearance. (Geol. Trans. Old Series, vol. i. p. 2.) Owing to the verdant 

 slopes upon the summit and sides of the Wrekin itself, there is little opportunity of detecting all 

 the varieties of which it may be composed, but towards the centre of the hill are some protruding 

 knobs of dark green compact felspar, passing in one part into granular felspar, in another con- 

 taining crystals of common felspar and small grains of quartz. The conical knoll of Primrose 

 Hill at the south-west end of the Wrekin, is a deep red syenite, graduating on the western side into 

 compact felspar rock, coloured green by chlorite. Of this rock are several varieties, some of which 

 assume a finely laminated arrangement, others are very imperfectly laminated, and are mottled dark 

 green and pink. 



The stratified deposits through which the trap rocks of the Wrekin protrude, are of 

 the same age as the Caradoc sandstone : varieties of these strata are to be seen on the 

 flanks of the Ercal, Madox, and Primrose Hills, in highly inclined and vertical beds, 

 and the lithological characters are in some instances highly changed, as on the flanks 

 of the Caer Caradoc. The most striking example of alteration is where the sandstone, 

 preserving its bedded form, is changed into granular quartz rock, many specimens of 

 which being made up of pure white quartz, with particles of decomposed felspar, are 

 scarcely to be distinguished from primary granular quartz rock. This quartz rock in 

 the state of a brecciated aggregate, prevails in the knolls between the syenite of the 

 Ercal and that of Madox Hill. A beautiful example of this quartzified grit and sand- 

 stone is on the eastern, steep, woody side of the Wrekin, opposite to Willymoor. The 

 original lines of lamination are distinctly preserved, the beds varying from two inches 

 to two feet in thickness, and dipping 60° east-south-east, or away from the trap rock. 

 Quarries opened for the extraction of stone used in the manufacture of china 2 , expose 

 the sandstone in various degrees of alteration and traversed by a great number of sym- 

 metrical joints. On the faces of some of these beds I perceived impressions resembling 

 the casts of shells and ramose bodies, probably coralline, but they were too indistinct 

 to be even generically determined. 



There is also much of the quartz grit on the western slopes of the Wrekin, so that the same effects 

 have been produced in the sandstone on both sides of the trappsean ridge. Again, on the south- 

 eastern face of Primrose Hill are quarries, which exhibit in highly inclined strata, a passage from 

 a coarse granular sandstone, in parts micaceous and schistose on the exterior, to a hard rock, con- 

 sisting principally of grains of white and grey quartz, with particles of decomposed felspar. I have 

 yet described only that ridge which in strict geographical language is the Wrekin, but there are other 

 trap rocks which rise to the surface through the adjacent sedimentary deposits, in lines parallel to 

 the main direction of the principal eruption. On the north-western face of the hill, a long talus of 

 heavy clay and detritus obscures the relations of the strata for nearly two miles, but in the merl- 



1 Geological Transactions, vol. i. p. 210, Old Series. 



3 Coalbrook Dale. 



