ROCKS OF SHROPSHIRE. 651 
Following the ridge to the south-west, we come to a reddish 
felstone, the dip of which has been locally reversed by the disruptive 
greenstone. ‘This rock is continued for some distance. In places 
it is clearly banded into lamine of various colours, an alternation of 
dark chocolate with buff bands being the commonest variety. The 
laminz are sometimes contorted like the gnarled wood of an ancient 
oak. 
These Precambrian lavas are underlain near the summit by a 
greyish agglomerate, with fragments of brown felstone. The dip is 
northerly. 
At the summit and for some distance beyond is a considerable 
exposure of reddish and chocolate-coloured felstone. 
In the middle of the south-west slope, with the normal east and 
west strike, is a dark coarse tuff, undistinguishable in appearance 
from the beds near the cottage at the north-east end. 
Below the tuff we come to a compact red felsitic rock, underlain, 
in the saddle between the Wrekin and Primrose Hill, by typical 
agglomerate. 
Relations of the Wrekin aais to the flanking deposits. 
The volcanic rocks of the chain are fringed by quartzites *, 
which in every observed case (with one exception) dip away from 
the axis at an average of 45°. The exception is on the north-west 
side of the ravine, between the Ercal and Lawrence Hill, where the 
beds are nearly vertical, the dip being towards the axis. The base 
of the quartzite is brecciated, and the junction is evidently a fault. 
Towards the base the quartzite contains rounded fragments of 
banded felstone, similar to some of the Wrekin felstones. ‘The 
quartz rock is clearly younger than the axial rocks, and has been 
thrust up and thrown off on every side by the upheaval of a rigid 
wedge of the older series. Under the summit on each side, as 
shown in fig. 5, the quartzite appears to be absent; and it is pre- 
sumed that the crest of the Wrekin was an island in the Pre- 
cambrian ocean, and by its partial denudation furnished the felstone 
fragments imbedded in the quartzite. On the north-west the 
Bunter Sandstone is faulted down against the quartzite. On the 
south-east, the quartzite is succeeded by the Hollybush Sandstone, 
and the Hollybush Sandstone by the Tremadoc shales of Shineton, 
the junctions in both cases being parallel lines of fault. 
Figs. 4 & 5 will illustrate the series just described. Fig. 4 is a 
longitudinal section through the chain from end to end. ‘The dips 
are not fully filled in, only those being indicated which are ascer- 
tained with reasonable certainty. The quantity of dip cannot be 
shown, the section, as in the transverse section, fig. 3, being taken 
at an acute angle with the dip. The underground extension of the 
dolerite neck is, of course, hypothetical; it should be represented, 
if the space permitted, as sending off three dykes to the north-east. 
Fig. 5 is more instructive, since the true direction of the strikes is 
shown, and the relations of the flanking formations are indicated. 
* Described in Quart, Journ, Geol. Soc. vol. xxiv. p. 754. 
