ROCKS OF SHROPSHIRE. 649 
altered felspathic tuff, dipping north at 50°, and cut through by 
three basaltic dykes, which strike towards a mass of dolerite in the 
Wrekin. The ridge is flanked by quartzite on both sides, the 
beds on the south-east being succeeded by the Hollybush Sandstone 
and the Shineton Shales. 
4, The Wrekin (figs. 3, 4, 5). 
Details.—At the north-east end of the hill, opposite the great 
quarry in Lawrence Hill, there are numerous exposures of dark 
grey and reddish tuff, similar to the Lawrence-Hill series. In a 
large opening at the foot of the ascent, the tuff beds are pushed out 
into a rounded anticlinal spur. This contortion appears to be due 
to the intrusion of the mass of dolerite to which reference has been 
made. Two of the three Lawrence-Hill dykes are also visible on 
this side of the ravine; and it is evident that both the contortion 
and the dykes are due to the same cause. Between this point and 
the dolerite mass the tuffs are somewhat disturbed, the dip being 
pushed round to 20° west of north. Near the cottage the tuff is a 
breccia, which is sometimes conglomeratic, the pebbles consisting of 
felstone, pitchstone, and less frequently of quartz. The subjoined 
section shows the lie of the tuffs which compose the north-east end 
of the Wrekin, with their relation to the flanking deposits. 
Fig. 3.—Section across the Wrekin, north-east end. 
Faults. Fault. 
Seale about 8 inches to 1 mile. 
1. Bedded Precambrian volcanic tuff, dipping north. 
2. Quartzite (probably Precambrian), 
3. Hollybush Sandstone. 
4, Shineton Shales (Tremadoc). 
Ascending the hill above the cottage, we reach a round bare 
hump, the exposed apex of the greenstone mass*. It is composed 
of dark green dolerite, which in some parts is agglomeratic, in others 
amygdaloidal, with nuclei of calcite. In its colour, state of de- 
composition, and in all other respects this rock resembles the dykes 
of Lawrence-Hill quarry, with which it is undoubtedly connected. 
It would appear to have been an ancient volcanic vent. It is the 
only greenstone found in the entire Wrekin chain f. 
aoe noticed by Mr. Allport in the paper to which reference has been 
mace. 
t I have since detected greenstone at the S.W. end. 
