THE AVONIAN OF THE AVON GORGE 
89 
descend in the sequence, and whereas we have contented our- 
selves with a rather hurried examination of the rocks south of 
the fault, knowing that we should meet the same beds again 
north of the fault, we shall study the rest of the section more 
leisurely and shall pause at frequent intervals to consider what 
were the circumstances under which the beds were laid down. 
The beds dip southward under one another at a uniform dip 
of nearly 30°, without a break in the succession, and the rocks 
can be examined, practically bed by bed. 
The Avon section is probably the most complete section of 
the Carboniferous Limestone Series to be met with anywhere 
in the British Isles. 
Dibunophyllum-Zone (D). ’ 
Upper subzone (D^). 
The first exposure met with is a mural face at 
Plate IX. . ^ 
Bound Point. The rocks are here massive and 
red stained ; the predominant rock-types are rubbly and encrin- 
ital limestones, but there are intercalated beds of pure grit and 
thin quartz-conglomerates. Af> the base of the series, just south 
of Point Villa, is a massive quartz conglomerate about 3 feet 
thick. 
Such a variation in lithic structure indicates considerable 
movement of the sea floor, the total variation amounting to a 
change from clear water conditions, at a moderate depth, to the 
circumstances of an actual beach. We may also notice that the 
variation was oscillatory, for the same succession of rock types 
is repeated, as shown in the descending sequence : — 
Grit. 
Limestone. 
Quartz Conglomerate. 
Grit. 
Limestone. 
Lower subzone (DJ. 
The exposure at Round Point ends just south of Point Villa 
^ The sequence is best studied in the exposures at the side of Bridge 
Valley Road. 
H 
