a. 
VOL. XIV. (1) PRE-RHATIC DENUDATION 47 
Toe PRE-RHATIC DENUDATION 
OF THE 
BRISTOL AREA: 
BY 
C. CALLAWAY, M.A., D.Sc., F.G.S. 
(Read March sth, 1901). 
On the visit of the Club to Clifton in September, 1900, 
several geological questions of some complexity were 
raised, but in the brief time at our disposal they received 
only a partial answer. One of these was the unconformity 
between the Paleozoic rocks and the overlying Mesozoic 
strata. Near Sea Mills, the so-called Dolomitic Con- 
glomerate (Upper Trias) was seen to be resting upon the 
upturned edges of the Old Red Sandstone. In the road 
leading up to Clifton Down the same conglomerate was 
observed clearly to overlie ata discordant angle the Upper 
Limestone Shales of the Carboniferous Series; while on 
Clifton Down detached patches of Lower Lias were noticed 
in fissures of the Upper Carboniferous Limestone. The 
unconformity is, therefore, very distinct. It indicates, in 
fact, one of the most important breaks in the geological 
succession, representing the vast period intervening 
between the Coal Measures and the Upper Trias. My 
purpose in this paper is to describe the sequence of events 
which, in our own area, occupied this interval in earth 
history. Fig. 1 shows the unconformity just described. 
To obtain a clear idea of the significance of the un- 
conformity, it will be necessary to briefly sketch the 
succession of phenomena that led up to it. In the 
