18 SKETCH OF THE GEOLOGICAL HISTORY OF THE BRISTOL DISTRICT. 
consists practically entirely of limestone. Succeeding the Lias come 
the deposits known as the Cephalopod bed and the associated Mid- 
ford sands. The latter show much variation in thickness. At 
Stinchcombe the sands are 230 feet thick, and at Sodbury 185 feet; 
here they underlie the Cephalopod bed resting directly on the Upper 
Lias. Further south at Midford they are about 100 feet thick, while 
still further to the south they become rapidly thinner, being reduced 
to 5|- feet at Timsbury and disappearing to the south of Wellow. 
In the southern part of the area too, while there is a well-marked 
bed rich in Cephalopods, it is not the equivalent of that further to 
the north, as it underlies the sands instead of overlying them. 
The succeeding Inferior Oolite ^ beds yield some of the finest of 
the Jurassic freestones, and have been quarried since Roman times 
at Dundry. They are finely exposed at Doulting, Vallis vale, and 
at Stroud, Stinchcombe, Wootton-under-Edge, and other places along 
the edge of the Cotteswolds. Much attention has been paid to them 
in recent years by Messrs. Buckman and Richardson, showing the 
presence of local non-sequences or the absence of certain of the life- 
zones. Of the 27 sub-divisions which these authors recognise in the 
Inferior Oolite series not one is traceable over the whole area, this 
being in most cases clearly not due to lithological changes, but to 
local erosion and non-sequence. 
The most complete development of the Inferior Oolite is at Leck- 
hampton hill outside our area ; here it is about 200 feet thick, con- 
sisting of the Ragstone series above, the Freestone series in the 
middle, and Pea Grit series below, but as the Inferior Oolite is 
traced southwards along the Cotteswold escarpment, all the middle 
and lower beds gradually die out, till at Bath the Upper Trigonia 
Grit, the lowest bed of the Ragstone series, rests directly on the 
Midford sands. At Dundry an important bed of freestone comes on 
above the Upper Trigonia grit, and in the Eastern Mendips a second 
bed of freestone, the Doulting stone occurs at what according to 
Mr. L. Richardson is a still higher level. Neither of these freestones 
is represented as such in the Cotteswolds. In the eastern Mendips, 
at the well-known Vallis quarries, the Upper Trigonia Grit and the 
Dundry freestone have disappeared, like the Freestone and Pea Grit 
series further to the north, so that the Doulting beds rest directly 
on the Carboniferous Limestone. 
Resting on the Inferior Oolite is the Fuller’s Earth, a marly clay 
with hard bands. Though seen in small exposures at many points 
in the district, and reaching a thickness of 130 feet at Wootton- 
1 For general accounts of the Lower Oolitic rocks see H. B. Woodward, 
‘Mem. of Geol. Survey’, “The Jurassic rocks of Britain, vol. iv., the 
Lower Oolitic Rocks of England”; J. W. Tutclier, “ The Lower Oolites near 
Bristol”, ‘Proc. Bristol Nat. Soc.’, New Series IX. (1898-1900), p. 150; for 
the Dundry exposures, S. S. Buckman and E. Wilson, ‘ Q. Journ. Geol. 
Soc.’, LII. (1896), p. 669, and ‘ Proe. Bristol Nat. Soc.’, New Series, VIII. 
(1896-98), p. 188; for the Bath-Doulting district, L. Richardson, ‘ Q. Journ. 
Geol. Soc.’, LXIII. (1907), p. 383. 
