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CHAPTEE XII. 
GREAT OOLITE SERIES. 
FOEEST MARBLE AND BRADFORD CLAY. 
(BRADFORDIAN.) 
GENERAL ACCOUNT OP THE STRATA. 
IN the old Forest of Wychwood (or Whichwood) to the north- 
east of Burford in Oxfordshire, certain beds of shelly oolitic 
limestone are quarried here and there for road-metal and for 
building walls. A century ago the stone was employed locally 
for chimney-pieces in farm-houses and cottages, and being 
polished for the purpose, it was known in the country round as 
the Forest Marble. This name was adopted in 1799 by William 
Smith, as a geological term for the strata, which he found to rest 
on the Great Oolite and to be overlaid by the Cornbrash : but 
like other of Smith's terms, it was, I believe, first published in 
1813 by the Rev. Joseph Townsend. 
No formation with which we have to deal is more variable in 
its particular characters than the Forest Marble, though taken as 
a whole it forms a fairly well-marked division, extending from the 
Dorsetshire, coast near Bridport and Weymouth inland to the 
neighbourhood of Buckingham. 
The beds consist of shelly oolitic limestones, and thin flaggy 
limestones generally much false-bedded, and they comprise also 
clays and shales with thin layers of gritty limestone. In some 
places thicker beds of gritty or sandy limestone are intercalated 
with the limestones, especially in the upper part ; and in others, con- 
siderable beds of buff or brown sand appear, with layers and large 
concretionary masses or doggers of calcareous sandstone. 
More often the mass of blue shelly and oolitic limestones con- 
stitutes a middle division, being overlaid and underlaid by shales 
and clays. The lower clays near Bradford-on-Avon and other 
places contain at their base an abundance of fossils ; and this 
division, though nowhere of great thickness, constitutes what is 
known as the Bradford Clay. 
The thickness of the Forest Marble near Bridport and Wey- 
mouth is about 80 or 90 feet ; near Sherborne, in Dorsetshire, 
130 feet; near Bath and Cirencester, about 100 feet; while in 
Oxfordshire it is rarely so much as 50 feet thick, and in some 
places not more than 12 or 15 feet. Further to the north and 
north-east, we find occasional beds that may represent the strata, as 
near Blisworth ; but shelly limestones of similar character occur 
apparently at different horizons in the Great Oolite Series, as at 
Alwalton near Peterborough, so that different stratigraphical 
divisions become needful in that area. 
Organic Remains. 
Among the fossils of the Forest Marble (including the Bradford 
Clay) Lamellibranchs and Brachiopods are the more abundant. 
