248 
CHAPTER IX. 
GEEAT OOLITE SERIES. 
GREAT OOLITE AND STONESFIELD SLATE. 
GENERAL ACCOUNT OF THE STRATA. 
REFERENCE has previously been made to the introduction of 
the term Great Oolite (p. 228). It is used by the Geological 
Survey to include the beds which in Wiltshire, Somersetshire, 
Gloucestershire, and Oxfordshire, occur between the Fuller's 
Earth and Forest Marble. The formation thus consists of a 
variable set of oolitic freestones, hard shelly limestones (rag), 
and earthy and compact white limestones and marls; together 
with occasional layers of calcareous sandstone, and the fissile 
sandy and oolitic limestones that constitute the so-called " Stones- 
field Slate." Locally the following subdivisions may be 
made : 
f bp- ("False- bedded oolites - Kemble Bedg. 
| pq M Pale earthy white limestones, I 
Upper Division. ( ^ 'o < sometimes oolitic, or with I White 
| P* I scattered oolitic grains ; [~ Limestone. 
\jt~fo L and marls - - -j 

["False-bedded oolite the main "1 Bath 
building-stone - - -} Freestone. 
Lower Division. <; Lower Ragstones ; and fissile cal- ] gtonesfi Id 
| careous sandstone and oolitic > gi 
L. limestone ; and clays - -) 
It will be found that these divisions are by no means persistent, 
that the upper beds are in places partially overlapped by the 
Forest Marble, and the lower beds by higher stages of the Great 
Oolite. Pebbly oolite-beds, indicating local erosion, are occa- 
sionally met with. The thickness of the series ranges from 100 
to 130 feet. 
Lonsdale noted the chief changes undergone by the Great 
Oolite when traced north of Bath, and first pointed out the 
stratigraphical position of the Stonesfield Slate, which had pre- 
viously been grouped with the Forest Marble and thus supposed 
to overlie the Great Oolite. The correct view was originally 
suggested to him by Grreenough.* Messrs. Brodie and Buckman, 
from a study of the Stonesfield Slate of the Cotteswold District, 
concluded, in 1844, that " it is part of the Great Oolite, or at least 
not sufficiently distinguishable from it, to entitle it to rank as an 
independent formation."f This view is true enough from a 
stratigraphical point of view ; while regarded from an economic 
* Proc. Geol. Soc., vol. i. p. 415. 
f Quart. Journ. Geol. Soc., vol. i. p. 224. 
