GREAT OOLITE. 249 
and also from a pal aeon tological point of view, the Stonesfield 
Slate is of great importance. 
The Stonesfield Slate is but locally developed, and appears to 
be intimately connected with the Fuller's Earth below and to 
merge upwards into the Great Oolite above. Thus it occupies a 
position analogous to that of the Collyweston Slate, which links 
together the Lower Estuarine Series and the Lincolnshire Lime- 
stone. Traced to the north-west beyond Stonesfield and Chipping 
Norton, both Fuller's Earth and Stonesfield Slate are represented 
by the Upper Estuarine Series. 
In 1857 Prof. Hull divided the Great Oolite of Gloucestershire 
and Oxfordshire as follows* : 
-pr f Marls and white limestones, usually devoid of oolitic 
Upper Z,one. ^ structure, and evenly bedded. 
T / False-bedded oolitic freestone, shelly limestones, 
ae ' \ clays, and sandy flags (Stonesfield Slate). 
In the Lower Zone Prof. Hull placed the building-stones of 
Minchinhampton, Taynton, &c., regarding them as on the same 
geological horizon as the Stonesfield Slate of Sevenhampton, 
Eyeford, &c. In the Lower Zone, also, were included portions 
of the Northampton Sand. (See p. 146.) 
The lower beds evidently represent the shallower-water con- 
ditions. In the Upper Zone the fossils, though seldom fragmentary, 
occur often in casts, and appear to have been buried where they 
lived. The stratigraphical evidence has shown that the true 
Northampton Sand can be separated from the Great Oolite 
Series with which at one time it was confounded ; and the Stones- 
field Slate, wherever it is developed, occurs at the base of the 
main freestones. 
None of the subdivisions of the Great Oolite can be regarded 
as very constant : although broadly speaking we can recognize a 
lower division of sandy and oolitic flags and current-bedded 
oolite, and an upper division of soft earthy limestones and marls, 
over great part of the area. To the north-east of Oxfordshire 
other stratigraphical subdivisions become necessary. 
The freestones of Bradford-on-Avon, Bath, Corsham, Minchin- 
hnmpton, and Taynton degenerate, further north and are not 
distinguishable ; and from the neighbourhood of Buckingham 
through Northamptonshire and Lincolnshire, the white limestones 
and associated marls (belonging to the Upper Division of the 
Great Oolite) form the chief portion of the formation to which 
the term of Great Oolite Limestone is applied. This division 
rests on the Upper Estuarine Series, and is overlaid by the Great 
Oolite Clay, with only occasional beds that present the characters 
of Forest Marble. 
In the neighbourhood of Minchinhampton and for some distance 
northwards, it becomes a matter of difficulty to separate the 
Great Oolite and Forest Marble, for in this area there is a con- 
siderable development of false-bedded oolites above the white 
* Geol. Cheltenham, p. 53. See also Geol. Parts of Wilts and Glouceatershire, 
p. 12 ; Quart. Journ. Geol. Soc., vol. xvi. p. 72. 
