ODLING : CORRELATION OF THE UPPER AND MIDDLE OOLITES 279 
Cornbrash passes into the Kellaways, and often its exact junction cannot 
be defined ; thus further showing the affinity of the Cornbrash to the 
Middle rather than to the Lower Oolites. Secondly, the Kellaways 
often becomes locally of great importance, sometimes entirely replacing 
the Oxford Clay. Of this fact more will be said later. Thirdly, we 
find a bed of Oolite, the Hambleton Oolite, capped by calcareous grits 
separating the Lower Calcareous Grits from the L^pper Corallian. 
Fourthly, Supra -Corallian beds occur, represented by the Upper 
Calcareous Grits. Fifthly, no Portland or higher Jurassic beds are 
definitely recognizable, except possibly at Speeton, 
Taking these beds seriatim, we begin with the Cornbrash, which, 
in Yorkshire, probably represents only the uppermost beds of the 
southern counties.* That it is homologous to the south country Corn- 
brash is fairly clear, but it was probably deposited in an area cut off 
from the main mass by some land barrier. Petrologically and 
palseontologically the two types differ considerably, and a geologist 
from the South of England might well be excused in not at first sight 
recognizing the Yorkshire beds as Cornbrash. The succeeding beds, 
the Kellaways into which the Cornbrash m.erges, are of very special 
interest. The lower beds — for instance, those exposed round South 
Cave — are evidently true Kellaways, characterized by the abundance 
of specimens of Kepplerites calloviense, but the greater part of the Kella- 
ways to the North of the Vale of Pickering — i.e., round Roulston Scar 
— appear to be of a different age. Not only does it represent an 
arenaceous facies of the Oxford Clay, but it may in part locally 
represent Lower Corallian, and even the base of the Upper Corallian, 
since among other fossils Fox-Strangways mentions Perisphinctes 
plicatilis, the zone-fossil of the' Upper Corallian. 
The diagram (p. 280) indicates the general relationship of these 
interesting beds. I 
To this replacement of Oxford Clay by Kellaways Beds is due the 
success of an artesian borehole sunk at Oswaldkirk, near Gilling, on 
the suggestion of Prof. Kendall. Here the thickness of Oxford Clay 
* Buckman, S. S., Proc. Yorks. Geol. Soc, Vol. XVII.. p. 191. 
f Reference should also be made to Jurassic Rocks of Britain^ 
Part I., Plate 5. 
