A HISTORY OF BEDFORDSHIRE 
The Cornzrasu consists of tough pale-grey rubbly limestone, usually 
shelly and sometimes sandy, and occurring in irregular layers parted by 
bands of softer limestone and occasional seams of marly and sandy clay. 
In most of its exposures it is seen to be crowded with fossils, chiefly 
Lamellibranchiata, the prevailing genera being Avicula, Ostrea, Pecten, 
and Lima. It is by some geologists considered to be distinct from the 
Great Oolite, and by others to be a member of it, being everywhere its 
highest subdivision. It appears to have been laid down at a considerable 
distance from land in a rather shallow sea varying in depth from time to 
time. Rarely exceeding ro feet in thickness, and being a persistent and 
well-marked formation, it is of value in the determination of the general 
dip of the strata. The river Ouse, in its devious windings through Bucks 
and Beds, has cut through it into the Great Oolite Limestone, the in- 
clination of the river-bed being a little less than the dip of the Corn- 
brash. Thus at Bradwell near Stony Stratford the river-bed is 200 feet 
above mean sea-level, and the Cornbrash just comes up to the 300 feet 
contour-line ; at Harrold the height of the river is 130 feet, and that of 
the Cornbrash 210; and at Bedford the river is 80 and the Cornbrash 
120 feet above sea-level. ‘There appears to be a local upheaval at Brad- 
well in Bucks, but in its range through Beds the dip of the Cornbrash 
seems to be very slight and fairly uniform, its direction being considerably 
to the east of south-east. It follows that this is the direction of the dip 
of the Jurassic strata above and below which are conformable with it, 
while the Cretaceous rocks dip in a more southerly direction. 
The Cornbrash is quarried for building, road-making, and lime- 
burning. Its presence near Bedford was known in the early days of 
geology (so far back as 1818), when it was called the ‘ Bedford Lime- 
stone.” To the rubble on its surface the name ‘Cornbrash soil’ was 
given, this being an old agricultural term for certain stony or brashy 
soils which are well suited to the growth of corn.’ The average width 
of its exposure in the county is about a quarter of a mile and does not 
vary greatly, 
UPPER JURASSIC 
afk Teh ti Kimeridge Clay . . Zone of Ammonites biplex 
Reunerdgan t eae Clay a he plleasill 
(= Corallian) 5 A. perarmatus 
Oxfordian | Oxford Clay and 9 A. cordatus 
Kellaways Rock { A. jason 
The Kerraways Rock is usually considered to be a subordinate 
division of the Oxford Clay, coming in above the lower portion of the 
clay, the great mass of which is always above it. Although it is so 
mapped by the Geological Survey, it would perhaps be better either to 
call the lower bed of clay the Kellaways Clay, as suggested by Mr. H. 
B. Woodward, or to group the clay and ‘rock’ together under the name 
of Kellaways Beds. While the clay indicates a rather deep sea, the rock 
1 H. B. Woodward, Furassic Rocks of Britain, iv. 380, 451. 
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