A HISTORY OF BEDFORDSHIRE 
The geological formations represented in Bedfordshire, with their 
chief lithological characters and approximate thickness, are given 1n the 
table on the preceding page, in descending order, the names of the for- 
mations which do not come to the surface in the county being printed 
in italics. 
“In the following account of the Jurassic and Cretaceous rocks, at 
the head of each division are given the geographical names adopted for 
the formations or their subdivisions by continental and by some English 
geologists, the lithological names in general use in this country, and the 
life-zones represented in the county. 
LOWER JURASSIC 
Toarcian . . Upper Lias . . Zone of Ammonites communis 
The oldest formation of the occurrence of which within the county 
we have actual evidence is the highest division of the Lower Jurassic 
series, the Upper Lias, and that does not come to the surface, having 
only been met with in well-borings at Sharnbrook and Felmersham, 
where it appears as a blue clay. The greatest thickness passed into being 
66 feet, it is not likely that the lower zone of the Upper Lias, that of 
Ammonites serpentinus, has been reached. The strata rise towards the 
north-west, and both zones crop out in Northamptonshire. The mud 
of which the Liassic clays are composed was probably derived from 
the erosion of Carboniferous shales, the sediment having been deposited 
in the sea whilst its bed was sinking, a process which had been going 
on throughout Permian and Triassic times. 
MIDDLE JURASSIC 
Cornbrahh . . . . Zone of Ammonites discus 
Bathonian{ Great Oolite . . . 5 A. gracilis 
Upper Estuarine Series Ss Modiola imbricata 
Bajocian Inferior Oolite . vs Ammonites opalinus 
The Inrertor Ooutrs is represented only by the Northampton Sand, 
a passage-bed between the Lias and the Oolites, and by some geologists 
considered to belong to the older formation. It has been sunk into at 
Wymington, yielding a supply of water. It comes to the surface in the 
adjoining county of Northampton, where it consists of sandy ironstones 
with a thin bed of coarse oolitic limestone on the top. It represents 
the Midford Sand of Dorset and Somerset and the lower part of the 
Inferior Oolite of Cheltenham, and indicates a change of conditions to 
a more shallow sea than that of the Liassic period. 
The Upper Estuarine Seriss is the oldest formation which comes to 
the surface in the county. At Bedford it is 70 feet beneath the surface, 
and its outcrop, which is not a continuous one, is some miles to the 
north-west. It consists of sand and sandy clay of various colours, with 
irregular layers of limestone here and there, and is of fluvio-marine 
origin, showing alternations of marine and freshwater conditions, and 
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