At Bletchley fragments of granitic rock were obtained in a boring from depths of 400 and 407 feet from the surface. The evidence as to their precise mode of occurrence was by no means clear, but probably the rock was present as boulders in the Kellaways Beds which form the basement portion of the Oxford Clay and consist of hard calcareous sandstones and clays.[1] Water which was obtained proved to be very saline.
A boring at Stone near Aylesbury was carried to a depth of 570 feet through Portland Beds, Kimeridge and Oxford Clays into the Great Oolite. It was made in search of water and was unsuccessful. [2]
LIAS
The oldest formation exposed in Buckinghamshire is the Upper Lias, which comes to the surface in the northern part of the county. There can be no doubt that both Middle and Lower Lias occur also in that region underground, but we have no definite particulars regarding them. It is probable that the Middle Lias (Marlstone) was reached at a depth of about 100 feet at Stony Stratford, and at a depth of about 200 feet beneath Drift and other deposits at Brickkiln farm to the south- east of that town, where a rock-bed yielded a scanty supply of brackish water. [3]
Even the Upper Lias is nowhere well exposed. It appears in the higher part of the Ouse valley south-west of Turweston, where it is faulted on the east against the Great Oolite Limestone. It occurs also in the Tove valley above Castlethorpe. Both these tracts are meadow- land, and the sub-strata are in a measure concealed by alluvium. No sections of the strata have been recorded, but in adjoining parts of Northamptonshire we know that the Upper Lias consists mainly of a mass of bluish-grey clay, which is locally worked for brickmaking. It contains small nodules of limestone or cement-stone, selenite and pyrites, and it yields Ammonites communis, A. fibulatus, many Belemnites, Leda ovum, Inoceramus dubius, and other fossils. The lowermost portion comprises alternations of clay or shale with limestones, and these yield remains of fishes and insects, Ammonites serpentinus, etc. They indicate marine con- ditions and water shallower than that in which the thick series of over- lying clays was deposited.
INFERIOR OOLITE SERIES
Again we find representatives of an important division which is but poorly exhibited in the county, and in this case poorly developed. The Inferior Oolite Series, so prominent in the Cotteswold Hills, undergoes such considerable changes as we pass into the midland counties that distinct stratigraphical divisions are needful. In place of a great series of marine sands, oolitic freestones and rag beds yielding numerous fossils,
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