Page:VCH Buckinghamshire 1.djvu/41

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 * Approximate equivalents
 * in the west of England
 * Great Oolite Clay
 * Forest Marble
 * Great Oolite Limestone
 * Great Oolite
 * Upper Esturine Series
 * Fullonian or Fuller's Earth
 * }
 * Great Oolite Limestone
 * Great Oolite
 * Upper Esturine Series
 * Fullonian or Fuller's Earth
 * }
 * Fullonian or Fuller's Earth
 * }

The which enters but little into the surface geology, consists of black, grey, reddish, greenish and bluish clays, with white and brown sands, much like the Lower Estuarine Series. Nail-head spar, a form of calcite, is frequently present. These beds occur at Stoke Goldington and along the borders of the Ouse from Weston Underwood to near Olney, where they are from 15 to 20 feet in thickness. Formerly they were regarded as Upper Lias.

They have been proved in borings in Salcey Forest, and at Deanshanger on the Northamptonshire borders, and also at Stony Stratford. To the south-west of that town the Upper Estuarine Series rests directly on the Upper Lias clays, and it may do so near Olney.

The consists of white limestones, marls and compact grey limestone. Some layers contain scattered grains of oolite, others are largely oolitic and false-bedded, while some are sandy and minutely current-bedded. The upper beds comprise compact shelly limestone with the gasteropod Nerinæa, and with many lamellibranchs such as Cyprina, Astarte, Gervillia, etc. Other bands yield corals, Lima cardiiformis, Terebratula maxillata and Clypeus.

The Great Oolite Limestone which extends over much of the northern part of the county forms an undulating well-wooded district. The higher tracts are however largely covered by Boulder Clay: hence there is a mixed soil of chalky clay on which beans and wheat are cultivated, amid other arable tracts of stonebrash and much dairy land.

Numerous quarries are to be met with from Turweston and Biddlesden to Shalstone, in Stowe Park, along the Ouse valley at Water Stratford and Buckingham, at Leckhampstead and onwards by Calverton, Bradwell, Great Linford, Stony Stratford and Wolverton. Some of these quarries are but 10 or 15 feet in depth and many are now disused.

The stone has been employed for building purposes, but even when well-seasoned before use it is by no means durable, and it is not to be compared with the Great Oolite (Bath stone) of the west of England. The argillaceous nature of the limestone causes the lime to be strong and better adapted for mortar than for agricultural purposes.

In a pit at Bradwell near Newport Pagnell, beneath the Great Oolite Clay, about 16 feet of Great Oolite Limestone has been exposed, comprising pale earthy, shelly, and oolitic limestones, the lower layers false-bedded and containing veins of selenite. This mineral occurs also in thin seams an inch or two thick between the bands of stone. Most probably it is due to the decomposition of pyrites in the clay above, and