GEOLOGY 



CORNBRASH 



This formation consists of earthy and shelly limestone with marly 

 or clayey bands, altogether from 5 to 8 feet in thickness. Among 

 fossils 'Terebratula intermedia^ Waldheimia otiovata, Avicula ecbinata, 

 Pholadomya and Ostrea flabelloides may usually be found. Although 

 insignificant in thickness and of no economic importance in Bucking- 

 hamshire, the formation is of interest as being one of the more persistent 

 bands in the Jurassic system. 



North of Buckingham a large outlying mass of Cornbrash almost 

 concealed beneath Oxford Clay and Glacial Drift occurs between Akeley 

 and Thornborough. On the south side of the Ouse the formation 

 extends from Barton Hartshorn to Tingewick, and eastwards from 

 Beachampton, Bradwell, Great Linford and Newport Pagnell to near 

 Newton Blossomville. Over much of the area the Cornbrash is con- 

 cealed by Drift, and the broad outcrop is indefinite ; moreover it was 

 extended more than it should have been on the geological survey maps 

 by the inclusion of the Great Oolite Clays. 1 



The formation is brought to the surface in inliers at Marsh Gibbon 

 and West Stan Hill by an anticlinal structure which has disturbed and 

 faulted the beds from Islip in Oxfordshire in a north-easterly direction. 

 At Akeley north of Buckingham we again meet with an anticline with 

 a northerly trend where the Cornbrash, Great Oolite Clay and Great 

 Oolite Limestone have been bent into an arch, locally eroded, and ex- 

 posed beneath the Kellaways Beds. 2 



OXFORD CLAY 



As its name implies this is a great clay formation ; it occupies a 

 vale chiefly of grass land with many dairy farms, and it forms part of 

 a famous hunting country. It extends from Gawcott, Steeple Claydon, 

 Grendon Underwood and Ludgarshall to Winslow, Whaddon Chase, 

 Bletchley and. Fenny Stratford in the Ouzel valley, and thence to 

 Chicheley and Astwood. The vale is an undulating one, rising at 

 Knowl Hill between Edgcot and Middle Claydon into a conspicuous 

 elevation, but the surface is modified by coverings of Boulder Clay and 

 Drift Gravel, to the presence of which the scattered villages are to be 

 attributed, as the gravels yield springs and furnish limited supplies of 

 water to shallow wells. Many of these however have become polluted 

 owing to defective sanitary arrangements, and deeper or distant supplies 

 of water have to be looked for. The clay is locally dug for the 

 manufacture of bricks, tiles and drain-pipes. 



Resting on the Cornbrash there is usually about 10 feet of clay 

 which is overlain by the yellow sands, sandstones and loams, all belong- 

 ing to the Kellaways division, and about 20 or 30 feet in thickness. 

 The lower beds are much better exhibited in the adjoining county of 

 Bedford, but they have been exposed at Akeley, Padbury and Little 



1 Green, Geology of Banbury, etc. p. 30. 

 * 'Lower Oolitic Rocks of England,' Geol. Survey, p. 450. 

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