A HISTORY OF BUCKINGHAMSHIRE 



During the formation of the Gault the Lower Greensand was 

 extensively eroded, as well as the various Jurassic rocks. The Gault 

 was spread over their worn surfaces, resting in places in the Vale of 

 Aylesbury on Lower Greensand, Purbeck and Portland Beds and Kime- 

 ridge Clay ; and between Wing and Soulbury on Corallian and Oxford 

 Clay. 



GAULT 



The Gault, a stiff dark blue and pale calcareous clay with concretions 

 of carbonate of lime or ' race,' occupies a considerable tract, and is more 

 calcareous in the northern part of the area. It occurs at Wing, Cubling- 

 ton, Mentmore, and thence from Cheddington it comes to the surface 

 over the Vale of Aylesbury by Stoke Mandeville and Ilmer to Towersey. 



The Lower Gault, which is characterized by Ammonites interruptus 

 and A. lautus, together with Belemnites minimus, attains a thickness of 

 from 140 to 150 feet. About 20 or 30 feet from the base there is a 

 band of phosphatic nodules, and other nodules are found at the junction 

 with the Upper Gault. The Upper Gault characterized by Ammonites 

 rostratus is 70 or 80 feet thick. 



The lower band of phosphatic nodules was formerly worked at 

 Towersey, and between Ford and Moreton, south-east of Dinton, and 

 near Bishopstone. The seam, which is but 3 or 4 inches thick, is made 

 up of buff and black nodules, comprising coprolites and phosphatized 

 shells of the Gault fossils A. rostrafus, A. vartcosus, Inoceramus sulcatus, 

 etc. The upper band of nodules, about 1 8 inches thick, was at one time 

 worked at Puttenham, Cheddington and Slapton. 1 



The soil of the Gault is naturally thin, so that the land is often 

 heavy, cold and tenacious, and best adapted for pasture. From infor- 

 mation communicated by the Rev. F. W. Ragg, it appears that as late 

 as the fifteenth century, before the district was drained, there were many 

 swampy tracts and two or three lakelets in the vale north of Marsworth. 

 The soil is however much modified in places by the scattered Drifts 

 and by downwashes from the neighbouring hills of Upper Greensand, 

 Lower Greensand and Portland Beds. Hence it is that the celebrated 

 Vale of Aylesbury, ' the pastoral garden of the county,' which extends 

 from Mentmore and Cheddington to Ilmer and Waddesdon, while 

 mainly a clay country of Gault and Kimeridge Clay, has a soil improved 

 by the waste of the bordering and outlying hills, as well as by the 

 superficial drifts; and thus it ranks high as grazing and dairy land. 2 

 The Gault is utilized in many places for brickmaking. 



UPPER GREENSAND 



This formation, which enters largely into the scenery of many 

 southern counties, is thin and impersistent in Buckinghamshire, being 

 in fact largely replaced by the Gault clay. It comprises greenish (glau- 

 conitic) sands and marls, with layers of fine-grained clayey calcareous 



1 Jukes-Browne, Cretaceous Rocks of Britain, i. 275, 277, 280 ; and Quart. Joun. Geol. Sac. 

 xxxi. 264. 2 See C. S. Read, Joum. Roy. Agiic. Soc. xvi. 281. 



