A HISTORY OF BUCKINGHAMSHIRE 



Evidently it lies unconformably on the Purbeck and older strata, 

 and yet curiously enough in some of the lower bands of ferruginous 

 sandstone there have been found remains of freshwater shells, Unio, 

 Cyrena and Pakufau, which led Fitton, John Phillips and also Prestwich 

 to regard these beds as of Wealden age. 1 Now elsewhere, where 

 Wealden Beds occur, they are comformable with the Purbeck Beds, 

 and the explanation given by other geologists, that these fossiliferous 

 layers are freshwater beds of Lower Greensand age seems most reason- 

 able. 2 It may be remarked that John Morris noted the occurrence of 

 freshwater mollusca at Hartwell, and he mentioned the finding of the 

 Wealden plant, Endogenites erosa, near Stone church, probably at the 

 base of the sands. 3 At Muswell Hill Unio porrectus, a Wealden species, 

 has been found. We have however no grounds for concluding that 

 Wealden species of freshwater mollusca died out at the close of the 

 Wealden period, and the stratigraphical evidence is in favour of group- 

 ing with the Lower Greensand all the strata about to be described 

 which occur between Shotover and Woburn. It may be useful to group, 

 as Mr. A. M. Davies has done, the beds at Muswell Hill, Brill, Long 

 Crendon, Oving and Quainton under the old name of Shotover Beds. 

 These beds attain a thickness of about 50 feet. 



Elsewhere near Aylesbury, at Bishopstone, Haddenham and Stone 

 the sands and hard ferruginous layers have yielded impressions of marine 

 Lower Greensand fossils, Exogyra sinuata, Lima and Pecten, and these 

 beds, which may belong to a newer stage than the Shotover Beds, are 

 grouped as Bishopstone Beds by Mr. Davies. 4 



The precise relation of these two divisions to the thick mass of 

 Woburn Sands may well be left an open question probably both are 

 represented in that thick series. 



Much of the Lower Greensand in the outlying hills consists of 

 coarse and fine sands 20 feet or more thick with hard concretionary 

 masses, the sand being in places clean and white, and adapted as near 

 Stone for glass-making, for which purpose it was formerly sent to 

 Birmingham. At Stone it is cemented in places into hard and irregular 

 siliceous concretions of such grotesque forms that they are known as 

 ' bowel stones.' Elsewhere the sands are of various tints, some red and 

 orange-coloured, the coarser sands containing pebbles of quartz, quartzite 

 and lydian stone. Thin seams of ironstone occur as well as beds of 

 clay, while fuller's earth and ochre were formerly dug at Brill, and 

 whitish pipeclay is met with at Oving. 



The soil in general is a reddish brown sandy loam, and the strata 

 are usually water-bearing, having at Stone furnished a good supply. 

 Further on towards Woburn, where there is a greater thickness of the 

 sands, larger permanent supplies of water may be expected, but that 



1 Phillips, Geology of Oxford and the Valley of the Thames, pp. 410, 412, 418 (1871) ; Prestwich, 

 Geology, ii. 264. 



2 E. Hull and W. Whitaker, Geology of farts of Oxfordshire and Berkshire, p. 15 ; A. H. Green, 

 Geology ofBanbury, etc. p. 50 (1864). 



3 Geol. Mag. pp. 458, 459 (1867). 4 Proc. Geol. Assoc. xvi. 45, 50. 



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