A HISTORY OF BUCKINGHAMSHIRE 



Woolston. Among the fossils which they yield are Ammonites calloviensis, 

 A. gowerianus, A. kcenigi and Gryphcea bilobata. The middle division, 

 which comprises shales and clays with much pyrites, is characterized by 

 Ammonites Jason, A. lamberti, Belemnites oweni and Cerithium muricatum ; 

 the strata have been opened up along the Great Central Railway near 

 Charndon, also near Winslow and at Fenny Stratford. The highest 

 division, consisting of clays, contains Ammonites cordatus, Belemnites 

 hastatus and great numbers of Gryphcea dilatata ; and it is well exposed 

 in a brickyard by Quainton Road station. 



CORALLIAN 



Between the Oxford and Kimeridge Clays there is usually developed 

 a series of sands and calcareous sandstones, oolitic limestones and coral 

 beds, grouped as the Corallian formation. In Buckinghamshire these 

 rock beds are not present in any conspicuous form ; they terminate north- 

 east of Wheatley in Oxfordshire, and thence until we reach Upware in 

 Cambridgeshire the formation is represented almost wholly by clay to 

 which the name Ampthill Clay was given by Professor H. G. Seeley. 



In the absence of the Corallian stone beds the probable equivalents 

 have been shown on the geological survey map as extending through 

 Shabbington, Ickford, Worminghall, Oakley and Boarstall, and thence 

 from Dorton by Wescot to Quainton. Further on the Ampthill Clay 

 outcrops between North Marston and Granborough, at Stewkley and 

 onwards to the south of Linslade church. 



The beds comprise dark clay and shale with selenite, and they 

 contain Ammonites cordatus and var. excavates, A. plicatilis, A. vertebralis, 

 Belemnites abbreviates, Gryphcea dilatata, Ostrea discoidea, and also Ostrea 



deltoidea. 



There is a mingling of forms elsewhere belonging to the Oxford 

 and Kimeridge Clays, and this is natural, as the conditions of deposition, 

 in the absence of the Corallian rock beds, were more uniform ; but it 

 is only by attention to the fossils that the division can be recognized. 

 West of Boarstall a hard cherty band has been observed, which helps to 

 form the gentle escarpment of Pans Hill. It has yielded Ammonites 

 cordatus and A. vertebralis. 1 



KIMERIDGE CLAY 



This clay formation extends from the Thame valley near Thame 

 to the neighbourhood of Brill, Nether Winchendon and Waddesdon, and 

 eastwards to Aylesbury, Quarrington, Hardwick, North Marston, Dunton 

 and Stewkley. It occupies the lower grounds in a part of the celebrated 

 vale of Aylesbury, which is diversified by numerous outlying hills of 

 Portland and Purbeck Beds, with here and there coverings of Lower 

 Greensand and Gault. It consists mainly of dark shale with occasional 

 bands of septaria. In the lower beds Ostrea deltoidea is to be found, 

 higher up Exogyra virgula is characteristic, and the upper beds contain 



1 Green, Geology of Banbut-y, etc. p. 44. 

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