12 



Geology and Physiography 



at Upware were the subject of a detailed study by Keeping, who in 1883, 

 from examination of over 15,000 specimens, arranged the species in three 

 morphological series, wliich are preserved in the Sedgwick Museum. 



GAULT 



The Gault is summarised in the table below, based on the work (some 

 unpublished) of Dr Spath, whose identifications of the ammonoid faunas 

 of Cambridgeshire have established their horizons with greater precision 

 than was hitherto possible. 



The Lower Gault is exposed, although very badly, at Upware, where a 

 fairly large ammonite fauna typical of the dentatus-zone has been fovmd; 

 the beds are a dull tenaceous clay, but the lowest layers are glauconitic and 

 sandy. A boring at Chapel Lane, Wicken passed through 59 ft. of Gault 

 Clay; the top 18 ft. were calcareous clay, below which was a bed 5 ft. 

 thick with ammonites characteristic of the orhignyi-varicosum zones. Ammo- 

 nites were not recorded in the lower 36 ft., the base of which was sandy 

 with a few pebbles. This section illustrates a point which must be borne in 

 mind when reading the above table. These records are based entirely on 

 ammonites, which are rarely foimd throughout the whole of a section. 

 Further, the Gault is badly exposed. Lack of records from the upper 

 Lower Gault, for instance, may possibly be due to non-exposure. Ammonites 

 typical of the base of the Upper Gaidt have been found at Landbeach^ 



