IN THE ANGLO-PARIS BASIN 73 



(Virginia Water), but the information is very incomplete, and in the case of the last 

 boring mentioned it is highly suspect. The location of the borings is shown in 

 text-fig. 1. 



Addington 



The boring at the Croydon Waterworks, Addington Pumping Station on the E. 

 side of Featherbed Lane (TQ 371628) yielded a core, parts of which are preserved in 

 the Institute of Geological Sciences. The Upper Gault-Lower Gault junction con- 

 sists of a phosphatic nodule bed with cristatum Subzone fossils and was reached at 

 about 879 feet (267-91 m.) depth. This is underlain by grey shelly clay represented 

 by fragments of core from between 880 and 882 feet (268-22-268-83 m.) and which 

 yield Inoceramus concentricus and poorly preserved ammonites which could indicate 

 either a loricatus or lautus Zone age. No further core fragments have survived from 

 the remainder of the Lower Gault sequence which has a total thickness of 22 feet 

 (6-70 m.). This boring is situated 9 \ miles WNW. of the section at Dunton Green at 

 the outcrop (p. 26) and indicates that the thin development of Lower Gault there 

 continues along the WNW. direction. 



Richmond 



The boring at the old Richmond Vestry Waterworks, Water Lane, Richmond 

 (TQ 17657470) was first described by Judd and Homersham (in Judd 1884) and 

 subsequently by Whitaker (1889 ; 214-217). Spath (1926a ; 151, 1930a ; 294) 

 demonstrated the presence of the Euhoplites inornatus band at the base of the orbignyi 

 Subzone (Upper Gault) and that the Lower Gault is also present. 



The Gault core was stored in the British Museum (Nat. Hist.) for many years before 

 being transferred to the Institute of Geological Sciences and is, unfortunately, in a 

 dirty state. /. sulcatus is still present at a depth of 1116 feet (340-15 m.), and by 

 1119 feet (341-07 m.) /. concentricus is present. The Upper Gault-Lower Gault 

 junction occurs, therefore, between these two depths. The base of the Gault was 

 located at a depth of 1139 feet 6 inches (347-16 m.) and so the Lower Gault is between 

 20 feet 6 inches (6-25 m.) and 23 feet 6 inches (7-16 m.) thick. No subzonally 

 diagnostic ammonites are present in the Lower Gault core. The base of the Gault 

 rests upon 10 feet (3-04 m.) of sediments tentatively classified with the Lower Green- 

 sand which in turn rests upon Jurassic sediments. In the Griffin Brewery boring at 

 The Mall, Chiswick, 3^ miles to the NE. of the Richmond boring, the Gault rests 

 directly upon Devonian sediments of the London Platform. The age of the base of 

 the Gault at Chiswick is, however, unknown. 



Egham (Virginia Water) 



This boring situated at the Holloway Sanatorium, Egham (TQ 002685), was 

 described by Dewey (in Dewey et al., 1925 ; 128). He records a band crowded with 

 /. sulcatus between depths of 1358-1360 feet (415-91-414-52 m.) some 67 feet (20-42 m.) 

 above the base of the Gault. From the basal nodule beds, Templeman collected 

 ammonites which led Chatwin to conclude (in Dewey et al., 1925 ; 130, 132) that the 

 base of the Gault was of Upper Gault age providing another example of overlap. 



