414 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 21, 



Prestwicii, 1850-54. 



Proposed Classification. 



London Clay. 



Basement- 

 bed 

 of the 

 London 

 Clay. 



Woolwich 

 and 



Reading 

 Series. 



Thanet 

 1^ Sands. 



Clay. 

 ( Thin pebbly loam &c. of the ) 

 western part of the London 

 Tertiary District. 



Thin clayey pebble-bed of [ 

 Lewisham, &c. ) 



■{ Highest sands of Upnor, the ^ 

 Reculvers, &c., with pebbles at 

 the bottom. 



Part of the sandy pebble-bed 



of Kent (Blackheath, Abbey 



^ Wood, Shottenden Hill, &c.). 



( Part of the sandy pebble-bed 



of West Kent (Sunderidge near 



Bromley, &c.) 



Sands, shell-beds, mottled "i 

 clays, lower pebble-beds (un- 

 fossiliferous and local), and 

 pebbly greensands of West 

 Kent and of part of East Kent. 

 Mottled plastic clays, sands, 

 &c. of the western part of the 

 London Tertiary District and 

 (^ sands of East Kent. 



l Sands, sandy marls, &c. 



Basement- 

 bed. 



Oldhaven 

 Beds. 



Woolwich 



and 



Reading 



Beds. 



Thanet 

 Beds. 



London 

 Clay. 



Having, I trust, clearly stated what is here meant by " Oldhaven 

 Eeds " a short account of the diiferent members of that series will 

 now be given. 



(a) At the bottom of this series at Upnor there is a thin irregular 

 layer of pale greenish-yellow sand, crowded with shells (Cyrena, 

 Ostrea, Ceritliium, Melania) and filling small hollows in the underly- 

 ing sand of the Woolwich Beds. This is not constant, being cut off in 

 many places by the pebble-bed above, the lower parts of the hollows, 

 however, being often left as separate patches. This bed is very 

 local; indeed I do not remember having seen it anywhere else, 

 though it may occur in places at the great Eeculvers section. Pos- 

 sibly, too, the thin bed of sand with shells which next underlies the 

 London Clay at the Brockwell Hall Brickyard, Dulwich '*, may be 

 the same as the above, which it is not unlike. 



(/3) The characteristic sandy pebble-bed which nearly everywhere 

 occurs at the bottom of this series, varies in thickness from a few 

 inches to rather more than two feet in the Canterbury and Reculvers 

 district. At the former place, and for a few miles to the west, it 

 often undergoes a great change in structure, the pebbles being re- 

 placed by a mass of sandy brown iron- ore, sometimes 5 feet thick. 

 Here and there a few pebbles occur below, and scattered through, 

 the stone, which in some places contains many casts of shells. At 

 one pit near Boughton-under-Blean all the fossils are of estuarine 



* See Geol. Siu-vey Mem. on Sheet 7, pp. 23, 24. 



