Henry Bassett, Jun. — Oldhaven Beds at Ipswich. 455 



the pit is now being filled up. It seems as though, the two types of 

 pebble-bed shaded more or less into one another, and, although 

 occasionally the two occur one above the other, this is not usual. 



The following represents a section at a spot where both types 

 occurred together : — 



Feet. 



London Clay. Brown and grey bedded clay (with pyrites and seleuite) ... 14 

 Basement-Bed op i Brown bedded loam with two thin dark clay bands 



London Clay. \ containing pyritised fragments of wood, etc 3 



r. -D f Bed of well-roiled black flint pebbles OJ 



0^°«^^^^^^^°^-{ Clay pebble-bed 2 



■n -R i False-bedded, pale yellow sand, with occasional small 



READING iiEDS. j pebblcs of clay and raco near the top (seen) 6 



Another point of interest is that the shells only occur in those 

 parts of the pebble-bed which contain a considerable amount of 

 clay pebbles, only sharks' teeth occurring in the parts consisting 

 entirely of flint pebbles. This, no doubt, is due to the clay having 

 protected the shells to a certain extent from the solvent action of 

 percolating water. 



Ou glancing at the list of shells from this spot it will be seen 

 that nearly all of them belong to marine genera. This, of course, 

 might be considered a good reason for including these pebble-beds 

 in the basement-bed of the London Clay rather than classing them 

 as Oldhaven Beds. In spite of this, however, it seems to me that 

 the beds under discussion have as much right to be considered as 

 belonging to the Oldhaven Series as the beds in many other places 

 whose right is hardly questioned. In many cases the Oldhaven 

 Beds difi'er from the overlying London Clay and the Woolwich and 

 Beading Beds below chiefly in their lithological characters, which 

 indicate strong currents and disturbed conditions. The assemblage 

 of marine and fresh- water shells is by no means always found. 

 Take, for example, the case of the Oldhaven Beds at Sundridge 

 Park or Elmstead Cutting, Kent. Fossils are exceedingly 

 abundant there, the most common being species of the genera 

 Ostrea, Pectunciilus, and Corbula ; fresh- water shells, however, form 

 only a very small percentage of the total, and they, moreover, 

 nearly always are very much worn and have the appearance of 

 drifted shells, while the marine shells are not worn at all. The 

 beds here also show well two other characteristics of the Oldhaven 

 Beds, namely, the sudden way in which they thicken out and 

 the erosion of the underlying Woolwich and Reading Beds. Thus, 

 in a distance of about a quarter of a mile, the Oldhaven Beds at 

 Sundridge Park tunnel thicken from about a couple of feet to 

 nearly 40 feet, at the same time scooping down into the underlying 

 beds, so that finally they rest on Thanet Sand.^ Both these features 

 are seen, though on a smaller scale, in the corresponding beds at 

 Ipswich, the sudden variations in the thickness of the beds having 

 already been mentioned, while the erosion of the Reading Beds can 

 be inferred from the occurremce of the clay pebbles. 



The occurrence of the bed of clay pebbles containing large 



1 See Whitaker, " Geology of London and Part of the Thames Valley," vol. i. 



