J. S. GARDNER ON THE LOWER LONDON TERTIARIES. 197 



13. On the Lower Eocene Section between Reculvers and Herne 

 Bat, and on some Modifications in the Classification of the Lower 

 London Tertiaries. By J. S. Gardner, Esq., F.G.S. (Read 

 January 10, 1883.) 



The Lower London Tertiaries were defined by Presfcwich as con- 

 sisting of three divisions. Two of these were relatively homogeneous 

 in composition ; but the third was made up of very varied materials. 

 The extreme care and accuracy with which these divisions were 

 traced out over the whole of the Eocene area in England, and sub- 

 sequently correlated with those of the French area, led to their speedy 

 and universal recognition. No modifications in this classification were 

 even suggested until 1866 *, when Mr. Whitaker, while unreservedly 

 adopting Prestwich's divisions of" Thanet Beds " and " Woolwich and 

 Beading Beds," making, indeed, copious use of his observations, separated 

 portions of his " basement-bed " of the London clay, where this was 

 assigned any considerable thickness, together with a small portion 

 of his Woolwich and Reading beds, as " Oldhaven Beds," and thus 

 almost restricted the " basement-bed" to the inconsiderable thickness 

 of coarser material which nearly everywhere forms the base of the 

 London Clay. Almost the only criticism that can be urged against 

 Prestwich's classification is that he places the " basement-bed " of the 

 London Clay in a different group of the Eocenes from the London 

 Clay itself, his nomenclature implying a closer relationship than he 

 admitsf. But the Survey, on the other hand, have unfortunately 

 adopted a name (" Oldhaven") which not only does not exist on the 

 maps, but is scarcely known at the locality, an inquiry for " Oldhaven 

 Gap," where the beds are typically developed, being useless even at 

 the gap itself, which is known and mapped as " Bishopstone Gap." 



Stratigraphieally, however, and perhaps as measures of time, these 

 divisions leave little to be desired ; and it is only from certain other 

 points of view that this proposal to modify them may be justified. 



Before entering into the details of the subject, it is advisable at 

 least to endeavour to realize as far as possible the conditions under 

 which the Lower London Tertiaries were produced. Although this 

 must always to a great extent be a matter of theory and mere, con- 

 jecture, a large amount of inference may be safely drawn from our 

 actual present knowledge. 



Of all facts patent to those who study the Eocenes in our own or 

 in adjacent areas, the near proximity of land and fresh water through- 

 out the whole series is the most obvious. Next, speaking of marine 

 formations only, it is observed that the faunas which succeed each 

 other stratigraphieally are by no means the most closely related to 

 each other palaeontologically, but that beds separated by great vertical 

 thicknesses contain faunas far more nearly allied than do those in 



* Quart. Journ. Geol. Soc. vol. xxii. p. 412. 

 t Whitaker, I c. p. 413. 



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