XXXH INTRODUCTION'. 



numerous chert-bands. There is a sharp lifchologieal break 

 between them and the superimposed Gauit clays, but, as (Gregory 

 (1895) points out, it is probable that the very top of the 

 " Lower Cfreensand " sands represents the beginning of the Gault 

 period. 



The following are the principal local deposits to be included 

 in the Lower Greensand (Gregory, 18D5, p. 100) : 



( Including Folkestone Beds of Folkestone, 

 excl. mannnillare zone. 



Sandgate Beds. 



1. Upper Aptian, . _ . , -. 



Phosphalic Beds o( Great Chart. 



I Bargate Bods of Guild ford. 



Fuller's Earth Series of Kutfield. 

 Faringdon Sponge Gravels. 

 I Lower Greensand of Upware and Bedfordshire. 



2. Lower Aptian, i Uythe Beds, and Kentish Rag. 



or < Main Chert Series of Godalming, HiiHlhoad, Ewhurst, 



Bedoulian. I and Leith Hill. 



3. Rhodanian ... Atherfleld Clay. 



The characteristic fossils of the above beds arc given by 

 Gregory (1895, p. 103) in the table copied on p. xxxiii. 



Thus the Lower Greensand beds are all marine, and they 

 represent the influx of the Aptian sea into the Wealden area. 

 All the divisions of this scries, according to Jukes-Browne 

 (1911, p. 295), "are the deposits of a shallow sea, rather deep 

 and muddy at first, but becoming shallower afterwards. These 

 beds are thickest to the south, and thinnest to the north, and 

 as an illustration of this it may be mentioned that they total 

 about 270 ft. at Maidstone, while at Chatham, only 8 miles 

 northward, they have shrunk to 40 ft.'' 



The exact limits of land and sea at this time are very 

 uncertain. That there was continental land to the north semis 

 established, though its shore-limits cannot be exactly traced : 

 also it appears evident that the arm of the sea of which the 

 Lower Grecnsands represent the successive floors, was in con- 

 nection with a long, south-easterly running gulf. Before the 

 true marine conditions of the Aptian established themselves in 

 the Wealden area, there must have been an intermediate period 

 which, according tojudd (1871), is represented by the Punfield 

 fluvio-marine series. 



