CHALK. 415 



In West Kent and East Surrey the divisions of the Chalk have 

 been marked out by Mr. Caleb Evans ; the names Riddlesdown, 

 Purley, Kenley, Whiteleaf, and Marden belonging to places 

 between Croydon and Oxtead. 



The Riddlesdown Beds occur at Purley, and were formerly grouped as the 

 Upper Chalk of Kenley, hence the Kenley Beds now include only the Lower 

 Chalk of Kenley as originally described. The thicknesses of the divisions of the 

 Lower Chalk are given approximately in the Table (p. 403). Galerites coiiicus is 

 characteristic of the zone of iMicrasier cor-aiigiiimtm. Mr. Evans observes that 

 Holastcr siibglobostis has not yet been obtained from Oxtead. The Chalk of Graves- 

 end is, he thinks, slightly higher in the series than that of Charlton and Croydon, 

 as it contains Bekmniiella fniicronaia. ' 



One of the most interesting discoveries in the Chalk with flints 

 was that of a granitic boulder which was found in a pit opposite 

 the ' Royal Oak' at Purley, near Croydon. It was a rounded and 

 waterworn block originally about three feet long, and was accom- 

 panied by some decomposing fragments of 'greenstone' and with 

 a mass of siliceous sand. Mr. Godwin-Austen considered that an 

 ice-floe was the agent by which alone such a block could have been 

 lifted from the coast and conveyed far out to sea. It probably came 

 from Scandinavia. Coal has been found in the Chalk near Dover.'^ 

 (See p. 395.) 



There are many pits where the Chalk may be studied and from which fossils 

 maybe collected, at Lewisham (Loam-pit hill), Charlton, Dartford, Camden Park 

 (between Bromley and Chiselhurst), Greenhithe, Northfleet, and Gravesend. 



In East Kent the total thickness of the Chalk has been estimated 

 at from 700 to 800 feet ; its thickness at the boring at Chatham was 

 proved to be 682 feet. The Chalk of the Isle of Thanet has been 

 described by Mr. Whitaker and Mr. G. Dowker, while an excellent 

 description of the Chalk of Dover was published many years ago 

 by William Phillips.^ The following table shows the chief litho- 

 logical divisions which have been made (see Fig. 69) : — 



Upper Chalk ( Chalk with few flints. Margate Chalk.* 



ooQ feet ' ) Chalk with numerous flints, both tabular and nodular, 

 or more' ) Broadstairs* or Ramsgate Chalk. ^ 



I Chalk with many flints. St. Margaret's Chalk.^ 

 Middle Chalk, | Chalk with few flints. Dover Chalk. ^ 



240 feet. \ Chalk without flints. Shakespere's Cliff, Dover. 

 Lower Chalk, 1 Grey Chalk and Chalk Marl. ) ,, ^ ,, 



180 feet. \ Chloritic Marl. (See p. 388.) ) Near Folkestone. 



Between Broadstairs and Ramsgate the beds are affected by a number of faults. 

 At Cliff End, Birchington, and Kingsgate Bay, many Ammonites are to be seen in 

 situ in the chalk, and in 1874 Mr. F. A. Bed well recorded as many as eighty-nine 



^ On some Sections of Chalk between Croydon and Oxtead, Geol. Assoc. 1S70 ; 

 P. Geol. Assoc, v. 149. 



- Q.J. xiv. 252, xvi. 326. 



3 T. G. S. V. 16. 



* These names were applied by Mr. Whitaker, Q.J. xxi. 395. 



^ These names were given by Mr. Dowker, from St. Margaret-at-Cliffe by the 

 South Foreland, north-east of Dover, etc. G. Mag. 1870, p. 466. 



