TIIK CRETACEOUS SYSTEM 17-') 



\v.-:iM. Isle of Wight. Thirknew. 



K.-t. 



/"Folkestone Beds /Carstone ) 1crt . ortn 



v . I Sandgate Beds \Sand-rockSeriesJ 



1 | Hythe Beds . Ferruginous sands . . .280 to 520 



^Atherfield Clay Athertield Clay . . . 60 to 130 



Wn ,, / Weald Clay . Weald Clay . . . . up to 900 



B \Hastings sands Not seen . . . . up to 1000 



Wealden Beds. In the Wealden area the Wealden Beds 

 are divisible as follows, all the divisions being thickest in the 

 western and thinnest in the eastern part of the area. 2 Still farther 

 east borings through the Chalk between Canterbury and Dover 

 have shown that it gradually thins out ; thus at Brabourne it is 

 only about 56 feet, and in the Dover boring about 80 feet, while 

 at Fredville it is less than 40 feet thick : 



Feet. 

 Weald Clay ...... 900 to 350 



fTunbridgeSand . . . 380 to 150 

 Wadhuwt Clay . . . 160 to 100 

 Ashdown Sand . . .500 to 200 



1940 to 800 



The Ashdown Sand consists of soft buff or white sand and 

 sandstone : lit is 400 feet thick in Ashdown Forest, and forms 

 the high ground of Crowborough Beacon (800 feet high). Near 

 Hastings and Fairlight the lower part of this sand is replaced by 

 clays with interbedded sandstones. Plant -remains are the only 

 fossils, and it is the Fairlight Clay which has yielded the species 

 mentioned on p. 471 ; the stems of Tempskya, formerly called 

 Endogenites erosa, being common. 



The Wadhurst Clay, though never more than 160 feet thick, is 

 palaeontologically important, as it is rich in fossils, and contains 

 a bone-bed near Battle, from which many reptilian bones and 

 teeth have been obtained. It consists of clays and shales, with 

 bands of irregular layers of hard calcareous sandstone (Tilgate 

 stone). The fossils are Viviparus fluviorum, Cyrena media, teeth 

 of Lepidotus Mantelli, Hybodus basanus, Goniopholis crassidens, 

 with bones of Iguanodon and Megalosaurus. 



The Tunbridge Sands are similar to the Ashdown Sands. 

 Near Hastings their thickness is only 150 feet, but it increases 

 westward, a set of mottled clays and shales appearing in the middle 

 of the sands, and becoming of sufficient importance to deserve a 

 separate name, the Grinstead Clay. In the upper sands of the 

 Cuckfield district, which is often called the Tilgate Forest, there are 

 large concretionary masses of calcareous grit or sandstone, such as 

 were termed Tilgate stone by Dr. Mantell. It was in these masses 



