LOWEE GREENSAND. 53 



division of the Folkestone Beds corresponding to the Carstone of 

 the Isle of Wight can be recognised on the MainLand. The 

 Carstone thickens in the Isle of Wight towards the north-east, yet 

 in the part of the Weald which is nearest to the Island, the 

 Folkestone Beds preserve their character of fine-grained quartz 

 sand up to within a foot or two of the base of the Gault. But on 

 the other hand the base of the Gault invariably consists of a more 

 or less pebbly grit, or of a sand with phosphatic nodules. At 

 Steep Common, near Petersfield, the Gault is green and sandy 

 towards the base, contains phosphatic nodules, and rests on a 

 *' brown and green sand, with large pebbles, and at one place 

 phosphatic nodules at base." ^ Further east, near Midhurst and 

 Pulborough, the base is formed by a pebbly grit, varying from 

 3 to 10 inches only in thickness, but conspicuous from its extreme 

 hardness and from its deep-brown or blood-red colour. The 

 pebbles in this band range up to half an inch in length, and 

 their presence, together with the gritty character of the rock, dis- 

 tinguish it, even apart from its hard ferruginous cement, from the 

 fine-grained sand of the Folkestone Beds. Elsewhere in the 

 Weald the base of the Gault is marked by nodules of phosphate 

 of lime or of iron pyrites, the hard pebbly grit described above 

 beino; confined to the neio-hbourhood of Midhurst and Pulborough. 

 Associated with the nodules, and likewise in a phosphatic state, 

 there are fossils of Gault affinities, viz.. Ammonites Beudantii, 

 A. mammillaris, Exogyra conica, Inoceramus Salamoni, Natica 

 fjaultina, and others, which have led to the remark that the 

 Folkestone Beds are more closely connected Avith the Gault than 

 with the underlying Sandgate Beds. In 1 859 Professor A. Gaudry 

 remarked that the sands at the top of the Lower Greensand at 

 Folkestone and Wissant in the Bas-Boulonnais contain Ammonites 

 mammillaris, and proposed to group these sands with the Gault on 

 that account.t In 1868 Mr. Topley noticed that at Folkestone 

 the Folkestone Beds both pass lithologically up into the Gault, 

 and also contain in their upper part " nodules with Gault-like 

 fossils," X and the same view of their relationship was taken by 

 M. Barrois, who mentions that not only are several fossils of the 

 Ammonites mammillaris zone, which in France is included in the 

 Gault, found in the upper part of the Folkestone Beds, but that 

 the brachiopods which occur in this zone are especially abundant 

 in the lower part of the same strata. He concludes that unless 

 the Folkestone Beds, like the A. mammillaris zone, are classed 

 with the Gault, there is no satisfactory upper limit to the Aptian 

 in England. § Mr. Price, on the other hand, would retain the 

 zone of A, mammillaris in the Upper Neocomian.|| 



* Geology of the Weald, p. 142. 



t Bull. Soc. Geol. de France, ser. 2, vol. xvii. p. 32. 1860, 



% Ou the Lower Cretaceous Rocks of the Bas-Boulonnais, &c. Quart. Journ. 

 Geol. Soc., vol. xxiv. p. 474. 1868. 



§ L'Age des " Folkestone Beds " du Lower Greensand. Ann. Soc. Geoloyique 

 duNord, t. iii. p. 23. 1875. 



11 Monograph of the Gault, 1880, p. 35. 



