CHAPTER II. 



THE WEALDEN BEDS. 

 Introduction. 



These beds rise to the surface on the southern and eastern 

 sides of the Island, where they have been elevated along the 

 anticlinal axes of Brixton and Sandown. The entire area occupied 

 by them is very inconsiderable, not exceeding five square miles ; 

 and there is "no good section inland. On the coast, however, for 

 six miles from Compton Bay tc Atherfield, they are well exhibited 

 in the cliffs {see Plates T. and II.), and there is also a tolerably 

 fair exposure of them on the coast in SandoAvn Bay. The lowest 

 beds exposed in the Island are the variegated Wealden clays and 

 sandstones of Brook Bay. Judging from the section at Swanage, 

 where the whole of tlie Wealden formation is displayed, there may 

 be about as great a thickness of these beds below the sea-level in 

 the Isle of Wight, as is seen cropping out in the cliffs. 



The Wealden Beds include two different but perfectly conform- 

 able types, the one consisting of dark-blue or almost black shales, 

 evenly bedded and splitting into thin laminae, together with 

 layers of shelly limestone and ironstone, and very thinly laminated 

 " paper-shales," crowded with the shells of minute ostracoda 

 (Cyprids). Fossils are abundant in this type, though the number 

 of genera is somewhat limited. Paludina, Cyrena (Cijclas), and 

 Unio OQCxxv m profusion everywhere, and Vicarya {-^Cerithium^ 

 Melania, Potamides of previous writers) is abundant at Atherfield. 

 This type is found invariably at the top of the Wealden formation, 

 immediately under the Lower Greensand, but appears also to be 

 interstratified with the type now to be described. 



Fig. 1. Fig. 2. 



Cypridea spiniyera. Sow. Cyrena. 





Fig. 3. 



Pa hi din a Jiu v io ru m , Sow. 



The other type, under which the Wealden beds appear, is that 

 of red, green, and variegated marls and clays (curiously resembling 

 the Keuper Marl), with numerous included bands of sandstone of 

 variable thickness. The bedding is far from regular, and fossils 

 are comparatively scarce. A large freshwater shell {Unio vaJdensis, 

 Mant), dirfted wood in great abundance, the remains of fit^h, a^^ 

 the water-worn bones of terrestrial reptiles are met with throughout 

 the group. 



A 2 



