1846.] PRESTWICH ON THE ISLE OF WIGHT TERTIARIES. 241 



bf^en practicable without a further hydrographical change ; whereas 

 at both Alum Bay and White ClifF Bays we find them overlaid by 

 several hundred feet of marine beds : it therefore follows that a con- 

 siderable deepening of the sea must have taken place subsequent to 

 the formation of the Bognor beds, and prior to or during the accu- 

 mulation of the overlying sands and clays forming the mass of the 

 London clay in the Isle of Wight, and at Bracklesham Bay and 

 Barton. 



That this disturbance was of greater importance than any of the 

 preceding ones in the Eocene period, is evident from the more greatly 

 altered palaeontological and lithological conditions of the deposits. 

 In France the preceding argillo-siliceous system is succeeded by the 

 M'ell-known calcareous system of the calcaire grossier, and in En- 

 gland by the argillaceous system of the London clay. The change 

 however is not sudden ; the lower beds, both in France and Hamp- 

 shire, still continue to exhibit some evidence of similar origin, and 

 in the former country the ' Glauconie grossiere ' underlies the cal- 

 caire grossier ; while in the latter we find at the Isle of Wight a like 

 predominance of argillaceous and calcareous greensandsin the lower 

 London clay beds. 



The period in question was one of slow but considerable transition ; 

 and as such it is characterized by coarse drift sands and variable 

 strata, resulting from the repeated change of land and sea levels. 

 Whether the whole of the series between the Bognor beds and the 

 Headon Hill sands at Alum Bay and White ClifF Bay are synchro- 

 nous, is a point which requires for its elucidation a careful examina- 

 tion of the district between these two places. I think it is probable 

 however that they will be found to be so. At Alum Bay no animal 

 remains have hitherto been discovered in the lower part of this series, 

 although at White ClifF Bay they abound ; and at both places the 

 remains of vegetables and plants are common. Should a further 

 palaeontological examination confirm the view that the Bognor beds 

 are synchronous with the * Lits coquilliers,' then the superposition 

 of the strata between them and the upper London clay will agree 

 with that of the glauconie grossiere. In both cases the action of 

 strong currents in the production of coarse sand and gravelly beds is 

 exhibited, accompanied always by more or less green-coloured sand. 

 Although perfectly distinct in lithological appearance, the fossils of 

 the glauconie grossiere can scarcely be distinguished from those of the 

 lower calcaire grossier, into which it passes ; and of these two divi- 

 sions this series of beds in the Isle of Wight may therefore prove to 

 be the equivalents, although in greater development. The Veneri- 

 cardia planicostata, Turritella sulcifera and Nummulites Iccvigatns-, 

 &c., abound alike in both countries in the coarse sandy lower beds. 



It is notwithstanding the case, that in this lower part of the series 

 the number of species at present found in the Isle of Wight is not 

 sufficiently great to establish an extensive comparison. In the range 

 of these beds further to the eastward they become however highly 

 fossiliferous ; for although their superposition is not exhibited, 

 there can be, I think, little doubt that the Bracklesham Bay beds 

 belong to this period, as the mineral composition is the same ; and 



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