124 GEOLOGY OF THE ISLE OF WIGHT. 



CHAPTER X. 

 OLIGOCENE. 



Inteoduction. 



The Fluvio-marine or Oligocene Beds of the Isle of Wight 

 were first described by Webster, who divided them into Lower 

 Freshwater, Upper Marine, and Upper Freshwater, but treated 

 as extensions of the beds in Headon Hill a large series of fluvio- 

 marine beds really lying above the Upper Freshwater * It was 

 not till the year 1853 that the complete succession was satisfac- 

 torily made out, though Prof Prestwich had already, in 1846,t 

 suggested that the beds seen in Hamstead Cliff were higher than 

 any of the beds at Headon. In 1853 Edward Forbes showed that 

 above Webster's " Upper Freshwater " o£ Headon Hill, there is 

 found a thick series of beds divisible into several zones characterised 

 by distinct species of fossils. J A few years later, in 1856, the 

 observations on which Forbes had been engaged up to the date of his 

 death were published in the Memoirs of the Geological Survey, 

 but the incomplete state in which many of the notes were left 

 rendered it very difficult for Mr. Godwin- Austen, who edited the 

 book, to do full justice to Forbes work. The divisions and mea- 

 surements made by Forbes have been adopted with very little 

 alteration in the present Memoir. Later observers have some- 

 times grouped the beds differently ; but this grouping is so much a 

 matter of opinion, and there is such an entire absence of real breaks, 

 that until stronger evidence is brought forward it seems unnecessary 

 to depart from the classification and nomenclature adopted by 

 Edward Forbes. 



The following brief summary of the views taken by some of 

 the able geologists who have written on the geology of the strata 

 under notice, may not be out of place here. 



Professor Thomas Webster gave the earliest and perhaps the 

 best account of the Fluvio-marine series, founded on observa- 

 tions made in the years 1811-13, and contained in Sir Henry 

 Englefield's work on the Isle of Wight,§ published in 1816. In 

 those letters Professor Webster divided the section at Alum Bay 

 into Lower Freshwater, Upper Marine, and Upper Freshwater 



* Sir H. C. Englefield. A description of the Principal Picturesque Beauties, 

 Antiquities, and Geological Pheuomeua of the Isle of Wight. With Additional 

 Observations on the Strata of thu Island, &c. by Thos. Webster. (London, 1810), 

 p. 22G. 



f On the Occurrence of Cypris in a part of the Tertiary Freshwater Strata of the 

 Isle of Wight. Rep. Brit. Assoc, for 1846, Trans, of Sections, p. 56. 



J Quart. Journ. Geol. Soc, vol. ix. p. 259. 



§ The letters of Professor Webster are illustrated by large copperplate views of 

 cliffs and coast scenery which, for accuracy and spirited execution, have pcrhapi 

 never been surpassed as drawings illustrating geological phenomena. 



