134 



GEOLOGY OF THE ISLE OF WIGHT. 



Lower Headon 

 Beds. 



Ft. In. 



Hard irregular band of sandy marl ; green 

 and brown and containing ferruginous 

 patches - - - - 2 to 4 



J Impure limestone, with an undulating irregu- 

 ' lar surface - - - - -06 



Pale-green marly sand or sandy marl 4 in. to 6 



Light-grey sand, with occasional bright ferru- 

 ginous stains in lines and patches. Pota- 

 momya at the base - - - - 1 6 



Verdigris-green marls and clays, with occa- 

 sional Paludina and lines of Potamomya in 

 the lower 6 inches - - - - 5 



Limestone (second ledge of the Chine). 

 Potamomya at the top, Limnaa, Planorbis. 



6 inches to 8 



Light-grey sands, becoming ferruginous to- 

 wards the bottom - - -13 to 16 



Line of lignite 1 inch. Hard band of variable 

 thickness 1 inch. Imperfect limestone 

 with Limncea, Planorbis, Paludina (Lignite 

 sometimes disappearing) 3 inches - - 9 



Light-green clay weathering brown and be- 

 coming harder and concretionary at the 

 base 4h, feet and sands, clays and marls at 

 the upper 3 feet - - - - 7 6 



The detailed sections ojiven above will show how thin and 

 variable are the minor divisions which go to make up the Headoii 

 Beds at the western end of the Island. This variabihty largely 

 accoimts for the difficulty that is sometimes felt in correlating 

 the beds at Keadon Hill with those in Col well Bay. But if 

 instead of attempting to compare isolated sections, certain marked 

 beds are followed continuously through the cliff, the connexion 

 becomes much clearer.* 



So many geologists visit this part of the Island that it will be 

 useful to add a few notes which may assist in the tracing of the 

 beds, and in the identification of the principal fossiliferous zones 

 where the connexion is hidden by landslips. 



To obtain a general idea of the structure of the beds, it will 

 be desirable first to examine the cliff from a boat at a distance of 

 half or three-quarters of a mile off Totland, though a very good 

 view may be obtained from the end of Totland Pier. By thus 

 first examining the cliff from a distance, one is enabled to re- 

 cognise the true structure of the Oligocene Beds, and is not so 

 liable to be misled by changes in the direction of the coast, or by 

 landslips — both fertile sources of error in estimating the relative 

 position or dip of beds in these soft deposits. 



Examined this way, the coast section shows that there is a high 

 nortlierly dip at the west end of Headon Hill, where the cliff runs 

 north and south, but that directly the trend of the coast changes so 

 that the cliff runs [)arallel to the axis of elevation, the dip apparently 



* A valuable horizontal section will be found in the paper by Messrs. Keeping and 

 Tawney, " On the Ueds at Headon Hill and Colwell Bay." Quart. Journ, GeoL 

 Soc, vol. xxxvii. (1881) p. 85, 



