UPPER GREENSAND. 389 



the island at the southern base of the Chalk hills to Sandown Bay ; 

 and it is exposed again to the south between Chale Down and 

 Dunnose. It consists of calcareous sandstones, chert-beds, and 

 yellowish-grey micaceous sands, having a thickness of about 

 150 feet. The higher beds have been quarried on the north side 

 of Shanklin Down, and in other places, for building-stone ; while 

 the cherty strata furnish an excellent stone for road-mending.^ 



The following section at Ventnor was noted by Mr. Mark W. 

 Norman : " — 



Chalk. Chloritic Marl 8 feet. 



i Chert and sandstone 24 ,, 



Sandstone and rag beds 62 ,, 



Yellow sands 30 ,, 



Rag I „ 



The Upper Greensand about Wantage and Wallingford, in 

 Berkshire, consists of soft dark-green sands (20 or 30 feet in 

 thickness), resting upon white siliceo-calcareous strata.^ The total 

 thickness of the formation at Woolstone is 60 feet, and at Didcot 

 upwards of 70 feet; while at Cuxham, near Watlington, in Oxford- 

 shire, it is 70 feet. (See Fig. 64.) 



Near Prince's Risborough, Mr. Whitaker describes the Upper 

 Greensand as consisting almost wholly of a soft white crumbling 

 sandstone, sometimes calcareous, overlaid by a thin deposit of 

 clayey greensand. The formation is not exposed further in a north- 

 westerly direction than West-end Hill, near Cheddington, and 

 Ivinghoe, in Buckinghamshire.* In Cambridgeshire and adjoining 

 counties the ' coprolite ' beds (Cambridge Greensand) were at one 

 time considered to represent the Upper Greensand, but while 

 carrying on the Geological Survey in Bedfordshire and Hertford- 

 shire, Mr, Whitaker concluded (in 1868) that the nodule-bed was 

 really the base of the Chalk Marl, an opinion which has been 

 corroborated by the researches of Mr. Jukes-Browne. (See sequel.) 



In the deep boring at Harwich the thickness of the Upper Green- 

 sand has been estimated to be about 20 feet, and in the Carrow 

 boring, Norwich, about 7 feet ; but its presence in these localities 

 is considered somewhat doubtful. In the Kentish Town well- 

 section the thickness, according to Mr. Whitaker, is 13 feet 9 

 inches.^ 



In Wiltshire the Upper Greensand has a thickness of from 60 feet 

 at Swindon to 150 feet further south; in the upper part it consists of 

 sandstone and chert, and in the lower of light brown and grey sands 

 with glauconitic grains. Near Wroughton the boundary of the Gault 

 and Upper Greensand is much obscured by landslips.*^ The Green- 



1 Geol. I. of Wight, p. 24. 

 "^ G. Mag. 1882, p. 440. 



3 E. Hull, Explan. Sheet 13 (Geol. Survey), p. 18. 

 * Jukes-Browne, Q. J. xxxi. 265. 

 ® Guide to Geol. London, ed. 4, p. 20, 



^ W. T. Aveline, Explan. Sheet 34 (Geol. Survey), p. 34 ; see also Godwin- 

 Austen, Q. J. vi. 461. 



