90 GEOLOGY or THE ISLE OF WIGHT. 



as of the other Secondary Rocks. The Upper Chalk becomes 

 devoid of flints but very nodular in the lower 20 feet, and has as its 

 base a conspicuous band of green-coated nodules, about 4 inches 

 thick (Chalk Rock), below which the section runs as follows ; — 



Near Punfield Cove. 



fHard, rough, and lumpy chalk 

 Smoother chalk, thick-bedded, with partings 



Middle Chalk, ,l,f™''^^ p" - - - - 



,,, p . '< Melbourn Rock . . - - 



^^ ■ Smooth chalk with conchoidal fracture, with 



several partings of marl . . - 



Fine marl (? Belemnitella Marl) 



r Alternations of chalk and marl in beds of 



Lower Chalk, J 1 to 2 feet, with an occasional line of 



132 feet. | nodules, some of which are green like those 



L of the Chalk Rock - - - 132 



243 



2. The ISoiithern Doions. 



The outliers of chalk, which cap these hills, consist of the 

 Lower, Middle, and a mere film, if any, o£ the Upper Chalk, the 

 Chalk-with-flints (and according to M. Barrois the whole of the 

 Middle Chalk) having been denuded away. The tops of the hills, 

 however, are so thickly overspread with flint gravel, a residue of the 

 mass of beds that have been removed by subaerial agencies, that it 

 is not possible to say what is the highest bed present beneath this 

 covering. 



In the outlier of St. Catherine's Down the dip is at a gentle 

 angle to the east-south-east — that is, about the same as that of 

 the Lower Cretaceous Rocks seen in the coast.* The thickness of 

 chalk forming the outlier amounts to about 180 feet, and must 

 therefore belong wholly to the Lower Chalk. But it is noticeable 

 that the hill is capped with flint gravel, a relic of the Upper 

 Chalk, that must have been slowly let down from above by the 

 dissolving away of the chalk. The best exposures of the beds are 

 to be met with in a large marl-pit at the north end of the outlier. 

 They consist of alternations of chalk and marl generally in thick 

 beds, and are traversed by a small fault running about E. 10° N. 

 with a downthrow to the south. 



A second outher, scarcely separated from the first, occurs on the 

 brow of Gore Cliff. The beds, well exposed along the cliff, 

 with the underlying Chloritic Marl, are very fossiliferous. This 

 outlier evidently forms the northern flank of a chalk-hill, of 



* It was stated by Captain Ibbetsoa that an unconformity between the Upper 

 and Lower Cretaceous llocks was visible in the Isle of Wight {Quart. Jotirn. Geol. 

 Soc. vol. iii. n. 315. See also Judd on the Punfield Formation, ib. vol. xvii. p. 221, 

 1871). This statement was founded on a mistaken idea that the Chalk of the 

 Southern Downs is horizontal, while the easterly dip of 2° of the lower rocks, as 

 seen in the cliff section at Atherfield, was supposed to be maintained beneath them. 

 Neither supposition is correct. 



