86 GEOLOGY or THE ISLE OF WIGHT. 



The evidence on which the base of the Upper Chalk has been 

 traced across the Downs to Carisbrook is somewhat scanty. 

 Middle Chalk is seen in the road at the top of Shorwell Shute, in 

 a pit at Cheverton, at Rowborough, and in a pit at Bowcombe, 

 while the Upper Chalk is exposed in pits on the southern and 

 eastern brows of Idlecombe Down. In one spot only, namely a 

 cart-road running northwards from Rowborough, a poor exposure 

 of the Chalk Rock may be seen. There are sections of Upper 

 and Middle Chalk close together in a lane leading up the hill to 

 the north-west from Bowcombe, but no section of the Chalk Rock. 

 In Carisbrook, however, this latter subdivision is well exposed. 

 We first see it in a cutting where three lanes meet near Clatter- 

 ford. Thence it runs along the south front of the hill on which 

 the castle stands (the hill being a portion of the escarpment of the 

 flinty Chalk), to a quarry near the Convent, where the following 

 section occurs : — 



Quarry east of Carisbrook Castle. 



Ft. In. 



Nodular chalk with grey flints. 

 Do. without flints 



Smoother chalk . - - 



Marl . - - . 



Upper Chalk <( Rough hard chalk - - - 



Dark marl . - - - 



Hard chalk - - - - 



Chalk f Line of green-coated nodules 

 (^ Rock \ Nodular chalk 



r Smooth chalk . . - 



Middle Chalk-^ Thick-bedded smooth chalk with partings o£ 



L marl at 2 to 4 ft. intervals - - 60 0-f- 



The occurrence of the nodular bed here was first noted by 

 Mr. Vfhitaker in 1865,* but, the Chalk-with-Hints not being 

 exposed at that time, he was unable to correlate it positively 

 with the Chalk Rock. The fault mentioned above runs W. 15° S., 

 very nearly along the strike of the strata which it throws 

 down to the north, its effect being to depress out of sight an 

 unknown thickness of the upper beds of the Middle Chalk. 

 The dip points a little west of north at 42°. 



The Middle Chalk and Melbourn Rock are exposed in an old 

 pit half a mile further east, on the west side of the Shide and 

 Gatcombe road, the section being as follows : — 



Pit on the east side of Mount Joy. 



Ft. In. 



Chalk in beds of 2 to 3 feet thickness, with bands of marl, 

 top not seen ...--- 



Thin-bedded chalk with bands of greenish marl, about 

 Chalk with yellowish nodules (Melbourn Rock), about 

 Marl (? Belemnitella Marl) - - - - - 



The pit is now occupied by farm-buildings, and the section 

 somewhat obscured. The nodular bed was first noticed and 



* Quart. Journ. Geol. Soc, vol. xxi. p. 403. 



