LOWER CHALK —OXFORD AND BUCKS. 
181 
Melbourn Rock, etc. (see p. 460) - - - 
r Yellowish, shaly marl, with lenticular lumps of hard 
chalk at its base - - 
Hard solid white chalk ^ 
Layer of soft grey marl ------- 
Tough greyish-white blocky chalk - seen for 
Lower 
Chalk. 
ft. 
16 
The upper part of the Lower Chalk was formerly exposed in a 
continuous section along the cutting of the L. and N. W. Railway 
notth-west of Tring Station. A small synclinal flexure brings in the 
Belemnite Marls about a quarter of a mile north-west of the station. 
Below these there is about 20 feet of whitish blocky chalk, passing 
down into greyish chalk, and just one mile from the station a bed of 
hard grey sandy “ rag ” rises from the floor of the cutting and forms 
a conspicuous band on each side as it rises toward the surface, 
its dip being about 2°. This bed is 2 feet thick, contains many 
green-coated nodules, and resembles that at Butler’s Cross above 
described. The chalk below is wet, dark grey and somewhat marly. 
Beyond this the face of the cutting is much obscured by fallen debris, 
but the Totternhoe Stone does not crop out till near the end of the 
cutting, about two miles from the station. 
Probably the beds undulate somewhat, for if the dip was con¬ 
tinuous the total thickness of chalk between the Totternhoe Stone 
and the Belemnite Marl would be double what it ought to be, and its 
real thickness is not likely to be more than 80 feet. 
i, 
2 
Fig 43.—Part of a Quarry at Pitstone, near Tring. 
3. Melbourn Rock 2. Belemnite Beds. 1. Whitish Lower Chalk. 
. A quarry near Pitstone, N.E. of Tring, exposes the Belemnite Beds 
near the entrance, the central band of white chalk being 
here 2 feet thick, while the layers of marl above and below are not 
more than 6 inches thick ; the lower one, however, yields the charac¬ 
teristic Belemnite (Actinocamax plenus). Fig. 43 is a rough 
sketch of this section 
