460 
THE CRETACEOUS ROCKS OF BRITAIN* 
Passing into Buckinghamshire, the base of the Melbourn Rock 
is exposed in a small pit by the farm called Brimmers, south of 
Princes Risborough, about 6 feet of hard rough nodular rock 
being seen in 1885. 
A complete exposure of the Melbourn Rock is shown in the 
quarry near Butler’s Cross or Chalkshire. The details of the 
Lower Chalk here have been given on p. 179 ; those of the 
Middle Chalk are as follows : — 
o U 
-Q O 
Soil and thin-bedded chalk, with a few nodules - 
( Marly chalk with loose nodules and a layer of hard 
white compact rock ------ 
Hard rough yellowish nodular rock in two beds, with 
a layer of greenish-grey marly chalk between 
Laminated marly chalk ------ 
Hard whitish rock, with many layers of small 
nodules, in three beds. 
Lower Chalk- - - 
feet 
o 
Ij 
3i 
i 
5 
24 
The upper part of the Rhyne. Cuvieri zone is exposed in the 
quarries at the east end of Bacombe Hill, w T est of Wendover; it 
is hard, cream-coloured, and lies in fairly regular beds. The lower 
beds and the Melbourn Rock can be seen in the road-cutting 
nearer Wendover. 
Between Wendover and Tring these beds are seen in a quarry 
on White Hill, a mile north-east of Halton ; the lowest consist 
of hard nodular yellowish chalk with partings of shaly marl and 
contain Rhynchonella Cuvieri above are thick beds of hard heavy 
chalk crowded in some places with fragments of Inocemmus 
mytiloides. Calerites subrotundus also occurs. These beds pass 
up into the chalk of the overlying zone. 
The Melbourn Rock is clearly exposed in a quarry by the side 
of the main road east of Buckland Wharf, the succession seen 
in 1884 being : — 
feet. 
Rubbly chalk, passing down into hard yellowish nodular chalk 
with Rhynch. Cuvieri -------- 
7 Hard and massive yellowish rock, rough and 
Mel- nodular on a weathered face - 
bourn , Thin parting of grey marl. 
Bock. i Hard yellowish rock enclosing several layers 
of small nodules ------- 
Lower f Belemnite Marls (see p. 181). - 
Chalk. I White blockv chalk - . 
8 
4 
4 
3 
10 
Terebratulina Zone. 
The best exposure of the Terebratulina zone in Oxfordshire 
is a quarry near Potter’s Farm, nearly three miles east of 
Wallingford. The lower level shows about 15 feet of soft 
white blocky chalk, with a few large scattered flints; 
about 3 feet from the top is an irregular layer of grey laminated 
marly chalk. The upper level was disused and talnsed in 1886. 
The chalk is burnt for lime. 
