File:The Quarterly journal of the Geological Society of London (13365240155).jpg

1850..
PRESTWICH ON THE LOWER TERTIARY STRATA.
259
tiaries. They enable us to trace the sands and mottled clays with-
out much difficulty over a large district ; but although these lower
tertiary beds are so frequently worked, and their relation to the
chalk underlying them is often shown, the sections nevertheless
rarely exhibit the overlying lower beds of the London clay.
At the base of the chalk hills between Inkpen and Basingstoke
there are a considerable number of sections, more or less perfect,
of these lower tertiary beds. One of the best and most illustrative
is in a brick-field at Itchingswell, two miles westward of Kingsclere.
(See fig. 4.)
Fig. 4. — Section at Iti/ / //
d ~~t b
b. London clay ; upper part bluish grey passing down into brown ; sandy at base ; a few calca-
reous concretions, and a few fossils. (The lower part of this bed should perhaps be in-
cluded in "c")
c. Ferruginous sand and iron sandstone mixed with green sand, and full of round flint pebbles,
varying in size from 1 to 14 inches in diameter ; no fossils except a few teeth of Lamnce,
d. Mottled clay and sands.
The chalk outcrops at a distance of about 50 feet from " e."
Organic remains of stratum "c," at Itchingswell.
Cancellaria laeviuscula, Desh. Nucula.
Cytherea obliqua, Desh. Panopsea intermedia, Sow.
Ditrupa plana, Sow. sp. Pectunculus Plumsteadiensis, Sow.
Ostrea, large species.
These fossils occur at the base of "6," just above "c."
A section at Chinham, one mile and a half north-east of Basing-
stoke, on the line of railway from that town to Reading, showed the
basement conglomerate bed passing gradually upwards into the mass
of the London clay. The organic remains were numerous, but in a
very friable state. (See fig. 5.)
Fig. 5. — Section at Chinham.
•London clay ; thin-bedded brown clay with-
out fossils passing downwards into dirty
yellow sands with seams of brown clay,
and then into a sandy light-coloured clay
" c," with seams of green sand and a few
round flint pebbles occasionally concreted
into small flat masses by carbonate of
lime ; traces of vegetable matter ; shells
abundant in the seams and patches of
green sand, but very friable and generally
in the state of casts. Average thickness
of " c" 5 feet.
Mottled red and brown clays ; upper surface slightly uneven and worn.
The junction with the chalk, which crops out immediately on the
opposite side of the small valley formed in these lower sands, is not
exposed.
Organic remains of stratum '^c,*' at Chinham.
Cassidaria striata. Sow. Fusus, small species.
Cardium Plumsteadiense, Sow. Modiola elegans, Sow.
Cytherea ovalis, var. ?, Sow. Natica glaucinoides. Sow.