File:The Quarterly journal of the Geological Society of London (13071044613).jpg

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PEOCEEDTNGS OF THE GEOLOGICAL SOCIETY.
.Dec. 19,
stiff whitish clay, wholly unstratified, containing much chalk debris
and occasional quartzose erratics. Its appearance is so like that
of the Bonlder-clay (No. 7 of figs. 2 & 3) which caps the high land
on each side of the valley, that but for its position it could not be
distinguished from it. It occurs at a slight elevation from the bot-
tom of the valley, resting on the chalk, and is from 9 to 15 feet in
thickness. In one part of the pit it is capped by laminated sands
and clays, which since their deposition have been subjected to dis-
turbance and denudation, as represented in the accompanying section.
Pig. 1. — Section exJiibitecl hy the pit at Trowse Junction, being that
shown below the Railivay EmbanTcment in Jig. 2.
1. Chalk. c. Laminated blue clay, passing up
a. The clay. into
b. Yellow sand, passing up into d. Yellow sand.
e. Warp.
In May 1866, Mr. Searles Y. Wood, Jun., while examining the
country for the purpose of tracing the extension of the ChiUesford
beds in this district, discovered a still more extensive development
of what I believe to be the same deposit, about three miles further
down the valley, near the Lunatic Asylum, and within a few hun-
dred yards of the well-known Thorpe crag-pit. In this case there
are no laminated beds overlying it, and the clay is of a somewhat
darker colour ; but in other respects it corresponds with that of the
last section, resting as in that case on the chalk, and but slightly
elevated above the level of the Eiver Yare. Not only is there here
a large pit where the clay is exposed, but the turnpike road is cut
through it for some distance.
Pigs. 2 and 3 will show the position of the deposit relatively to
the other beds of the district.
It will be observed that, in fig. 3, the Boulder-clay No. 7 is not
represented as occurring on the north side of the valley, its place
being supplied by the coarse plateau gravel No. 8. This gravel ex-
tends for some miles over what is known as Mousehold Heath, a pla-
teau to the north-east of Norwich, forming a sheet, in places, from
15 to 20 feet in thickness. It has apparently been formed by the
destruction of the Boulder-clay No. 7. That the Boulder-clay No. 7
formerly existed on this side of the valley is shown by the presence of
outliers further to the east. One of these outliers (that at Strump-
shaw) is overlain by the gravel No. 8.