Geoscience Reference
In-Depth Information
sea up to a level 25 m above the present sea level. The next episode recorded in the
sequence represents the deposition of gravels, sands and muds in a river delta that built
outwards into a lake. It seems that the Nar Valley was dammed at this time by Wolsto-
nian ice sheets (180,000 years old), which must have entered the Fenland basin from
the northwest, creating a lake.
A final dramatic episode in the history of this Landscape is marked by the Hun-
stanton ice-laid till, which was deposited just inland of the present coast of northwest
Norfolk during late Devensian times, about 20,000 years ago. The topography of the
landscape in these recent times must have been quite similar to that of today, because
the Devensian ice sheets that spread across the North Sea basin were stopped by slopes
similar to those that currently face the Fenland Basin and the North Sea.
Landscape C: North Norfolk coast and the Late Cretaceous Chalk hills
The Chalk hills of Norfolk form more than half of the land area of Area 16, forming a
broad belt trending roughly north-south, with the chalk strata tilted to the east by less
than 1 degree. Most of the Landscape is covered by a thick surface blanket, so the easi-
est way of looking at samples of the Chalk is to look at the local buildings that are made
from it. White Chalk is often used as a building stone and is generally quarried from
the particularly resistant layers known as 'clunch'. Flints from the Chalk (Fig. 296) are
also commonly used as a facing material.
FIG
295.
Wall faced with blocks of gingerbread Carstone bedrock.
FIG
296.
Flint nodules in Chalk at West Runton, 2 km east of Sheringham.
