Geoscience Reference
In-Depth Information
Some 450,000 years ago, the Anglian ice sheet covered - at its maximum extent-
the whole of this Landscape, deflecting the ancestral Thames to its present more south-
erly route. When the Anglian ice sheet melted, it left up to 30 m of ice-laid depos-
its. Most of the natural topography of the present-day Landscape is the result of river
erosion, which has cut shallow valleys through this and into the Early Tertiary mud-
stones.
Landscape E: The Fen edge
In the northeast corner of Area 13, the wide, shallow valleys of the Great Ouse and
Cam slope very gently towards the sea. The covering of the lower parts of these valleys
with mud and peat during the recent Flandrian rise of sea level has produced local arms
of very flat Fenland that is more fully described in Area 15.
The Fens surround the Isle of Ely (
e1
), a low upland that has been carved in Late Jur-
assic mudstones capped by Early Cretaceous Lower Greensand, an extension of our
Landscape
B
. Other local fenland features in the Cam valley are due to a patch of Late
Jurassic limestones a few kilometres across near the village of Upware (
e2
), and a ridge
of Anglian ice-laid material on which the village of Wicken (
e3
) stands.
FIG
243.
Former area of Soham Mere, just southeast of Ely (Fig. 237,
e4
). (Photography
held at Cambridge University Collection of Air Photographs, Unit for Landscape Model-
ling)
Wicken Fen (
e3
) is a nature reserve famous as one of the first places in the country
where determined efforts were made to preserve a rapidly disappearing natural envir-
onment. It was purchased as a small sample of Fen wetland environment at a time
when aggressive draining of the surrounding farmland was threatening its existence.
