22
THE ESSEX NATURALIST
Indications of Climate
The fauna is not extensive enough to give a very clear climatic
picture. There is nothing in the list which is not now British.
The most obvious "northerner" is Agabus congener, with which
one Lexden specimen is compared, for it extends over the whole
of Fennoscandia and in Britain occurs mainly in Scotland, the
Lake District and North Wales—but it has also been recorded in
three southern English counties. The rest of the beetles do not
support any interpretation of a rigorous climate. Plateumaris
braccata does not extend farther north than Yorkshire in Britain.
In particular the three species Rantus grapii, Colymbetes fuscus
and Donacia semicuprea have present-day distributions whose
northern limits are shown in Fig. 3.
The insect fauna therefore suggests a climate no more severe
than that of the southern third of Sweden at the present day, and
it need not have been any different from Essex now.
It will be noted that Wollaston's statement about none of the
remains being British is completely wrong.
General Conclusions (F.W.S., A.J.S., and R.G.W.)
Although the botanical evidence indicates an environment in
which trees were scarce, this does not necessarily mean that the
climate was arctic. If we take into account also the occurrence
of Dicerorhinus hemitoechus and the general tenor of the insects,
we are forced to the conclusion that the climate was temperate—
possibly a little cooler than to-day, but not even necessarily so.
The environs of the Lexden pool must have been extensive open
grassland to explain the paucity of tree pollen. Very clearly,
however, Wollaston's invocation of a "Lusitanian" climate is
unwarranted. There is nothing in the fauna or flora of a
Mediterranean character.
The age of the deposit is uncertain. One can only point out
that the height relationships of the terrace are very close to those
of the Ilford Terrace and the association of Dicerorhinus
hemitoechus with a primitive form of Mammuthus primigenius
supports such a correlation. It would be stretching limited
evidence too far to go beyond this or to attempt to place the
Lexden deposits in the Hoxnian rather than in the Eemian Inter-
glacial on our present knowledge.
References
Fisher, O. (1863). On the Brick-pit at Lexden, near Colchester.
Quart, J. Geol. Soc. London, XIX: 393.
Sparks, B. W. & West, R. G. (1959). The palaeocology of the interglacial
deposits at Histon Road, Cambridge. Eiszeitalter und Gegevwart,
10: 123.