File:The Quarterly journal of the Geological Society of London (13364942025).jpg

1849.. AUSTEN ON THE VALLEY OF THE ENGLISH CHANNEL. 89
Eastern counties. These rocks belong to the Northern ocean area, and
must have passed from that into the area of the English Channel.
We thus arrive at the precise date at which the English Channel be-
came sufficiently depressed so as to be occupied by sea, as well as at
the date of the subsidence of the chalk strata along the north and
south line before indicated, and which produced the Dover Straits.
The movement of the drift materials over the Northern and German
ocean area during the pleistocene period was from north to south ;
and when the Channel valley was opened to the waters of that period,
the drift was continued with a like direction into that area : in hke
manner the chalk-flints of the eastern portions were made to travel
west ; and in the meagre character of the marine fauna of the raised
beds of the Channel, we see that it was influenced by arctic currents,
and not southern ones as at present.
The levels of the portions of the littoral zone of the pleistocene
period in the English Channel show the depression of that area to
have been rather lower at that time than it is at present. There would
also appear to have been an intermediate level, of which the shingle bed
between Brighton and Rottingdean is a familiar illustration — a level
which was of sufficient duration to allow of the formation of cliffs ; the
Elephant bed, as it is named by Dr. Mantell, belonging to a vast series
of deposits, to be noticed in the sequel, and of the age of the drift.
Fig. 4.
Fig. 3.
The drift beds are the uppermost portion of the pleistocene group ;
and under the name of diluvium were long since traced down into the
Thames valley, and fully described as to their characteristic admix-
ture of northern materials by Dr. Buckland. On the south side of
the Thames they may be seen extending over the surface of the ter-
tiary district, in many instances overlapping it, and resting on older
denuded strata. But as we approach the district where the physical
features of the AVealden begin to show themselves, these accumula-
tions diminish in thickness, till at length we reach an area over which
no trace whatever of them is to be fomid. This termination of the
pleistocene drift takes place by a well-defined marginal bed, of which
clean sections have recently been exhibited in the cuttings of the
Reading and Reigate Railway. The detail of about twenty miles of this
coast-line, where it ranges across the county of Surrey, will be sufficient,
as all that I wish is to connect the pheenomena north of the Weald