14 
the stream that separated the Isle of Thanet from Kent, are situated 
on the Thanet sands. 
These sands, partly underlying London and the north of the 
Thames, here a permeable bed, form, from their geological position, 
a water-bearing stratum, the source in part of the London_ artesian 
wells. They are not found in the Hampshire basin, but are represented 
in Belgium by the Landenian sands, and in the Paris basin by the 
sands of Bracheux. ‘They are of marine origin, and the fossils in- 
dicate, according to Mr. Prestwich, a comparatively temperate 
climate. In this vicinity, they are unfossiliferous ; but Mr. Cooper 
has obtained a shark’s tooth (Lamna) from them.* 
These marine beds are succeeded by the next, or Woolwich 
and Reading series,} partly of fluviatile, estuarine and marine 
origin, showing a further change in the physical conditions of the 
district—evidence of land surfaces down which rivers flowed, 
teeming with molluscous life, which have left traces of the shell 
beds at Park Hill, Duppas Hill, East Croydon Station, and 
the Croydon Sewage and Gas Works, Waddon,} from whence 
* This formation which up to this neighbourhood forms but a narrow tract between 
the other Eocene beds and the Chalk, now gets much thicker, takes up a larger space at 
the surface, and runs out in spurs with well marked features, and for the most part not 
capped by the Woolwich Beds. It may be well seen in the road-cuttings at Beddington, 
which have the usual picturesque look of the deep-cut lanes of a Thanet Sand country, 
and in a railway cutting south of the village. 
Another spur spreads over Waddon Court to the southern side of the railway ; and 
a third, with a small capping of gravel and of the Woolwich Beds forms Duppas Hill, on 
the western side of Croydon, and reaches to within a quarter of a mile of Hayling House, 
on the hill just to the east, where the sand is again hidden by gravel. 
On the eastern side of the Croydon valley this formation and the Woolwich Beds 
together form one well-marked escapement. The junction of the former with the chalk 
is well shown in the railway-cutting on the northern side of Coombe Lane, and in a large 
pit about a quarter of a mile further east. At the former place the junction is rather 
irregular, and shows a slight dip to the north; at the latter it is even and regular. At 
both there are flints at the base of the sand, which in this neighbourhood is from 30 to 50 
feet thick.—Whitaker, ibid, p. 61. 
+ This series so named by Prof. Prestwich, from the circumstance that the leading 
characters of the deposit are well seen at those two localities, is an intricate and curious 
series. At many places it consists of a bright red clay, mottled with various other 
colours ; at others these clays are mixed with beds of sand; elsewhere the series is com- 
posed of beds of pebbles, with layers of sand and carbonaceous clays, and further east of 
silicious sands only. In some places eastward it contains entirely marine fossils ; nearer 
London, a mixed group of brackish and fresh-water fossils prevail exclusively; whilst 
the mottled clays further westward contain no fossils at all (except Ostrea Bellovacina 
at their base), and all these are on the same horizon.—‘‘The Ground Beneath Us,” 
1857, p. 58. 
{ At Duppas Hill, Croydon, a small outlier is for the most part hidden by the 
gravel that caps the hill. There was once a brickyard here, in the plastic clay. 
Some very large and fine specimens of Ostrea Bellovacina were got from the 
bottom bed in the excavations for some new houses (1870) on the southern side of the 
Waddon Road, between the parish church and the railway, and with them avery fair 
specimen of a fossil lobster (Hoploparia gammaroides), the first I believe found in this 
bed, which is in the collection of Dr. A. Carpenter, of Croydon. The section was :— 
aos Mottled plastic clay. 
Reading Beds. ) Cjayey green sand. 
Thanet Sand. 
In the old gravel pit at the south-eastern corner of the outlier (and north of the 
road) there are the same beds beneath the gravel, but both the plastic clay and the green 
sand are very thin. 
There is perhaps a patch of the Woolwich beds on the Croham Hurst outlier, 
south of Croydon, though any of this formation that may be present is hidden by the 
thick mass of flint-shingle, forming the top of the hill and belonging to the Oldhaven 
Beds.—Whitaker, Mem, Geol. Surv., vol. iv., p. 111. 
