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18
SUPERFICIAL GEOLOGY
Superficial deposits making up the area of the Borough of
Greenwich are found to be (a) alluvium, a damp clay soil,
impervious to water and generally not more that about 15 feet
thick and (b) gravel and sand of various ages, highly permeable to
water and not usually more than 20 feet thick. These two
series are in the Post Pliocene or tertiaries or drift series, whilst
of the Eocene tertiary formations we have (1) the London clay,
a stiff bluish clay impervious to water of not more than 450 feet
deep; (2) the lower London tertiary consisting of pebble beds,
sands, clay and loam, more or less permeable and of a thickness
not exceeding 190 feet and (3) chalk, permeable, highly absorbent
and about 800 feet thick.
These various deposits are found distributed roughly as follow:—
The alluvium stretches along the River bank, commencing towards
the east at a point on the Riverside in the Royal Dockyard
premises, Woolwich: thence roughly following the Woolwich
Road and keeping parallel to it on the north side, at a distance
of about one hundred yards, until Blackwall Lane is reached,
where the line of Pelton Road is followed up to the River Bank,
the alluvial deposits finishing off at this point altogether and
commencing again on the River Bank at a point near Greenwich
Pier: thence crossing Creek Road, near St. Peter's School, the
Southern Railway, near the siding, between Greenwich Station
and the Deptford Creek, very nearly along the line of Norman
Road, crossing the Greenwich High Road almost in line with
Egerton Drive, across Blackheath Road to the Borough boundary,
thence also following that boundary along the Deptford Creek
to the point where the boundary leaves that water, whence the line
of alluvial deposits follows roughly the contour of the River
Bank, at a distance of about one hundred and fifty yards. The
remainder of the district of St. Nicholas, not included in the
above delineation, is on gravel and sand.
The gravel and sand commences eastwards at a point on the