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180 GEOLOGY OF NEW YORK CITY ,
down a slope to the factory site of the Kreischerville tile-pipe works.
Some
of the clay exposures are colored in strips; sands overlie the clays
unconformably; some pits are almost entirely in sand with ferruginous
infiltrations; the depth may be two hundred feet; the country is
undulating, knobby, and disturbed. Kreischerville can be directly
reached from the Richmond Valley station by carriage.
Dr.
Hollick shrewdly observes that " the Cretaceous area is of importance
as the region from which a permanent water supply may probably be
obtained. Throughout the area underlain by Cretaceous strata a reliable
water supply may probably be obtained by wells driven to the proper
horizon."
The Ice Age was
the next period which registered its presence in the surface rocks of
the Borough of Richmond, and left over the greater part of it the
commingled mass of stones, earth, boulders, sands, gravel, and clay. It
is treated in the accompanying paper. The strictly modern period
succeeded, and those present features of the island were then added
which surrounded it with deep beds of sand, built up extensive marsh
lands, cut down its hills, and sculptured its drift into ravines and
valleys.
A
very notable Quaternary fossil was uncovered on Staten Island in the
Moravian Cemetery at New Dorp, in a swampy depression filled with
decaying vegetation. Beneath the usual accumulations in such basins,
sand, logs, and cones were found. The cones belonged to the white
spruce (vide Dr. A. Hollick), Picea canadensis, a tree
of a high northern range. " The spruce cones were at a distance of
about ten feet from the surface, distributed in considerable numbers
in a layer about a foot in thickness, while below this was found a mastodon's tooth
at a depth of about 25 feet. The entire deposit bore every indication
of having been laid down in still water in a continuous and unbroken
series of layers, and inasmuch as it was in a morainal basin it must
all have been post-morainal in age." (Proc. Nat. Sci. Ass. Staten
Island, Vol. VII, p. 29.)
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