|
206 GEOLOGY OF NEW YORK CITY
|
||
|
|
||
|
tures
of quartz and feldspar, while the traps and sandstones told at once the
distant seat of their initial appearance in the world's geological
history, vis., northern New Jersey.
A
very striking and effective boulder may be seen south of the turnpike
road, now traversed by a trolley line running to Silver Lake, in the
middle of a sloping field, at Stapleton, and immediately opposite the
paper mill (Fig. 48). This huge monolith of granite measures, in the
pyramidal portion exposed above ground, six feet by twelve feet, by
eleven and one-half feet, and if fully revealed would probably measure
one-quarter more. It contains strings of tourmaline crystals.
The
fossils taken in the drift on Staten Island belong, so far as they have
undergone extreme transportation, to the Paleozoic rocks (see p. 4).
They number 112, and are apportioned to the various geological members
of that age as follows, in their succession: Potsdam 1, Hudson River 5,
Lower Helderberg 55, Oriskany 20, Schoharie 32, Upper Helderberg 1,
Hamilton 1.
It
is quite obvious that their significance is limited by the three
horizons, Lower Helderberg, Oriskany, and Schoharie, which, in central
east New York, approach the Hudson River, and the inference is
suggested that these siluric and devonic fossils have been carried to
Staten Island by the Hudson River gorge ice element of the great glacier. In the prolongation of the direction of the few discernible stria? on Staten Island rocks, which are N. 130 W. and N. 200
W., we meet a vast development in southern New York, beyond the
Highlands of Orange County, N. Y., and Sussex County, N. J., of the
Upper Devonian rocks, in the sandstones of the Portage, Chemung, and
Catskill; and except, as through attrition and reduction into sand,
they have become unrecognizable, these rocks are not found on Staten
Island. They are structurally apt to form blocks, fragments, boulders,
and separate masses, through weathering. Why should not the glacier
have picked them up and carried them southward. If it did not do so,
the explanation is to be sought in the lofty barricade of the High-
|
||
|
|
||