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MANHATTAN ISLAND
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the
deeper ocean. This depression or gulch is a channel unmistakably
walled in or banked, and the width of the channel widens and narrows,
as might be expected in a river course making its way through
obstructions, at angles or bends.
The
clay bottom of this channel seems to be regarded as due to the
extension seaward of the Tertiary " sandy clay strata " of New Jersey,
or the channel itself represents the movement seaward through its
eroded layers of the Hudson River over the coastal plane. At the same
time it seems probable that through a large part of the region
traversed by the Hudson River channel the stream has made its way
through glacial drift, superimposed upon the Tertiary clays, etc. This
channel, as mentioned above, deepens again from the distance of
eighty-five miles from Sandy Hook to the one hundred and fifth mile
from the same point. This seaward extension is characterized by an
increased depth, beginning with 360 feet and increasing to 1,200 feet
within the first mile. It is three miles wide. The greatest depth of
474 fathoms is at the outlet. Here occurs a bar with a depth of 200
fathoms. This very deep gash is regarded as a submerged fiord into
which the channel, which precedes it from the Lower Bay outward,
empties. However interpreted, this remarkable trough and its sudden and
extreme deepening into its canon-like embouchure into the ocean
certainly indicate the early prolongation of the Hudson River over a
widely extended coastal region, composed of cretaceous and Tertiary
clays and glacial detritus, resting on a foundation of crystalline
rocks, at a time, of course, when the whole region was elevated above
the waters of the ocean which now cover it.
The
foregoing details of the coastal submarine conformation of the Hudson
River by Lindenkohl has been modified by Dr. J. W. Spencer to this
extent: " Lindenkohl thought that the canon was terminated by a bar,
but Dr. Spencer has determined that no bar exists, and that the canon
cuts through the edge of the continental bench about eight miles
farther. It then widens to a valley, which can be readily recognized for
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