4 GEOLOGY OF NEW YORK CITY
and in Long Island Sound. The
combination of the Acadian and Appalachian protaxes determined the
existence of the great' Middle Bay' of the Atlantic Coast (the '
Southern Bay' of Dana extended from Florida to Cape Hatteras,
the' Eastern Bay' from Nantucket Island northward), and in the region
of their junction lies the Bay of New York with the mouth of the Hudson. Thus, the foundations were laid in Archaean time."
Spurs
from the Archaeanterrane reached southward in Westchester County, New
York, and western Connecticut, and one of these formed the nucleal
member of the Geology of New York, a peninsulated tract built outward
by additions of sediments. This tract, elevated, by reason of very
extraordinary superficial contraction of the earth's crust, became
variously modified by metamorphism, invaded by dike rocks, and
mineralized by chemical readjustment of its elements. It remained
apparently unmodified, except as acted upon by atmospheric agencies
and by the ice of the Ice Age, and it also remained permanently above
the ancient seas throughout the long periods of geologic time from the
close of the Lower Silurian to modern and recent days. But on Staten
Island and on Long Island later deposits, younger than the Paleozoic,
appear.
Geologic
Time has been separated by American geologists into a number of
subordinate time groups, each one of which, in the main, exhibits a
more or less homogeneous, or at least, typical fauna, consistent with
and defined by its own limits; while within a larger unit of time
(Cambrian, Lower Silurian, Upper Silurian, Devonian, Carbonic, [etc.),
the assemblage of these more specific horizons still express a faunal
stadium or stage. The chart of geologic time, prepared and recognized
by American geologists, follows:
