of
the land at the shore of the ocean. The streams which reasserted the
pre-existing re-entering bays on the north side of the moraine, and
which to-day are seen as emarginations, or angular flooded recesses,
were developed as the ice front shrank from the moraine. It held
between its retreating face and the morainal slope, on the south, an
included body of water in which again new deltas and fan-shaped plains
of sand were formed. Some such chancery of the waters issuing from the
glacier is designated by Woodworth as the Port Washington Stage.
In
order, however, to determine whether in such a confinement the water
was the glacial water or moving tides, he has had to determine whether
there was a partial submergence of the island, in which case the
deltoid formations he has traced at Manhasset might be purely marine in
derivation. He traces a shore line 2 to 3 miles east of Jamaica at
about 80 feet above the sea level, on the front of the moraine; he has
observed the steep margin of the moraine west of Prospect Park and
finds no evidence of sea action there, but eastward, at Oyster Bay,
there is controvertible evidence of a sea plain at 60 or more feet
elevation. This coincidence (about) with the Port Washington level
might argue for a common marine level in front and back of the moraine.
The Jamaican depression is here introduced as the cause of a
deformation, a wrenching, in its connection with the higher levels, of
the underlying coastal plain formation anterior to the completion of
the moraine and its frontal plain. The Jamaican Bay depression, it may
be said, is a distinct subsidence, produced possibly by the weight of
the ice on soft clay beds, accompanied by the partial elevated Far
Rockaway ridge, raised by isostacy. Crease lines of drainage converge
in all directions to this depression. (Veatch regards Jamaica Bay as a
vestige of the earlier Sound River basin, partially filled.)
In
this way Woodworth establishes his Port Washington glacial lake (Map
III.), the banks of which were the ice front on the north and the
moraine on the south. It drained west-wardly from Hempstead Harbor into
Manhasset Bay (shown
