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_The Catskill Delta in the Post-Glacial Hudson Estuary._ By =William
Morris Davis=. (From the Proceedings of the Boston Society of
Natural History, Vol. XXV., 1891).
The post-Tertiary trenches of the Hudson and its tributaries are in the
main filled with clay beds, which, covered by a thin deposit of sand,
rise in terraces 130, 150, or even 180 feet above tide-water. These
clays are the result of a late glacial or post-glacial submergence of
the valley, but their upper surface does not indicate the amount of
their submergence, as they are bottom deposits. Delta deposits made by
the tributary streams, where they entered the Hudson estuary, would
indicate the amount of submergence.
Such deposits are found on the Catskill a mile north of Cairo, and
eroded remnants are traceable for three or four miles down stream.
The surface is characterized by great numbers of water-worn stones
up to fifteen or eighteen inches in diameter. The lobate margin,
where present, is poorly defined. These deposits range from 290 feet
(aneroid) above tide, up river, to 270 feet further down. One-tenth of
a cubic mile of material seems to have been washed into the Catskill
trench at the point of this delta between the time of the ice departure
and the elevation of the land. Subsequent terracing has removed half
that amount.
The course of the Catskill at Leeds, where it crosses a ledge of hard
Corniferous limestone is probably of post-glacial superimposed origin,
but the preglacial valley cannot be definitely fixed.