Abstract

The Almond Dam near Hornell, in south-central New York, is at the site of a glacial diversion of Canacadea Creek. Here the diversion valley is about 1200 feet wide, with rock about 75 feet below the creek level. The rock in the preglacial valley is considerably deeper, and the valley is about twice as wide. The diversion valley is filled with blue till, above which are water-lain deposits with an overlying brown till. The Canacadea Valley thus indicates three advances of ice sheets, to form the diversion and to deposit the blue and brown tills in this valley. The valley of Purdy Creek shows similar conditions.

At eight other localities, local changes occurred at or near the close of the last glaciation. At the Arkport dam site, the preglacial valley has been blocked by glacial deposits, and the stream has cut a new, meandering channel in the rock wall south of the old valley. This new valley has been partly refilled with stream gravels. Farther upstream, near Bishopville, is a similar stream diversion. At the dam sites on Carrington Creek, Big Creek, and Karr and McHenry Valley creeks and on Cunningham and Hammer creeks the history appears to have been identical. These represent postglacial drainage changes.

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