THIN-FILM, CHANNELIZED DRAINAGE, OR SHEETFLOODS BENEATH A PORTION OF THE LAURENTIDE ICE-SHEET - AN EXAMINATION OF GLACIAL EROSION FORMS, NORTHERN NEW-YORK-STATE, USA

Morphologic analyses of characteristic bedrock erosion forms found in northern New York State, USA were used to reconstruct the subglacial c onditions under which they may have been produced. Observations from s ites on Wellesley Island, N.Y., at Point Salubrious, N.Y., and at an o pen pit mine near Balmat, N.Y., were combined with regional mapping of a diverse suite of glacial erosion forms in order to establish the ar eal extent and significance of subglacial drainage in northern New Yor k. Results of these site-specific and regional studies are the basis f or discussion of the probable role of subglacial meltwater in the regi on. Bedrock erosion forms preserved at various locations in northern N ew York are interpreted as products of flow separation of localized su bglacial meltwater during ice/bed decoupling. The regional distributio n of these forms indicates that they are largely restricted to pre-exi sting subglacially-modified bedrock valleys that served as subglacial tunnel channels. Regionally extensive, deep, subglacial meltwater flow , characterized as sheetfloods, is not required to account for the ero sional features described from specific sites in northern New York Sta te.