Stratigraphic Evidence of a Pre-Wisconsinan Interglaciation in the Adirondack Mountains, New York

Abstract

Multiple tills separated by interbedded lake sediments were temporarily exposed during open-pit mining at Sanford Hill, near Newcomb, in the central Adirondack Mountains of northeastern New York. Radiocarbon ages of wood fragments from brown clay between two tills at that site indicate an age older than 55,000 yr B.P. A pollen profile in the brown pond clay (Tahawus clay) records a transition from initial domination by pine, spruce, and birch to an oak pollen zone. The upward disappearance of spruce and decrease of pine and birch are accompanied by diversification and increase in hardwood pollen. This assemblage includes several warm-climate hardwood species that are not represented in the postglacial flora of the region, suggesting that the biota existed during an interglacial or interstadial interval that was warmer and/or longer than postglacial time. Accordingly, the Tahawus clay is tentatively assigned to the Sangamon interglaciation, and probably to marine oxygen isotope substage 5e. Truncation of the Tahawus clay by glacial erosion may account for the absence of a Sangamon paleosol.