THE MAPLETON MORAINE: A PROBABLE PORT HURON EQUIVALENT IN NEW YORK’S FINGER LAKES

The Port Huron Moraine in Michigan’s Lower Peninsula has long been recognized as an important and major moraine system attributed to a major readvance of glacial ice occurring between 12-13ka ¹⁴C yr BP. While correlative moraine positions have been suggested in Wisconsin and to the Alden Moraine near Buffalo, New York, a correlative ice margin in the Finger Lakes has remained elusive. Recent geologic mapping and stratigraphic investigations near Union Spring, NY provide new details on the chronologic assignment of the Mapleton Moraine.

The Finger Lakes in central New York have most recently been glaciated by the Ontario Lobe of the Laurentide Ice Sheet. Located 40 kilometers north of Ithaca, NY on the east side of the Cayuga Lake Basin. The Mapleton Moraine consists of an easily traceable and fairly continuous ridge first observed near Mapleton, NY. The moraine exists as a subtle rising ridge 5-15 meters in height on the northern rim of Great Gully and extends for more than 50 kilometers trending northeastward to Auburn, NY. LiDAR data clearly indicate its association with constructional topography northeast of Owasco Lake. On the north side of the moraine margin subtle undulating ridges parallel the principle margin creating a hummocky appearance whereas the distal edge appears to have well defined border with an oblique orientation to that of nearby ice margins to the south. Meltwater channels are traceable back to the margin however, unlike in Michigan there are no well-defined fans associated with this margin.

We collected more than 20 cores in an isolated basin immediately adjacent to the Mapleton Moraine in an attempt to recover stratigraphic details of the depositional history of this basin and recover any possible plant macro fossils for radiocarbon dating. A basin stratigraphy only 2.7 meters thick terminating on glacial till consistently yielded an abundance of organics, however the dominant materials recovered deep in section within the laminated silts are dryas leaves. To date we have obtained more than 20 radiocarbon dates on the stratigraphy, dates are internally consistent, do not indicate any mixing or inversion and appear to provide a robust record of deglaciation that confidently assigns an age of approximately 12,650 radiocarbon years as the age of the Mapleton Moraine.