CONSTRAINING LAURENTIDE ICE SHEET MELTWATER ROUTING CHANGES IN EASTERN NEW YORK STATE USING BERYLLIUM-10 DATING

It has been postulated that as the Laurentide Ice Sheet (LIS) retreated north of the Adirondack Mountains, meltwater routing shifted from the Mohawk valley spillway at the southeastern margin of Glacial Lake Iroquois (GLI) to its northeastern margin at Covey Hill. The extreme increase in discharge associated with the meltwater rerouting caused a jökulhlaup event that breached the terminal moraine dam in Narrows, NY, and subsequently discharged into the Atlantic Ocean. We collected eight samples for cosmogenic Beryllium-10 (¹⁰Be) exposure dating from a strath (bedrock) terrace at Moss Island, which lies along the Mohawk River that likely became abandoned during the meltwater rerouting event. If the ¹⁰Be ages overlap with the onset of the Intra-Allerød Cold Period (IACP; ~13,350 cal. yr BP), this would support the hypothesis that GLI meltwater rerouting triggered the Intra-Allerød Cold Period (IACP), as has been proposed (Donnelly et al., 2005). Alternatively, significantly younger ages could indicate knickpoint migration of Little Falls, now ~1.5 km upstream of the Moss Island strath terrace. ¹⁰Be ages will be presented at the conference.