Middle Wisconsin glaciation in the Genesee Valley, NY: A stratigraphic record contemporaneous with Heinrich Event, H4

Two lacustrine deformation tills with ages corresponding closely to North Atlantic Heinrich event, H4, are preserved in the Genesee Valley on the western edge of the Finger Lakes region of New York State. The locality is at the convergence of a major north-flowing river with the Laurentide ice sheet and results in unusual preservation of datable organics. Intact Middle and Late Wisconsin glacial sequences are preserved above a Middle Wisconsin interstadial disconformity within a bedrock trough that has dimensions similar to those of the larger Finger Lakes. The shallow burial depth and age of the disconformity (circa 35,000 14C years BP) demonstrate that deep erosion of Finger Lakes bedrock troughs cannot be presumed to have occurred during all major glacial advances. The preserved glacial stratigraphy indicates that proglacial and substrate conditions, as well as the rate of ice advance, may cause a wide variation in the ability of ice sheets to cause deep basal erosion during major glacial stadials. The evidence also demonstrates that Middle Wisconsin ice advanced more than 30 km south of the Lake Ontario shoreline in west-central New York. Other buried wood of Middle Wisconsin age in the Genesee Valley suggests that the recoverable record of Early(?) and Middle Wisconsin glaciations in New York is more diverse than is documented in the existing literature.