Chronology and stratigraphy of the Imlay Channel in Lapeer County, Michigan, USA

Abstract

The Imlay Channel in Lapeer County, Michigan, was one of two outlets for the glacial Lake Maumee phase of ancestral Lake Erie. Fifteen new radiocarbon and optical ages from within and adjacent to the Imlay Channel constrain sedimentation rates within the channel and the timing of regional deglaciation. For nearly 50 years, the deglaciation of this region of Michigan has been based on a single age from the Weaver Drain site located near the Imlay Channel, and a new radiocarbon age of 16.7–17.0 cal ka BP from 3 km east of the Imlay Channel supports this long-standing deglacial age. On average, there is a 14 m thick sediment fill within the channel. Radiocarbon and optically stimulated luminescence ages reveal that much of the alluvial fill was deposited by 14.9 ka, and alluvial fans building into the channel stabilized in the early Holocene. Cross-sections along and perpendicular to the Imlay Channel, built from geotechnical borings and water-well records, reveal a current-day bedrock sill elevation at 235 m a.s.l. that would have permitted drainage of all stages of glacial Lake Maumee in the past.