New radiocarbon age dates for the Cheboygan bryophyte bed in northern lower Michigan indicate that the bed was not deposited during the Mackinaw interstade, as was previously proposed, but is correlative to the Two Creeks forest bed deposited during the Two Creeks interstade approximately 11 850 BP. Furthermore, the till overlying the bryophyte bed does not represent continuous deposition by ice throughout the Two Creeks interstade, as proposed by others, but represents deposition during the Greatlakean stade. A major implication resulting from the reassignment of the age of the Cheboygan bryophyte bed is that the Straits of Mackinac could have been ice free during the Two Creeks interstade and that during that time the Kirkfield phase of glacial Lake Algonquin may have extended into the Lake Michigan basin.

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