INTERBASIN MELTWATER EXCHANGE ACROSS EASTERN UPPER MICHIGAN IMMEDIATELY PRECEDING THE "9.3 KA EVENT"

Recent studies of the terminal stages of glacial Lake Minong in the Lake Superior Basin have refined histories of that lake’s early Holocene meltwater receipt, water plane fluctuation, and final draining. Taken together, these findings suggest the possibility that, just prior to the breach of Minong’s southeastern rim (“Nadoway Barrier”) and the resultant massive release of isotopically light meltwater to the NAO (“9.3 ka event”; Yu et al., 2010. Science 328, 1262-1266), a transgressing Lake Minong (Breckenridge et al., 2010. J. Paleolimnology, DOI10.007/s10933-010-9447-z) ascended the Tahquamenon Valley and discharged briefly across the Superior-Michigan height of land to Lake Chippewa. In support of this “two-outlet” scenario, we present rebound-adjusted topographic profiles of the Tahquamenon and Manistique River valleys and field evidence from ground penetrating radar (GPR), optical (OSL) dating of surface sand dunes and sand sheets and ¹⁴C dating of wood recovered from the floor of Kaks Lake in the Tahquamenon River valley. Early Holocene interbasin passage of meltwater from the Superior Basin to the Lake Michigan Basin would provide an alternate explanation for signals of isotopically light meltwater reported from the southern Lake Michigan Basin.