ABSTRACT This field guide examines the evidence for multiple readvances of the Superior lobe, as well as the morphological and sediment record of glacial lakes in the western Lake Superior basin. During each readvance of the Superior lobe, ice went a shorter distance, reached a lower elevation, and laid down a finer-grained till due to incorporation of proglacial lake sediment. There are three distinct tills, which are correlated to three readvance phases: the St. Croix/Automba, Split Rock, and Nickerson. A red clay typically caps the stratigraphy at lower elevations in the basin. This clay may be a fourth till associated with a late readvance, perhaps equivalent to the Marquette phase in eastern Lake Superior. Alternatively, the red clay may be lacustrine. At issue are the potential hydraulic connections between glacial Lake Agassiz and the Atlantic Ocean during, and after, the Younger Dryas, because a readvance would fill the western Superior basin with ice and prohibit eastern Lake Agassiz drainage. Additional stops highlight the strandline and sediment record of the youngest glacial lake phase (glacial Lake Duluth), including the inspection of Lake Superior sediment cores that are archived at the National Lacustrine Core Repository in Minneapolis. The goals of the selected stops are to underscore the current understanding of the late glacial history of the western Superior basin and to provide new insights to spark discussion.

ABSTRACT The deglaciation history of northeastern Minnesota and northwestern Ontario is outlined using geological and ichthyofaunal evidence from the continental to local scales. Both published and new data indicate the existence of eastern outlets drawing from pre-and-early Agassiz lakes. Part of the Arctic watershed was impounded between the Duluth Complex highlands and the retreating Rainy lobe. These outlets had their flows routed through the “Keating Complex” and the “Gunflint Arrow Lakes Corridor.” Discharges around the Duluth Complex’s northeast limb reached the Superior basin along Superior lobe ice, then exited down existing pre-glacial river valleys and a prominent, “valley-type” topographic bench between Hovland and Grand Marais, Minnesota.

ABSTRACT Reconstructing the drainage from glacial Lake Agassiz to explain episodes of abrupt climate change during the last glacial termination has a long and colorful past. The type strandlines in the basin are named for the towns of Herman, Norcross, Tintah, and Campbell. Optically stimulated luminescence dating of these and other strandlines from the southern basin of Lake Agassiz enables estimating times of water level stability and outlet incision. Tracing strandlines to the north is complicated by their increasing number and often discontinuous nature. Much of the meltwater entering the Mississippi River was channelized through Lake Agassiz’s southern outlet. The spillway is floored by boulder lags and bedrock. Two cores penetrating through to bedrock have provided the most detailed history of southerly lake drainage. On the first day of the trip, we will travel to strandlines on both sides of the southernmost Agassiz basin and view the glaciolacustrine stratigraphy at Fargo, North Dakota; on the second day, we will visit more strandlines and the southern outlet spillway.