Geology of the Ice Age National Scenic Trail

Northern Green Bay Lobe and Langlade Lobe Ice Age Trail Segments

T his group of eight trail segments follows end moraines (SB 6) of the Green Bay Lobe (figs. 1, 3), which flowed toward the northwest from the Green Bay lowland, and of the Langlade Lobe, which flowed southwestward out of the Lake Superior basin (figs. 200, 201). The western end of these segments is at the boundary between the Langlade Lobe and the Wisconsin Valley Lobe, which flowed southeastward into this area. From the eastern edge of the Langlade Lobe westward (fig. 201), the moraines are characterized by high-relief hummocky topography (SB 10). There are some tunnel channels (SB 17), but they are not as abundant as they are along the western side of the Green Bay Lobe. Conversely, ice-walled-lake plains (SB 15) are a more common landform in the moraines across northern Wisconsin than they are to the south. Extensive peat bogs are also more frequent in the moraines across northern Wisconsin than they are to the south, partly because of climate and partly because of the more acidic nature of the soils formed on the glacial deposits of the northern lobes. The flow direction of the Green Bay and Langlade lobes is indicated by the orientation of drumlins (SB 8) that formed behind the ice edge (fig. 200). Although there are no precise dates on when these lobes advanced to their maximum positions, relative ages are distinguishable at the junctions of the lobes. Figure 201 shows the crosscutting relationships between various ice margins in this area where the three lobes come together. The Hancock Moraine, the outermost end moraine of the Green Bay Lobe in the area south of Antigo, appears to be overridden by the Almond Moraine. The present interpretation is that the Almond Moraine is the outermost moraine from there northeastward to where Green Bay Lobe deposits are covered by Langlade Lobe deposits. The maximum advance of the Langlade 261 Northern Green Bay Lobe and Langlade Lobe Ice Age Trail Segments Figure 200. Shaded relief of the northern Green Bay Lobe and Langlade Lobe IAT segments (red): (81) Ringle, (82) Eau Claire Dells, (83) Plover River, (84) Kettlebowl, (85) Lumbercamp, (86) Old Railroad, (87) Highland Lakes Eastern, (88) Highland Lakes Western, (89) Parrish Hills. Blue arrows show ice-flow direction. Yellow lines and numbers indicate major highways. Cities and villages shown (yellow): (An) Antigo, (A) Aniwa, (C) Crandon, (L) Lily, (La) Langlade, (M) Monico, (P) Parrish, (R) Rhinelander, (SL) Summit Lake. Names of geologic features are shown on figure 201. (Base map constructed from USGS National Elevation Dataset and modified by WGNHS.) Figure 201. Extent of late Wisconsin glacial advance in north-central Wisconsin. The Green Bay Lobe ice flowed into the area from the southeast , the Langlade Lobe ice flowed from the northeast, and the Wisconsin Valley Lobe ice flowed from the north and northwest. Compare the ice-margin positions with the shaded-relief of figure 200. (From Mickelson 1986.) 264 Northern Green Bay Lobe and Langlade Lobe Ice Age Trail Segments Lobe built the Parrish Moraine, which overrides the Almond Moraine (fig. 201), so the Parrish Moraine is somewhat younger than the Almond Moraine. The Green Bay Lobe advanced into this area across Paleozoic dolomite and sandstone before flowing over Precambrian rock. As much as 50 percent of the pebbles in the Green Bay Lobe till are dolomite, whereas dolomite pebbles are almost absent in the till and outwash of the Langlade Lobe. Both lobes picked up boulders of Wolf River granite (discussed in the introduction to the chapter on the western Green Bay Lobe segments), so both areas are characterized by many granite boulders at their surfaces. When the glaciers sat at the Almond and Parrish moraines, drainage was restricted by uplands to the west, and outwash streams flowed southward into what is now the Eau Claire River and through the Eau Claire Dells. Outwash more than 100 feet thick filled the area between the two moraines. This large outwash plain is called the Antigo “flats” (figs. 201, 202). At that time, the land was still mostly free of vegetation, and silt-sized (SB 21) particles were picked up and blown across the flats. Eventually several feet of this loess (SB 8) accumulated here. This fine-grained sediment holds moisture and, when draped over welldrained sand and gravel, makes excellent farmland. Cultivation for potatoes and other crops is widespread. In fact, Antigo silt loam, the soil covering...