Pleistocene Geology of Chippewa County, Wisconsin

Wisconsin Geological and Natural History Survey Bulletin 103
by Kent M. Syverson
Department of Geology, University of Wisconsin, Eau Claire, WI 54702
syverskm@uwec.edu, Phone (715) 836-3732, Fax (715) 836-5627

ABSTRACT

Chippewa County was glaciated many times during the Pleistocene Epoch. The earliest known glacial advance was the Reeve Phase that occurred more than 780,000 years ago. No till of this advance has been found in Chippewa County, but ice flowing from the west dammed the Chippewa River and its tributaries and rhythmically bedded silty and sandy sediment of the Kinnickinnic Member of the Pierce Formation was deposited in these lakes. After ice wastage and a long period of weathering and erosion, reddish-brown sandy loam till of the River Falls Formation was deposited by the Superior and Chippewa Lobes more than 130,000 years ago during the Baldwin, Foster, and Dallas Phases. Thick gravelly stream sediment was deposited in western Chippewa County as the ice wasted. During the following period of weathering, soil-derived clay accumulated in the uppermost 5 m of this stream sediment. Erosion has destroyed the original glacial topography associated with these early glacial phases, and dendritic stream valleys deeply dissect the glacial sediment and Paleozoic bedrock in areas glaciated before the Wisconsin Glaciation.

During the early part of the Wisconsin Glaciation, the Chippewa Lobe advanced during the Hamburg Phase to deposit reddish-brown, sandy loam to loam till of the Merrill Member of the Lincoln Formation in southeastern Chippewa County. Later, the Chippewa Lobe readvanced over the northeastern part of Chippewa County during the last part of the Wisconsin Glaciation from 9,500 to 26,000 years ago and deposited reddish-brown till of the Copper Falls Formation. Ice-wedge casts in Chippewa County indicate that permafrost conditions existed during the early part of this interval. Several phases of the Chippewa Lobe are recognized during the last part of the Wisconsin Glaciation. The earliest advances, the Early Chippewa and Stanley Phases, left few traces in the landscape. The ice margin then retreated at least a few kilometers, and the low- to moderate-relief Perkinstown moraine was formed in eastern Chippewa County during the Perkinstown Phase. During the Late Chippewa Phase, the Chippewa Lobe flowed into western Chippewa County and formed the high-relief Chippewa moraine. Water from the melting ice deposited an extensive outwash plain along the Chippewa River system. The Perkinstown and Chippewa moraines contain hummocks, kettles, ice-walled-lake plains, and eskers, as well as one tunnel channel. A decrease in the amount of sediment supplied to the Chippewa River system near the termination of the Wisconsin Glaciation caused major incision of the Chippewa River and its tributaries. A well-defined series of terraces formed, the highest of which is the Wissota terrace.

Selected photographs illustrating the glacial geology of Chippewa County, WI, from Bulletin 103.

Many UW-Eau Claire undergraduate students conducted research projects to help me with field, lab, and data-crunching aspects of the Chippewa County project. Students include Peter Bement, Tim Cummings, Kristie Franz, Kristen Hanson, Mark Holmes, Tyler Mace, Jeff Schels, Heather Spehle, Amy Jo Steffen, Katie Thornburg, Jeremy Treague, and Maria Waggoner. To them I owe my sincere thanks!

Chippewa Moraine Ice Age National Scientific Reserve

The Chippewa Moraine Ice Age National Scientific Reserve in northwestern Chippewa County contains excellent examples of an end moraine, outwash plains, kettle lakes, hummocks, and ice-walled-lake plains with local relief up to 50 m (Black, 1974; Cahow, 1976; Franz and others, 1996; Syverson, 1998b). The Chippewa Moraine was included in the Ice Age National Scientific Reserve in 1971 to protect the glacial features for the enjoyment of future generations.

The Chippewa Moraine Visitor’s Center on County Highway M east of New Auburn (see photo above) was dedicated in fall 1992, and it contains exhibits installed by the National Park Service during summer 1997. The area provides excellent hiking and snowshoeing opportunities. A hiking guide explaining the glacial landforms of the Chippewa Moraine Reserve and the included segment of the Ice Age National Scenic Trail is available at the Visitor’s Center (Syverson and others, 1995).

Hummocks and kettle lakes in the Chippewa Moraine Ice Age National Scientific Reserve region, May 2004.

Ice-walled-lake plains

	Unstable-environment ice-walled-lake plain in foreground with a sharp-crested rim ridge in the background. The ice-walled lake probably had drained before sediment from the ice surface slumped onto the lake plain and formed the steep rim ridge. View is looking northeast from State Highway 64. Located near Himple Lake.
Laminated silt and silt loam deposited in an offshore environment, Plummer Lake ice-walled-lake plain, Chippewa Moraine Ice Age National Scientific Reserve (bore hole CH-436, depth 10 ft (3 m)).	Deltaic foreset bedding in the Bob Lake ice-walled-lake plain, SE ¼ SW ¼ Sec. 14, T31N, R8W, Bob Lake Quadrangle. Foresets dip southward into the former ice-walled lake. Field notebook and shovel indicated for scale.
Glacial sediment deposited on top of the Chippewa Lobe Variable sediment of the Copper Falls Formation in a hummock, SW ¼ SW ¼ Sec. 34, T30N, R7W, Crescent Quadrangle. Blade of shovel marks the contact between matrix-supported, gravelly sandy loam (top) and well washed sandy gravel (bottom). Crude stratification in the upper unit is typical for gravity-flow sediment.	Glacial outwash from the last part of the Wisconsin Glaciation Coarse proximal outwash of the Copper Falls Formation, NW ¼ SW ¼ Sec. 5, T30N, R8W, Bloomer Quadrangle. The gravel and sandy gravel fines upward and was deposited within 100 m of the former ice margin by water flowing from right to left. This gravel-rich sediment is an ideal source of commercial aggregate. Shovel and clipboard at base of outcrop for scale.
Glacial outwash from before the Wisconsin Glaciation
Clay cementation of River Falls Formation outwash in the soil B horizon (SE 1/4 Sec. 26, T28N, R10W, Albertville Quadrangle). The clay has been derived from the weathering of minerals in the glacial stream sediment for more than 130,000 years.	Lake Superior agate found in River Falls Formation stream sediment in southwestern Chippewa County. The agates show that the Superior Lobe of the Laurentide Ice Sheet extended into the western part of Chippewa County. Photograph by Richard Mickelson.