QUATERNARY GEOLOGIC MAP OF WAUPACA COUNTY, WISCONSIN

Located in east-central Wisconsin, Waupaca County was glaciated by the Green Bay Lobe of the Laurentide Ice Sheet during the last part of the Wisconsin Glaciation, 30 to 11 ka BP. The terminal moraine that formed during the Last Glacial Maximum is located about 10 miles west of the county. The western half of Waupaca County is underlain by deposits of the Bowler and Elderon Phases, which occurred ca. 18 to 16 ka BP. Bowler Phase ice marginal landforms are mainly ice-contact outwash faces. These features were deposited by meltwater flowing westward from the ice margin. This meltwater collected in a series of meandering outwash streams that flowed southward. The meanders developed because streams formed in lowlands between bedrock uplands. The uplands are covered with drumlins. Their long axes reflect westward ice movement. Till in the western half of the county is the brown, sandy (sand:silt:clay of 84/9/7) diamicton of the Horicon Member of the Holy Hill Formation. Lowlands in the western half of the county are underlain by meltwater stream deposits, most of which contain collapse features.

 Glacial deposits in the eastern half of the county are from the Middle Athelstane Phase, dated to ca. 14 to 13 ka BP. Till in this area is the Kirby Lake Member of the Kewaunee Formation, which is a reddish brown, silty and clayey (sand/silt/clay: 24/42/34) diamicton. The ice limit during deposition of the Kirby Lake till is rarely marked by a constructional feature (moraine or ice-contact face); instead, it is usually just the feather edge of the Kirby Lake till. Glacial lake sediments in the eastern area are from both the Middle and Late (ca. 13 to 12.7 ka BP) Athelstane Phases. Dunes and sand sheets are extensively developed on the lake plain. Optically stimulated luminescence (OSL) ages on these eolian sands indicate the dunes were deposited ca. 12 to 13 ka BP. In places, a veneer of sheet sand was deposited ca. 60 to 100 yr BP according to OSL dates. Dune slip faces reflect northerly and northwesterly winds. Finally, peat, deposited in the postglacial and Holocene, occurs in many lowland areas.