Dawn Chapel

Unconsolidated glacial deposits that cover Sheboygan County vary from 300 feet (91 m) thick in the western part to only a few feet thick (less than a meter) in some areas of the eastern part. The area was completely covered by ice during the Late Wisconsin maximum (ca. 20,000 - 16,000 years BP). At this time, the Green Bay and Lake Michigan Lobes of the Laurentide Ice Sheet converged in what is now western Sheboygan County, near the present position of the Kettle Moraine. Brown sandy till and related deposits of the Horicon and New Berlin Members of the Holy Hill Formation were deposited at this time. During deglaciation of the Kettle Moraine, a large quantity of sand and gravel was deposited on stagnant ice, which later melted out to produce the distinctive hummocky landscape of the Kettle Moarine.

After the Late Wisconsin maximum, the Green Bay Lobe never again advanced into Sheboygan County. However, a series of readvances of the Lake Michigan Lobe later deposited the gray clayey till and related deposits of the Oak Creek Formation (ca. 14,500 - 13,300 years BP) and the reddish-brown clayey till and related deposits of the Kewaunee Formation (ca.13,000-12,200 years BP) in the eastern part of study area. Members of the Kewaunee Formation present in Sheboygan County include the Ozaukee, Haven and Valders. In addition, a minor readvance of the ice margin after deposition of the Haven Member, but before deposition of the Valders Member, is informally named the Weeden till.

The western limit of the Oak Creek advancings, for the most part, is coincident with the western limit of the Ozaukee advance in the southern part of central Sheboygan County. This documents the Oak Creek ice advance farther west in this area than previously thought.

Diamicton and other materials older than the Late Wisconsin maximum occur as a patchy distribution beneath the younger surface material. Three reddish-gray diamicton units of possible Middle or Early Wisconsin age (ca. 70,000 - 28,000 years BP) occur beneath outwash of the New Berlin Member near the Kettle Moraine and may be time correlative with the reddish-colored Roxana Silt of the Mississippi Valley. The youngest of these units (Bed 1) was deposited between 34,610 +/-190 years BP and 26,400 +/- 920 years BP and has physical characteristics similar to the Capron Member of the Zenda Formation in southeastern Wisconsin, which previously had no age control. The older units (Bed 2 and 3) may correlate with members of the Walworth Formation (Illinoian age) or may represent previously unrecognized Early Wisconsin age glaciations.

A bedrock valley over 200 feet deep (60 m) and over a mile wide (1.6 km), that is mostly filled with Quaternary deposits, trends north-south through the central part of the county with an abrupt 90-degree turn to the west in northern Sheboygan County. The bedrock valley evidently drained southwards and can be traced to southern Wisconsin where it joins the Troy Valley in Walworth County.

Modern drainage across Sheboygan County evolved during and after glaciation, and is well developed in the eastern part of the county where former ice marginal positions associated with the clayey deposits of the Kewaunee Formation tend to influence drainage patterns. Wave-cut shorelines south of the city of Sheboygan record evidence of former Calumet - 620 feet (189m) and Toleston - 605 feet (184m) high lake levels, while north of the city of Sheboygan one wave-cut bench records evidence of the former Glenwood - 640 feet (195m) high lake level. River terraces along the Sheboygan, Onion, and Mullet Rivers appear to be graded to these former lake levels.