TILL DEPOSITION AND CLAST PAVEMENT FORMATION, DOOR COUNTY, WISCONSIN

A clast pavement within and beneath clay-rich, reddish brown till of the Glenmore Member (Kewaunee Formation) was formed beneath the late Wisconsin Green Bay Lobe by the process of lodgement, the same process that deposited the till. This interpretation is based on stratigraphic relations, pebble fabrics in till, and striations on and shape of clasts in the pavement. The Glenmore till is the uppermost unit exposed in the wall of the Soil Specialists' gravel pit, located one half mile south of Sturgeon Bay, Door County, Wisconsin. This till is the surficial material in much of southern Door County and is considered to be the only one of several reddish-brown till members of the Kewaunee Formation that is present in the county (Brown, 2001). In northern Door County, an older, yellowish brown till occurs at the surface, indicating that if younger reddish brown till was deposited, it subsequently was eroded. It is the northernmost feather edge of the Glenmore till that is exposed in the gravel pit. The till thickens from less than one meter in the pit's north wall, where the clast pavement separates the till from underlying sand and gravel, to three meters in the southwest wall, where the clast pavement occurs within the till at a depth of up to two meters. Pavement clasts were neither transported nor abraded greatly because they are not extensively striated or faceted, even on their upper surfaces. Because strong pebble fabrics in the till and striae on the stone pavement are parallel to nearby drumlins composed of Glenmore till, the till and pavement are considered to have formed subglacially. Strong, consistent pebble fabrics throughout the till and sand plowed up in front of a boulder at the base of the till provide evidence for deposition by lodgement. Presumably, the pavement represents an interval when only large clasts were lodged and then abraded, but till was maintained in transport.