The extent and boundaries of extinct Lake Scuppernong, Jefferson County, southeastern Wisconsin

The extent and boundaries of extinct Lake Scuppernong in Jefferson County, Wisconsin, are examined by analyzing the glacial, deglacial, and postglacial sediments. In particular, evidence for postglacial lacustrine sedimentation was found in the field, in geologic logs, and in water well data reports. In addition, soil pits and auger holes examined in the southern half of Jefferson County consisted predominantly of muck, laminated silt loam, and sandy loam. Also, the majority of well transects examined in Jefferson County have wells containing laminated or non-laminated silt and clay at altitudes at or below 840 feet. The sand and gravel pits and the lithology of lowlands below 840 feet in the southern half of Jefferson County contain outwash sediment that terminates lowlands that are characterized by the dominance of laminated silt and clay. The laminated silt and clay of such areas are interpreted as lake bottom sediment of Glacial Lake Scuppernong.; The previously documented Glacial Lake Hubbleton covering only most of the northwestern part of Jefferson County extends more southwards and eastwards forming a large lake area that I consider part of Glacial Lake Scuppernong covering approximately half of Jefferson County. Glacial Lake Scuppernong's extent in Jefferson County is much less in areal extent than that previously proposed. The evidence for the existence of Glacial lake Scuppernong in Jefferson County is based on the current available data, but the timing, stages of formation, and levels of Glacial lake Scuppernong are not well known. Based on my information, I suggest that Glacial lake Scuppernong was formed in two stages evidenced by the two minimum lake levels, 855 ft (261 m) and 840 ft (256 m), corresponding probably to the formation of the Lake Mills and Green Lake moraines. The timing of the last stage in the formation of Glacial Lake Scuppernong probably followed the formation of Green Lake moraines. The previous work done in Jefferson County on bedrock topography, the thickness of unconsolidated material, the laminated silt and clay in inter-drumlin areas, and the presence of megafauna, all, support my conclusion of the existence of Glacial Scuppernong in Jefferson County at an altitude of 840 ft (256 m).