Periglacial Features in the Driftless Area of Southern Wisconsin

Effects of late Pleistocene permafrost on the landscape of Wisconsin, USA

“…Block streams in the Baraboo Hills have been described by Smith (1949), Attig et al (1990), and . They consist of large boulders of Baraboo quartzite that accumulated in the lower part of shallow valleys in the steep anks of the Baraboo Hills (Fig.…”

“…Where glaciated, the talus has been removed or buried under till. The talus was never reactivated in the glaciated area, indicating the talus formed during or before the height of glaciation, when permafrost was present (Smith 1949;Black 1968Black , 1974Attig et al 1990). Similar talus, composed of blocks of Barron quartzite, occurs in Barron County in northwestern Wisconsin (Johnson 1986).…”

“…We have no indication that they are still moving. Smith (1949) thought they formed in the presence of permafrost because they resemble block streams active today in polar regions.…”

“…Other areas on the anks of the Baraboo Hills are covered by debris blankets with the pore space between the boulders lled with ner debris (Smith 1949). The debris blankets are vegetated and generally lack the conspicuous lobate topography of the open-work boulder gravel.…”

“…However, little evidence was presented until the work of H. T. U. Smith (1949), who made a detailed study of possible periglacial features, including talus cones, boulder streams, and rubble mantles, in the area of the Baraboo Hills and Blue Mounds in southern Wisconsin (Fig. 1).…”