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Syverson and Patrick M. Colgan, The Quaternary of Wisconsin: An Updated Review of Stratigraphy, Glacial History and Landforms. In J. Ehlers, P.L. Gibbard and P.D. Hughes, editors: Developments in Quaternary Science, Vol. 15, Amsterdam, The Netherlands, 2011, pp. 537-552. ISBN: 978-0-444-53447-7. © Copyright 2011 Elsevier B.V. Elsevier. Author's personal copy Chapter 42 The Quaternary of Wisconsin: An Updated Review of Stratigraphy, Glacial History and Landforms Kent M. Syverson1,* and Patrick M. Colgan2 1Department of Geology, University of Wisconsin, Eau Claire, Wisconsin 54702, USA 2Department of Geology, Padnos Hall of Science, Grand Valley State University, Allendale, Michigan 49401, USA *Correspondence and requests for materials should be addressed to Kent M. Syverson. E-mail: [email protected] 42.1. INTRODUCTION et al., 2011). Ice from the Keewatin ice dome to the north-west (e.g. the Des Moines Lobe; Fig. 42.2) deposited silt-rich, cal- Wisconsin was probably glaciated dozens of times during careous tills. Ice from the Labradoran ice dome to the north- the Pleistocene Epoch (2.58–0.012 Ma), but stratigraphical east flowed out of the Superior lowland and deposited red- units provide direct evidence for at least four glaciations. dish-brown tills with Precambrian basalt, banded iron forma- Even though Wisconsin lies well north of the maximum tion and reddish sandstone erratics (e.g. Superior Lobe and extent of Quaternary glaciations, the Driftless Area in the other smaller lobes; Fig. 42.2). Labradoran ice flowing out south-western part of the state remained unglaciated of the Green Bay and Lake Michigan lowlands (e.g. Green (Fig. 42.1). Glacial, alluvial and aeolian sediments from BayandLakeMichiganLobes;Fig.42.2)depositedcalcareous several glaciations and interglacials are present, but age tills whose grain size was strongly influenced by ice-dammed control for all except the Late Wisconsinan Glaciation lakes within those lowlands. (marine isotope stage 2 or MIS 2) is limited to palaeosols Syverson and Colgan (2004) summarised the glacial his- and palaeomagnetic data (Whittecar, 1979; Baker et al., tory of Wisconsin (including an extensive literature review 1983; Jacobs and Knox, 1994; Miller, 2000). Radiocarbon which is not repeated here). Since that publication, the analyses are numerous for deglaciation after 13.0 14 Pleistocene lithostratigraphy of Wisconsin has been C ka BP, but they are rare for the rest of the Wisconsinan reviewed and updated (Syverson et al., 2011) to incorporate Glaciation (MIS 2–4). Limited optically stimulated lumi- more recent research findings. Additionally, our knowledge nescence (OSL) and cosmogenic radionuclide (CRN) data of ice dynamics and landform genesis has expanded as more are also available for the Late Wisconsinan Glaciation. has been learned more about modern ice sheet analogs. In this review, all ages are reported in thousands of cal- Here, we summarise our current understanding of the gla- endar years (ka) unless stated otherwise. Radiocarbon ages 14 cial history of Wisconsin and suggest areas of future ( C ka BP) have been converted to calendar years using research. CALIB v. 5.0 (Stuiver and Reimer, 1993). OSL and CRN age estimates are assumed to be roughly equivalent to cal- ibrated radiocarbon ages. Numerical ages of stratigraphical boundaries are taken from charts produced by the Subcom- 42.2. EARLY PLEISTOCENE GLACIATIONS mission on Quaternary Stratigraphy of the International Three formations might represent at least two pre-Illinoian Union of Geological Sciences (Gibbard and Cohen, glaciations in Wisconsin. These units have been assigned an 2008). We also use the current definition of the base of Early Pleistocene age based on intense weathering charac- the Holocene as 11.7 ka (Walker et al., 2009). teristics and reversed remanent palaeomagnetism. The units Glacialsedimentcoversapproximatelythree-fourthsofthe underlie sediment assigned to the Illinoian Glaciation (MIS 145,000 km2 land surface of Wisconsin (Figs. 42.2–42.4). 6 or 8) and are sometimes referred to informally as pre-Illi- Ice flowing from three major source regions deposited sedi- noian (older than MIS 6 or 8). Tills of the Pierce Formation ment (Mickelson et al., 1984; Attig et al., 1988; Syverson of western Wisconsin (the ‘old grey’ till of Leverett, 1932) Developments in Quaternary Science. Vol. 15, doi: 10.1016/B978-0-444-53447-7.00042-8 ISSN: 1571-0866, # 2011 Elsevier B.V. All rights reserved. 537 Author's personal copy 538 Quaternary Glaciations - Extent and Chronology FIGURE 42.1 Map of Wisconsin and surround- ing states relative to the maximum extent of gla- cier ice during the Quaternary (modified from Hobbs, 1999). The Driftless Area in south-west- ern Wisconsin does not show evidence for burial by glacier ice. The shaded area of patchy, eroded till displays the same deeply incised river valleys as the Driftless Area and has been referred to as the ‘pseudo-driftless area’ by Hobbs (1999). and Marathon Formation in north-central Wisconsin 42.2.2. North-Central Wisconsin (Syverson et al., 2011) are the most extensive (Figs. 42.4 and 42.5). The Wausau Member of the Marathon Formation in north- central Wisconsin is a silt-rich, intensely weathered till (Fig. 42.5). No similar till units have been found in the rest 42.2.1. Western Wisconsin of Wisconsin, and the Wausau Member may be evidence for Tills of the Pierce Formation in western Wisconsin are grey an extremely old glacial event. The Medford and Edgar to brown, calcareous (where unleached), silt rich, kaolinite Members of the Marathon Formation are calcareous and silt rich and they probably represent an ice advance from a Kee- rich (Figs. 42.4 and 42.5). These tills contain less kaolinite watin source during at least two events (Baker et al., 1983; than the Hersey Member of the Pierce Formation, but oth- Johnson, 1986; Thornburg et al., 2000; Syverson et al., erwise they are very similar (Muldoon et al., 1988; Attig 2011). Till of the Woodville Member of the Pierce Forma- and Muldoon, 1989; Thornburg et al., 2000; Syverson tion marks the first ice advance (Fig. 42.5). Peat and wood et al., 2011). The Marshfield moraine contains 30–50 m overlie the Woodville Member till at the type section (Attig of Edgar till (Weidman, 1907, p. 452; Clayton, 1991), et al., 1988, p. 8 and 11). and this is the only primary glacial landform that remains Keewatin-source ice flowed south-east across the Mis- from a pre-Illinoian ice advance. sissippi River during the later Reeve Phase, deposited the Hersey Member of the Pierce Formation in western Wis- 42.2.3. Southern Wisconsin consin and dammed the major south-easterly flowing trib- utaries of the Mississippi River (Baker et al., 1983; Johnson, In south-eastern Wisconsin, till is present in erosional rem- 1986). The resulting ice-dammed lakes extended at least nants outside of end moraines deposited during the Wiscon- tens of kilometres east of the modern Mississippi River val- sinan Glaciation (Alden, 1918). Bleuer (1970, 1971) and ley. Silt- and clay-rich lake sediment of the Kinnickinnic Whittecar (1979) proposed that some of the silt-rich, calcar- Member of the Pierce Formation was deposited in these eous grey till units were deposited during a pre-Illinoian ice lakes (Fig. 42.5). Based on lake sediment elevations and advance from the east out of the Lake Michigan lowland. varve counts, the lakes might have covered an area of These till units have been observed beneath Illinoian till 5800 km2 for more than 1200 years (Baker, 1984; Syverson of the Walworth Formation in southern Wisconsin (Bleuer, et al., 2011). 1971, p. 143; Miller, 2000, p. 116). Author's personal copy Chapter 42 The Quaternary of Wisconsin 539 FIGURE 42.2 Major ice lobes during the Late Wisconsinan Glaciation (inset, modified from Clayton et al., 2006). The shaded-relief image of Wisconsin shows the following major features: BR, Baraboo Range; DA, Driftless Area; GB, Green Bay; KM, Kettle Moraine; LW, glacial Lake Wisconsin bed. Image was created from USGS 3 arcsec digital elevation data. Illumination direction is approximately 315, and sun angle is 25. 42.2.4. Ice Extent and Chronology (1988) described till in the Bridgeport terrace of the Wis- consin River (ca. 3 km east of the Mississippi River junc- Ice extent and the chronology concerning these pre-Illi- tion). This till formed during a pre-Illinoian ice advance noian events are poorly known. Any original glacial land- to the south-east across the Mississippi River (Knox and forms other than the Marshfield moraine have been Attig, 1988) with an ice margin closely following the loca- completely removed by extensive erosion, and weathered tion of the Mississippi River (Figs. 42.3 and 42.6A; Clayton till remnants are widely scattered and buried by younger et al., 2006). sediment. The Powers Bluff chert dispersal fan (Fig. 42.3, Till units with reversed remanent magnetism provide location PB) suggests that pre-Illinoian Keewatin ice flo- some age control for pre-Illinoian till units.