Revisiting the Distribution and Geomorphology of Sand Stringers Beyond the Ice Margin

Mataitis, Richard J.; Larson, Phillip H.; Running, Garry L.; Schaetzl, Randall J.; Bowen, Mark W.; Faulkner, Douglas J.; Rittenour, Tammy M.; Nelson, Michelle S.; Burds, Luke; Schirmer, R

doi:10.1130/abs/2019am-336744

Cited by 1 publication

(7 citation statements)

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“…Based on the distribution of sand dunes and loess, Schaetzl et al (2018) concluded that strong westnorthwesterly winds were a common occurrence in the Chippewa Valley in the immediate postglacial period. OSL ages on several of the hundreds of parabolic dunes, sand sheets, sand ramps, and sand stringers in the Chippewa Valley roughly bracket the OSL date from the Henning site, indicating that aeolian activity was ongoing between c. 13 and 9 ka (Schaetzl et al 2014(Schaetzl et al , 2018Millett et al 2018;Mataitis et al 2019;Millett 2019). Recall that the OSL ages of these sandy aeolian landforms represent the waning phase and stabilization of sand transport, as climate warmed and vegetation cover and soil moisture increased across the Chippewa Valley.…”

Section: Discussionmentioning

confidence: 84%

“…2018; Mataitis et al . 2019; Millett 2019). Recall that the OSL ages of these sandy aeolian landforms represent the waning phase and stabilization of sand transport, as climate warmed and vegetation cover and soil moisture increased across the Chippewa Valley.…”

Section: Discussionmentioning

confidence: 99%

“…Recent work on extensive sandy aeolian deposits, e.g. sand stringers, parabolic dunes, sand ramps, climbing dunes and sand sheets, throughout the Chippewa Valley and neighbouring landscapes corroborates this interpretation (Millett et al 2018;Mataitis et al 2019;Shandonay et al 2020). In the lee of these large ridges, loess deposits are protected from erosion, and/ or loess from sites farther west has been secondarily deposited on top of them (Schaetzl et al 2014).…”

Section: Introductionmentioning

confidence: 89%

“…A variety of aeolian sediments mantle much of the study area. Loess data from sites in southeastern Minnesota support the notion of westerly and northwesterly winds for the primary period of loess deposition in the region, between c. 26 and 20 ka (Mason et al, 1994a,b;Zanner 1999;Mataitis et al 2019). Loess, derived from these western sources, including the Mississippi River Valley, still covers many of the broad, stable uplands here (Hole 1950;Scull & Schaetzl 2011), but is usually absent from many areas in the central Chippewa Valley, where it appears to have been transported out of the valley by west-northwesterly winds (Schaetzl et al 2018).…”

Section: Introductionmentioning

confidence: 90%

“…2018; Mataitis et al . 2019). Because the Driftless Area was at times almost surrounded by ice, cold conditions during the last glaciation (Late Wisconsin, Marine Isotope Stage, MIS 2) must have been persistent here, hence its nickname ‘Up in the refrigerator’ (Mason 2015).…”

Section: Figmentioning

confidence: 99%

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Luminescence dating of sand wedges constrains the Late Wisconsin (MIS 2) permafrost interval in the upper Midwest, USA

Schaetzl

Running

Larson

et al. 2021

Boreas

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Large parts of the upper Midwest, USA were impacted by permafrost during the Last Glacial Maximum (LGM). Even though permafrost persisted as the Laurentide Ice Sheet began to recede, direct age control of this interval is largely lacking. To better temporally constrain the permafrost interval in western Wisconsin, we identified two sites, outside the Late Wisconsin (MIS 2) glacial limit, that contain relict, ice‐wedge pseudomorphs, initially interpreted to be sand wedges, hosted within well‐drained outwash deposits. The pre‐Wisconsin (>MIS 5) host material commonly displays up‐turned bedding near the contact with the wedges, indicative of well‐formed features. The wedges are filled with well‐sorted, gravel‐free, medium and fine sands, and lack evidence of post‐formational disturbance, pointing to an aeolian sand infill and confirming them as sand wedges. Ventifacts on nearby uplands attest to windy conditions here in the past. Optically stimulated luminescence (OSL) ages on five sand wedges indicate that they filled with sand between c. 19.3 and 18.3 ka at the southerly site and between c. 15.1 and 14.7 ka at the northerly site, which is closer to the LGM margin. Sand wedges at the latter site were wider and had more complex morphologies, possibly suggesting a longer interval of formation and/or more intense permafrost. We also examined a site along a ridge crest, between the two wedge sites, which displayed interbedded loess and sand, dated by OSL to 12.7 ka. Together, these results point to dry, cold, windy conditions in west‐central Wisconsin, within 100 km of the LGM limit. At this time, aeolian sands were being transported across a landscape with (at least scattered) permafrost. The OSL results suggest multiple phases, or perhaps time‐transgressive, sand‐wedge formation, associated with permafrost between c. 19 and 15 ka, with dry, windy (and likely, cold) conditions persisting until at least 12.7 ka.

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