Redefining the Middle Wisconsin Sheldon Creek Boundary in North Central Iowa

Tassier-Surine, Stephanie; Hydroscience, Iihr; Kerr, Phillip; Bettis, E. Arthur; Woida, Kathleen; Quade, Deborah

doi:10.1130/abs/2018nc-312945

Cited by 1 publication

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“…Beyond the Late Wisconsin terminus, the youngest glacial till deposits of the Dows Formation are not present, and few glacial landforms, such as moraines or eskers, are identified (Tassier-Surine et al, 2018). A regional erosional event during the Late Wisconsin Episode subdued the topography and eroded older features and sediment, removing these landforms and eliminating key stratigraphic markers such as the Sangamon Geosol (Ruhe et al, 1968;Ruhe, 1969;Mason, 2015).…”

Section: Introductionmentioning

confidence: 99%

Defining the Sheldon Creek Formation, a Middle Wisconsinan (MIS 3) till in Iowa, USA

Tassier‐Surine,

Kerr,

Kilgore

et al. 2024

J Quaternary Science

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A pre‐Late Wisconsinan, post‐Illinoian, till sheet has long been recognized in north‐central Iowa, but has not been formally recognized or defined until now. Early researchers referred to these deposits as the ‘Tazewell’, and the term ‘Sheldon Creek’ was more recently used informally by the Iowa Geological Survey in guidebooks and reports. Recent mapping has extended the eastern margin significantly past previous interpretations. The Sheldon Creek Formation has similar lithologic characteristics to the overlying Alden Member of the Dows Formation, and the two units are distinguished mainly by stratigraphic position. Differentiation from underlying Pre‐Illinoian till units is accomplished using lithology, primarily matrix grain‐size and sand fraction lithology. A suite of 22 radiocarbon ages indicate two distinct, separate groupings within the Sheldon Creek data. These data strongly suggest ice advanced south to 42° N twice, once during Marine Isotope Stage (MIS) 3 and again during late MIS 3 or possibly early MIS 2. The presence of the Laurentide Ice Sheet in northern Iowa during MIS 3 has significant implications for ice sheet reconstructions during this interval.

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Section: Introductionmentioning

confidence: 99%