Morphology and stratigraphy of aeolian sand stringers in southeast Minnesota and western Wisconsin, USA

Abstract

Sand stringers are subtle, aeolian landforms that reach hundreds to thousands of metres in length and lack a slipface. While hundreds of sand stringers exist beyond the Last Glacial Maximum margin in the Upper Midwest, USA, little is known about the timing and nature of their formation. This research characterizes the morphology and stratigraphy and provides geochronological data from two sand stringers in the upper Mississippi River basin in Minnesota and Wisconsin.The sand stringers investigated have similar west-northwest to east-southeast orientations and are located $100 km from each other on uplands west and east of the Mississippi River valley. The sand stringer in Goodhue County, Minnesota (GC site) is $870 m long and 50-80 m wide. To the east, the sand stringer in Eau Claire County, Wisconsin (ECC site) is $925 m long and 30-50 m wide. The main body of the GC sand stringer is characterized by an $80-270 cm-thick silt-rich surface unit overlying a sandy unit that is underlain by a dark brown paleosol, while the main body of the ECC sand stringer is sandier/coarser, stratified, and overlies outwash. 14 C ages, interpreted as minima, at GC indicate formation began prior to 25-20 cal yr BP, while OSL and 14 C ages indicate ECC formed $11.25-8.9 ka. We interpret the main body of GC as equivalent to Peoria Loess, with minor inputs of reworked outwash. We interpret ECC as composed of reworked outwash and local bedrockderived sands. Pedogenesis at GC and ECC indicates stabilization with possible minor modification of near-surface sediments through the Holocene. Differences in stratigraphy and chronology between the two sites highlight the complexity of aeolian systems in the Upper Midwest, interpreted as indicative of the variety of sediment sources contributing to landform development via aeolian processes due to spatial and temporal variability in deglaciation and permafrost melting.

Introduction to the Women in Geomorphology special issue

“…• the morphology and chronology of sand stringers along the margin of the last glacial maximum (Shandonay et al, 2022);…”

“…Country of lead author a References Goodman et al, in press;Guiney & Lininger, 2022;Hinshaw et al, 2022;Hovenga et al, 2021;Lane et al, 2022;Lininger et al, 2021;McKenzie et al, 2022;McKeon et al, 2022;Mossa & Chen, 2022;Opalka et al, 2022;Patton et al, 2022;Quock et al, 2022;Rathburn & Ely, 2021;Regalla et al, 2022;Reitman et al, 2022;Shandonay et al, 2022;Valentine et al, 2022;Wohl, 2022;Zhang et al,…”

“…Glacial geomorphic studies are represented by papers examining topographic controls on ice flow and glacier front recession (Davies et al, 2022); moraine dynamics in the context of climate change (Rowan et al, 2022); and streamlined sub‐glacial bedforms (McKenzie et al, 2022). Eolian processes and landforms are examined in papers on the morphology and chronology of sand stringers along the margin of the last glacial maximum (Shandonay et al, 2022); the influence of sorting and bedforms on the magnitude of coastal eolian transport (Uphues et al, 2022); grainflow morphology on the slipface of barchan dunes (Zhang et al, 2022); and dust deposition in an ice‐free area of West Greenland (Van Soest et al, 2022). Lacustrine environments are represented by an examination of paleolacustrine landforms (Adolph et al, 2022).…”