![]() ![]() For soil horizons, prefix 2 indicates unit 2 and prefix 3 indicates unit 3.įigure S5. ![]() and 3C strat.) consist of 1–10 cm-thick intercalated layers of sand, loamy sand, and sandy loam. Median particle size (μm) and soil horizonation for all ECC sand stringer cores. Grain size distributions and USDA textural class for GC sand stringer: (a) 45 samples distributed throughout the silt-rich unit 1 (Ap, A, B, and BC horizons) for all cores (b) 30 samples from the underlying sand-rich unit 2 for cores 1, 2, and 5 (2C horizons) and (c) 50 samples from the underlying sand-rich unit 2 for cores 3, 4, and 6 (2B, 2C, and 2Ck horizons).įigure S4. For soil horizons, prefix 2 indicates unit 2 and prefix 3 indicates unit 3.įigure S3. Median particle size (μm) and soil horizonation for all GC sand stringer cores. OD values greater than 30% are considered to have high dispersion.įigure S2. The overdispersion (OD), or scatter beyond instrumental error, for each sample is indicated. Results are shown as probability distribution plots on the left and radial plots on the right. Equivalent dose ( D E) distributions for OSL samples. 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.Įsp542-Figures_S1-S6.zip7-zip archive, 3.9 MBįigure S1. Pedogenesis at GC and ECC indicates stabilization with possible minor modification of near-surface sediments through the Holocene. We interpret ECC as composed of reworked outwash and local bedrock-derived sands. We interpret the main body of GC as equivalent to Peoria Loess, with minor inputs of reworked outwash. 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.ġ4C ages, interpreted as minima, at GC indicate formation began prior to 25–20 cal yr BP, while OSL and 14C ages indicate ECC formed ~11.25–8.9 ka. To the east, the sand stringer in Eau Claire County, Wisconsin (ECC site) is ~925 m long and 30–50 m wide. The sand stringer in Goodhue County, Minnesota (GC site) is ~870 m long and 50–80 m wide. 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. 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. 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. Sand stringers are subtle, aeolian landforms that reach hundreds to thousands of metres in length and lack a slipface. ![]()
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