Soil spatial variability on a Middle to Late Pleistocene scroll bar deposit of the Pee Dee River, Atlantic Coastal Plain, South Carolina

Authors: Bradley E. Suther*, Kennesaw State University, David S. Leigh, University of Georgia, George A. Brook, University of Georgia, LinHai Yang, Shaanxi Normal University
Topics: Geomorphology, Soils
Keywords: alluvium, argillic horizon, Quaternary, spatial variation, Ultisols
Session Type: Virtual Poster
Day: 4/9/2021
Start / End Time: 3:05 PM / 5:50 PM
Room: Virtual 52
Presentation File: No File Uploaded

Soils were examined on an optically-dated >114.2±11.3 ka scroll bar deposit of the Pee Dee River in South Carolina to determine the number of profiles needed to represent soil variability within an individual scroll bar prior to characterizing a soil chronosequence on similar landforms across multiple fluvial terrace levels. Fifty pedons randomly spaced along a 750 m transect following the scroll bar ridge crest were described from bucket auger borings. Properties known to be effective chronosequence parameters were measured. Soils include Hapludults, Paleudults, and Paleaquults that together display respective Bt horizon thickness, solum thickness, and rubification mean (range) values of 97 (40-132) cm, 151 (90-175) cm, and 26 (8-40) Buntley-Westin index units. A resampling procedure was applied to profiles to determine the appropriate per scroll bar pedon sample size for other sites. One hundred trials of each sample size of n=2 through n=50 were drawn with replacement from the 50 values for key morphological parameters obtained from observed profiles, and the standard deviation of each trial was calculated for each property. Analysis of resampled standard deviations suggests a 20-30 pedon sample size sufficiently characterizes soil morphological variation. Scroll bar soil variability is considerable and reflects variation in local relief and the thickness and texture of vertical accretion deposits that comprise soil parent material. Pedons exhibit increasing Bt horizon thickness and clay content and decreasing rubification in the downstream direction along the scroll bar, which features a downstream decrease in surface elevation and downstream fining and thickening of vertical accretion sediments.

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