79-2 Shedding light on slowly eroding landscapes: OSL sensitivity and soil stratigraphic evidence of hillslope response to Quaternary river incision, southern Piedmont, USA.

Session: Soil, Dust, and Everything in Between: Current, Quaternary and Earlier Geological Processes and Records

Presenting Author:

Martha Eppes

Authors:

Eppes, Martha Cary¹, Vaughan, Nora², Tanski, Natalie M.³, Nelson, Michelle Summa⁴, Rittenour, Tammy M.⁵, Ferguson, Terry A.⁶, Wegmann, Karl W.⁷, Harmon, Melissa⁸

(1) UNC Charlotte, Charlotte, NC, USA, (2) Lehigh University, Bethlehem, PA, USA; UNC Charlotte, Charlotte, NC, USA, (3) University of Oklahoma, Oaklahoma, USA, (4) VA Dept. of Energy, Geology and Mineral Resources Program, Charlottesville, VA, USA, (5) Utah State University, Logan, UT, USA, (6) Wofford College, Emeritus, Spartanburg, SC, USA, (7) NC State University, Raleigh, NC, USA, (8) UNC Charlotte, Charlotte, NC, USA,

Abstract:

The dynamics of slowly eroding, nonglaciated humid temperate soil landscapes - and the contributions therein of dust - are generally understudied in the context of regional Quaternary landscape evolution and climate. In the southern Piedmont of the United States, a growing body of data provides evidence of episodic cut-fill cycles occurring in hollows and low-order watersheds (e.g., Ferguson et al., 2024) that are characterized by 10Be-derived basin-averaged erosion rates on the order of 10m/my (Reusser et al., 2015; Vaughan et al., in review). These cycles are superimposed on relatively fast (on the order of 50-100 m/my) long-term incision of major rivers draining the Atlantic (e.g., Mills, 2000; Arey, 2018). In this study, we combine detailed, classical soil field and laboratory data with a relatively novel application of optically stimulated luminescence (OSL) sensitivity measurements to explore the evolution of hillslope soils in low-order watersheds at the Redlair Observatory, North Carolina, USA, a typical landscape within the southern Piedmont. 

Building on the assertion that Piedmont hillslopes are sensitive to propagating waves of incision by adjacent tributary channels, which initiate at major rivers and terminate at regional watershed divides, we examine the soil stratigraphy of ~30 soil pits spread across such a transect from the North Fork of the Catawba River up to its regional divide with the Catawba River.  Buried soils are found in a majority of examined exposures, with up to three distinct episodes of deposition evident on some slopes. 14C dates on these buried soil stratigraphic units range from ‘legacy’ to early Holocene. Buried soils are less prevalent closer to the regional watershed divide. There, both surface and buried soils are overall much more well-developed (as evidenced by depth to bedrock, morphology, clay content, extractable Fe ratios, and bulk chemistry). Our preliminary analysis suggests that these well-developed soils exhibit consistently higher fast-component OSL sensitivity values, presumably reflecting the overall slower long-term erosion rates and resultant prolonged sediment retention of those slopes.  In ongoing work, we explore the relationship between OSL sensitivity and soil properties, hillslope aspect, and slope position to gain new insights into the possibility of eolian contributions and to explore how sediment accumulates and mobilizes across landscapes that are commonly considered  ‘stable’.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9951

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