40 Aeolian Systems in Time and Space

This session explores research focused on all aspects of aeolian processes and landforms, including dunes, dust, and loess in modern and ancient aeolian systems on Earth and other planets.

Sunday, 19 October 2025
1:30 PM - 5:30 PM
HBGCC, 212AB

Measuring California Ventifact Erosion and Exposure Across Different Timescales Using Luminescence and Cosmogenic Radionuclide Rock Surface Techniques

Paper number: 40-12
Program: Technical Sessions
Time: 4:15 PM – 4:30 PM

Authors

Abstract

Ventifacts—rock surfaces abraded by wind-blown sand in arid environments—preserve evidence of long-term aeolian erosion. Yet, erosion rates for these objects remain poorly constrained, largely due to a lack of methods suited for quantifying hard-rock erosion on Holocene timescales and small spatial scales. This study addresses that gap by estimating erosion rates at two southern California sites: Silver Lake, near Baker; and Garnet Hill, near Palm Springs. We combine optically stimulated luminescence (OSL) depth profiles with in situ cosmogenic radionuclide (CRN) analysis to constrain erosion rates across different temporal and spatial scales.

OSL samples were collected from the surfaces of 10 ventifacts using a coring drill or angle grinder, then cored and sliced into ~1.2 mm rock wafers. Infrared-stimulated luminescence (IRSL) and post-IRSL signals from the crushed wafers were measured using an automated Risø TL/OSL reader. For CRN, several-centimeter-thick slabs (~200 cm²), were extracted from the same ventifacts, using an angle grinder and chisel. These samples were processed at the National Science Foundation / University of Vermont Community Cosmogenic Facility to isolate quartz for ²⁶Al and ¹⁰Be extraction (at UVM), and ¹⁴C extraction (at Purdue). Topographic shielding was assessed via clinometer survey, and self-shielding was calculated using Balco’s (2014) algorithm applied to 3D structure-from-motion (SfM) models.

Due to the different integration depths and averaging times of OSL and CRN methods, we can reconstruct erosion histories at multiple spatial and temporal scales throughout the Holocene at both sites, offering insights into past local climate changes. Initial results from ²⁶Al suggest long residence on hillsides, on the order of 25 to 109 ka, suggesting these boulders may retain nuclide inventories that accumulated prior to ventifact formation. Apparent erosion rates from ²⁶Al results range from 6 to 30 mm/ka. Absolute OSL erosion rates depend significantly on the assumed kinetic order, being either consistent with, or lower than, CRN rates. Relative OSL results across ventifact surfaces show no systematic difference in apparent erosion rates across major erosional features (ex. flutes, scallops), consistent with published expectations of peak ventifact formation during the middle Holocene (Laity, 1995). Forthcoming CRN data will allow us to compare the concentrations of multiple isotopes to examine the influence of inheritance or changing erosion rates.

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

doi: 10.1130/abs/2025AM-414212

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