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

Wind-Driven Sediment Transport and Landform Development on the Rio Grande Deltaic Plain

Paper number: 40-3
Program: Technical Sessions
Time: 2:05 PM – 2:20 PM

Authors

Abstract

The Rio Grande delivers sediment to the Gulf of Mexico, forming a dynamic delta landscape. Avulsions in the lower delta have created abandoned channels and floodplains that now host shallow lakes and aeolian features known as lomas, which are low dunes primarily composed of silt. Although such fine material can be transported long distances (several kilometers), the loma at Laguna Larga, the subject of this study, occurs just ~250 m from its sediment source, suggesting that the mechanisms driving loma formation may not involve single-particle transport. This study investigates the processes controlling the entrainment, transport, and deposition of silt-sized particles contributing to the loma at Laguna Larga. We deployed three sediment traps along a transect oriented with prevailing winds, extending from the lake edge to the loma. We also deployed a mast with three anemometers placed at logarithmically spaced heights (0.115, 0.555, and 1.475 m) to measure wind velocity profiles. Sediment samples from both the traps and lake-adjacent flats were analyzed for grain size using a CILAS 1190 laser particle-size analyzer. Shear velocity (u*) and near-bed shear stress for sediment entrainment (τc) were calculated using standard transport equations. Between April and June 2025, average u* was 0.17 m/s, with weekly averages ranging from 0.12 to 0.21 m/s. Corresponding shear stresses ranged from 0.02 to 0.05 Pa. These values are sufficient to entrain only the finest particles (< ~11 µm), based on critical shear stress estimates for D₅₀ values ranging from 7 to 75 µm. However, calculated advection length scales (Lₐ) for <11 µm particles at average wind speeds (5.5 m/s) range from 550–5500 m, substantially farther than the ~250 m transport distance to the loma. This mismatch suggests that particles are not traveling as individual grains, but rather as cohesive aggregates that settle much closer to their source. These findings highlight the importance of aggregation in aeolian sediment transport and help explain the localized formation of the loma at Laguna Larga. As such features shape delta topography, understanding these processes is essential for interpreting landscape evolution in arid deltaic systems.

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

doi: 10.1130/abs/2025AM-414227

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