GSA Connects 2022 meeting in Denver, Colorado

Paper No. 29-11
Presentation Time: 9:00 AM-1:00 PM


BECKHAM PATE, Savana, SPERRY, Matthew, MERZ, Madilyn, GILLIS, Morgan, GOKEY, Kailee, MCLEOD, Claire and KREKELER, Mark, Department of Geology & Environmental Earth Science, Miami University, 118 Shideler Hall 250 S. Patterson Ave., Oxford, OH 45056

Desert soils have the potential to serve as monitors of local and regional environments. In this work, we report results from a detailed electron microscopy-based study of desert soils in central Nevada. Samples were collected from the southern region of the Big Smoky Valley ~20 miles north of the historic mining town of Tonopah. Four 45 cm soil pits were dug within a 20m2 area. While the regional landscape is dominated by alluvium, Oligocene-Miocene basalt flows outcrop immediately to the west of the sampling location. Over 20 samples were collected from each pit, including from the topsoil and 4-5 other soil horizons. Additionally, when present plant samples were collected, an index count of vegetation was performed to evaluate this area's biodiversity. Six plant species were discovered: Grayia spinosa, Tetradymia glabrata, Artemisia arbuscula, Lycium andersoii, Artemisia spinescens, and Aristida purpurea. Percentages of these species were determined at 0.05%, 1.5%, 2%, 3.6%, 5.7%, and 86.3% respectively. The Shannon-Weiner diversity index of this area was 0.586. Munsell Color Chart values were recorded for each soil sample, all representing variances within the yellow-red (YR) hue. Soil samples were subsequently analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. In-depth electron microscopy of each soil horizon from each pit allowed for the characterization of the naturally occurring particles, the identification of anthropogenic contributions, and documentation of textural variations within the samples. Microscopy revealed the presence of minerals with chemical compositions dominated by iron, calcium, silica, aluminum, and titanium with various oxides also present. Technogenic spherules were also identified and likely originated from nearby industrial activity. Aerial deposition, stormwater run-off (although rare), and agricultural activity are all potential avenues through which contamination of desert soil could occur. This study looks to provide an environmental reference for the region and results will be compared to recent work which characterized nearby sand dunes. Further research collected soils aims to better understand the relationships between anthropogenic activity, soil development, and the local flora and fauna.