New Mexico Geological Society Annual Spring Meeting — Abstracts

Particle size distribution of soils play a crucial role in controlling the flow of water through the critical zone, making it an important quality to consider for environmental restoration. Recent studies have found that geophysical analyses of soils can give insight into their particle size distribution. It would be useful to have a quick, non-invasive method of identifying soil types; this study aims to use magnetics surveying for that reason.

The location of this study is a recreational area called Valley Creek Park in the Upper Valley of El Paso, Texas. Recent efforts have been made to restore this area by planting riparian species such as Rio Grande Cottonwoods, which tend to have higher survival rates in coarse-grained, non-saline soils. Geophysical surveys have the potential to be implemented before introducing riparian plant species to determine if an environment will facilitate their survival. Magnetics surveys can be used to estimate the particle size distribution of soils by relating a soil’s grain size to its magnetic qualities; smaller grain sizes tend to have lower magnetite content and therefore a lower magnetic signature, and vice versa. This study utilizes a magnetometer survey to estimate grain size variations in soils along a transect. These magnetics readings will be compared to data from laser diffraction particle size analyses of soils from the same area to test correlation between the two data sets.

Preliminary analysis of magnetics data show anomalies which appear to be too large to attribute to grain size variations alone. The results from the laser diffraction particle size analysis show varying particle size distributions not only at different locations within the study site, but variations with depth as well. This is likely due to earlier deposition in historic channels of the Rio Grande which are no longer existent due to channelization of the river in the 1930’s. Comparison of the magnetics and laser diffraction particle size analysis data is not possible until the large anomalies in magnetics are ruled out. A Ground-Penetrating Radar (GPR) survey will be conducted along this same transect to see if these anomalies can be attributed to a metallic object below the surface of the study site. If that is the case, then the data can be considered without the anomalies, and the magnetics and laser diffraction particle size analysis data can be tested for a correlation.