For the fall semester of 2014, I enrolled in one of the capstone courses for geology students at NDSU – Field Geology. This course is designed to teach field methods as well as scientific writing, kind of like “Field” at other universities but less intense. The second week of the fall semester we headed west to the Little Badlands, a roughly 8 square-mile area southwest of Dickinson, ND. During the week we were there, we broke out into teams of 2-3 to map the bedrock of the entire area, gathering rock descriptions, structural features, and fossils within the sedimentary Paleogene-Miocene rocks.
Upon the return to NDSU after the week in the field collecting strikes and dips, descriptions, measured sections, notes, and photos, the rest of the semester is spent writing a scientific report of the area to explain the faulting history, sediment sources, and rock descriptions. The writing portion also includes a geologic map created using ArcGIS. This introductory course into field methods and scientific writing helped me gain experience and appreciation for the type of work geologists do and how to translate all the field notes and data into a report that pulls everything together while still making it concise and interesting for the reader.
Salt-affected soils in eastern ND
From May to November 2015, I worked with Dr. David Hopkins and Dr. Tom DeSutter from the NDSU Soil Science department on developing methods for soil micromorphology and using it to study salt-affected soils in eastern North Dakota. Soil micromorphology studies the porosity, mineral composition and distribution, soil fabric, and weathering characteristics of the soil at the microscope level to get a very detailed picture of how the soil behaves as a whole. For my work, I researched and developed methods for making soil thin sections from soil samples collected from a salt-affected soil near Embden, ND. Salt-affected soils are characterized by extremely high amounts of sodium salts. In high concentrations, sodium salts are detrimental to soil fertility because they disperse when wet and compact when dry. Plant roots are unable to penetrate these “hard pans” in dry conditions, so only very tough grasses can grow in this type of soil.
We sampled the soil profile at our sampling site and carefully labeled each intact block of soil for orientation. In the lab, the large samples were carefully broken apart to obtain smaller pieces for impregnation with a polyester resin. Once impregnated, the resin hardened for roughly 3-4 weeks. After this period of time the sample blocks could then be cut and polished on the PetroThin thin-sectioning machine to a thickness of 30 microns, the thickness required for microscope viewing. The thin sections were analyzed under a petrographic polarizing light microscope for mineral composition, porosity, fabric, and salt distribution. Our soil profile contained four separate horizons, and thin sections were made from each horizon and also from the horizon boundaries, when possible.
The results of the study concluded that while the highly soluble sodium salts were not visible in thin section, possibly due to dissolving under the different temperature and humidity in the lab, calcium salts were easily visible in the lower horizons filling in pores and channels. The grain size and porosity also changed dramatically through the profile. Especially interesting were the illuvial clay cutans that lined the pores one of the lower horizons, indicating the downward movement of clay particles through weathering. The results of this study were presented at the Geological Society of America National Meeting in Baltimore, MD, in November 2015.