Authors: Kylie Hansen
Mentors: Janis Boettinger
Insitution: Utah State University
Cache Valley, Utah, has unique soils due to environmental events such as Pleistocene pluvial Lake Bonneville. This lake extended about 20,000 square miles in Northern Utah, and its depletion left numerous shorelines, the most relevant being the Bonneville and Provo shorelines. These various water levels influence the geological formations in Cache Valley and the different characteristics of soil formation. An important soil-forming factor used to characterize varying soils is the parent material. Parent material is the original sediments the soil formed on and can be various things such as sediments deposited by gravity, streams, lake sediments, or wind. These different materials depend on the location and alter the soil properties. A dominant soil parent material in the Lake Bonneville area is sediment deposited by this lake. This type of parent material is identifiable by coarser-sized sediments, such as cobbles, gravel, and sand. This pattern is evident on terraces in Cache Valley’s lower soil layers, but the near-surface layers have fewer rock fragments and more fine sand, silt, and clay. This distinct difference in particle size leads to the question of what is the parent material source in the surface horizons of soil formed in Lake Bonneville deposits in Cache Valley. There is not much literature on this question and little documentation compares the soil profiles for different Lake Bonneville terrace levels (Bonneville shoreline compared to Provo shoreline). We hypothesize that the different particle sizes of parent material in the surface of soils formed dominantly in Lake Bonneville deposits is eolian sediment transported and deposited by wind. To determine this, we will sample soils across Cache Valley and analyze the fine and very fine sand sediments in plane-polarized and cross-polarized light. This process will identify various minerals within each soil horizon, showing possible differences in the upper and lower horizons. The minerals present in each soil will indicate the parent materials, allowing us to understand what is causing the different textured horizons in these soils and where the sediment originated from.