Electronic Theses and Dissertations

Date of Award


Document Type


Degree Name

M.S. in Engineering Science

First Advisor

Ronald C. Counts

Second Advisor

Jennifer N. Gifford

Third Advisor

Brian F. Platt


University of Mississippi

Relational Format



The Upland Complex (UC) on the southern half of Crowley’s Ridge in Northeastern Arkansas is a 2.6 to 0.2 Ma high-energy, braided sand and gravel containing two thin zones of clay preserved near the top of the UC. Minimum age of the clay was acquired from overlying Brown and Foreman (2012) thermoluminescence ages and maximum age was acquired from Odom et al. (2019) Al/Be age of the basal UC. This project aims to discern if these clay layers formed from pyroclastic material and if so, what the provenance of the parent material is. The investigation of the clay layers included a lithofacies analyses coupled with X-ray diffraction (XRD) and Scanning Electron Microscopy-Energy Dispersive X-ray spectroscopy (SEM-EDS). SEM-EDS analysis of the clay identified igneous minerals such as sanidine, volcanic glass, albite, leucite, and pumice grains. XRD analysis indicated that kaolinite content in the gravels and sands was higher than in the clay, which is interpreted as an in-situ weathering product.. This is in contrast to the clay rich layers which are dominated by illite-smectite, indicating an igneous origin. The presence of igneous components and the occurrence of montmorillonite and altered volcanic glass indicates the clay has a pyroclastic origin. Igneous components identified in SEM-EDS were not limited to clay layers, but were also present in the clay fraction of sands and gravels. The lithofacies analysis identified nine lithofacies organized into four architectural elements. The gravel and sand lithofacies were organized into gravel bars and bedform architectural elements interpreted as braided ancestral Mississippi River deposits. Clay layers were assigned an abandoned channel architectural element and interpreted as abandoned bar chute deposits. In this instance, ash fall layers were deposited in a high energy fresh water environment and then altered into smectite. The alteration of smectite to illite-smectite likely occurred through K-fixation induced by repetitive wetting and drying cycles. Potential sources of the igneous material include the Valles Caldera, Yellowstone Caldera, Acoculco Caldera, and Long Valley Caldera, however the Yellowstone eruptions seem most probable because of their explosive and voluminous eruptions

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