60-38 Chemical and Physical Characteristics of Mudstone Beds of the White River Group, South Dakota

Session: 2YC and 4YCU Geoscience Student Research Poster Showcase

Presenting Author:

Authors:

Abstract:

The White River Group is a series of Eocene to Oligocene aged sedimentary deposits dominated by mudstones that outcrop extensively in western South Dakota. These mudstones have potential as a material resource for ceramics and may provide insight into paleoclimatic change in the region during the Eocene-Oligocene Transition, however there is only limited data on their chemical and physical properties. The object of this study is to characterize the chemical and physical properties of White River Group mudstones from near the Eocene-Oligocene Transition and provide preliminary insights into their use for ceramic art and engineering, paleoenvironment reconstruction, and geoarchaeology. Samples were collected from six mudstone beds exposed in a representative outcrop and analyzed using x-ray diffraction to determine mineral phases, x-ray fluorescence of general elemental chemistry, sedimentation for grain size analysis, and physical tests measuring shrinkage and firing characteristics. Results showed samples to be broadly similar in chemistry aside from calcium concentration, but contrasting in mineralogy and in the results of higher temperature firing. XRD shows the main clay phases shift from montmorillonite to illite up section, and calcite appears in the younger beds. High plasticity makes all clays examined good for ceramic arts, though without temper they have high shrinkage and low dry strength. The flux behavior of calcite in the upper beds make these clays natural glazes at higher kiln temperatures. White River Group mudstones have potential as a ceramic material resource for artists as pottery and glazes as well as industrial use (e.g., bricks). However, these mudstones require significant processing and modification for use as a ceramic material, which may explain its lack of use by early Native Americans in the region. Mineralogical shifts may indicate changes in depositional and weathering environment in the region during the Eocene-Oligocene Transition.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9446

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.