Clay minerals of the Jurassic Arapien, Twist Gulch, and Morrison Formations of Central Utah
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Date
1981
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The Ohio State University
Abstract
Twenty-one samples from the Jurassic Arapien, Twist Gulch, and Morrison Formations in central Utah were collected during the summer of 1980. The whole fractions of these samples were x-rayed in order to determine the major constituents. All contained quartz and feldspar; most contained calcite and dolomite. Gypsum, halite, and either hematite of goethite occurred in some. Clay fractions of each sample were x-rayed twice, once before salvation in ethylene glycol, and after salvation, in order to classify the clay minerals as either smectite, illite, kaolinite, chlorite, or mixed-layer clays. Although no clay group was completely confined to any single formation, smectites occurred mainly in the Morrison, with minor occurrences in the Twist Gulch deduced from very weak peaks. Mixed-layer clays occurred in both the Arapien and the Twist Gulch, but not in the Morrison. The Arapien and the Twist Gulch could be distinguished from one another by particle size, as the Twist Gulch contained a smaller percentage of clay sized particles.