Correlation of Jurassic sediments of the Carmel and Twin Creek Formations of southern Utah using bentonitic characteristics (OFR-169)

B. H. Everett, B. J. Kowallis, E. H. Christiansen, and A. Deino

The Jurassic Carmel Formation and Twin Creek Limestone of southern and central Utah are thought to be time equivalent deposits of marine carbonate and terrigenous sedimentary rocks that document a transgression of a shallow epeiric sea that extended southward from Canada to slightly beyond Carmen Junction, Utah. Lithologies of the two formations are similar to some extent. The interpretation of time equivalency is based on similar fossil assemblages of pelecypods and gastropods placing the age of the lower portion of both formations as Bajocian. However, in some areas fossils are not diagnostic or are non-existant, making correlation within and between the two formations difficult. Both formations contain bentonites (altered volcanic ash layers) that can be used in correlations.

The purpose of this study was to collect bentonitic ash samples from the Twin Creek Limestone and the Carmel Formation, note their stratigraphic occurrence, radiometrically date the samples, and examine other characteristics of the bentonites to determine if bentonitic ashes found in these formations could be correlated, both within and between the two formations.

Other Information:
Published: 1990
Pages: 60 p.
Location: Emery County, Kane County, Utah County, and Washington County
Media Type: Paper Publication