LITHOLOGY, STRATIGRAPHY, AND PALEONTOLOGY OF A SECTION OF THE LATE TRIASSIC CHINLE FORMATION NEAR CEDAR CITY, UT

The Upper Triassic Chinle Formation is a widespread, predominantly fluvial unit that occurs throughout the Four Corners region of the southwestern United States and is well-known for its rich assemblages of paleontological resources. While the biota and stratigraphy of the Chinle Formation have been well-studied at occurrences in New Mexico, portions of Utah, and Arizona, especially at Petrified Forest National Park, comparatively little literature exists concerning this formation in southwestern Utah. We present an analysis of a stratigraphic section of the Chinle Formation measured at the mouth of Cedar Canyon near Cedar City, Iron County, Utah. Four distinct units occur at this section: a basal mudstone-dominated “Lower Member” of Knudsen (2014) likely representing floodplain and lacustrine facies, a thick sequence of coarse-grained channel sandstone referable to the Shinarump Conglomerate — the basal unit of the Chinle elsewhere in most places —, a sequence of colorful channel sandstones and floodplain siltstones and mudstone, and an upper unit of red and purple paleosol mudstones with pedogenic carbonates forming ledges underlain by nodules. The latter two units are potentially referable to the Cameron Member and the informally named “Purple Pedogenic Beds” of Martz and others (2015), respectively, based on their likely equivalence with sections measured by these workers in nearby Zion National Park. Fossil material, including vertebrates (temnospondyl amphibians and aetosaurs), plants (indeterminate petrified wood), and ichnofossils (coprolites and invertebrate burrows), is present at this section, indicating potential for paleontological surveys in the region that could add important context to our understanding of Chinle Formation paleoecology and necessitating stewardship of the site given its location adjacent to State Route 14 and proximity to a populated area.