Walnut Canyon National Monument: Paleontological resource inventory (non-sensitive version)

Boudreau, Diana; Tweet, Justin; Santucci, Vincent

Walnut Canyon National Monument (WACA) protects a dense concentration of exceptionally well-preserved prehistoric cliff dwellings on the southern Colorado Plateau. Established by presidential proclamation in 1915, the monument contains more than 500 archeological sites along ten kilometers (six miles) of Walnut Creek. WACA is justifiably well-known for its cliff dwellings, built by the Sinagua people hundreds of years ago. These people took advantage of the ledge-and-recess erosion of rock outcrops in Walnut Canyon to make their homes. In addition, the deep pools and reliable flow of the creek made the canyon a rare and valuable home for the Sinagua people and supports the rich biological communities in this dry landscape. After the eruption of Sunset Crater Volcano in the 11th century, the population of the area grew significantly and people began constructing dwellings in the limestone alcoves below the canyon rim. Walnut Canyon’s ancient dwellings and rich assortment of plants, animals, and fossils hold traditional cultural importance for numerous tribes in the Southwest. For the Native American people, whose ancestors occupied the canyon for about 150 years, these sites contain evidence and information that verify oral histories and maintains cultural identities. Volcanic eruptions and other geologic processes, combined with ancient and modern human influences in the area, highlight the dynamic nature and interplay of social and environmental history. Aside from its value as a classroom for science and anthropology, the monument represents an outstanding scenic and recreational attraction for visitors and local residents. Walnut Canyon cuts through three geologic formations of early Permian age (approximately 275 million years ago), in ascending order the Coconino Sandstone, Toroweap Formation, and Kaibab Formation. They record an environmental transition from a dune field (Coconino Sandstone) to a shallow sea (Kaibab Formation). Quaternary deposits can also be found within the national monument. It is within the limestone and dolomite beds of the Kaibab Formation, which were repurposed by the Sinagua people as roofs and floors, that we can find abundant fossils. Paleontological resources have been documented in Walnut Canyon as early as 1893. Since that time many publications have touched on WACA’s geology and paleontology, but there has never been a formal park-specific paleontological inventory. To address this, in 2017 a field survey of WACA was conducted to revisit previously known fossiliferous sites, document unreported localities, and assess outside collections at WACA repositories. During the 2017 survey, 28 fossil localities were documented in the monument, and collections at Museum of Northern Arizona (MNA) and Western Archeological and Conservation Center (WACC) were assessed. The most common fossils documented from WACA include brachiopods (lamp shells), bivalves (clams, oysters, etc.), and gastropods (snails). Scaphopods (tusk shells), crinoids (sea lilies), and trace fossils were also documented. In addition to backcountry areas, all public trails were surveyed, as they are frequently used by the public and can be utilized for interpretive programs. In addition, these public localities are at a higher risk for unauthorized fossil collection.

Walnut Canyon National Monument: Paleontological resource inventory (non-sensitive version)

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