Mesa Verde National Park: Paleontological resource inventory (non-sensitive version)

Harrison, G.; Tweet, Justin; Santucci, Vincent; San Miguel, George

Although there is a long history of geological study in and around Mesa Verde National Park (MEVE), and outcrops at and around the cuesta have been used to provide names and definitions for several formations, the fossils of the park have attracted limited attention. MEVE’s rocks contain a detailed record of about 10 to 15 million years of shifting coastal and marine environments in the Late Cretaceous, approximately 90 to 75 Ma (million years ago). The surficial deposits of the park have been explored to a limited extent and have produced some paleoecological materials, including pollen of Holocene age. Fossils found in MEVE’s Cretaceous rocks represent organisms from a variety of settings, from calm offshore marine waters to coastal swamps and rivers. There are four geologic formations, in ascending order (oldest to youngest): the Mancos Shale, Point Lookout Sandstone, Menefee Formation, and Cliff House Sandstone. The marine Mancos Shale has yielded diverse fossils, including terrestrial pollen and spores, plant fragments, bivalves, ammonites, gastropods, worm tubes, crinoids, fish teeth, invertebrate burrows, fecal pellets, foraminifera, coccoliths, other calcareous nannofossils, and dinoflagellates. The nearshore Point Lookout Sandstone has the least diverse fossil record of the four formations, but invertebrate trace fossils, bits of wood, and bivalve and ammonite shells are occasionally found. The terrestrial Menefee Formation has abundant but little-studied plant fossils, including conifer trunks and foliage and other organs of ferns, cycads, conifers, and angiosperms. Finally, the nearshore Cliff House Sandstone includes both mollusks and the most significant vertebrate remains from the park. Among the vertebrates are sharks, rays, bony fishes, turtles, plesiosaurs, mosasaurs, and dinosaurs. Some of the Cretaceous fossils appear to represent undescribed species, such as a Palaeoaster-like fruit from the Menefee Formation, a leaf in the genus Platanites from the Menefee Formation, a sea star from the Cliff House Sandstone, and chimaera egg cases from the Cliff House Sandstone. In addition, MEVE collections include some fossils from outside of the park, notably Mancos Shale fossils from a project to define a principal reference section of the formation and Naturita Formation ammonites from the vicinity. The Upper Cretaceous fossils from MEVE are among the best in the National Park Service, and many of them can be placed in a detailed geologic section, further increasing their scientific value. Although the fossils of the park have long been overshadowed by the world-class archeological resources, it is hoped that this inventory and other ongoing efforts will attract more research. In addition, the Quaternary fossils found to date suggest that further exploration is merited and will provide information useful for understanding the conditions that attracted the Ancestral Puebloans and later caused them to leave the area. The fossils of MEVE present a rich resource for education, interpretation, and scientific research.

Mesa Verde National Park: Paleontological resource inventory (non-sensitive version)

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