Yellowstone Paleo Survey: Stratigraphy


W.H. Weed produced the first paper on Yellowstone's sedimentary rocks in 1896, and with J. P. Iddings prepared maps that established the earliest stratigraphic column for the park in 1899. Later work by J. D. Love (1956), E. T. Ruppel (1982) and others established the need to consider the stratigraphy of the northern part of Yellowstone separately from the south-central part. See Figure 1, Stratigraphic nomenclature of sedimentary rock units in Yellowstone National Park (from Ruppel 1982).

Most of Yellowstone National Park is covered by Tertiary and Quaternary volcanic and glacial deposits. Older Paleozoic and Mesozoic rocks are exposed in a few areas where erosion and glacial scouring has uncovered these unites. Precambrian through Late Cretaceous rocks are exposed in the Gallatin Range. Jurassic and a thick section of Cretaceous rocks are found on Mount Everts. Precambrian and Paleozoic units outcrop in the northeast corner of the park. Paleozoic rocks are also exposed in the Birch Hills and Snake River areas along the southern boundary of Yellowstone.

Large portions of the park are covered by Tertiary volcanics. There is the potential for vertebrate fossils in the Absaroka Volcanic Supergroup (Middle Eocene). The Hoodoo Basin in the eastern portion of the park may have potential for vertebrate fossils. This area is remote, but it may be accessed by a Forest Service road or on the trail into the park at Bootjack Gap. The Wapiti and Aycross formations contain Bridgerian vertebrate fossils on the east flank of the Absarokas. Lower Tepee Trail Formation is late Bridgerian to early Uintan. Middle and Upper Tepee Trail Formation has yielded Uintan fauna. Tepee Trail flora is known from Kisinger Lakes area, Bridgerian fauna from Togwater Pass area.

Figure 1. Stratigraphic nomenclature of sedimentary units in Yellowstone National Park (adapted from
Ruppel, 1982).

Fossil Chronology