John Day Fossil Beds

By: Austin Urrutia

John Day Fossil Beds National Monument

is a U.S. National Monument in Wheeler and Grant counties in east-central Oregon. Located within the John Day River basin and managed by the National Park Service, the park is known for its well-preserved layers of fossil plants and mammals that lived in the region between the late Eocene, about 45 million years ago, and the late Miocene, about 5 million years ago. The monument consists of three geographically separate units: Sheep Rock, Painted Hills, and Clarno.

Averaging about 2,200 feet (670 m) in elevation, the monument has a dry climate with temperatures that vary from summer highs of about 90 °F (32 °C) to winter lows below freezing. The monument has more than 80 soil types that support a wide variety of flora, ranging from willow trees near the river to grasses on alluvial fans to cactus among rocks at higher elevations. Fauna include more than 50 species of resident and migratory birds. Large mammals like elk and smaller animals such as raccoons, coyotes, and voles frequent these units, which are also populated by a wide variety of reptiles, fish, butterflies, and other creatures adapted to particular niches of a mountainous semi-desert terrain.

The John Day Fossil Beds National Monument lies within the Blue Mountains physiographic province, which originated during the late Jurassic and early Cretaceous, about 118 to 93 million years ago. Northeastern Oregon was assembled in large blocks (exotic terranes) of Permian, Triassic, and Jurassic rock shifted by tectonic forces and accreted to what was then the western edge of the North American continent, near the Idaho border. By the beginning of the Cenozoic era, 66 million years ago, the Blue Mountains province was uplifting (that is, was being pushed higher by tectonic forces), and the Pacific Ocean shoreline, formerly near Idaho, had shifted to the west.