Photograph of the skull of the extinct horse Miohippus in side view. The skull is relatively complete, with missing areas reconstructed.

Fossils of the Columbia Plateau

Simple map identifying the Columbia Plateau physiographic region of the western United States.

Page snapshot: Introduction to the fossils of the Columbia Plateau region of the western United States.


Topics covered on this page: Paleozoic fossils; Mesozoic fossilsCenozoic fossils; John Day Fossil Beds; Eocene Clarno Formation; Oligocene John Day Formation; Miocene Mascall Formation; Miocene Rattlesnake Formation; Quaternary fossils; Resources.

Credits: Most of the text on this page comes from "Fossils of the Western US" by Brendan M. Anderson, Alexandra Moore, Gary Lewis, and Warren D. Allmon, chapter 3 in The Teacher-Friendly Guide to the Geology of the Western US, edited by Mark D. Lucas, Robert M. Ross, and Andrielle N. Swaby (published in 2014 by the Paleontological Research Institution; currently out of print). The book was adapted for the web by Elizabeth J. Hermsen and Jonathan R. Hendricks in 2022. Changes include formatting and revisions to the text and images. Credits for individual images are given in figure captions.

Updates: Page last updated September 1, 2022.

Image above: Skull of an extinct horse (Miohippus), John Day Fossil Beds National Monument. Photo by U.S. National Park Service (public domain).

Paleozoic fossils

The fossil brachiopod Titanaria is found in Mississippian rocks in northern California (Baird Shale, Shasta County) and central Oregon (Coffee Creek Formation) and is among the largest brachiopods in the world. Titanaria's shell reached widths (along the hinge line) of more than 35 centimeters (14 inches). 


Photograph of a brachiopod shell with a scale bar underneath it.  The scale bar is 90 millimeters long and less than half the full width of the shell.

The brachiopod Titanaria from the Mississippian of Oregon. Specimen from the U.S. National Museum of Natural History (Smithsonian), photographed by Wade Greenberg-Brand. Originally published inThe Teacher-Friendly Guide to the Geology of the Western US.

Mesozoic fossils

During the Jurassic and part of the Cretaceous, ammonoid cephalopods and bivalves were abundant and diverse in the shallow sea that covered this region. Vertebrate fossils are found occasionally, including sea crocodiles and pterosaurs.


2-panel image showing photographs of bone fragments from a Jurassic sea crocodile found in Oregon. Panel 1: Partial upper arm bone. The bone is oriented horizontally, with a rounded end to the left and a broken end to the right. It is about 9 centimeters long. Panel 2: Part of a vertebra.

Bone fragments (left, part of a humerus, or upper arm bone; right, part of a vertebra) of Zoneait nargorum, a so-called "sea crocodile" (that is not closely related to modern crocodiles) from the Jurassic Snowshoe Formation of Oregon. Photo of USNM PAL 256441 and USNM PAL 256443 by Michael Brett-Surman (Smithsonian National Museum of Natural History, public domain).


2-panel image of a pterosaur from the Cretaceous of Oregon. Panel 1: Photograph of several bones, including an upper arm bone. Panel 2: Silhouette of a pterosaur showing the positions of the bones in the left image in the arm and spine.

The pterosaur Bennettazhia oregonesnis from the Cretaceous of Oregon. Left: An arm bone (humerus) and a vertebra. Photo of USNM V 11925 by Michael Brett-Surman (Smithsonian National Museum of Natural History, public domain)Right: Silhouette reconstructing the possible appearance of Bennettazhia and the position of the bones in the left image in the skeleton. Illustration by Dean Falk Schnabel (Wikimedia Commons, Creative Commons Attribution-ShareAlike 3.0 Unported license, image cropped and resized).

Cenozoic fossils

Several sites in Oregon and Washington preserve abundant Cenozoic terrestrial fossils, especially plants and mammals, as a result of widespread volcanic activity in the area. During the Neogene, the Columbia Plateau was covered in large volcanic outflows of flood basalt. These outflows are associated with the same hot spot that now heats Yellowstone National Park. Some of these lava flows overran forests, leaving behind empty molds of trees.

At some localities, such as Ginkgo Petrified Forest State Park in Washington, petrified (permineralized) wood has been preserved either by burial within lake sediments or in volcanic mudflows. Examples of petrified wood types preserved in this region include ginkgo, conifers (pine, Douglas fir, bald-cypress-like), and many angiosperms (sycamore, sweet gum, alder, elm, tupelo, hickory, oak, and cherry).


Photograph of Ginkgo Petrified Forest State Park in Washington. The photo shows a chunk of a petrified log in the foreground that is white and orangey-brown in color. More large chunks of wood are sparsely scattered in the background. The ground surface is flat and has a layer of gravel on it. In the background is a fence made of rectangular stone posts linked by cables or chains. 

Middle Miocene petrified logs at Ginkgo Petrified Forest State Park near Vantage, Washington. Photo by Sean O'Neill (flickr, Creative Commons Attribution-NoDerivs 2.0 Generic license).


Figure with photograph of six petrified wood specimens from the middle Miocene of Washington. Four specimens are shown in cross section, one is shown in long section, and one is shown in both cross and long section. The woods are a mix of conifers and angiosperms (flowering plants).

Petrified wood from the middle Miocene of Washington. A. Ash-like wood (Fraxinus), Ginkgo Petrified Forest. B. Conifer wood, cypress family (Cupressaceae), Saddle Mountain. C, D. Conifer wood, Umtanum Canyon. E. Wood of a member of the walnut family (Rhysocaryoxylon, Juglandaceae), Yakima Ridge Terrace Heights. F. Conifer wood, cypress family (Taxodioxylon, Cupressaceae), Saddle Mountain. G. Conifer wood, pine family (Piceoxylon, Pinaceae), Ginkgo Petrified Forest. Source: Figure 16 from Mustoe and Dilhoff (2022) Minerals 12(2) 131 (Creative Commons Attribution 4.0 International license, image resized).


John Day Fossil Beds

The Eocene to Miocene Clarno, John Day, and Mascall formations are collectively known as the John Day Fossil Beds. They span over 40 million years and can be best seen in and around John Day Fossil Beds National Monument in Wheeler and Grant Counties in north-central Oregon.

Eocene Clarno Formation

The Eocene Clarno Formation, exposed at several sites in central Oregon, consists of a series of volcanic ash deposits, which quickly buried plants and animals and protected them from decomposition. The resulting spectacular fossils include hundreds of kinds of leaves and seeds, as well as insects, mammals, and other animals. The famous Clarno “nut beds” exposed in Wheeler County in north-central Oregon have yielded more than 170 species of fossil fruits and seeds. Clarno fossil leaves include palms, bananas, and many flowering tree species. These fossils indicate that between 50 and 44 million years ago, the climate of what is now the Pacific Northwest was warm and humid.


Photograph of the pit of a fruit from the Eocene Clarno Nut Beds of Oregon. The fruit is broken open showing in inner lining of white crystal surrounded by a brown fruit wall.

Pit (hard, inner wall) from a fruit of Paleophytocrene, an extinct plant in the tropical family Icacinaceae, from the Eocene Clarno Formation, Oregon. The fruit pit has been broken in half and looks like a brown ring lined with white crystals. Photo of USNM PAL 354168 by Michael Brett-Surman (Smithsonian National Museum of Natural History, public domain).


Photograph of fossil walnuts from the Clarno Formation embedded in a rock. The rock as three nut in it. One is ovoid and smooth. One is a cast of the inside of a nut. The third is a nut in cross section, showing the chambers inside.

Fossil walnuts (Juglans clarnensis) from the Eocene Clarno Formation, Wheeler County, Oregon. Photo of YPM PB 035771 by Linda S. Klise (Yale Peabody Museum of Natural History/YPM, CC0 1.0 Universal/Public Domain Dedication, accessed via GBIF.org).


Photo of the skull of Zaisanamynodon protheroi, an extinct mammal related to modern rhinoceroses, from the Eocene Clarno Formation. The skull has a jaw with large teeth. The upper part of the skull is harder to see.

Skull of Zaisanamynodon protheroi, an extinct relative of rhinoceroses, from the Eocene Clarno Formation, Oregon. Fossil on display at the Thomas Condon Paleontology Center, John Day Fossil Beds National Monument. Photo by Steve Lew (flickr, Creative Commons Attribution-NonCommercial-SharkeAlike 2.0 Generic license, image cropped).


Oligocene John Day Formation

The Oligocene John Day Formation is another series of volcanic ash layers rich in fossil plants and animals, which formed between 35 and 25 million years ago. The climate was cooler, but species diversity was still high.

Fossils found in the John Day Formation include more than 60 species of plants, including the “dawn redwood” (Metasequoia), a relative of the living giant sequoias (Sequoiadendron gigantea) and coast redwoods (Sequoia sempervirens). Although dawn redwoods where once widespread in the northern hemisphere, China is the only country where they grow in the wild today. Dawn redwood differs from both giant sequoias and the coast redwood in that it is deciduous (meaning that it loses its leaves seasonally rather than remaining evergreen like most conifers). Examples of other plants from the John Day Formation include alder (Alnus), hornbeam (Paracarpinus), katsura (Cercidiphyllum), maple (Acer), and oak (Quercus).

The John Day Formation also contains more than 100 species of mammals, including entelodonts ("hell pigs"), oreodonts, other artiodactyls (even-toed hoofed mammals), nimravids (false saber-toothed cats), horses, rhinoceroses, camels, and rodents.


Mural of the Turtle Cover Member fauna and flora from the Oligocene of Oregon. In the picture, a forest grades into an open savanna or grassland. Horses and other herbivores can bee seen in the forest and grassland. A saber-toothed cat sits in a tree.

Mural depicting the plants and animals of the Oligocene Turtle Cove Member of the John Day Formation by Roger Witter. Photo by John Day Fossil Beds National Monument (Bureau of Land Management Oregon and Washington on flickr, Creative Commons Attribution 2.0 Generic license, image resized).


2-panel figure showing photos fossils of alder form the Oligocene John Day Formation. Panel 1: Alder leaves. The leaves are simple with pinnate venation and a toothed margin. Panel 2: A branch with two so-called cones, really clusters of female flowers or fruits.

Alder (Alnus) leaves and "cones" (groups of female flowers or fruits, but not true cones) from the Oligocene John Day Formation, Oregon. Fossils on display at the Thomas Condon Paleontology Center, John Day Fossil Beds National Monument. Left photo and right photo by National Park Service/NPS (public domain).


Photograph of the skull of Promeryocochoerus, an even-toed hoofed mammal from the Oligocene of Oregon. The skull appears complete and is robustly built.

Skull of the artiodactyl (even-toed hoofed mammal) Promerycochoerus from the Oligocene John Day Formation of Oregon. Photo by Bruce Martin (Smithsonian National Museum of Natural History, public domain).


Photograph of the skull of the fossil canid Mesocyon from the Oligocene of Oregon. The skull is shown in the side and appears complete. The teeth are sharp and the canines relatively long.

Skull of the canid Mesocyon from the Oligocene John Day Formation of Oregon. Photo by Michael Brett-Surman (Smithsonian National Museum of Natural History, public domain).


2-panel figure of photos of nimravid skulls from the Oligocene John Day Formation. Nimravids are an extinct group of cat-like animals. Panel 1: Small skull o of a dirk-toothed nimravid. Panel 2: Larger skull of the so-called John Day "tiger," which has saber-like canine teeth.

Skulls of nimravids, or false saber-toothed cats, from the Oligocene John Day Formation, Oregon. These animals appear cat-like, but are not true cats and are not related to true saber-toothed cats. Left: Dirk-toothed nimravid (Dinictis cyclops)Right: John Day "tiger" (Pogonodon platycopis). Photos by National Park Service/NPS (public domain).


Skull of an extinct beaver from the Oligocene of Oregon shown in side view.

Skull of a fossil beaver (Paleocastor peninsulatus) from the Oligocene John Day Formation of Oregon. Photo of USNM V 7722 by Bruce Martin (Smithsonian National Museum of Natural History, public domain).


Photographs of fossils of a birch mouse from the Oligocene of Oregon. Left: Skull shown in side view. Right: Unidentified bones embedded in a rock.

Skull (left) and bones (right) of a birch mouse (Proheteromys latidens) from the Oligocene of the John Day Basin, Oregon. This specimen was found on BLM land near John Day Fossil Beds National Monument. Photo by John Day Fossil Beds National Monument (Bureau of Land Management Oregon and Washington on flickr, Creative Commons Attribution 2.0 Generic license, image resized).


Miocene Mascall Formation

Following the eruption of the Columbia River Basalt flows, between 17 and 12 million years ago, further ashfalls from eruptions in the Cascades formed the early to middle Miocene Mascall Formation. The Mascall Formation preserves another diverse assemblage of mammals, including horses, camels, rhinoceroses, bears, pronghorn, deer, weasels, raccoons, cats, and mastodonts. Plant fossils include ginkgo, dawn redwood, oak, sycamore, hackberry, maple, and elm, reflect the region’s cooling climate during this time period.

The flood basalts also contain one of the world’s most unusual fossils, the “Blue Lake Rhino,” in Grant County, Washington. It is an external mold of a rhinoceros, which lived around 14.5 million years ago. It apparently formed when lava flowed into the water, forming pillows. These were still hot enough to be soft but not hot enough to completely burn away the body.


2-panel image of the ancient horse Archaeohippus from the Miocene Mascall Formation. Panel 1: Photograph of 10 teeth in two rows embedded in what appears to be a reconstructed piece of bone. Panel 2: Portion of a mural showing two Archaeohippus as they may have appeared in life. The horses are in a grasses area near a river that is flanked by dense stands of cattails.

An early horse (Archaeohippus) from the Miocene Mascall Formation, Oregon. Left: Fossil teeth. Right: Artist's reconstruction of Archaeohippus from a mural at John Day Fossil Beds National Monument. Left photo and right photo by National Park Service/NPS (public domain).


2-panel figure showing mammals from the Miocene Mascall Formation. Panel 1: Photograph of the heel bone fo a bear-dog. The bone is slightly elongated with knob exposed. Panel 2: Portion of a mural showing a bear-dog confronting a camel. The camel is rearing up and has its head turned to face the bear-dog. It is spitting at the bear-dog.

Mammals from the Miocene Mascall Formation, Oregon. Left: Heel bone of a bear-dog (Amphicyon). Right: Artist's reconstruction of a bear-dog (Amphicyon) chasing a camel (Miolabis) from a mural at John Day Fossil Beds National Monument. Left photo and right photo by National Park Service/NPS (public domain).


Photograph of the lower jaw of a gomphothere. The jaw has two short tusks protruding from its tip. The molars have multiple cusps and are mastodon-like.

Lower jaw of an gomphothere (Gomphotherium cingulatum), Miocene Mascall Formation, Oregon. Gomphotheres are elephant-like animals. Specimen on display at the Thomas Condon Paleontology Center, John Day Fossil Beds National Monument. Photo by daveynin (flickr, Creative Commons Attribution 2.0 Generic license, image cropped and resized).


Photograph of molars of Zygolophon, a mastodont, from the Miocene Mascall Formation. The teeth have high cusps similar to those of the mastodon. They are still rooted in a jaw fragment.

Molars of an early mastodont (Zygolophodon), Miocene Mascall Formation, Oregon. Photo by National Park Service/NPS (public domain).


Photograph of a chunk of brown rock with white hackberry seeds embedded in it from the Miocene Mascall Formation. The seeds are oval-shaped and many are broken open, showing hollow interiors.

Hackberry (Celtis) seeds, Miocene Mascall Formation, Oregon. Photo by National Park Service/NPS (public domain).


Miocene Rattlesnake Formation

The youngest fossil-bearing unit at John Day Fossil Beds is the Rattlesnake Formation, which dates to the late Miocene, about 7 million years ago. As with the older rock units, it preserves a diverse mammal fauna. These include animals like rodents, camels, horses, peccaries, rhinoceroses, shovel-tuskers (elephant-like animals), foxes, and short-faced bears. The world's oldest fisher (Pekania occulta), a type of mustelid (a group including weasels and skunks), has been recorded from this formation. 


Photographs of beaver teeth from the Rattlesnake Formation. The image shows the chewing surfaces and side views of two teeth. Each tooth is nearly square when viewed from above, with low cusps. When viewed from the sides, the teeth are rectangular.

Beaver (Castor) teeth (left, top view; right, side view), Miocene Rattlesnake Formation, Oregon. Photo by Bureau of Land Management/BLM and National Park Service/NPS (BLM of Oregon and Washington on flickr, Creative Commons Attribution 2.0 Generic license, image reconfigured, cropped, and resized).


2-panel figure of a shovel-tusker elephant from the Miocene Rattlesnake Formation. Panel 1: Photograph of two teeth in a tray of gravel. The teeth have multiple pointed cusps. Panel 2: Portion of a mural showing a shovel-tusker as it may have appeared in life. The animal is elephant-like, except the upper tusks are straight and pointed slightly downward, and two short tusks protrude from the lower jaw.

Shovel-tusker (Ambelodon) from the Miocene Rattlesnake Formation, Oregon. Left: Teeth. Right: Artist's reconstruction from a mural at John Day Fossil Beds National Monument. Left photo and right photo by National Park Service/NPS (public domain).


2-panel figure of the short-faced bear from the Miocene Rattlesnake Formation. Panel 1: Photograph of fossil teeth in a tray of gravel. The teeth appear to include canines and molars. Panel 2: Detail of a mural showing a short-faced bear as it may have appeared in life. The bear has long legs and is standing in a grassy landscape.

Short-faced bear (Indarctos oregonensis), Miocene Rattlesnake Formation, Oregon. Left: Teeth. Right: Artist's reconstruction from a mural at John Day Fossil Beds National Monument. Left photo and right photo by National Park Service/NPS (public domain).


Quaternary fossils

Large mammals, including woolly mammoths and camels dating from the Quaternary, have been found in a variety of locations representing ancient riverbanks and lakes. The oldest known mastodon (another relative of modern elephants) in North America comes from the Ringold Formation at White Bluffs in south-central Washington.


Photograph of dry ground with mudcracks. In the foreground, two large, circular depressions can be seen. These depressions are mammoth tracks.

Mammoth tracks (circular impressions) at Fossil Lake, Oregon, 2017. Photo by Greg Shine (Bureau of Land Management Oregon and Washington on flickr, Creative Commons Attribution 2.0 Generic license, image resized).


Photograph tooth shards from an extinct camel, Pleistocene, Oregon. The pieces of tooth are irregular in shape, thin, and off-white in color. 

Tooth shards from an extinct Plesitocene camel (Camelops). These specimens come from the Rimrock Draw Shelter, an important archeological site near Riley, Oregon. A stone tool and spearpoints have also been found at the site. University of Oregon Archaeological Field School (Bureau of Land Management Oregon and Washington on flickr, Creative Commons Attribution 2.0 Generic license, image resized).

Resources

Resources from the Paleontological Research Institution

Digital Atlas of Ancient Life Virtual Collection: https://www.digitalatlasofancientlife.org/vc/ (Virtual fossil collection featuring 3D models of fossil specimens sorted by group)

Digital Encyclopedia of Ancient Life: https://www.digitalatlasofancientlife.org/learn/

[email protected]: Earth Science of the Northwest-central United States: Fossils of the Columbia Plateau (continues coverage of the Columbia Plateau in Idaho): https://earthathome.org/hoe/nwc/fossils-cp/

[email protected]: Quick guide to common fossils: https://earthathome.org/quick-faqs/quick-guide-common-fossils/


Go to the full list of resources about fossils in the western U.S.

Go to the full list of general resources about fossils