John Day Fossil Beds National Monument paleontological hike
How would you like to travel back in time? You might be thinking, sounds like science fiction. And in a way, you would be right. But I am not talking about the sort of time travel involving flux capacitors or DeLorean time machines. Rather, the sort that uses dated rocks and hard scientific evidence to unlock the secrets of the Earth. I am talking about paleontology — a science dedicated to piecing together stories of the past.
In Oregon, there is one place that stands above the rest for this sort of time travel and that is John Day Fossil Beds National Monument. With that in mind, I reached out to Nick Famoso, Paleontology Program Manager for the Monument, to see if he might be my guide into Oregon’s past. He said, “Yes!”
A monument with 40 million years of time
Nick and I met at the Blue Basin parking lot in the Sheep Rock Unit of the park. Adorned in a park ranger uniform and sunglasses, Nick possessed a Marty McFly vibe when he introduced himself and told me about the park.
John Day Fossil Beds National Monument serves a special purpose — “to preserve and interpret the story of the geological past of the John Day region,” explained Nick.
The park represents over 40 million years of time. With the Sheep Rock Unit providing the longest geological record from about 33 million to 7 million years ago.
We decided to hike the Island in Time Trail, which takes you directly into a small section of the Sheep Rock Unit known as the Blue Basin or the Turtle Cove assemblage. Blue Basin rocks preserve a small slice of Oregon’s geological past — 30 to 29 million years ago — but offer an outstanding fossil record hidden in blue-green layers of sedimentary rocks.
Ashes to Ashes
The sun was high as we began our hike along the trail, headed toward Blue Basin’s interior. White puffy clouds floated by on a bright blue sky.
Before long something caught Nick’s eye — a bright white patch of ash hidden in the hillside.
“When you see pockets like that, that are bright white, it is most likely Mount Mazama ash,” Nick confirmed.
Mount Mazama is a Cascade volcano that erupted so explosively 7,700 years ago, it dropped several inches of ash over much of the Pacific Northwest, leaving a massive depression that would eventually become Crater Lake. The eruption now acts like a marker of time — anything above it, is younger than 7,700 years, anything below, older — as well as a record of Oregon’s volcanic past.
Fiery cloud of death from Oregon
Further into the canyon, Nick also pointed out a thick brown layer of rock that capped a section of the Blue Basin —Picture Gorge ignimbrite. Another clue to Oregon’s intense volcanic history.
Ignimbrites are made from hot pyroclastics, like ash and lava rocks of various sizes, that are ejected during a violent volcanic eruption, before consolidating or welding into solid rock. According to Nick, eruptions that form ignimbrites are massive — large enough to lead to large-scale changes in the flora and fauna.
“Imagine a fiery cloud of death,” Nick expounded when explaining how ignimbrites form.
In the case of the Picture Gorge ignimbrite, the Crooked River Caldera — a supervolcano that once covered several square miles in central Oregon — ejected so much hot material some 28.7 million years ago that any life in the vicinity, including in the John Day region, was incinerated by the blast.
As life returned following the eruption, it came back altered. According to Nick, this is typical following ignimbrite forming eruptions.
“Forests were reduced,” said Nick, “more areas opened up and grasslands established.”
Though some taxa persisted from before the eruption, overall fauna adapted to open habitats prevailed. Burrowing beaver and gophers were common. Running mammals, including horses and camels, as well as the first running predator in Oregon, Daphoendon, were more abundant in the period following the eruption.
Busy volcanoes create layered cake
Nick and I walked deeper still into the otherworldly badlands, on dry, dusty ground, crossing several small footbridges.
Below the ignimbrite, layers of pale multicolored rock shot up before us — a layered cake of geology.
Before and after the Crooked River eruption, volcanism in Oregon was busy. Volcanoes east and west of John Day erupted frequently, spewing rhyolite ash that piled up and weathered into clay and silt, eventually hardening into siltstone and claystone.
The brown and tan layers of our geological cake are unaltered siltstone or claystone. Other layers tell a different story.
“Blue-green colored layers,” Nick explained, “is from a mineral called celadonite.” Celadonite forms when hot water chemically weathers volcanic soils before solidifying into rock.
White shelf-like layers are volcanic tuff — formed from the ejected ash from more explosive eruptions. Each layer represents only one eruptive event.
All this layering — or stratigraphy — allows paleontologists to divide time into subunits, characterized by their ashes and geological composition. Each layer of colorful rock represents a different time frame and different environment.
“The ashes are like page numbers,” Nick said. Each layer represents about 10,000 years.
All in all, at Blue Basin, there are 7 subunits — numbered B through F with some letters divided further.
It’s sedimentary, my dear
Nick directed me over to a spot where rocks were crumbling from the hillside. You could see material falling from the exposure — a perfect place to look for fossils!
John Day Fossil Beds National Monument, perhaps not too surprisingly, is known for its fossils.
Which raises the question — Why? Why is John Day a hotbed for fossils?
This can be answered in one word — water.
Though hard to imagine now, with the hot summer sun beating down on us in a dry, desert environment, Blue Basin was once a wide, river valley. A river valley that flooded frequently, depositing sediment along its banks and into its floodplains — sometimes burying the remains of dead animals or plants, and preserving them in sedimentary rock.
Collecting fossils
Now, looking at the crumbly hillsides, it was easy to see how water was still at work — this time eroding away the layers of rock and exposing fossils.
On any given day,” said Nick, “ten field collections might be extracted from this unit.”
Considering that Blue Basin has been studied for over 30 years, that is a lot of fossils!
According to Nick, “a collection” is a fossil “that can be identified to a fairly high level.” In other words, identifying that a fossil came from a mammal would not constitute a collection, but identifying the fossil came from a rhino, that would!
“What is most important is the context,” explained Nick. So, in addition to gathering the fossil, additional information is gathered.
Any specimen found loose, or “in float,” is put into a bag with any other material that is found within a three-meter area.
Fossils that are found “in situ,” or in the rock, also require detailed documentation of fossil location and position in the rock, as well as other contextual information.
It should be noted that fossils are collected in the park only by permit. Individual collecting is not allowed, Nick warned, and is a “bad idea for science.”
Evidence of past life
“Fossils are evidence of past life,” Nick stated.
So, what life existed in Oregon’s John Day region?
One of the best records of life at Blue Basin is found in the blue-green layers of the Turtle Cove Assemblage from 29 million years ago — just before the Crooked Caldera Eruptions.
Imagine expansive open areas with rolling hills and dales. The climate would have been dry and cool — suitable for the hardwood forests.
As for the animals, there were a lot of them! According to Nick, the diversity of life that once existed in the John Day region was tremendous with at least 100 different extinct species of vertebrate life found in the Turtle Cove assemblage.
Most abundant were herbivores, specifical ruminants like Hypertragulus — a mouse-deer creature — which make up about 47% of fossils collected in the Turtle Cove Member. There were also sheep-like and pig-like ungulates, small horses and massive rhinos.
Evolution see-saw
Carnivores, though not as abundant as herbivores, were diverse 29-million-years-ago. At any given time, there would have been up to 10 species of dogs, each with their own role to play in the ecosystem.
Now, there are few dog species, or canids, in Oregon. And many older lineages have gone extinct as other groups, like weasels, began to dominate and take on the role of some of these dog species.
“Depending on what is going on and the evolutionary process,” said Nick, “the pendulum swings” and dominant groups die off. Nick described these shifts as “the evolution see-saw.”
Though Nick was quick to clarify that a decline in dog species, doesn’t mean that dogs are less evolved than say weasels. There is no hierarchy to life.
“No animal or plant that is alive today is no more or less evolved than anything else alive today,” said Nick. It just doesn’t work that way.”
Survival of the fittest
Nick and I were now deep into the badlands — walls of rock towering over us. Off a short spur, we reached an informational sign and an encased replica of a tortoise fossil from the genus Stylemys — the belly of the beast protruded from the rock.
Stylemys were lands tortoises — their physiology not all that different from turtles today. Nick pointed out how the two plates, known as plastrons, of the fossil were tilted inward — “a male,” Nick noted, “ concave so he doesn’t roll off.”
Modern male turtles today still have concave plastrons for mating. Traits like this, that provide a reproductive advantage, tend to persist in the fossil record. After all, survival of the fittest requires the ability to replicate.
Extinction
A short while later, we reached another short spur and signed fossil replica — this time of a sheep-like creature, known as an Oreodont. Contorted and missing limbs, the fossil replica of the Oreodont lay awkwardly under the casing. The contortion is a clue to its life as a prey species.
Nick pointed out other features. The Oreodont’s fang-like canines used for snapping branches, depressions above the cheekbones providing space for large chewing muscles — both clues that Oreodont’s were herbivores.
He also pointed out a small depression on the face — the location of a scent gland, present in some ungulates today.
Today, despite their long history in North America, the entire diverse group of Oreodonts are all extinct. A reality that gives one pause — most of the branches of the tree of life end in a dead end.
Small things
Next to the Oreodont fossil replica was a thick layer of sandstone jettying out toward us.
“This is a channel or river deposit,” Nick said pointing at the layer of rock.
He explained that river deposits are unique in that they produce a lot of small fossils, like rodents, that have small home ranges — telling us a lot about local conditions.
As Nick puts it, “smaller things tell us a lot more about the environment than bigger things.”
Nick elaborated, “Rodents are uniquely adapted to their environments.” Thus, when a species disappears in a region, for example, that can indicate a local environmental change.
Nick used the example of a small deer-like mammal, Hypertragulus, that disappeared from the Great Plans of North America, but persisted in the west for several millions of years more.
A specialist
Nick and I continued down the trail until we reached a final fossil replica. The replica was of a false saber-toothed cat — a nimravid.
Twenty-nine million years ago, three or four species of nimravid coexisted as specialized carnivores, each relying on a different food source for survival. This worked great for a time, as it reduced competition between species.
However, as the environment changed and food sources became scarce, being a specialist was not such a great thing. And eventually the entire nimravid family went extinct.
According to Nick, being a specialist was not easy in Oregon’s changing environment.
“Unless you are a bone crusher. There always seems to be enough bones…,” he smirked.
Amphitheater
Eventually, Nick and I reached the very end of the hike — a place known as the amphitheater. Here it is easy to see the many layers of colorful rock reaching back into the ages. The “pages of time” literally surround you.
Nick called out each layer: lower green is unit C, browns unit D, the ledge layers E1-E3, followed by the Blue Basin Tuff and unit F, with dark Picture Gorge ignimbrite capping it all.
Layers and layers of rock containing fossils of past life, telling a 29-million-year-old story.
Storytelling
After a few minutes taking in the amphitheater, Nick and I made our way back to the trailhead. As we walked, he said something that struck me:
“I tell students all the time that the most important thing, as a scientist, is that you have to be able to communicate what you have done to somebody else. Because if you can’t, what is the point of doing it in the first place?”
Paleontologists are storytellers. They take us back in time to better understand the future. Oregon’s story is dramatic — punctuated by fiery volcanic eruptions, changing climates and a serious of unique life forms — but it is also a lesson in understanding occurrences of change.
Life is a state of flux. And you don’t need a Flux Capacitor to see that.
The Hike
Trailhead: Blue Basin Parking Lot/Island in Time Trail
Distance: 1.2 miles
Elevation Gain: approximately 250 feet
Details: Restrooms at the trailhead. Plenty of parking available. No passes required for entry. Hike the 3.25-mile (750 elevation gain) trail for a birds-eye view of Blue Basin from the same parking lot.
Emily Parent is a science educator, freelance writer, self-professed nature nerd, and avid hiker. To read more of her writing about science and nature in the outdoors visit www.trailscholar.com
Nicholas Famoso (Nick) is the Paleontology Program Manager and Museum Curator for John Day Fossil Beds National Monument. Nick got his bachelor’s degree from South Dakota School of Mines and Technology where he studied fossil mammals and marine reptiles. He later went on to earn his master’s degree and Ph.D. from the University of Oregon in geological and earth sciences.
