Hike with a Paleontologist

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. 

Yes, I am talking about paleontology— a science dedicated to piecing together stories of the past. Stories of the evolution of a planet; stories of volcanism and climate change; of life adapting to land and to air; of speciation and mass extinctions. Just to name a few. 

With this in mind, I met up with Nick, Chief Paleontologist, John Day Fossil Beds National Monument, at the Blue Basin Trailhead in the Sheep Rock Unit of the Park, for a short hike and to listen to some of these stories.  

Hang onto your hats kiddos—we are headed back in time!

The Hike

• Trailhead: Blue Basin Trailhead
• Distance: 1.3 miles
• Elevation Gain: about 220 feet
• Details: There is ample parking at the trailhead and a pit toilet. Look for signs for the Island in Time Trail. There is also a 3+ miles Blue Basin Overlook trail you can take from the same location.

Rock Records

According to Nick, one of the main reasons why the John Day Fossil Beds National Monument was established was to “preserve and interpret the story of the geological past of the John Day region.” 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. 

Nick and I met up to hike the Island in Time Trail, which takes you into a small section of the Sheep Rock Unit known as the Blue Basin and/or the Turtle Cove assemblage. The fossils found in the Blue Basin represent a relatively small slice of geological time, from 30 to 29 million years ago, but a well-preserved slice. Within this small slice, each layer of ash can be dated to about 10,000 years. As Nick explained—”the ashes are like page numbers” allowing for very precise (geologically speaking) dating of fossils found in the rocks.

Condon 

Nick and I started down the trail but quickly stopped short. Before going back in time millions of years, we needed to go back just 150 to meet a man named Thomas Condon. 

As Nick relayed the story:

Condon was born in Ireland before moving to New York as an older child. He always had an interest in rocks and fossils. He even had a small collection that he brought with him to the states.  As an adult, Condon’s fascination grew. Even after becoming a reverend and moving to Oregon, he continued to collect and discuss his fossils.

Eventually, Condon set up his ministry in The Dalles, Oregon where he developed a reputation—spreading, not only his religion, but his passion for geology. His reputation grew to the point that visitors, usually soldiers, that passed through would bring him fossils collected during their travels.  Many of these fossils came from the John Day region. 

Intrigued by these gifts, in 1865, Condon decided to visit the John Day region himself. A visit that would change his life and the face of paleontology in Oregon forever.

From that point on, Condon traveled and collected fossils all over Oregon, adding to his personal collection along the way. Eventually, Condon would become Oregon’s first state geologist and the first natural history faculty member at the University of Oregon, where his fossils still make up their core collection. 

Nick explained that Condon would have specifically visited the Blue Basin. “What Blue Basin is really interesting for is getting directly into the rock layers Condon would have been working with.”

Fossil Land

Following in Condon’s footsteps, Nick and I resumed our hike. But before long something caught his eye.

Nick pointed to a bright white patch of ashy looking material in the rock layers. “When you see pockets like that,” he said, “that are bright white, it is most likely Mount Mazama ash.”  Mount Mazama erupted 7,700 years ago, dropping several inches of ash over much of the Pacific Northwest, leaving a massive depression that would eventually become Crater Lake.

I asked Nick, why the Mazama layer could only be seen in this small pocket and not as a continuous layer within the earth’s crust. He explained, in a perfect scenario, Earth material is laid down in even horizontal layers under the action of gravity—what is known as original horizontality. However, most landscapes are not flat, and Earth material doesn’t settle in place. Instead, paleotopography—the shape of the land in the past—shifts material, changing where and how much is deposited across the landscape. For example, you might find an eight-foot ash deposit in one place (perhaps a basin of some sort), while in another place the deposit may be only two feet deep, or not exist at all.

These basic principles also help explain why fossils are only found in certain places on Earth. As the sediments involved in fossil bed formation are also influenced by paleotopography.

Floodplain Deposits

However, the shape of the land is not the only important factor for fossil bed formation. The movement of water and wind is equally important. As agents of erosion and deposition, water and wind influence where sediment accumulates, potentially burying the remains of organisms and creating the conditions for fossil formation.

The fossil beds at Blue Basin formed in a river valley that experienced frequent flooding. With each flood, sediment was deposited on the banks, and in the floodplains of the river, burying animal remains in its wake. Overtime, sandstone, siltstone, claystone, and other sedimentary rocks formed, preserving hard materials, like bone, that would fossilize.

Colorful Rocks

Moving deeper down the trail, Nick and I entered an otherworldly basin of pale-colored rock. The walls of the basin, like a layered cake—with each layer a different color and thickness. 

Nick explained how each layer formed. Blue-green colored layers are attributed to the mineral celadonite— formed during diagenesis—the conversion of sediment to rock. Brown colored layers are claystones that didn’t undergo a secondary alteration process. Bright white ledges are volcanic tuff —formed from the compaction and cementation of volcanic ash. Embedded in the rock layers were also concretions—compact masses of sedimentary rock that form around a nucleation site, like a bone. Fossils can sometimes be found encased in concretions. 

Ultimately, the stratigraphy of rocks helps paleontologists establish boundaries between subunits of rock—each of which represents slightly different environments.  In Blue Basin, there are 7 subunits that have been characterized by their geological composition and ashes—B through F with some letters divided further. 

A Layer of Ignimbrite 

Nick also pointed out a thick brown layer of rock that capped a section of the Blue Basin rocks. This layer is visible at various places within the Sheep Rock Unit, as well as other areas in the Park. 

The layer is ignimbrite, rock formed by the consolidation of pyroclastics, or as Nick put it—”a fiery cloud of death.” These “death cloud rocks” were the result of eruptions from the Crooked River Caldera—a now extinct supervolcano that once covered several square miles in central Oregon. 

Fueled by an early version of the Yellowstone hotspot, The Crooked River Caldera eruptions would have been huge—on a scale far beyond what we have seen in human history. For his dissertation, Nick studied the impacts and recovery of life following ignimbrite eruptions, finding that these sorts of large impacts seemed to have equally large, long term impacts over time.  In the case of the Picture Gorge ignimbrite, there is evidence that the landscape changed from more forested to less forested due to the eruptions. 

Hidden in the Rocks

According to Nick, stories of change are what make paleontology such an important field of study. Stories about changing climates, mass extinctions, and catastrophic events are all hidden in the rocks. If we pay attention to these stories they can help us gain perspective on issues we face today.  

For example, scientists agree that we are in the middle of a sixth mass extinction brought on by human activity.  But because it is occurring on a time scale that is outside human experience—thousands to millions of years—we don’t see it. Paleontology can help us understand this discrepancy, giving us the opportunity to respond accordingly. 

Collecting Fossils

Nick and I hiked deeper into the badlands of the Blue Basin. Nick said that on any given day, approximately 10 field collections might be extracted from this unit. Considering that the Blue Basin for over 30 years, that is a lot of fossils!

I asked Nick, what exactly constitutes “a collection?” He responded, “Usually something that can be identified to a fairly high level.”  For example, identifying a tooth as Mammalian would not constitute a collection. But identifying a tooth is from a rhino, well then you have something! Teeth, bones, seeds, tracks, and/or traces of past life could potentially end up in a collection.

However, no fossil is collected alone. “What is most important is the context,” explained Nick. Gathering material and carefully documenting where a fossil is found is often more important than the fossil itself.

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 info. Either way, the more contextual information gathered, the better! 

Past Life

“Fossils are evidence of past life.” So, what life existed in Oregon’s John Day region about 29 million years ago? 

Well first, picture a river valley; open and expansive with rolling hills and dales. The climate would have been dry and cool—suitable for the hardwood forests and open meadows that permeated the landscape at the time.

And 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 has been found in the Turtle Cove assemblage.

Herbivores

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 Oreodonts—large sheep-like and pig-like even-toed ungulates of which there are no modern descendants. As well as one to two species of horse, like Miohippus, a three-toed horse.  And, for good measure, large rhinos roamed the valley. 

Carnivores

Then there were the carnivores.  Though not as abundant, the diversity of carnivores that existed 29 million years ago is impressive. At any given time, there would have been up to ten species of dogs, like Mesocyon, coexisting together by taking on unique roles in the ecosystem.

In contrast, today there is only one living species of dog in the world. The rest have gone extinct as other groups of organisms, like weasels, came onto the scene. Nick said that this evolutionary see-saw is pretty typical of life on the planet. “Depending on what is going on and the evolutionary process,” the pendulum swings and different groups of organisms become more dominant.

Nick was also quick to point out that this doesn’t mean that one group of organisms is better in some way than another. “No animal or plant that is alive today is no more or less evolved than anything else alive today,” said Nick. “Fish used to be the most dominant things,” explained Nick, then reptiles. Mammals and birds came later, but they aren’t more evolved.  If you want to get really technical, you might say all vertebrates are really just a bunch of fish—we are all equally evolved from a common fish-like ancestor. Just because some species don’t look much like fish anymore, doesn’t make them better. 

A Word On Plant Fossils

There were of course a lot of plants in existence 29 million years ago, but you won’t find a lot of plant fossils in the Turtle Cove collections. Why? Well for one, in general, plant fossils are harder to find.  You might get a part of a plant, like some wood or a leaf or root fossil, but rarely the entire plant fossil. This makes it difficult to get down to a species level of identification, explained Nick. More often paleontologists must be content with community-level identification of plants.

In addition, the conditions required for fossil formation is different for different forms of life. In the Blue Basin, the conditions were likely too destructive for plant fossils to really form. Though there are a few leaf and seed fossils found in the area, most plants would have probably washed away or been eaten during the flooding events that laid down so many vertebrate fossils. Old lake beds are often great places to find plant fossils, explained Nick, because the environment is calmer.  Plant fossil formation also depends on the acidity of the environment as well.

Replicate

One group of charismatic animals captured in the Turtle Cove rock layers are multiple species of a land tortoise—Stylemys. In fact, you can visit Stylemys on the trail! O.K., well not actual Stylemys, but a replica of a fossilized male. 

When we reached the replica, Nick and I stopped to chat.

There is a lot you can learn about an animal from a fossil. For example, in the case of our land tortoise, the plastron—the protective front of a turtle, opposite the shell—can tell you if the turtle is male or female. Nick explained that males have concave plastrons so that when they are mating with a female they do not roll off her.  This is true of turtles alive today. Thus this trait has been around a really long time, providing a direct link between the past and present.  From an evolutionary standpoint, this makes sense—a trait so vital to reproduction is bound to provide an evolutionary advantage. The survival of the fittest only works if you can “replicate.”

Replicate

Nick and I continued down the trail until we reached another fossil replica. This time it was of a sheep-like Oreodont.  A browser, the fossil showed pointed canines, used for snapping branches, and a large depression above the cheekbone, indicating huge strong chewing muscles. On the face there were also two other small rounded depressions—one for the eye and the other a scent gland that can be seen in even-toed ungulates today. Though it is unclear what the gland was used for by Oreodonts, one might predict its function was somehow beneficial to the organism—perhaps used in sexual selection.

However, though millions of years ago there were dozen of species of Oreodonts in North American, none exist today.  A placard found next to the fossil asks, “An evolutionary success?”

It is really easy to dismiss extinct species. But Oreodonts survived in North American forests for over 30 million years, much longer than most animals alive today. So as we learn about their loss, perhaps there is an even greater lesson to be taken from Oreodont success?

Small Things

As Nick and I stood by the Oreodont fossil, he also pointed out a layer of sandstone in front of us. He told me that this layer wasn’t the usual overbank deposits found throughout the basin, but an actual in channel or river deposit. 

The great thing about river deposits like this one is that they “produce a lot of smaller fossils…and smaller things tell us a lot more about the environment than bigger things,” said Nick. Because small mammals usually have smaller ranges, they provide information about local conditions. The populations of rodents living in the Blue Basin stayed in the basin and were endemic to the area. Rodent populations in other areas would also be uniquely adapted to their environments. 

Some small species can even act as geological time markers and can help paleontologists understand what is happening on a global level. Nick mentioned the Hypertragulus as an example. In the Great Plains, the Hypertragulus went extinct, while persisting several million more years in the west. By tracking differences in populations this way, regional stories unfold as scientists question the discrepancies. It raises the age-old question: Why?

The Species Problem

Before we moved on, Nick also brought up an important paleontological problem—the species problem.  In general, scientists define species of genetically similar organisms that can exchange genetics and/or interbreed. But, as Nick put it bluntly, “you can’t exactly put two fossils in a box and see if they make more fossils.” 

Therefore, defining a fossil species is complicated. In the past, species were defined based on theoretical ideas, like the likelihood of geographic separation between similar-looking fossil organisms. However, this is not a very reliable way of distinguishing between fossil species. There is a lot of natural variation within populations. Thus, simply finding small differences between two groups of similar organisms does not a species make.  

Nick shared an example of the species problem he encountered in his own work. He had looked at the differences between fossils from eight different species of horse. He compared the variation he found between these fossils to the variation found in modern horse and tapir species. The differences were not significant. Nick concluded that eight fossil species of horse were better grouped as two.

The Specialist Problem

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. Cousins of true cats, nimravids branched out from other carnivores about 16 million years ago.

During the time period associated with the Turtle Cove assemblage, only three or four nimravids coexisted.  They varied in size, with false-saber toothed cats the largest of the carnivores overall. 

However, despite their size, nimravids were more prone to extinction. You see, nimravids tended to be specialized meat-eaters. Meaning they relying on only certain food sources for survival.  In a stable, unchanging environment, this is not particularly problematic. It is actually a good way for species to carve out a role in the web of life.  

However, environments change and this is where being a specialist can be a huge disadvantage.  It is sort of like the old adage—don’t put all your eggs in one basket.  If that basket gets knocked over, no more eggs. 

Generalists, like many dogs, on the other hand, tend to do better, as they rely on a varied diet and lifestyle—they have their eggs in many different baskets. 

Of course, Nick added, being a bone crusher is one specialization that has been successful. There always seems to be enough bones. 

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 rock.  The “pages of time” literally surround you. Nick called out each layer: lower green is unit C, browns unit D, the ledgy 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

As we made our way back out to the trailhead, Nick and I continued to discuss what it is like to be a paleontologist. At one point, I asked him what he liked most about the work.  It wasn’t the story making, but the storytelling—the advocating for the fossil resources of the park that he felt was most important. 

It is the work of the paleontologist, not only to piece together these stories but also to tell them. As Nick said earlier during our hike: “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?”

I couldn’t agree more, Nick.

Nicholas Famoso (Nick) is the Chief Paleontologist 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 Masters and Ph.D. from the University of Oregon in geological and earth sciences.