Peabody Fossil Hunter

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Friday, July 15

In Uncategorized on July 16, 2011 at 2:20 am

Seven people, two sites, eight shovels, six pickaxes, five army backpacks, and 20 gnat-fighting car scent cards.

Over the past two weeks, we’ve done a lot—carved up the sloping “humps” of Camel Butte, crawled and shoveled the surface of Hoff Ranch, inspected anthills, battled ticks and gnats, and trapped a dozen horny toads.

We packed away about 130 gallons of dirt from the sites–enough to fill an aquarium built to house a Catshark–and spent about 100 hours collectively picking through it with tweezers and dental tools. We took 44 soil samples for pollen dating, and found about 40 hatched rattlesnake eggs.

In the end, our tray of findings represents a hefty slice of Cretaceous-Tertiary riverine taxa: crocodiles, lizards, garfish, turtles, champsosaurs, and most importantly, mammals–15 jaw fragments and a handful of teeth from condylarths and multituberculates.

One of three trays of finds.

Most of the material will go back to the Peabody Museum to be catalogued and researched. The pollen sample results will take a few months.Peabody Curator of Vertebrate Paleontology Eric Sargis will take the mammal finds with him to New Haven, each one wrapped in tissue and placed in individual boxes.

For two weeks, it’s been a success. Tomorrow, we’ll drive back to Rapid City, South Dakota and part ways until the fall.

Descending Camel Butte.

Thursday, July 14

In Uncategorized on July 14, 2011 at 11:35 pm

Yesterday, the Camel Butte crew battled strong winds that kept the gnats away but made even standing still a challenge. Cutting into the side of the slopes, the dirt blew horizontally out to the grasslands as soon as it hit the screens. We emerged with 25 gallons of matrix, and a few dirt unibrows.

By the end of the windy day, Anthropology major Greg Mittl had a dirt beard.

Today, heat was the challenge. We spent the day in two groups again, one collecting more matrix at Camel Butte and the other at Hoff Ranch prospecting for more mammal jaws. We also dug two trenches, which will allow geologist Antoine Bercovici to generate a timeline “anchoring” a few key fossil finds in the stratigraphic column.

Tuesday, July 12

In Uncategorized on July 13, 2011 at 1:27 pm

Read about Yale Geology graduate student Tyler Lyson’s recent research in Science, Nature, and ABC. Last year, he found a Ceratops’ brow horn at Camel Butte, a find supporting that the asteroid impact caused the extinction of non-avian dinosaurs.

Monday, July 11

In Uncategorized on July 11, 2011 at 1:24 am

We’ve found quite a lot of fossils in the past few days from the Hoff Ranch, and paleontologists with the Marmarth Research Foundation have found even more in past years. But fossils don’t mean much without knowing when they lived, and in what kind of environment. Today we followed French geologist Antoine Bercovici as he began the process of piecing together the history of the ranch’s buttes and ravines, based on their geologic bands of varying colors and textures.

When the meteorite hit the Yucatan Peninsula 65 million years ago, it pounded the ground beneath it hard enough to melted it, sending little bits of Mexico in all directions in the form of little glass droplets. Some of the impact’s projectiles—tectites and shocked quartz—had enough velocity to make two revolutions around the planet before landing. Because the impact was instantaneous and unparalleled, these spherical glass bits are one of the best indicators for finding what geologic layer the impact occurred in. The meteorite also brought in iridium, a dense silvery metal that is very rare in the Earth’s crust but much more abundant in meteorites.

The presence of iridium and tektites would be the clearest way to identify the K-T boundary in a geologic formation, but they’re rarely preserved well enough to measure.  In the end, scientists often use something much more commonplace to date the boundary: pollen.

Bercovici is a palynologist—he studies plant microfossils including spores, fungi, algae, and pollen. He looks at the amount and types of pollen embedded in each layer to infer what the paleoenvironment was like when each was formed.

To get a hold of good pollen samples, we had to be destructive. We picked a site—a gently sloping butte face close to a T-rex fossil, with clear banding. Then we cut it up. With pickaxes and shovels, we whacked a trench into its side, cutting a 30-foot-high staircase to expose fresh sediments safe from surface impurities. We hammered nails into every point on our new dirt staircase where the rock layers appeared to change. Finally, we climbed it, taking samples, measurements, and notes for each of the 21 layers.

Antoine Bercovici stands next to our freshly dug trench.

Once a lab in Canada dissolves out impurities with acid, Bercovici will look at each one under a microscope, noting the presence of pollens and other organic inclusions that can date the layer to a specific time period.

The impact obliterated much of the Earth’s vegetation. About 36 plant taxa went extinct—as much as a third of all pollen taxa. Whenever such ground cover is destroyed, even with recent events like the eruption of Mount St. Helens, ferns are the first plants to bounce back. Palynologists like Bercovici look for a spike in fern spores, and the presence of the taxa that went extinct, to pinpoint the layer representing the K-T boundary. Eventually, we’ll be able to match each fossil with its sedimentary layer. Most importantly, we’ll know what layer represents the K-T boundary—a key step to understanding what taxa survived the asteroid impact, and where on the timeline our fossil mammals fall.

Sunday, July 10

In Uncategorized on July 10, 2011 at 5:20 am

We’ve collected over 20 buckets of surface soil after a week of prospecting at the Hoff Ranch and Camel Butte. Each one of us can carry about four liters of matrix at a time, packed into army backpacks that we hike down slopes and grasslands back to the car. Prospecting and collecting, though, is just the first step. Next, we must sift through all the material.

Hiking backpacks of soil back down from Camel Butte.

After soaking out the mud and roots in a basin outfitted with bubbling PVC pipes, we spread the remaining mix to dry on tarps. Once that has dried, we sit down to pick, scooping it onto trays. Armed with steel dental tools, we sort through it piece by piece, separating out rock from bone.

Finding tiny fossils requires getting up close to the filtered pebbly matrix.

The pebbles and dried clay in the Camel Butte matrix prove straightforward to sort out. The Hoff Ranch matrix, on the other hand, is full of small chunks of coal–black and shiny, they look just like mammal teeth. The process takes a lot of patience. We’re looking for bones and teeth that can be smaller than oat grains and as thin as the tines of a fork. After hours of picking, our eyeballs start to cross. Nonetheless, we emerged from an afternoon of picking with a handful or two of recognizable fossils, among them a few tiny mammal teeth and a piece of a femur as thin as a toothpick.

The final product: the tiny upper premolar of a condylarth.

Saturday, July 9

In Uncategorized on July 9, 2011 at 6:36 am

Today we happened upon a different kind of mammal.

About the size and weight of a Volkswagen Beetle, the American bison is the largest mammal on the continent. The animal we call a buffalo took millennia to evolve from its ancestor that likely crossed the Bering Strait from Asia. It only took 50 years for North Dakota’s first white settlers to drive them to the brink of extinction. Now, a few hundred of the beasts roam the grasslands in Theodore Roosevelt National Park.

An hour’s drive north from Marmarth and a 10-mile hike into the park, we found ourselves face to face with about 30 of the colossal animals. Scattered across a raised plateau of grassland overlooking the Little Missouri River, they looked like giant mounds of brown dirt—until we got too close. With a keen sense of smell, bison become surprisingly nimble the second a person walks within sniffing range. As Matt Raudabaugh approached one particularly large lump, the bull jumped up to its full six-foot height to silently stare us down.

An American bison, or buffalo, weighs as much as a small car.

The bison weren’t the only giants we saw.

On the way into the park, we’d passed through an area known as the Burning Coal Vein, an underground swath of coal that was probably sparked by lightning or a prairie fire. Though it’s dwindled in recent years to a smolder creeping about 10 feet each year, the layer has been burning since the first white settlers came across it almost a century ago, spread out over a corner of the park.

You can’t see the vein from the surface—aside from the rotten egg smell of sulfur, all it emits is hot fumes. But those hot fumes are in the middle of shaping the badlands. Once the coal layer has burned into ash, it leaves weak cavities capable of cracking and caving overlying rock, cutting ravines and exposing a bright pink layer of cooked clay called “scoria.” The park paves its roads out of this brick-like gravel.

Paved in scorched clay, a road cuts through the Burning Coal Vein area of Theodore Roosevelt National Park.

Down the road and a few miles in via dirt trail, we came across another odd phenomenon: giant stone stumps scattered across a valley. The stumps rarely exceed five or six feet in height, but the chunks of petrified wood are all that’s left of an ancient subtropical forest.

About 60 million years ago, around the time when our mammal fossils were still alive, western North Dakota was covered in a dense forest with trees as wide as a standard interstate lane. It’s thought that the conifers, relatives of modern coastal redwoods, became petrified when mountain-building events in the Rockies dumped a coat of volcanic ash over them. Suffocated in an ash cast, the wood was unable to decay naturally. Instead, it absorbed mineralized groundwater that was eventually replaced by quartz crystals. Over time, the brittle splintery stumps eroded out, colored by impurities like iron, carbon, and manganese.

Five feet tall, Natasha Vitek stands next to a petrified tree stump.

Friday, July 8

In Uncategorized on July 9, 2011 at 4:50 am

Despite a 50% chance of rain, the group split up today to prospect at Hoff Ranch and collect more matrix from Camel Butte. By now we’ve gotten into the routine of shoveling, sifting, crawling, washing, and picking.

Shoveling matrix to sift through at Camel Butte.

Today’s finds yielded two more condylarth jaws and the blade-like tooth of a multituberculate, a group of mammals with a long fossil history that appears to have eventually been beaten out by rodents. Crawling around an area dotted with gar scales and bone, Stephen saw two shiny black molar cusps. After carefully digging around them, he found they were attached—the first condylarth upper teeth known from the area. This is an important find, since they appear to be the same species as the lower jaw Natasha found a few days ago. Having both upper and lower dentition gives us a more complete idea of what the species looks like.

After dinner, we explored the Mystic Theatre, a sagging 1914 building on Marmarth’s Main Street. It’s quiet most of the year, with two vintage film projectors collecting dust in an upper room, except for the Cowboy Poetry recitation each fall. The theater is in much better condition than much of Marmarth’s architecture—boarded up and deteriorating homes and businesses.

Inspecting an old projector at the Mystic Theatre.

Thursday, July 7

In Uncategorized on July 8, 2011 at 5:17 am

We returned to Camel Butte to collect soil matrix that could contain mammal teeth too small to spot crawling around on our hands and knees. Because they’re made of enamel, teeth are incredibly durable compared to the rest of the body. They’re all that’s left of some species, so we use subtle differences in the tooth shape and size to figure out what species are present, the relationships between the species, and also what they might have eaten.

The obstacle is that they’re only a few millimeters long, each smaller than a pea. Recovering them will require more than surface searching, so we carried about 16 large Ziploc bags full of fossiliferous dirt back down the butte to screen-wash at the lab. Once they’ve been washed and dried, we use dental tools to pick through the rocks and fragments for small fossils. Today’s picking yielded a few more condylarth teeth, tiny fish jaws, and the ever-present turtle shell fragments and garfish scales.

Wednesday, July 6

In Uncategorized on July 8, 2011 at 5:07 am

The gnats here are vicious—they go for the eyes and ears in particular. After a few days of swatting and cursing at them, we learned that car fresheners repel them better than any commercial bug repellent. The vanilla and “new car” scents work the best. They’ve been dangling off our hats ever since.

Tuesday, July 5

In Uncategorized on July 8, 2011 at 5:03 am

The Hoff Ranch north of Baker, North Dakota, houses all sorts of fossils, from a partially excavated Tyrannosaurus rex to a condylarth jaw Tyler found last summer. We spent the day crawling around areas of erosion with pieces of bone on the surface. We also picked through anthills, which have surfaces scattered with small fossil bits and teeth brought to the surface from burrowing ants.

 

A few vertebrae sticking out of the ground turned out to be a partially articulated hadrosaur, with 26 vertebrae, ribs, and a pelvic bone. We know a lot about hadrosaurs from a fossil Tyler found a few years ago, Dakota the “dinomummy,” whose lizard-like skin texture, webbed feet, and muscle mass are petrified along with its skeleton. A Nanotyrannus tooth (below) was found nearby.

Natasha found four mammal jaws, each about the length of a match. They likely belonged to condylarths.

A piece of a condylarth's lower jaw, with a few teeth included.