The Barefoot Paleontologist: A Summer Internship at Ashfall Beds

Adrienne Stroup MUS 670 11-1-12 A catastrophic event took place in nearly twelve million years ago, one that would be concealed in time and earth until 1971. A paleontologist named Michael Voorhies set out to map the stratigraphy of sediment layers in northeastern Nebraska, when he noticed a small fossil, which marked the start of one of the great discoveries in vertebrate . The jaw of a juvenile rhinoceros jutted out of the eroding hillside, and remarkably so was the rest of the skull. Excavation soon revealed that the entire skeleton of the animal was attached and completely articulated, something that is almost unheard of in the science of paleontology. Even more surprising was that it was not the only one. Over two hundred complete skeletons were removed in the late 1970s and accessioned into to the University of Nebraska’s State Museum collections in Lincoln. The site proved to be larger than anyone had expected, about one and half football fields in length. As more and more were uncovered, it was decided that they would remain in-situ on permanent display. The farm on which these fossils were discovered became the site of a unique institution; a joint project between the University of Nebraska-Lincoln (UNL) State Museum and the Nebraska Game and Parks Commission, combining the features of a natural history museum and a state park. A Visitor Center and an enclosure for the fossil bed, affectionately dubbed the Rhino Barn, were built and in 1991 the park was opened to the public. Ashfall Fossil Beds State Historical Park allows visitors to see a fossil site, celebrated world-wide for its incredible preservation of a fairly complete ecosystem, a waterhole where animals gathered to seek relief from ash filling the air and settling over Nebraska from the eruption of a super volcano. The volcano erupted in southwestern and its ash settled across the Midwest. It only fell for a few days but its effect on Nebraska would last millions of years. Barrel bodied rhinos, giant tortoises, three toed , , and saber-toothed deer are just a few of the dozens of species that have been found there. As one of seven interns, I had the pleasure to work with Dr. Voorhies for most of the summer, benefiting from his wealth of knowledge about the site. As an emeritus curator of the UNL State Museum and retired professor, he spends many hours volunteering at the park. In fact, only two permanent employees, Rick Otto and Sandy Mosel, run the entire facility. The park really depends on the interns to continue excavating in the Rhino Barn, sorting for microfossils in the Discovery Shelter, preparing fossils in the Prep Lab, and above everything else provide educational experiences and make ourselves available to answer visitors’ questions. The Rhino Barn houses the remaining part of the site, more than half of which remains unexcavated. When the park opened in 1991, the original barn was much smaller; basically it was a two bay garage. Soon the excavation had to be halted when everything inside was uncovered, though the site extended far beyond its foundation. Three years ago, fundraising efforts allowed for a new 17,000 square foot building to be constructed. The Theodore F. and Claire M. Hubbard Family Foundation gave UNL over a million dollars to build the new facility, and thus it was officially named the Hubbard Rhino Barn. According to Dr. Voorhies, the Hubbards are very active philanthropists, and they have donated large sums of money to not only build the new barn, but the Discovery Shelter as well, in addition to helping out the Omaha Zoo and other science education efforts throughout Nebraska. The new barn allows visitors to view what has been uncovered in the past, as well as see new discoveries being made every day. We work very closely with the fossils and have to be extremely careful when walking through the ash bed, therefore we are asked to work barefoot. In fact, we are discouraged to even walk through the previously excavated section of the ash bed. This is because walking through it will cause loose ash to become airborne and settle on the fossils, and then the entire ash bed has to be dusted off with soft brushes. The bigger risk is the possibility of tripping and stepping on a fossil, which would surely break it. Typical fossils are created when mineral-rich ground water, sometimes called “hard water,” penetrates organic material that has been quickly buried, such as animal bones. As the organics decay the minerals are left behind, creating an exact replica of the bone out of rock. Sand is superb for the fossilization process, but ash, which is volcanic glass, does not allow ground water to seep through it as easily. Therefore, only the outside layer of bone in the ash bed is fossilized; the inside, which is porous with a honeycomb-like structure, is still original bone. This is both helpful and problematic when excavating. Each intern is assigned an area to excavate, digging only through the bottom two feet of ash to the contact between the ash and the sand layers. Here is where we find the fully articulated skeletons. When we think we have found bone, our first clue is a smooth texture and a slightly different color. Here is where we slow down and examine the area by tapping the surface with a scalpel. Bone will make a sharper, hollow sound as opposed to the dull thud when tapping surrounding ash. By keeping our scalpels parallel with the ground surface we are less likely to gouge and crack the fossilized but fragile outer layer of bone. Instead, the scalpel usually glides right over the fossil. Visitors often remark on how tedious it must be to sit inches away from the ash and scrape away at it for hours in crouched positions, but it goes rather quickly, especially since most of the ash is very soft. Small tools are used to remove the layers of ash and then brushes and scoops collect the loose ash into buckets, which are dumped into a skid loader hopper that is finally deposited into a ravine on the park property. Great efforts are made to keep the ash from getting kicked up into the air, but over time the ground water seeping through the ash layer rendered it more dense so there is little risk of breathing in too much ash inside the barn. In addition, many people ask if fossils are also found beneath the ash bed, and if we will eventually remove all of the skeletons to get to them. Fossils are found in the lower sand layer, but excavation in the barn focuses on the Ashfall event. The older fossils beneath the ash were deposited before the event and are only individual scattered bones, not complete skeletons. Furthermore, if the Ashfall specimens were removed there would be no fossil bed to see and little reason to have a state park. Seeing the animals in the exact, unchanged positions is unique and tells us much more about the site and what happened there than if all the skeletons were removed and reassembled elsewhere. When visiting a museum, many people are unaware that the fossilized bones on display often come from many different individuals to create a complete skeleton. When found, the bones are usually scattered around and some may be missing. The classic example is the Brontosaurus, which was renamed Apatosaurus, meaning deceptive lizard, because for over a hundred years the dinosaur had the wrong skull attached to it at Yale’s Peabody Museum. At Ashfall, the entire animals are perfectly preserved, and there is no mistake that the rhinos and horses looked the way they did. One interesting thing about working in the barn was realizing how different the styles of excavation are between archaeology and paleontology. When Rick showed me around and told me where to begin excavating, I felt a little lost. There was no datum stake to record excavation depth below ground surface, no string lines to indicate the boundaries of my workspace, no need to dig in perfectly level ten-centimeter levels, and no paperwork. The field work that I had done in the past was much more regimented, which is logical since the data collected would be the only remaining evidence of the site after construction begins, at least with the cultural resource management I have been contracted to do in the past. There is a reason why one of our phases of fieldwork is called “Data Recovery.” At Ashfall, the site is mapped periodically, and nothing is removed, so the documentation is a little more relaxed. We do not even screen the ash after digging. Since we work so closely to the ash, anything small would be noticed, but there is a bigger reason and one that further explains the story of Ashfall. The animals died over a period of four to six weeks. The smallest of which, such as the birds and turtles, succumbed to the ash’s effects within a few hours of the fall. Wind blew the ash around like snow where it drifted and settled into the lowest point on the landscape, which is why almost eight feet of ash is found at Ashfall, further indicating that it was a watering hole. In two to three weeks the camels and horses would have died and lastly the rhinos, around four to six weeks. Therefore, the smallest animals are more likely to be found in the top of the sand layer, with the larger animals in the initial two feet of ash. We know this by digging into the sand layer but not inside the barn. Along the outside of the barn is the Digging Deeper Quarry where the ash layer had been removed in the 1970s and the underlying sand is sorted and sifted through, yielding bones and teeth of tiny animals such as birds, turtles, mice, frogs, salamanders, snakes and even seeds from ancient hackberry trees. The Discovery Shelter is where we screen the sand for these tiny remains, which we call microfossils. Sand from this quarry is placed in a wooden frame with the bottom covered in fine mesh window screen. It is then sprayed with a garden hose to wash away the tinier grains of sediment. After the large clumps are broken up and washed away, the sand is left to dry. The water rinses the fossils clean, and the sand clumps together as it dries. One handful at a time, this mixture of dried sand that look looks like Grape Nuts cereal, which we call concentrate, is sorted on a paper plate with a small paintbrush. Visitors are encouraged to walk through the Discovery Shelter and watch the sorting process, ask questions and view some examples of microfossils found in the past. Snake vertebrae, frog leg bones, pond turtle and tortoise shell pieces are among the most commonly found. The first and last fossils I found by sorting were the most exciting. On my first day I recovered a pocket mouse jaw complete with four teeth. For perspective, it is about the length of a grain of wild rice. During my last shift in the Discovery Shelter, I found two teeth belonging to two different species never found at Ashfall before. One was a molar of a very large mole. The species could not be determined but it is larger than modern mole, and smaller than the giant mole that has been found at the park. The other tooth belonged to a small deer- like animal called a Pseudoceras. Fossil remains of this animal are extremely rare in general, making it an even more exciting find. Many of the fossils are left in the Discovery Shelter for patrons to touch and look at, but the rare or unusual ones are taken back to the Prep Lab. Located in the Visitor Center, the Prep Lab is where fossils are prepared for display and research purposes. Here patrons can watch interns work and interact with us through large open windows. The fossils we work on are cataloged and added to the collections in Lincoln, though some are put on display in the Visitor Center. Since no fossils are removed from the Rhino Barn, what do we work on in the lab? During construction, any fossils in the way of the Rhino Barn’s foundation were removed. The park also has a great relationship with the community and the staff periodically conducts digs at local sites on privately owned ranches. For most of the summer, the other interns and I prepared a rhino skull, which was found last summer at one of our localities, called the Golter Site. This is a lengthy, careful, but very enjoyable process. The preparation process starts with a field jacket, made with Plaster of Paris and strips of quilt batting. When a fossil is found in the field, it is quite exciting and the urge to immediately dig it out of the ground is very strong. This is dangerous, however, because when the fossil is first uncovered it is damp and very fragile. As it dries it becomes stronger, but it can still break. Even though fossils are essentially rock, and can be very heavy, they must always be handled gently and carefully. Therefore, only the top of the fossil is uncovered to figure out its size. Then we dig around it, leaving at least two inches of matrix (the substance the fossil is buried in, in this case it is sand) around the bone, creating a pedestal. Wet paper towels or toilet paper is then applied to the exposed bone to protect it from direct contact with the plaster, and finally the plaster- soaked batting strips are placed around the pedestal and allowed to dry. Once dry, the jacket is popped out of the ground with trowels or a shovel and turned upside down, creating what looks like a plaster bowl containing the fossil inside. The jacket keeps everything in place during transportation back to the lab, and then the fun can really begin. Small tools like scalpels and dental picks are used to clean away the matrix surrounding the bone. The process is pretty low tech. Plastic spoons are utilized to scoop up the loose matrix and collected in a bucket. The techniques employed in the lab are essentially the same as in the Rhino Barn, but on a more detailed level. Once all the sand is removed from the bone, a consolidant is applied. Consolidant is a solution made of a type of plastic that has been dissolved in acetone. There are many different kinds, but we primarily use polyvinyl acetate, also called PVA or B-15. The liquid plastic is applied repeatedly, one coating at a time, slowly giving the bone more strength. As it dries, the acetone evaporates leaving behind a thin veneer of plastic, which is absorbed by the porous bone, hardening it. A thicker version of this solution is made with a higher plastic to acetone ratio, creating a glue that can be used to mend broken fossils. Modern techniques for fossil preservation have improved a great deal. Only solutions that can be reversed are used, and the type of consolidant is often recorded on the back of the collections identification label. Once the exposed side of the fossil is prepared, the side covered by the field jacket must also be prepared. Thus, a bedding jacket is then made to allow the fossil to be flipped over safely to complete the preparation. This jacket is very important, as it will give the entire fossil support not only during the preparation process, but for long-term storage in the collections as well. The same technique is used and the only difference is that this jacket is form fitted to the fossil. Care must be taken to create a jacket that is snug but not tight, as constriction of the drying jacket can in fact make it impossible to remove without breaking the fossil, and like previously stated everything we do in the lab should be reversible. Cleaning the fossil goes beyond making it look nice. The purpose of prep work is to stabilize the fossil for long-term display and storage, and sometimes the cleaning process reveals more clues about the animal’s life. The first project I had in the lab was preparing a rhino radius, one of the lower front leg bones. At first it seemed like the bone was just broken, but in fact, it appeared to have tooth marks along one of the breaks. Dr. Voorhies believes that a large bone-crushing dog, called an most likely scavenged the rhino’s remains. Another example is after we finished working on the rhino skull, it was my responsibility to clean the tartar off the teeth. Using a dental pick, I carefully scraped the teeth, collecting a large enough sample of tarter to be analyzed for phytoliths, which are microscopic mineral deposits created by plants. If the analysis comes back positive for phytoliths, it may be possible to tell what type of grass the rhino ate. Since this skull was from a different site that is only eight million years old, as compared to the almost twelve million year old Ashfall site, it would be interesting to compare the diet of the Golter Site rhinos with the Ashfall rhinos, which are actually two different species. The skull we worked on is now displayed side by side with an Ashfall rhino skull that was rescued from one of the foundation trenches, allowing visitors to observe the subtle differences between the two rhino species. My supervisor, Rick Otto, often stressed that our most important task at the park was interpretation for the visitors. Interpretation allows us to make the fossil bed and all we do at the park relevant to our patrons. Within five days after an orientation session with Rick and Dr. Mike Voorhies, and following along on Sandy’s and Rick’s tours, I started contributing to the interpretation of the site. At first I was quite nervous about the idea of talking to visitors, but quickly fell into the routine and really enjoyed it. With seven interns and three workstations, we had a schedule that rotated us every day, with a different station before and after lunch. Our days off were even staggered, so that there were always five of us at the park, which is open seven days a week. Therefore, there was always one person in the Prep Lab, one person in the Discovery Shelter and three people in the Rhino Barn. Within the barn, we take turns, one person talking to visitors and two excavating. We make it a point to inform visitors that we are there to answer their questions. Of course there are visitors who only ask about my background like, “Where are you from? Are you a student at UNL? How did I find out about this place?” and other similar questions. Then there are the visitors who get really involved with their visit, asking the previously stated background questions and a lot more. The excitement in the visitors was infectious, and I really started to love explaining the story and science of the park. Visitors came from countries such as France, Spain, India and England, but mostly from the United States. We also had Amish visitors, a group of nuns, some Boy Scout troops, scientists, but mostly average folks on vacation. One group of visitors came in on a slow afternoon and talked to me for at least forty-five minutes. They were an attentive, interested group, and even though they could have answered many of their questions by reading the displays in the Visitor Center, they chose to ask me to explain the Ashfall story. As a museum student, this could sometimes be a little frustrating, knowing what it takes to create informative texts for displays, but hopefully talking to me gave them a more memorable and educational visit. Everyone learns in a different way, and providing written text as well as one on one interaction with interns allow visitors to learn in a way that best suits them. Some people come through the barn having read every display in the Visitor Center, giving them the basis for more in-depth questions. Others read the displays and are satisfied with the amount of information provided and come to quietly view the fossils in the Rhino Barn. Others zoom through the Visitors Center to see the rhinos and ask us to explain the Ashfall event from the beginning. On one hand it can be discouraging when it is clear someone did not pay any attention to the displays, but on the other hand museums are designed to educate the public in a non-traditional, non-linear format. When I take admissions on the weekends, I inform patrons to start with the displays in the Visitors Center, but it is only a suggestion. Even the park itself is set up in a very non-linear way. With separate buildings across many acres of park land, visitors are free to roam the paths, and explore the various buildings and discover what they have to offer at their own pace. In addition to my other responsibilities at the park, with the official title of ExplorOlogy Intern, I assisted the ExplorOlogy Paleo Expedition group. ExplorOlogy is a program sponsored by the University of Oklahoma’s Sam Noble Museum. It provides Oklahoma high school students with various science-based summer trips and activities, such as Paleo Expedition. A group of eleven students came to visit Ashfall for three days and participating in the main activities the interns do everyday, supervised by us of course. We had them in teams of two or three excavating in the Rhino Barn, sorting for fossils in the Discovery Shelter, and preparing fossils in the lab. The next two days I accompanied Dr. Voorhies, Rick and another intern to the Golter site, where we did some field collecting. I was in charge of mapping and assigning field numbers to each fossil discovery, as well as making plaster jackets to safely transport the fossils back to the park. We use this site to demonstrate different field techniques to the students, aside from the ones they learn in the Rhino Barn. This is not only a great public outreach program but it is also an example of the local community working together with the park. The site is named for and located on a cattle ranch owned by a local resident named Paul Golter. The park frequently takes groups there to excavate and collect fossils. Many rhino and tortoise bones have been found there, along with the complete rhino skull that was prepared in the lab this summer. A participant of another annual dig, the Friends of the Museum Dig, found it last summer. What is really exciting is that a couple of the ExplorOlogy students uncovered a rhino jaw close to where the skull had been found. By the end of the summer, when the skull and the jaw were completely prepared, we took the opportunity of a slow afternoon, visitor-wise, and left the barn unattended for a while to see if the jaw belonged to the skull. Based on the alignment and wear of the teeth, Dr. Voorhies determined that the skull and jaw did indeed come from the same rhino! Overall, the students really seemed to enjoy their few days at Ashfall, and I was happy to help out the staff with the dig and help provide the students with a fun and hopefully unforgettable experience. In August, I had the opportunity to visit a museum similar to Ashfall called the Mammoth Site, in Hot Springs, South Dakota. I had applied to their internship program as well but am very happy with my decision to work at Ashfall instead. The Mammoth Site, like Ashfall, has a fossil bed completely enclosed in a large building, along with exhibits, and a prep lab. The site itself is amazing – a huge sinkhole that had once attracted mammoths to its warm, spring-fed waters, and eventually trapped them within due to its steep, slick sides. Much like Ashfall, the site is surrounded by walkways for visitors to get a better look at the fossils left in place. However, one major difference is their style of interpretation. The Mammoth Site receives a lot of foot traffic, being in the heart of the Black Hills, close to many other tourist destinations such as Mount Rushmore and the annual Sturgis Bike Rally, therefore crowd control is more necessary there than at Ashfall, which is rather isolated. Their way of dealing with this is through staggering the number of entering guests with mandatory timed tours. This is quite effective, but what is less effective is their interpretation and availability to visitors. The tours are scripted and though my tour guide, who was fresh out of high school and presented the material provided to him clearly and effectively, lacked the knowledge to answer my more technical questions. “What type of consolidant do you use?” and “what is your policy for removing fossils from the bone bed?” may not be a typical questions asked by most visitors, but not getting those answers lessened the experience for me. (This was true for a few other fellow Ashfall interns who visited the museum as well.) There were no interns at the site that day, and excavation only takes place in July – mostly by volunteers. I wonder what do the interns do, if they do not excavate or give tours? The prep lab was huge and impressive but empty with narrow glass windows that do not open, which are the only way visitors can see in or interact. There is a sign that says, “We can hear through the glass, feel free to ask questions” but honestly, it is not an inviting atmosphere to ask questions and learn about the lab. Though the Mammoth Site was interesting and visually impressive, Ashfall and the level of interpretation we are required to provide, spoiled me a little, but that just proves to me that Ashfall is very successful in its attempts to interpret the site for all ages and educational backgrounds. Overall, this summer was full of incredible learning experiences, and absolutely confirmed my choice to pursue a career in museum work was the right one. I learned about an amazing event in the Earth’s history, and life after the dinosaurs in America’s heartland. Who knew camels and rhinos once roamed the prairie? I gained more experience in fossil preparation and discovered how surprisingly different paleontological fieldwork is from archaeological. However, the most surprising aspect of the experience was how much I loved interacting with the public. Even if everyone asks the same questions day after day, I had to keep it in perspective. This is their first visit here, and possibly their only visit, they may have asked the same questions the previous family did but I need to remember that everyone’s experience is unique to them even if they are the same questions to me, and provide each visitor with the attentive answers they deserve. It is a bit daunting at first, especially when I do not know the answer to a question, but when I see the excitement in their faces, mostly because the site is incredible, but partly because I was able to explain something or point out an interesting fact or just chat about science, it made the difference between a good and a great day at work.