Footprints in the Mud: The Search for 23 Million Year Old Mammal Tracks
BY WHITNEY WORRELL ABOVE: The original trackway sample My path to trace fossil research started when I decided to write a summer research proposal last year. I have always wanted to do paleontology, that part was easy, but the geology department didn’t have any active paleontology research that I could take part in. Thankfully, my advisor, Professor Kena Fox-Dobbs, helped me create a project to satisfy my “must include fossils” requirement. Kena showed me a specimen that had been in our teaching collection since 1964, a nondescript chunk of sandstone, on the top of which is a tiny, yet very clear, set of footprints. On the back of the specimen is “Benham Creek” and some coordinates. The original finder of the specimen was a student at UPS in the early 1960’s who had found it on the ground during his own summer research, noted its location, and gave it to the department where it had not been investigated furtheruntil now. I was lucky to have my research project funded, and I set out to study this mysterious trackway in sandstone.
I can remember standing there for the first time realizing the seemingly impossible task I had agreed too: try and find more of these miniscule footprint fossils in this area, where Mount Saint Helens had famously erupted and then there was a landslide, among the many other things that had occured in the area in the past 23 million years. The coordinates were to a spot on the side of Forest Road 25 in the Gifford-Pinchot National Forest, just northeast of Mount Saint Helens. According to other research and geologic maps, the rocks in the area are about 23 million years old. The site is a road cut, a portion of rock that had been cut away to make a road through the area, and heavily forested. My first visit to the site was daunting; I had been optimistic about the research, there was a lot of exposed rock, but there was also a turbulent river, with numerous downed trees from a landslide ten years prior.
Fortunately, I had a wonderful support team for the field work portion of my research. The department had hired a student, Audrey, to help where needed, and I was lucky to have her with me for the entire week I was going to be in the field. Additionally, my mom, Betty, and my dog, Molly, joined us at the campsite for good company. Kena and another research student would join us the next day. Audrey and I had a lot to accomplish in the first couple of days at the site before the others arrived. To begin, we took measurements of the site, broke it up into 7 sections and measured the thicknesses of the layers of rock in each section. The layers of the site were not horizontal; they dipped in such a way that we could measure layers on top of other layers simply by walking to the next section over. The first day, Audrey and I gathered samples to bring back to the lab and classify the sedimentology -which includes the grain size and other observations about the rocks themselves- noted the thickness of layers, and broke open just about every rock we could find looking for signs of fossils. We found fossil leaves and wood fragments that day. It was exciting despite the fact that they were not the elusive footprints.
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