Summer Summary Series: Luke Weaver and Hell Creek

A Summer Spent Touring the Cretaceous of Montana

 By Luke Weaver

My advisor, Greg Wilson, has been doing research in the Hell Creek region of northeastern Montana (near Jordan) for over 20 years; a field research program inherited from his Ph.D. advisor, world-renowned paleomammalogist, Bill Clemens (UC Berkeley). The Hell Creek region is one of the few places in the world that preserves rock formations that span the Cretaceous-Paleogene (K-Pg) boundary (ca. 68–65 million years ago [Ma])—an interval which captures the mass extinction event (66 Ma) that wiped out all non-avian dinosaurs, and set the stage for placental mammals to radiate. As such, the fossils from before and after this extinction boundary provide unique insights into both the potential causes of the mass extinction, and the timing and patterning of ecological recovery in its aftermath. In totaling the collective research endeavors of Bill and Greg, we can track nearly 50 years of continuous paleontological field research that has been carried out in the Hell Creek area (1972–2019), resulting in one of the best collection of K-Pg vertebrates in the world. So, it is perhaps no surprise that each summer, if you’re a member of the Wilson Lab, you spend it in Hell Creek.   However, this summer marked a change in the objective of Wilson Lab field research. The goals of this summer were not just to collect more Hell Creek fossils (come to the 2^nd floor of the Life Sciences Building and you’ll begin to understand why…), but rather to document the geologic setting of our major fossil localities and better constrain their stratigraphic relationships. Furthermore, we planned to run exploratory campaigns in both earlier Cretaceous and later Paleogene rock units in order to begin expanding the scope the high-resolution vertebrate fossil record we have amassed in the Hell Creek.In late June, Brody Hovatter (fellow Wilson Lab grad student) and I kicked off this 2019 field campaign with a handful of undergraduate volunteers in tow. Brody has been doing fieldwork in the Hell Creek since 2014, and I have been since 2015. Upon setting up camp at Hell Creek State Park, along the banks of the Fort Peck Reservoir (Fig. 1), we were immediately joined by Ray Rogers (geologist/taphonomist) and Kristi Curry Rogers (dinosaur paleontologist) from Macalester College in St. Paul, MN. 

Figure 1. The Wilson Lab Camp along the banks fo the Fort Peck Reservoir in Hell Creek State Park

Figure 2. Ray Rogers sharing some geology knowledge with me, Brody Hovatter, and Jojo (a Macalaster undergrad)

They arrived with 12 undergraduate students for the first leg of their immersive, month-long undergraduate field research course. Through the course of their stay, Ray helped us refine our geological understanding of our field area (Fig. 2), and the UW crew helped orient the new students to field research techniques in the Hell Creek. Following a dramatic thunderstorm finale, the Macalester crew moved on, and we awaited our next arrivals. 

Figure 3. BIOL 475 students learning how to measure geologic section in Hell Creek

Dave Grossnickle (Wilson Lab postdoc) and Alex Brannick (fellow Wilson Lab grad student), aided by Henry Fulghum (Wilson Lab undergrad/wonderboy), arrived near the end of June with a large group of UW Biology and Earth and Space Sciences (ESS) students as part of the BIOL 475 Paleobiology Field Methods course. Quick on their heels was Paige Wilson (Wilson/Strömberg Lab grad student), with a few ESS undergrad volunteers. Dave, Alex, and Henry worked to train the BIOL 475 students on the ins-and-outs of paleontological, sedimentological, and stratigraphic fieldwork (Fig. 3)—all of which directly contribute to the broader Wilson Lab research objectives. Paige and her team worked to collect plant macrofossils (i.e., leaves), microfossils (i.e., pollen and phytoliths), and sedimentological data from her localities spanning the K-Pg boundary. Her dissertation research is focused on understanding how plant communities changed leading up to, and across, the K-Pg mass extinction, and how floral changes might have influences observed changes in vertebrate communities during this interval. Shortly after the 4^th of July, I departed the Wilson Lab camp for a quick detour in southern Montana to work in the Early Cretaceous-age (ca. 125–105 Ma) Cloverly Formation with Mike D’Emic from Adelphi University (Long Island, NY). In the five days I was out with Mike and his crew, we visited a few historic quarries, including the dinosaur quarry that produced the holotype of Deinonychus (a medium-sized theropod dinosaur that provided some of the earliest evidence for birds being dinosaurs; Fig. 4). And, much more interesting to me, we explored the quarry that produced the holotype specimen of the carnivorous mammal Gobiconodon, whose cousin, Repenomamus, is known to have feasted on juvenile dinosaurs. Although these visits were a great bucket list check for me, my primary objective for this trip was to assess the potential for the Cloverly Formation to produce a sizeable sample of tiny mammal teeth. The prospects look good, and I hope to return with Mike and crew next summer.

Figure 4. Me at the holotype Deinonychus quarry. I’ve never been so happy to see a dinosaur quarry….

The next objective for the summer was to explore the Judith River Formation of northern Montana. This formation is roughly 10 million years older than the Hell Creek Formation we usually work in (ca. 80–75 Ma), and we hoped to begin collecting mammal, and other vertebrate, fossils from this unit to better understand how vertebrate communities changed from the Judith River to Hell Creek transition. So, I left southern Montana to meet up with Greg, who was flying into Billings, MT from Seattle. The next morning, we left for the Havre, MT, to meet up Mark Goodwin (Fig. 6), a dinosaur paleontologist from UC Berkeley. For decades, Mark has worked in the Judith River Formation, collecting both dinosaur and mammal fossils for UC Museum of Paleontology.            Over the course of about a week, Greg, Mark, and I toured Judith River exposures in northern Montana, collecting fossils and bags of fossiliferous sediment (Fig. 5) that we would later screenwash in order to bolster our samples (like panning for gold). The trip was a major success, and early sorting of the sediment we collected has produced over 25 mammal teeth… and we’ve only scratched the surface. Next summer, we plan to target these Judith River localities with the sort of fervor given to the Hell Creek, with the aim of building a collection comparable to the Hell Creek Formation. From there, we can begin to untangle the evolutionary history and ecological structure of these earlier mammalian communities.          

Figure 5. Greg Wilson and I collecting sediment from a famous Judith River fossil locality

Figure 6. Mark Goodwin pointing out numerous tyrannosaurid teeth and other vertebrate and invertebrate fossils at a locality in the Judith River Formation

We then returned to the Hell Creek base camp to regroup and tackle a few more projects in the area. Then, Greg, myself, and Tom Tobin—former UW ESS grad student, now an Assistant Professor at the University of Alabama—went south to Terry, MT to do some prospecting in the Lebo and Tongue River Formation, which lie atop the early Paleogene beds that are exposed in our research area (Fig. 8). The Lebo and Tongue River were deposited during the middle and late Paleocene (ca. 64–58 Ma); therefore, fossils recovered from these rocks could help us gain a long-term picture of how terrestrial vertebrate communities recovered in the aftermath of the K-Pg extinction. The exposures near Terry are steep, and the rocks are not very fossiliferous—all of which resulted in long, grueling days with few fossils to show for it. However, we did find a few promising sites and are hopeful that future expeditions will produce something worthwhile.

Figure y. Greg Wilson and Tom Tobin discussing geology in the Terry Badlands

Finally, after returning from Terry, we prepared for the final leg of the field season—The Discoveries in Geosciences (DIG) Field School. The DIG is a four day, immersive field experience for K-12 teachers, where we teach them paleontological and geological field methods, then give them tools and resources necessary to incorporate these lessons into the classroom (Figs. 8, 9). The DIG this year was led by Greg, Brody, Alex, Dave, and Paige, and the teachers who participated were some of the best we’ve ever had. If you would like to learn more about the DIG Field School, or know someone who might be interested in applying, please visit: https://www.burkemuseum.org/education/educators-and-schools/dig-field-school.

Figure 8. Jordan Claytor (Wilson Lab grad student) and Henry Fulghum explaining how to collect vertebrate microfossils during the DIG Field School

Figure 9. Alex Brannick teaching DIG teachers how to put a plaster jacket on a dinosaur bone

Once the dust settled, and the teachers were gone, Brody, Alex, and I were left with a few undergrad volunteers to wrap up the remaining field projects, pack-up camp, and head back to Seattle. After putting a plaster jacket on a Triceratops skull, and attending the wedding/reception of a local rancher’s son, we returned to Seattle with two trucks full of fossils, rocks, and slightly less sediment than usual. The work we completed this summer laid the groundwork for a new phase of Wilson Lab field research, and the prospects look good.
Luke Weaver is a 5th year PhD student in Greg Wilson’s lab.