GETTING OUR DUCKS (AND OTTERS, BEAVERS, AND PECCARIES) IN A ROW: NEW RESEARCH BY THE HAGERMAN PALEONTOLOGY, ENVIRONMENTS AND TEPHROCHRONOLOGY (PET) PROJECT AT HAGERMAN FOSSIL BEDS NATIONAL MONUMENT, IDAHO

Hagerman Fossil Beds National Monument (Idaho, USA) preserves a diverse Pliocene (Blancan North American Land Mammal Age) fauna with close to 200 species. Hagerman is noted for its Horse Quarry but also for its carnivorans, birds, and numerous holotypes, including species unique to Hagerman. The fossil-bearing, fluvial-lacustrine deposits at Hagerman span over 800,000 years and reflect a changing environment and community related to global climate change, localized lake fluctuations and other hydrological (e.g., riverine and wetland) shifts, and transcontinental faunal migrations. To understand the effects of a changing landscape on the Hagerman faunal community and to better infer ecological relationships requires stratigraphic facies correlation between fossil localities.

Multiple ash deposits punctuate Hagerman’s geologic landscape, but we currently lack the degree of tephrostratigraphic or other lithostratigraphic facies control needed to accurately correlate our fossil localities across time or space. Small to moderate offset faults have been recognized, which may have an effect on inferred stratigraphic relationships of localities. Even the depositional environment of the renowned Hagerman Horse Quarry is poorly understood. The Hagerman Paleontology, Environments, and Tephrochronology (PET) Project is an inter-agency collaboration between the National Park Service and United States Geological Survey formed to address these issues. Our current focus is to source, date, and effectively trace volcanic ash layers across Hagerman, allowing for spatial-temporal correlation of these localities and a developmental tephrostratigraphic framework from which to better reconstruct Hagerman’s ancient landscapes and faunal communities. Geochemical signatures obtained from fresh samples of silicic and basaltic tephra have already allowed for us to extend the areal distribution of several ash layers and trace their eruptive sources. Further work is anticipated in order to refine dates on several of the tephra and possibly obtain dates on previously undated material. This research allows us to fine-tune first and last appearance dates for taxa and reconstruct individual landscapes and associated faunal communities for specific slices of time at this important Pliocene fossil site.