The Jefferson River Project
- Sari B. Dersam
- Apr 9
- 3 min read
The Jefferson River Project takes place on a private farm along a Pleistocene channel of the Jefferson River in Jefferson County, Montana. The area is on the northwestern edge of the GYE, at the base of the Tobacco Root Mountains foothills.
The site being investigated by AERI is located on an isolated, stabilized T2 Pleistocene terrace within the river channel, and sedimentation suggests that the terrace's depositional environment was driven by persistent, low-energy flood events, as evidenced by overbank deposits.
AERI researchers were initially drawn to the site after a complete bifacial tool, technologically consistent with Early Archaic or Late Paleoindian technologies, was found eroding out of a frequented moose wallow.
Further organic duff removal from the surface of the locality revealed varying forms of lithic debitage and formal tool fragments, as well as a complete Scottsbluff hafted knife or drill (13cm) made out of a non-local gray chert. This discovery immediately sparked interest in the site, but due to scheduling and funding constraints, it could not be addressed until the 2025 season.
Though it was the Paleoindian association that initially attracted AERI to this locality, further investigation of the now secondary channel of the Jefferson River, on which the site resides, revealed itself to have once been the primary channel of the river system, and was even the original river channel navigated by the Corps of Discovery when the Lewis and Clark Expedition came through the Whitehall area between July 26th and July 31st in 1805. The channel was diverted to its current course sometime after 1805 and before 1840.
Over a 7-day session in August of 2025, AERI scientists, student researchers, U of M students, volunteers, and local members of the public joined us as we slowly unveiled the history of this site and its many potential uses.
The site, now known as the Kingfisher site, contained an unexpectedly high density of formal, highly curated lithic tools distributed stratigraphically across sequences of overbank deposits.
Considering diagnostic surface artifacts linked to the Scottsbluff or broader Cody techno-complex recovered, it should have been unsurprising that other diagnostics encountered could be of the same age, yet it was still surprising when, less than 15cm below the surface in a level where multiple flakes were recovered, the base of a Paleoindian Fishtail techno-complex projectile point was discovered. Even more exciting was that this was a point style representing the older Fishtail Complex variant regionally dated in sites like Mummy Cave, Medicine Lodge Creek, Game Creek, Osprey Beach, and the Lawrence site to between 10,705 and 10,330 Cal BP.
One of the 1m x 1m test units was taken further down from the main artifact cluster, only to continue to encounter beach sands and overbank deposits for another 40cm before encountering a second, deeper cluster of bifacial tools, consisting of different raw material sources and production styles, including one artifact that is reminiscent of a Folsom ultra-thin biface.
Yet the artifacts encountered were restricted to different levels of overbank deposits, potentially indicating that the site was heavily reoccupied during the early Holocene, with technologies possibly dating as early as 12,000 years before present and spanning up to 8,000 years before present.
A total of 15 formal bifacial tools were recovered from the site during the 2025 season, including 5 diagnostic points associated with the Middle and Late Paleoindian periods. After preliminary analysis is complete, AERI will return to the Kingfisher site in either the 2028 or 2029 field seasons to continue our investigations into this extraordinary site!
Read the whole 2026 annual report here:
AERI is a 501(c)(3) nonprofit that focuses on research and education regarding the natural and cultural histories of mountainous ecosystems. We synthesize our research findings with traditional wisdom to improve human-environment relationships and conservation practices in these beautiful landscapes.
AERI conducts research in the Greater Yellowstone Ecosystem (GYE), which is culturally significant—either through ceremony or as a direct homeland—to at least 49 affiliated tribal groups. We respectfully acknowledge the peoples on whose traditional territories we reside and work. We work to honor their relationship to these lands, since time immemorial, and to follow their example in caring for this place for generations to come.
Comments