Biogeomorphic processes and archaeological site formation in Absaroka Mountains of northwestern Wyoming
Bechberger, Jillian M.
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Archaeologists frequently associate Thomomys talpoides, the Northern Pocket Gopher, with the loss of stratigraphic integrity (Bocek 1986; Morin 2006). Disturbance from subsurface burrowing and the redistribution of sediment can result in both lateral and vertical movement of cultural material. However, fossorial activity does not necessarily negate the research potential of a site. Burrowing mammals may actually reveal previously unidentified archaeological sites, help land managers develop effective site testing plans and evaluate site significance, and contribute to a better understanding of a region’s archaeological record and past environmental conditions. This research explores the influence of pocket gopher activity on site formation at a high elevation prehistoric flaked stone scatter in the Absaroka Mountains of northwestern Wyoming. Pocket gopher activity was documented at the site in a 1-hectare sample area surrounding a small sag pond. It was suspected the sediment pocket gophers transport to the surface while digging subsurface tunnels was eroding downslope into the small pond, burying cultural material. Archaeological data were examined in conjunction with pocket gopher behavioral patterns and geomorphic processes to better understand the affect of burrowing and sediment relocation on cultural material. Geospatial analysis was used to identify topographic controls on burrow placement. The physical characteristics of flaked stone recovered from pocket gopher disturbed sediment were compared with artifacts located on the undisturbed site surface and subsurface artifacts collected during test excavation to identity patterns in distribution potentially resulting from gopher activity. Erosion from pocket gopher mounds was evaluated by comparing the sediment characteristics of active and abandoned burrows and using a GIS-based erosion model. Results show pocket gopher burrows occur most frequently on north facing slopes. Neither gradient nor elevation could be shown to significantly influence burrow placement. There were differences in the locations of winter pocket gopher activity and summer activity. The physical characteristics of artifacts found within pocket gopher disturbed sediment were indistinguishable from artifacts on the site surface. Subsurface flaked stone exhibited significant differences in the artifact characteristics examined at all depths. However, the vertical distribution of artifacts at the site was not consistent with patterns noted in other pocket gopher impacted archaeological sites. The erosion model indicated sediment from pocket gopher disturbed areas at the site would be deposited in the sag pond, however the amount of predicted accumulation did not correspond with accumulation calculated using radiocarbon dated samples collected from known depths. The impact of pocket gopher activity on the lateral and vertical movement of artifacts at 48PA2874 could not be definitively demonstrated. This project provides a general background for further research on pocket gopher impacts to archaeological material in alpine settings. With additional research the effect of pocket gopher activity on artifact distribution in high elevation environments can be better understood.