Magnetic susceptibility investigations were conducted at an Awatixa Hidatsa village (32ME11, also known as Sakakawea Village) along a cutbank at the Knife River Indian Villages National Historic Site (KNRI) in central North Dakota, USA. This extensive exposure provided a superb opportunity to correlate magnetic susceptibility measurements with a variety of subsurface features. These features were visible in the cutbank, and also recorded in cutbank profiles completed in the late 1970s in work supervised by Robert Nickel and Stanley Ahler. The susceptibility studies are part of a larger program of geophysics at KNRI that commenced with pioneering surveys of John Weymouth and Robert Nickel, also in the 1970s, and continued with extensive surface-based magnetic surveys over the interior portion of the site in 2012 by the National Park Service. Our magnetic susceptibility study differs from other geophysical efforts in that measurements were collected from the vertical cutbank, not from the surface, to investigate different feature types within their stratigraphic context and to map small-scale vertical changes in susceptibility. In situ measurements of volume magnetic susceptibility were accomplished on the cutbank at six areas within the village and a control location off-site. Samples were collected for use in soil magnetic studies aimed at providing an understanding of susceptibility contrasts in terms of magnetic mineralogy, grain size, and concentration. Distinctive susceptibility signatures for natural and cultural soils, different feature types, and buried soils, suggest that down-hole susceptibility surveys could be usefully paired with surface-based geophysics and soil magnetic studies to explore interior areas of this and other KNRI sites, mapping vertical and horizontal site limits, activity areas, features, and perhaps even earlier occupations. This study showcases the potential of cutbank studies for future geophysical survey design and interpretation, and also underscores the importance of information gained through pioneering studies of the past.

Bison (Bison bison) are one of the few terrestrial megafauna to survive the transition into the Holocene and provide a unique opportunity to study a species on a broad spatiotemporal scale. Today, bison are primarily managed in small and isolated herds with little known about their ancestral ecology. We studied the carbon and nitrogen isotopes of Northern Great Plains bison from the terminal Pleistocene and throughout the Holocene to gain insight into their paleoecology. This time span is contemporary with the first population bottleneck experienced by bison at the end of the Pleistocene and includes the second bottleneck which occurred in the late 19th century. Results were compared with modern bison herd isotopic values from Theodore Roosevelt National Park (TRNP). Patterns of isotopic variation found in bison over time indicate significant (δ13C p = 0.0008, δ15N p = 0.002) differences in diet composition and correlate with climate throughout the Holocene. Isotopic relationships described here reveal the plasticity of ancient bison in unrestricted rangelands during periods of climatic fluctuations. Managers at TRNP and elsewhere should pursue opportunities to expand bison range to maximize forage opportunities for the species in the face of future environmental change.

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