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8 Geophysical Signatures of Earthlodges in the Dakotas Jennifer R. Bales and Kenneth L. Kvamme In recent years the investigation of village sites in the Dakotas has seen the intensive use of geophysical surveys, a method that is becoming increasingly popular in the United States. Archaeological geophysics refers to the use of various instruments to remotely measure properties of soils and sediments, such as their magnetic susceptibility or conductivity. Archaeological features, including hearths, storage pits, and house ®oors, often possess physical properties that are different from those of the surrounding soil. Because of this, features can sometimes be identi¤ed as anomalous measurements against a relatively constant background. This makes it possible to obtain much of the same spatial information about features that is acquired during excavation but without the associated destruction to the site, the large amounts of time required, the high costs, and restrictions to limited areas (Bevan 1998; Clark 2000). Geophysical surveys have focused on village sites along the Missouri River because they represent intensive occupations with massive architectural constructions and other earth disturbances. These methods tend to work best at these sites because the large features and concentrated use lead to more pronounced alterations of physical properties and, consequently, to more successful detection compared with that at short-term open-air camps with few disturbances to the ground. With a suite of projects conducted in the region there are now enough data collected to begin to characterize the nature of geophysical signatures produced by earthlodges. This recent surge of geophysical surveys in the Middle Missouri subarea represents a new wave of archaeological investigations unparalleled since the Inter-Agency Archaeological Salvage Program of 1945–1969. While pioneering and signi¤cant geophysical work was conducted in the 1970s by John Weymouth and his associates (Weymouth 1976, 1979; Weymouth and Nickel 1977) utilizing early and now antiquated instrumentation, more recent projects utilize much more advanced and varied technologies that give multidimensional views of the subsurface and allow surveys of large areas in relatively small spans of time (Kvamme 2001a). The efforts of Weymouth and his colleagues in helping to establish archaeological geophysics in the Great Plains are acknowledged. Magnetometry, electrical resistivity, and ground-penetrating radar data from six Middle Missouri village sites are examined to compare the effectiveness of each method for mapping buried earthlodges and their internal features . Our results are illustrated at three different scales: the village level, the level of the earthlodge and its immediate environs, and that of the earthlodge interior. Geophysical methods can permit examination of such spatial attributes as the size, shape, and orientation of earthlodges, depths of ®oors below the surface, their spacing with respect to other lodges, their relative densities and arrangements within villages, and the interior layouts of hearths, storage pits, and roof support posts. This kind of information is useful for examining the way that past cultures utilized space and for potentially understanding the ideology that in®uenced the way site components were organized. Information about the distribution and frequency of such earthlodge features as storage pits may provide insights into population size, length of occupation, status differences within sites, or cultural differences between villages. Earthlodge shape is an important chronological indicator. Geophysical methods make it possible to study these attributes systematically for large samples of earthlodges, a feat that is not possible with traditional archaeological excavations owing to restrictions of time and cost. Moreover, geophysical techniques offer an alternative to excavation, allowing the noninvasive investigation and continued preservation of the depleted number of village sites that remain since the damming of the Missouri River. Our results support a growing realization that geophysical information alone can sometimes be used as primary data to directly address speci¤c questions about a site and the past. It is estimated that geophysical data have been collected from nearly 20 village sites in the Middle Missouri subarea (e.g., Kvamme 2001a, 2003; Toom and Kvamme 2002; Weymouth 1976, 1979; Weymouth and Nickel 1977). The type, extent, and quality of the geophysical data from these sites are variable. Six village sites are selected for this project on the basis of a combination of factors including the use of multiple geophysical methods, signi¤cant geographical coverage, and data quality. They also represent a range of cultural types over a broad span of time (Table 8.1; Figure 8.1). GEOPHYSICAL METHODS Archaeogeophysical surveys employ a variety of techniques to measure physical and chemical properties of near-surface deposits—usually the uppermost 1–2 m, although...

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