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Site name: Effigy Mounds National Monument


Nearest town: Prarie du Chien, Wisconsin; State/country: Iowa; Type of site: 3 prehistoric effigy mounds; Date of site: AD 800; Sponsor: U.S. National Park Service; Collaborators: Surveyed with help of students of NPS sponsored "Workshop in Remote Sensing."

Type of survey: Resistivity; Instrument: Geoscan Research RM-15; Prospection depth: 0.5 & 1 m; 0.5 m; 0.5 m; Sampling interval: 0.5 x 0.5 m; 1 x 0.5 m; 1 x 0.5 m; Area surveyed: 28 x 20 m; 44 x 37 m; 30 x 35 m; Date of survey: 5/99.


Comments: These effigy mounds, managed by the U.S. National Park Service, were surveyed by students of a workshop sponsored by the NPS entitled: "Recent Advances in Archeological Prospection Techniques." The results show the effigy cores to be composed of more resistant soils, with possible building episodes suggested by the clumping of similar values. The first, Little Bear was investigated at 2 depths and indicates discrete sections, particularly in the head and foreleg areas. The second, the Great Bear, also includes two circular mounds. The third, a bird effigy, shows a number of discrete zones, particularly the tail area. The low resistances surrounding each figure are probably due to water pooling and drainage from the mound.

Type of survey: Magnetic gradiometry; Instrument: Geoscan Research FM-36 fluxgate gradiometer; Prospection depth: up to 1.5 m; Sampling interval: 0.5 x 0.125 m; 1 m x 0.25 m; 0.5 x 0.125 m; Area surveyed: 28 x 20 m; 44 x 37 m; 30 x 35 m; Date of survey: 5/99.

Comments:These effigy mounds, managed by the U.S. National Park Service, were surveyed during a workshop sponsored by the NPS entitled: "Recent Advances in Archeological Prospection Techniques." The results show the cores to be composed of more magnetic earths than surrounding soils, probably because nearby topsoils (generally more magnetic) were scooped up to form the mounds (this would also cause the negative magnetic values surrounding each mound). Clumping of similar values may reflect building episodes. The first effigy, Little Bear, shows a more clearly defined "ear" than is seen in the resistance data (above). The large values at the right and bottom are due to NPS steel sign posts. The second effigy, the Great Bear, shows a core of more magnetic earth that is much narrower (about 5 m) than the 8 m width of this effigy (see the corresponding resistance image above). The magnetic data also clearly show 2 ears not seen in the resistance data. The third, a bird effigy, shows the left side of the body and the head to be quite distinct (compared to the resistance data), composed of more magnetic earth.

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(updated: 7/00)