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The University of South Dakota Archaeology Laboratory, with the support of the Missouri River Institute, conducted an airborne magnetic survey of the Missouri National Recreational River for the US Army Corps of Engineers, Omaha District, (contract #DACW45-01-P-0267, supervised by Rebecca Latka, Project Manager, Missouri National Recreational River). The primary goal was to identify buried or submerged cultural resources along the past and present Missouri River channel.
The Principal Investigator was Brian Leigh Molyneaux, PhD. TerraQuest Ltd., Mississauga, Ontario, Canada, an international specialist in airborne geophysical surveys, acquired the total field magnetic data between November 27 and December 12, 2001. CGI Controlled Geophysics Inc., Thornhill, Ontario, Canada, processed the raw flight data. ENW Services, Denver, Colorado, geophysical consultant, contributed survey design, oversight, post-acquisition data processing, geophysical interpretation, and base map creation.
The results indicate that the Missouri River Valley has an active geomagnetic response suggesting significant variability in the basement geological units. Prominent features include numerous anomalies within a generally high geomagnetic background in the Yankton area, several northeasterly striking linear anomalies crossing the river valley at Vermillion and Burbank, South Dakota, and an isolated, large circular anomaly on the floodplain opposite Ponca State Park, Nebraska. ENW filtered out the response due to geology using a process that favored short-wavelength anomalies of a size and shape consistent with cultural sources then isolated a scatter of anomalies with reference to the flight path. The Archaeology Laboratory created a GIS for the project and conducted a base-map analysis of each anomaly. The basemaps consisted of a series of Corps of Engineers maps drawn in 1881, a series of Missouri River Commission maps drawn in 1892, the most recent USGS 7.5' Quadrangles (as DRGs), and the most recent digitized aerial photographs (DOQQ). Of the 119 anomalies isolated, 99 proved to be above-ground structures or features associated with extant farmsteads or agricultural activity, 12 were Priority A anomalies (primary targets for further investigation), and 8 were Priority B anomalies (less distinctive but still worthy of investigation).
The Archaeology Laboratory recommended that the 20 prioritized anomalies be ground truthed, to determine the nature of their sources.