Geoarchaeological Methods in Iowa

Finding buried archaeological sites is one of the most vexing methodological problems that presently faces archaeologists in Iowa. Traditionally, the discovery of buried sites has been opportunistic and often serendipitous. Many buried sites are first discovered eroding from stream banks. Others have been found in the process of buildig roads, digging basements, or quarrying sand or gravel. 

Fortuitous discovery has its drawbacks. Stream bank exposures are often slumped over. Despite the thousands of miles of stream banks in Iowa, cutbanks that provide clear, clean exposures of alluvial sediments are relatively infrequent. Even more serious, sites discovered during construction or quarrying are usually seriously damaged before archaeologists can arrive to investigate.

Obviously, it is best to find the sites before they are damaged, either by construction, quarrying, or natural erosion. Archaeologists in Iowa seek buried sites in a number of ways, primarily using backhoes and soil augers. 

Backhoes can reach to depths of 3 m or more, but entering the narrow trenches to inspect the walls for arifacts and features is dangerous, unless costly and cumbersome shoring is installed. 

Soil augers have been used in Iowa to reach depths of over 8 m. The manual rotary augers used by the Office of the State Archaeologist, and others working in the state, bore a hole with a diameter of about 20 cm. If dug and screened in 10 cm levels, these tools are capable of detecting buried archaeological deposits and tracing their lateral extent. 

Geophysical methods of site detection, such as ground penetrating radar and soil resistivity, have not been extensively applied in Iowa, although their use will undoubtedly increase with future improvements in technology and interpretation.