Subsurface Imaging of a Late Woodland Effigy Mound Site : Lake Koshkonong Effigy Mounds, Wisconsin

Abstract

The preservation for Effigy Mound sites continues to be a concern. These landscape monuments and sacred sites remain poorly understood and require innovative, noninvasive, and nondestructive techniques for archaeological investigations. A collaborative study of a Late Woodland (ca. A.D. 700 - 1100) effigy mound site on the east shore of Lake Koshkonong was undertaken. The site, protected from excavation by Wisconsin State law, is within Jefferson County, southeastern Wisconsin. Previous geophysical tools (resistivity, EM) were employed to assess the site. Ground penetrating radar (GPR) transects were collected using a pulseEKKO 1000 unit with two antennae frequencies: 225 MHz (0.5 m antennae separation/step size of 0.1m) and 450 MHz (0.25 m antennae separation/step size of 0.05 m). The surveys were conducted along the length and width of several mounds with topographic data being collected with a Topcon laser level to geometrically correct the data. After data processing and using radar stratigraphic principles on the reflection patterns, internal stratigraphy within the mounds were observed. Together with the previous geophysical surveys, the results reveal a complex natural and cultural stratigraphy both within the mound features and between the mounds.