A multidisciplinary research team at The University of Akron in collaboration with Veris Technologies (Salina, Kansas) completed a successful pilot study using visible light and near infrared (NIR) spectroscopy to map and characterize the chemical composition of in situ subsurface archaeological features, without excavation, at three Native American sites in Kansas.
Fieldwork took place in the spring of 2016 at three Native American sites – the Kansas Monument Site (14RP1) and Tobias East and West (together 14RC8) in central Kansas, dating between roughly AD 1400 and 1900. The former site was a Pawnee Indian village with clear evidence of dozens of round houses, storage pits, palisades, and other features. Tobias East has been extensively surveyed and in an example of a council circle site. Tobias West, located across a shallow ravine from the eastern site, has only been explored through surface survey and is of unknown archaeological composition. In each case, a limited survey area was first defined on the basis of geophysical prospection using both magnetic field gradiometry and electrical resistivity. Once are area of interest was located and mapped, a minimally invasive shallow subsurface spectroscopy survey was conducted.
At each site, a 1m long metal probe attached to two spectrometers was pushed into the ground at regular intervals along a grid located over suspected archaeological features using a Veris P4000 hydraulic probe. The spectrometers recorded visible light and NIR spectra of the soil (350-2200 nm) in a continuous vertical column as the probe was inserted into the ground. At the same time, the team collected a series of physical soil cores, selectively sampled, within the survey area. Subsequent laboratory processing of the soil cores provided a chemical assessment of two dozen elements present in the soil. Using chemometric analysis, the data from the soil cores was combined with that from the VIS-NIR spectra and the data were extrapolated and converted into and series of 2D horizontal depth slices and then into 3D models of subsurface concentrations of different chemical elements. The resulting maps provided vital clues as to the nature and function of subsurface archaeological features such as pits, floors, and hearths and provided a “proof of concept” that it was possible to model archaeological features using in situ shallow subsurface spectroscopy with this minimally-intrusive technique.