Near infrared and hyperspectral studies of archaeological stratigraphy and statistical considerations

The paper proposes a methodology based on near-infrared (NIR) spectrometry for studying stratigraphy and depth profiles in archaeological excavations. The NIR spectra can be used to describe and complement the wet chemical analysis. Soil samples were collected from a 0.8 m deep stratigraphy of a Neolithic site that were analyzed by three different NIR instrumentations. Phosphate- and magnetic susceptibility and inductively-coupled plasma mass spectrometry measurements were also conducted as reference analysis. Principal component analysis on the data from three different NIR instrumentations gave useful score plots that allowed grouping of the samples. The results from the lab spectrometer were most useful, although the hyperspectral NIR camera was the fastest method to obtain spectra of many samples from one image. The paper shows how the NIR spectral data can be used for multivariate analysis to get meaningful conclusions on archaeological soils and sediments, especially in terms of understanding site development/phases and soil formation.