Spectrophotometric analysis of prehistoric pit fillings as an indicator for ancient topsoil parameters
Prehistoric pits are filled with ancient topsoil material, which has been preserved there over millennia. Often, the colours of pit fillings are specific for the time the soil material was relocated. Early Neolithic pit fillings, e.g., have a black to dark brown colour, while Iron Age pit fillings have a lighter grey colour.
Soil colours reflect soil characteristics, and the correlations between soil colour and soil components like charred organic matter or iron hydroxides can be measured using spectrophotometrical data. The development of a quantitative spectroscopic method based on soil colour spectra would enable the measurement of large amounts of samples, e.g. to investigate environmental or archaeological research questions on a regional scale.
The aim of this project is to assess soil profile information using VIS-spectroscopy, with a main focus on archaeological soil features, and to establish spectrophotometry as a rapid and reliable tool for the analysis of soils and sediments. Furthermore, we want to evaluate the colour differences of pit fillings that are typical for a prehistoric period.
Soil colour spectra are obtained in the 360 to 740 nm range using a field-spectrophotometer (CM-700d) and a lab spectrophotometer (CM-5). The spectrophotometric data is calibrated against large soil sample sets (archaeological sediment, recent toposoils and paleosoil sequences) that have been analyzed on iron, carbonates, organic carbon, and pyrogenic carbon (BPCA). The set of archaeological samples that covers material from the Early Neolithic to the Roman period was collected at excavations in the loess-covered regions of NW- and E-Germany. Models were build based on partial least squares regression. Additionally, we evaluated different colour index values (e.g. Redness Rating), as well as the effects of soil moisture and texture.