Chemometric tools for identification of wood from different oak species and their potential for provenancing of Iberian shipwrecks (16th-18th centuries AD)

Archaeological wood fragments from four Iberian shipwrecks (Belinho, Magdalena, Ribadeo and Yarmouth) and living tree cores of four oak species (Quercus faginea, Quercus petraea, Quercus pyrenaica and Quercus robur) were analysed by Fourier Transform Infrared spectroscopy (FTIR) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The use of multivariate statistical methods (principal components analysis and discriminant analysis) to the data obtained with both techniques enabled to differentiate between the oak species studied with high probabilities, and provided less robust but meaningful information on the archaeological wood samples analysed. Most of the samples from the Magdalena shipwreck exhibited FTIR and Py-GC-MS signals that resembled those of either Q. petraea or Q robur. The geographical distribution of these species is concentrated in northwest Spain, where this frigate is known to have been built, supporting the hypothesised use of local forest resources. The chemistry of the fragments from the Belinho, Ribadeo and Yarmouth shipwrecks were more similar to wood from Q. faginea and Q. pyrenaica, also pointing to forest from the Iberian Peninsula as most likely source. Our results show that FTIR and Py-GC-MS, in combination with multivariate statistical methods, are promising tools for provenance studies of archaeological woods. However, the chemical features of wood from alternative areas and species need to be analysed to fully explore this potential.