Oat chaff identification based on phytolith morphology and morphometry: A Viking-Age equestrian burial at Fregerslev, Denmark

In 2017, an equestrian burial dating to the late Viking Age was excavated in Fregerslev, Denmark. Metal finds have revealed spectacular remains of a horse harness and a quiver with 22 arrows. Apart from highly degraded pieces of fur, wood and leather, organic remains were scarce, or their association with the grave was unclear. However, analysis of a single block sample attested the presence of plant remains in the form of multi-celled phytoliths, so well preserved that they were most likely taphonomically undisturbed. Hence, phytolith and pollen analysis was applied to the complete grave to further investigate the presence of vegetative grave goods. The aim of the phytolith analysis was to get a better understanding of the grave and its contents. Questions were: 1) Which taxa and plant part(s) do the phytoliths in the area of the block sample represent? and 2) Was this material present all over the grave or deposited in a concentration? The initially attested phytoliths concerned a concentration of grass silica skeletons (multi-celled phytoliths), interpreted as horse fodder. In order to identify the material, both morphological and morphometric analysis were applied, based on a large number of chaff fragments and phytoliths. The results of the two methods were compared with reference material and subjected to statistical analysis. The majority of the phytolith concentration consisted of oat chaff. The bottom of the grave was covered with straw, mixed with some other plants. This study is of methodological relevance since it allows thorough analysis and comparison of both morphological and morphometric identifications. Additionally, it is one of the first times that morphometric identification criteria are applied to material from historical periods, for which these methodological approaches are mostly lacking, and to oat chaff phytoliths.Peer reviewe