Charred and shrunken pollen grains as a result of special depositional conditions in the Roman age Vesuvian area

Despite the sudden burial to which they were subjected during the eruption of 79 AD, many of the soil samples from the Vesuvian area are poor or devoid of pollen. This research assesses whether a carbonization process may be responsible for the complete or partial loss of pollen grains or, at very least, for them going unrecorded during pollen analyses. The discovery of a certain number of pollen grains in plant material from Oplontis has made it possible to investigate which heating conditions they may have been subjected to. For this purpose, in this study, modern pollen grains were exposed to different temperatures for different time intervals in order to observe their modification. The data collected indicate that exposure to high temperatures, even for a short time, can significantly impact pollen grains to the point of making them undetectable during palynological analyses. Modern pollen grains similar to those of Oplontis are observed after exposure to 300 °C for 15 min. The state of preservation of the Oplontis reticulate grains makes prolonged exposure to 300 °C or higher temperatures unlikely. The temperature indications obtained are compatible with data from other studies. The hypothesis of combustion may also explain the small dimensions of many grains found in the Vesuvian sites.