Organic materials may be preserved as a result of charring. Partial burning reduces the material to a carbon-rich residue. In the case of wood, this residue is familiar as charcoal. Other parts of plants may also be charred — seeds, grain, twigs, etc. Many organic materials may not retain their structure, and become an amorphous charred residue in the ashes of a fire. Charred remains are preserved on archaeological sites because carbon on its own, as an element, is relatively inert in the soil. The micro-organisms which would normally break down organic material are unable to make use of carbon in this form. Charcoal and charred seeds are therefore preserved for many thousands of years. They are a particularly good material for radiocarbon dating.
The Macmillan dictionary of archaeology, Ruth D. Whitehouse, 1983Copied