Carbon-14 dating is not the only scientific technique used in archaeology. Archaeometry encompasses many other investigative and dating techniques. Anthracology is a method practiced by CIRAM laboratories. For complete results, we study charcoal and identify wood species. Anthracology is one of the pillars of archaeobotanical studies, enabling us to understand how ancient human societies used materials. Anthracology also reveals the origin of wood samples, enabling us to differentiate between heartwood, branches and twigs. This makes it possible to avoid the "old wood" effect in carbon-14 dating.
Strict protocol and sophisticated equipment for anthracological studies
Anthracological studies require a meticulous sample preparation protocol. After refreshing surfaces with a razor blade, charcoal is analyzed anatomically along three axes: transverse, tangential and radial. Observation of the anatomical elements in all three dimensions enables us to determine the family and genus, and more rarely the species.
Observations are made using a stereomicroscope (Olympus® SZ61 binocular loupe) and a dark-field metallographic microscope (Olympus® BX53M), under "natural" light (calibrated white light), coupled with digital cameras.
To characterize the coals, the following information is collected:
CIRAM laboratories offer charcoal characterization using precise analysis and objective data such as :
1 - the presence of bark and pith: by simultaneously observing these two elements on a sample, we can deduce the size of the stem.
2 - Reaction wood (characteristic of small branches or leaning trunks). This criterion, combined with strong curvature, indicates a small branch.
3 - The presence of thylls: thylls form in the vessels of some hardwood species, during heartwood formation. The presence of thylls not only helps us to identify potential species, but also gives us an indication of where to sample.
4 - The presence of fungal hyphae: filaments may be found in the vessels. They correspond to the hyphae of fungi growing under aerobic conditions on the surface of a dead or dying tree only at high temperatures (summer season) and humidity levels of between 70 and 90%. The presence of hyphae gives us valuable information about the state of the wood before combustion.
5 - Degradation by insects or perforating worms: the presence of galleries in coals is evidence of an attack by insects or perforating glass. Charred organisms can be found in these galleries. This is proof that the wood was dead and worm-eaten before it was burnt. In some cases, the sapwood of a living tree can be attacked by such organisms.
6 - The presence of radial shrinkage cracks and vitrification: wood saturated with water will show a large number of shrinkage cracks. Vitrification is a complex phenomenon that occurs during combustion. Aspects of vitrification depend on the nature of the wood (species, size, moisture content) and combustion conditions (temperature and oxygenation conditions). We will distinguish 4 aspects of vitrification corresponding to 4 levels of carbonization:
- Matte appearance (level 0): coals are matte, gray or black in color. The anatomical structure is preserved.
- Shiny appearance (level 1): coals are dark to light gray in color and very shiny.
- Melted appearance (level 2): surfaces are very shiny and the anatomical structure is no longer discernible.
- Scoriaceous appearance (level 3): this is the last degree of vitrification, in which the coals are completely destructured.
7 - Grading: analysis of the curvature of the growth rings and the angle of the wood rays will identify the part of the tree from which the charcoal comes. Charcoal will be classified into 4 categories:
- Strongly curved rings: indicates very small-gauge wood
- Dark circles with moderate curvature
- Slightly curved rings: indicates the use of large-gauge wood (large branch or trunk).
- Rings with indeterminate curvatures
8 - Growth ring width and growth rate. Low ring widths indicate slow growth (unfavorable growing conditions or old trees). Wide ring widths, on the other hand, indicate strong growth (very favorable conditions or young trees). The rate of growth, i.e. the regularity of ring widths, indicates whether the tree has grown homogeneously or whether events have temporarily hindered growth (weather conditions, fungal attack, tree injuries, etc.).
9 - Traces of woodworking: grooves/scratches on the surface can attest to woodworking using tools.
For each archaeological site referenced, a systematic analysis of all charcoals will be carried out according to the criteria outlined above. Data will be compiled in the form of tables and graphs, and reported in an analysis report.
CIRAM, a specialist in carbon-14 dating and archaeomaterial analysis, offers a meticulous examination of your wood and charcoal. We are committed to delivering relevant and accurate results, and comply with current international standards.
