In archaeology the C-14 method has been an invaluable tool for dating of excavated objects of wood and other organic materials. The isotope C-14 is continously being formed in the athmosphere in the reaction between nitrogen and neutrons from the cosmic radiation. In CO2 in the athmosphere there will always be ca. 50 brd C-14 atoms pr. gram carbon. Since CO2 enters the nutritioal chain via the photosyntesis, all living tissue will contain the same concentration of C-14. This implies an activity of 0,19Bq pr. gram carbon. We "count" b-particles issued from the piece of wood and thereby estimate its age.
When a tree dies, it will no longer take any carbon into its organism, and the activity slowly dies out (T1/2=5730 years). If you can measure the activity of radioactivity, and apply the formula for degradation of activity, it is possible to determine the age of organic materials.
Datings on Melkoya
At Melkoya extremely little organic material is conserved. But charcoal is massively present, as remains from hearths and fireplaces inside and outside houses. Some places the charcoal represent burning of surface vegetation in prehistoric times. The majority of the charcoal samples are taken from profiles established through structures, so it is possible to accurately document the context of the charcoals and consequently the datings.
The datings from Melkoya show activities from mesolithic times to early metal age. The datings are now plotted onto drawings of the profiles, enabling us to closely study the formation of the archaeological material, and thereafter reach conclusions concerning the time of settlement and usage of the different structures. Here are shown maps with datings of the diffferent structures:
In addition we have made diagrams for each site with the datings ordered chronologically: