Carbon-dating of organic matter associated with disturbed soil horizon sites described above has given dates consistently around 300 years ago. With this type of dating, however, dates are normally only accurate to a within a few decades. Geologists and dendrochronologists from the University of Washington in Seattle have found a way to get more accurate dates.
The imageabove shows how it is possible to compare growth rings from old living trees with those from trees which died 100s of years ago.
They found that where the trees are exposed above the surface of the swamp the outside rings have been weathered away. By digging down into to the swamp, where the bark is still preserved, they were able to get samples of wood from the last year of growth.
