Dendrochronological dating (from the Greek dendron, tree, and chronos, time) is a method of dating a building by studying the growth rings of the tree trunks used for the frame.
This method allows us to obtain an absolute dating up to the year and the season of felling of a tree.
The process of dendrochronological dating involves a mixture of historical, archaeological and mathematical assumptions. Since the analysis is based on the radial growth of the trees used, the dating refers to their felling and not to their implementation.
This method was discovered at the end of the 19th century by an American, Andrew Eliott Douglas, who was an astronomer. He had the idea to compare the cyclic activity of the sun with the rings of a pine tree in Arizona.
How is this dating done?
First, a set of samples of the building to be dated are collected. In the existing structure, cores are extracted with an electric auger, the hole that is produced is then the size of a peg hole and does not endanger the building. When the building was built in several phases, as many samples must be collected as there are construction phases.
The anatomy of wood is different from one species to another. Trees of the same genus, living or having lived during the same period of time and subjected to similar environmental conditions, develop series of rings marked with common markers.
The principle of dendrochronology is based on this observation and it is by comparison that one establishes or not the synchronism between different series (which implies being able to have large databases), i.e. the contemporaneity between the trees, which allows dating.
The frame of the choir of the church of Notre-Dame de Vétheuil has been dated by dendrochronology. We are now certain that it dates from 1211 or 1212.
(Cf: Frédéric Epaud, Vincent Bernard. The evolution of church frames in the Val d'Oise, from the 11th to the 20th century. Revue Archéologique du Centre de la France, 2008).
It is also important to know that the DERAMAIX workshop - whose expertise is recognized in the restoration of historic properties - has carried out a xylo-dendrochronological study of the Vétheuil Passion altarpiece (15th-16th century) before proceeding with its restoration.
If you want to know more about the achievements of the dendrochronology laboratory which worked for the church of Vétheuil, it is here.
And if you are interested in dendrochronology, whose applications are numerous, follow this link
