[EternalVigilance]

Using tree rings to determine its age, Bleicher believes the door could have been made in

Ummmm...I'm thinkin' the tree would have stopped growing when someone made a door out of it.

[allmendream]

LOL. Well yes of course, but you see - in harsh years the tree rings are closer together - and in lush years the tree rings are further apart. By looking at the PATTERN of such you can correlate with OTHER trees and tree rings and figure out at what time the tree was growing.

Follow?

[SunkenCiv]

The date the wood was cut can’t be determined, IOW, the RC dates of the rings can (at best) be wiggle-matched against any established data (because there’s annual fluctuations in RC production and absorption) — unless there happens to be an outer ring with the bark attached. Then the year the wood was cut can be determined within the appropriate range of error.

A somewhat younger door was found in Greece some years back — it was still being used as a door, but apparently had been borrowed from an older derelict structure, and before that from an earlier derelict, etc, such that the RC date on the wood was (if memory serves) something like 2000 BC. Again, without a bark layer, it’s not possible to know when the wood was cut. :’)