Response: I asked several people who know about this field. Their responses are numbered below. C14 dating is very accurate for wood used up to about 4, years ago. This is only because it is well calibrated with objects of known age. Example: wood found in a grave of known age by historically reliable documents is the standard for that time for the C14 content. This standard content of C14 can then be used for wood not associated with a historically documented date.
Carbon dating accuracy called into question after major flaw discovery
Tree Rings are Used to Accurately Date Cataclysmic Prehistoric Events
Most people probably know that in order to figure out the age of trees, botanists will often count the growth rings. The reason is easy to understand. When a tree is vigorously growing, the cambium or inner bark is producing bark on the outside of the cambium and usually light-colored wood on the inside. This creates a light ring around the wood of the tree. When the vigorous growth stops, such as when a tree becomes semi-dormant in the winter, the cambium still produces wood on the inside, but it is usually more tightly packed and dense. It also has a darker color. The problem is that various things can slow down or stop the period of vigorous growth or cause it.
Cross-checking Dating Methods: Tree Rings, Varves, and Carbon-14
The science of constructing chronologies from tree rings is called dendrochronology. The basic concepts involved are not complex. Modern trees are known to produce one growth ring per year. This is a result of the annual cycle of seasons.
Carbon Dating - Dendrochronology As we've already seen, in order for Carbon dating to work we need to know what the C to C ratio was at the time of a specimen's death. If the ratio has fluctuated throughout the unobservable past and we can be sure that it has , how can we determine what the ratio was during the lifetime of a specimen that lived and died before we first began measuring the ratio? Advocates of the Carbon dating method have turned to "Dendrochronology" a. By carbon dating a piece of wood which has also been dated by counting its annual tree-rings, scientists can create a table by which they can convert the questionable Carbon years into true calendar years.