Another problem is that there may be gaps in the sequences of available timber, so that the chronology 'floats', or is not tied in to a calendrical date or living trees: it can only be used for .
Also, the tree-ring key can only go back a certain distance into the past, since the availability of sufficient amounts of timber to construct a sequence obviously decreases.
These variations, given favorable conditions, form a consistent pattern; and sections or cores taken from beams in ruins have been matched to provide a long chronology over large areas.
The central rings of this older tree may then be compared with the outer rings or a yet older tree, and so on until the dates reach back into prehistory.
Problems that arise are when climatic variation and suitable trees (sensitive trees react to climatic changes, complacent trees do not) are not be present to produce any significant and recognizable pattern of variation in the rings.
technique for measuring time intervals and dating events and environmental changes by reading and dating the pattern (number and condition) of annual rings formed in the trunks of trees.
The results are compared to an established tree-ring sequence for a particular region with consideration to annual fluctuations in rainfall which result in variations in the size of the rings laid down by trees on the outside of their trunks.
and that are thought to have been deposited at approximately the same time (being in or on the same matrix).
Objects are said to be in association with each other when they are found together in a context which suggests simultaneous deposition.
For example, stratigraphic units may be correlated using palaeontological criteria, methods, and position relative to the glacial-interglacial cycle by examining physical and biological attributes.
Correlation of fossil inclusions is a principle of stratigraphy: that strata may be correlated based on the sequence and uniqueness of their floral and faunal content.
The association of undated objects with artifacts of known date allows the one to be dated by the other.
When two or more objects are found together and it can be proved that they were deposited together, they are said to be in genuine or SYNONYMS OR RELATED TERMS: absolute dating; chronometry CATEGORY: technique DEFINITION: Any technique of dating that relies on chronological measurement such as calendars, radiocarbon dates, etc.
The methods have varying applications, accuracy, range, and cost.