Incremental dating techniques allow the construction of year-by-year annual chronologies, which can be temporally fixed (''i.e.,'' linked to the present day and thus
calendar
A calendar is a system of organizing days. This is done by giving names to periods of time, typically days, weeks, months and years. A calendar date, date is the designation of a single and specific day within such a system. A calendar is ...
or
sidereal time
Sidereal time ("sidereal" pronounced ) is a system of timekeeping used especially by astronomers. Using sidereal time and the celestial coordinate system, it is easy to locate the positions of celestial objects in the night sky. Sidereal t ...
) or floating.
Archaeologist
Archaeology or archeology is the study of human activity through the recovery and analysis of material culture. The archaeological record consists of Artifact (archaeology), artifacts, architecture, biofact (archaeology), biofacts or ecofacts, ...
s use tree-ring dating (
dendrochronology
Dendrochronology (or tree-ring dating) is the scientific method of chronological dating, dating tree rings (also called growth rings) to the exact year they were formed in a tree. As well as dating them, this can give data for dendroclimatology, ...
) to determine the age of old pieces of wood. Trees usually add growth rings on a yearly basis, with the spacing of rings being wider in high growth years and narrower in low growth years. Patterns in tree-ring growth can be used to establish the age of old wood samples, and also give some hints to local climatic conditions. This technique is useful to about 9,000 years ago for samples from the western United States using overlapping tree-ring series from living and dead wood.
The Earth's orbital motions (inclination of the Earth's axis on its orbit with respect to the Sun,
gyroscopic precession of the Earth's axis every 26,000 years;
free precession every 440 days,
precession of Earth orbit and orbital variations such as
perihelion precession every 19,000 and 23,000 years) leave traces visible in the geological record. These changes provide a long-term sequence of climatic events, recorded as changes in the thickness of sediment layers (known as "varve analysis"—the term "
varve" means a layer or layers of sediment. Typically, varve refers to lake or glacial sediment), as temperature induced changes in the isotopic ratios for oxygen isotopes in sediments, and in the
relative abundance of fossils. Because these can be calibrated reliably over a period of 40 million years this provides an alternate verification to
radiometric dating
Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to Chronological dating, date materials such as Rock (geology), rocks or carbon, in which trace radioactive impurity, impurities were selectively incorporat ...
in cases where sufficient record exists to provide a reliable trace.
[''Telling Time'', Nature, Nature Publishing Group, 2006, Volume 444/9, pp. 134]
Polarity reversals in the Earth's magnetic field have also been used to determine geologic time. Periodically, the magnetic field of the Earth reverses leaving a magnetic signal in volcanic and sedimentary rocks. This signal can be detected and sequences recorded, and in the case of volcanic rocks, tied to radiometric dates.
Another technique used by archaeologists is to inspect the depth of penetration of water vapor into chipped
obsidian
Obsidian ( ) is a naturally occurring volcanic glass formed when lava extrusive rock, extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Produced from felsic lava, obsidian is rich in the lighter element ...
(volcanic glass) artifacts. The water vapor creates a "hydration rind" in the obsidian, and so this approach is known as "hydration dating" or "
obsidian dating", and is useful for determining dates as far back as 200,000 years.
Techniques
Techniques of incremental dating include:
*
Dendrochronology
Dendrochronology (or tree-ring dating) is the scientific method of chronological dating, dating tree rings (also called growth rings) to the exact year they were formed in a tree. As well as dating them, this can give data for dendroclimatology, ...
* Sampling
Ice core
An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier
A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier ...
s
*
Lichenometry
In archaeology, palaeontology, and geomorphology, lichenometry is a geomorphic method of geochronologic dating that uses lichen growth to determine the age of exposed rock, based on a presumed specific rate of increase in radial size over time ...
*
Paleomagnetic dating
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Varves
*
Speleothem
A speleothem (; ) is a geological formation made by mineral deposits that accumulate over time in natural caves. Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depen ...
s
*
Acanthochronology
Acanthochronology is the study of cactus Thorns, spines, and prickles, spines or ''Euphorbia'' Thorns, spines, and prickles, thorns grown in time ordered sequence (i.e. in series). Physical, morphological or chemical characteristics and information ...
*
Sclerochronology
Sclerochronology is the study of periodic physical and chemical features in the hard tissues of animals that grow by accretion, including invertebrates and coralline red algae, and the temporal context in which they formed. It is particularly usefu ...
References
{{DEFAULTSORT:Incremental Dating
es:Datación de los restos