Incremental dating
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 or sidereal time) or floating.
The Earth's orbital motions (inclination of the Earth's axis on its orbit with respect to the Sun,
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 (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
- Sampling Ice cores
- Lichenometry
- Paleomagnetic dating
- Varves
- Speleothems
- Acanthochronology
- Sclerochronology
References
- ^ The axis of rotation is inclined 0.2 seconds from the axis of symmetry, with an observed effect that the axis of rotation moves about its axis of symmetry every ~440days. - Analytic Mechanics, Grant R. Fowles, 1962, Holt, Reinehart & Winston, New York
- ^ Telling Time, Nature, Nature Publishing Group, 2006, Volume 444/9, pp. 134