Geochronology is the science of determining the age of rocks, fossils, and sediments. A variety of dating methods are used by geologists to achieve this. // What is science? There are different theories of what science is. ... Jump to: navigation, search Our earth is composed of three main types of rock, each having been formed in its own special way. ... A fossil Ammonite Fossils are the mineralized remains of animals or plants or other traces such as footprints. ... Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. ...

Dating methods

• Radiometric techniques measure the decay of radioactive isotopes, and other radiogenic activity.
• Incremental techniques measure the regular addition of material to sediments or organisms.
• Correlation of marker horizons allow age-equivalence to be established between different sites.

Jump to: navigation, search Radiometric dating is a technique used to date materials based on a knowledge of the decay rates of naturally occurring isotopes, and the current abundances. ... A radionuclide is an atom with an unstable nucleus. ...

Radiometric dating

By measuring the rate of radiocative decay of a radioactive isotope with a known half-life, geologists can establish the absolute age of the parent material. A number of radioactive isotopes are used for this purpose, and depending on the rate of decay, are used for dating different geological periods. Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles (radiation). ... A radionuclide is an atom with an unstable nucleus. ... Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ...

• Radiocarbon dating. This technique measures the decay of Carbon-14 in organic material (e.g. plant macrofossils).
• Uranium-thorium dating. This technique is used to date speleothems, corals, carbonates, and fossil bones.
• Potassium-argon dating and argon-argon dating. These techniques are used to date igneous and volcanic rocks. They are also used to date volcanic ash layers within or overlying paleoanthropologic sites.

Other radiogenic dating techniques include: Radiocarbon dating is a radiometric dating method that uses the naturally occurring isotope carbon-14 to determine the age of carbonaceous materials up to ca. ... Carbon-14 is the radioactive isotope of carbon discovered February 27, 1940, by Martin Kamen and Sam Ruben. ... Uranium-thorium dating, also often referred to as thorium-230 dating, uranium-series disequilibrium dating or uranium-series dating, is a radiometric dating technique commonly used to determine the age of carbonate materials such as speleothem or coral. ... A speleothem (from the Greek for cave deposit) is a formal term for what is also known as a cave formation, or amongst cavers, collectively known as pretties. ... Orders see Anthozoa Corals are gastrovascular marine cnidarians (phylum Cnidaria; class Anthozoa) existing as small sea anemone-like polyps, typically forming colonies of many individuals. ... Carbonate is an anion with a charge of -2 and an empirical formula of CO32-. For an aqueous solution, carbonate exists in three forms. ... Grays illustration of a human femur, a typically recognized bone. ... Potassium-argon or K-Ar dating is a method used by archaeologists and geologists to ascertain the date of ancient mineral deposits. ... Argon-argon dating is a radiometric dating technique similar to that of Potasium-Argon. ... Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... This article is about volcanoes in geology. ... Diamond Head, a well-known backdrop to Waikiki in Hawaii, is an ash cone that solidified into tuff Volcanic ash is the term for very fine rock and mineral particles less than 2 mm in diameter that are ejected from a volcanic vent. ... Paleoanthropology is the branch of physical anthropology that focuses on the study of human evolution, tracing the anatomic and genetic linkages of pre-humans from millions of years ago, up to modern times. ...

• Fission track dating
• Cosmogenic isotope dating
• Paleomagnetic dating

Paleomagnetism refers to the orientation of the Earths magnetic field as it is preserved in various magnetic iron bearing minerals throughout time. ...

Incremental dating

Incremental dating techniques allow the construction of year-by-year annual chronologies, which can be fixed (i.e. linked to the present day and thus calendar or sidereal time) or floating. A calendar is a system for naming periods of time, typically days. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ...

• Dendrochronology.
• Ice cores.
• Lichenometry.
• Varves.

Pinus taeda Cross section showing annual rings, Cheraw, South Carolina Pine stump showing growth rings Dendrochronology or tree-ring dating is the method of scientific dating based on the analysis of tree ring patterns. ... An ice core is a tube of ice removed from an ice sheet. ... Lichens are a symbiotic relationship between algal and fungal communities and they increase in size radially as they grow. ... A varve is an annual layer of sediment or sedimentary rock. ...

References

Lowe, J.J., and Walker, M.J.C. (1997), Reconstructing Quaternary Environments (2nd edition). Longman publishing ISBN 0582101662

Smart, P.L., and Frances, P.D. (1991), Quaternary dating methods - a user's guide. Quaternary Research Associaton Technical Guide No.4 ISBN 0907780033

Faure, G. (1986). Principles of isotope geology. Cambridge, Cambridge University Press. ISBN 0471864129

Dickin, A. P. (1995). Radiogenic Isotope Geology. Cambridge, Cambridge University Press. ISBN 0521598915

Faure, G., and Mensing, D., (2005), "Isotopes - Principles and applications". Third Edition. J. Wiley & Sons. ISBN 0471384372

See also

• Arthur Holmes
• Fritz Houtermans
• Alfred O. C. Nier