Dating Techniques - Stratigraphy, Seriation, Faunal Dating, Pollen Dating (palynology), Amino Acid Racimization, Cation-ratio Dating - Relative dating, Absolute dating, Radioactive decay dating
methods dates sample product
Dating techniques are procedures used by scientists to determine the age of a specimen. Relative dating methods tell only if one sample is older or younger than another; absolute dating methods provide a date in years. The latter have generally been available only since 1947. Many absolute dating techniques take advantage of radioactive decay, whereby a radioactive form of an element is converted into a non-radioactive product at a regular rate. Others, such as amino acid racimization and cation-ratio dating, are based on chemical changes in the organic or inorganic composition of a sample. In recent years, a few of these methods have come under close scrutiny as scientists strive to develop the most accurate dating techniques possible.
Relative dating methods determine whether one sample is older or younger than another. They do not provide an age in years. Before the advent of absolute dating methods, nearly all dating was relative. The main relative dating method is stratigraphy.
Absolute dating is the term used to describe any dating technique that tells how old a specimen is in years. These are generally analytical methods, and are carried out in a laboratory. Absolute dates are also relative dates, in that they tell which specimens are older or younger than others. Absolute dates must agree with dates from other relative methods in order to be valid.
As previously mentioned, radioactive decay refers to the process in which a radioactive form of an element is converted into a nonradioactive product at a regular rate. Radioactive decay dating is not a single method of absolute dating but instead a group of related methods for absolute dating of samples.
Additional Topics
Seriation is the ordering of objects according to their age. It is a relative dating method. In a landmark study, archaeologist James Ford used seriation to determine the chronological order of American Indian pottery styles in the Mississippi Valley. Artifact styles such as pottery types are seriated by analyzing their abundances through time. This is done by counting the number of pieces of each…
Each year seed-bearing plants release large numbers of pollen grains. This process results in a "rain" of pollen that falls over many types of environments. Pollen that ends up in lake beds or peat bogs is the most likely to be preserved, but pollen may also become fossilized in arid conditions if the soil is acidic or cool. Scientists can develop a pollen chronology, or calendar, by…
This dating technique was first conducted by Hare and Mitterer in 1967, and was popular in the 1970s. It requires a much smaller sample than radiocarbon dating, and has a longer range, extending up to a few hundred thousand years. It has been used to date coprolites (fossilized feces) as well as fossil bones and shells. These types of specimens contain proteins embedded in a network of minerals su…
Although cation-ratio dating has been widely used, recent studies suggest it has many problems. Many of the dates obtained with this method are inaccurate due to improper chemical analyses. In addition, the varnish may not actually be stable over long periods of time. Finally, some scientists have recently suggested that the cation ratios may not even be directly related to the age of the sample. …
Thermoluminescence dating is very useful for determining the age of pottery. Electrons from quartz and other minerals in the pottery clay are bumped out of their normal positions (ground state) when the clay is exposed to radiation. This radiation may come from radioactive substances such as uranium, present in the clay or burial medium, or from cosmic radiation. When the ceramic is heated to a ve…
Uranium series dating techniques rely on the fact that radioactive uranium and thorium isotopes decay into a series of unstable, radioactive "daughter" isotopes; this process continues until a stable (non-radioactive) lead isotope is formed. The daughters have relatively short half-lives ranging from a few hundred thousand years down to only a few years. The "parent" is…
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