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Encyclopedia > Radiometric dating

Radiometric dating (often called radioactive dating) is a technique used to date materials, based on a comparison between the observed abundance of particular naturally occurring radioactive isotopes and their known decay rates.[1] It is the principal source of information about the absolute age of rocks and other geological features, including the age of the Earth itself. Among the best-known techniques are potassium-argon dating and uranium-lead dating. By allowing the establishment of geological timescales, it provides a significant source of information about the dates of fossils and the deduced rates of evolutionary change. Radiometric dating is also used to date archaeological remains and ancient artifacts, the best known technique in this field being radiocarbon dating. For other uses, see Isotope (disambiguation). ... Earth as seen from Apollo 17 Modern geologists consider the age of the Earth to be around 4. ... Potassium-argon or K-Ar dating is a geochronological method used in many geoscience disciplines. ... 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. ... For other uses, see Fossil (disambiguation). ... This article is about evolution in biology. ... For referencing in Wikipedia, see Wikipedia:Citing sources. ... Radiocarbon dating is a radiometric dating method that uses the naturally occurring isotope carbon-14 (14C) to determine the age of carbonaceous materials up to about 60,000 years. ...


The different techniques of radiometric dating vary in the timescale over which they are accurate, and their use may also be limited by cost.

Contents

Fundamentals of radiometric dating

All ordinary matter is made up of combinations of chemical elements, each with its own atomic number, indicating the number of protons in the atomic nucleus. Additionally, elements may exist in different isotopes, with each isotope of an element differing only in the number of neutrons in the nucleus. A particular isotope of a particular element is called a nuclide. Some nuclides are inherently unstable. That is, at some random point in time, an atom of such a nuclide will be transformed into a different nuclide by the process known as radioactive decay. This transformation is accomplished by the emission of particles such as electrons (known as beta decay) or alpha particles. This article is about matter in physics and chemistry. ... The periodic table of the chemical elements A chemical element, or element, is a type of atom that is defined by its atomic number; that is, by the number of protons in its nucleus. ... See also: List of elements by atomic number In chemistry and physics, the atomic number (also known as the proton number) is the number of protons found in the nucleus of an atom. ... For other uses, see Proton (disambiguation). ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ... For other uses, see Isotope (disambiguation). ... This article or section does not adequately cite its references or sources. ... A nuclide (from lat. ... Random redirects here. ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... For other uses, see Electron (disambiguation). ... In nuclear physics, beta decay (sometimes called neutron decay) is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. ... An alpha particle is deflected by a magnetic field Alpha radiation consists of helium-4 nuclei and is readily stopped by a sheet of paper. ...


While the moment in time at which a particular nucleus decays is random, a collection of atoms of a radioactive nuclide decays exponentially at a rate described by a parameter known as the half-life, usually given in units of years when discussing dating techniques. After one half-life has elapsed, one half of the atoms of the substance in question will have decayed. Many radioactive substances decay from one nuclide into a final, stable decay product (or "daughter") through a series of steps known as a decay chain. In this case, usually the half-life reported is the dominant (longest) for the entire chain, rather than just one step in the chain. Nuclides useful for radiometric dating have half-lives ranging from a few thousand to a few billion years. A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value. ... 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. ... In nuclear physics, a decay product, also known as a daughter product, is a nuclide resulting from the radioactive decay of a parent or precursor nuclide. ... Nearly all the decay products of radioactive decay are themselves radioactive. ...


In most cases, the half-life of a nuclide depends solely on its nuclear properties; it is not affected[2] by external factors such as temperature, chemical environment, or presence of a magnetic or electric field. (For nuclides which decay by the process of electron capture, such as Beryllium-7, Strontium-85, and Zirconium-89, the decay rate may be affected by local electron density, therefore these isotopes are not used for radiometric dating.) Although decay can also be accelerated by radioactive bombardment, such bombardment tends to leave evidence of its occurrence. These issues aside, the half-life of any nuclide is believed to be constant through time. Therefore, in any material containing a radioactive nuclide, the proportion of the original nuclide to its decay product(s) changes in a predictable way as the original nuclide decays. This predictability allows the relative abundances of related nuclides to be used as a clock that measures the time from the incorporation of the original nuclide(s) into a material to the present. For other uses, see Temperature (disambiguation). ... Magnetic field lines shown by iron filings Magnetostatics Electrodynamics Electrical Network Tensors in Relativity This box:      In physics, the magnetic field is a field that permeates space and which exerts a magnetic force on moving electric charges and magnetic dipoles. ... In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ... Electron capture is a decay mode for isotopes that will occur when there are too many protons in the nucleus of an atom, and there isnt enough energy to emit a positron; however, it continues to be a viable decay mode for radioactive isotopes that can decay by positron... For other uses, see Clock (disambiguation). ...


The processes that form specific materials are often conveniently selective as to what elements they incorporate during their formation. In the ideal case, the material will incorporate a parent nuclide and reject the daughter nuclide. In this case, the only daughter nuclides to be found through examination of a sample must have been created since the sample was formed. When a material incorporates both the parent and daughter nuclides at the time of formation, it may be necessary to assume that the initial proportions of a radioactive substance and its daughter are known. The daughter product should not be a small-molecule gas that can leak out of the material, and it must itself have a long enough half-life that it will be present in significant amounts. In addition, the initial element and the decay product should not be produced or depleted in significant amounts by other reactions. The procedures used to isolate and analyze the reaction products must be straightforward and reliable.[citation needed]


Blocking temperature

If a material that selectively rejects the daughter nuclide is heated, any daughter nuclides that have been accumulated over time will be lost through diffusion, setting the isotopic "clock" to zero. The temperature at which this happens is known as the blocking temperature and is specific to a particular material. diffusion (disambiguation). ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...


In contrast to the most simple radiometric dating techniques, isochron dating, which can be used for many isotopic decay sequences (e.g. rubidium-strontium decay sequence), does not require knowledge of the initial proportions. Also the argon-argon dating technique can be used for the potassium-argon sequence to ensure that no initial 40Ar was present.[citation needed] Iscochron dating is a type of radiometric dating. ... The rubidium-strontium dating method is a radiometric dating technique that geologists use to determine the age of rocks. ...


The age equation

Considering that radioactive parent elements decay to stable daughter elements [3], the mathematical expression that relates radioactive decay to geologic time, called the age equation, is [4]:

 t = frac{1}{lambda} {ln left(1+frac{D}{P}right)}
where
t = age of the sample
D = number of atoms of the daughter isotope in the sample
P = number of atoms of the parent isotope in the sample
λ = decay constant of the parent isotope
ln = natural logarithm

The decay constant (or rate of decay[5]) is the fraction of a number of atoms of a radioactive nuclide that disintegrates in a unit of time. The decay constant is inversely proportional to the radioactive half-life of the parent isotope, which can be obtained from tables such as the one on this page. A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value. ... The natural logarithm, formerly known as the hyperbolic logarithm, is the logarithm to the base e, where e is an irrational constant approximately equal to 2. ... 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. ...


Limitation of techniques

Although radiometric dating is accurate in principle, the precision is very dependent on the care with which the procedure is performed. The possible confounding effects of initial contamination of parent and daughter isotopes have to be considered, as do the effects of any loss or gain of such isotopes since the sample was created.


Precision is enhanced if measurements are taken on different samples from the same rock body but at different locations. Alternatively, if several different minerals can be dated from the same sample and are assumed to be formed by the same event and were in equilibrium with the reservoir when they formed, they should form an isochron. Finally, correlation between different isotopic dating methods may be required to confirm the age of a sample. Iscochron dating is a type of radiometric dating. ...


The precision of a dating method depends in part on the half-life of the radioactive isotope involved. For instance, carbon-14 has a half-life of about 6000 years. After an organism has been dead for 60,000 years, so little carbon-14 is left in it that accurate dating becomes impossible. On the other hand, the concentration of carbon-14 falls off so steeply that the age of relatively young remains can be determined precisely to within a few decades. The isotope used in uranium-thorium dating has a longer half-life, but other factors make it more accurate than radiocarbon dating.[citation needed] 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. ... Radiocarbon dating is a radiometric dating method that uses the naturally occurring isotope carbon-14 (14C) to determine the age of carbonaceous materials up to about 60,000 years. ...


Modern dating techniques

Radiometric dating can be performed on samples as small as a billionth of a gram using a mass spectrometer. The mass spectrometer was invented in the 1940s and began to be used in radiometric dating in the 1950s. The mass spectrometer operates by generating a beam of ionized atoms from the sample under test. The ions then travel through a magnetic field, which diverts them into different sampling sensors, known as "Faraday cups", depending on their mass and level of ionization. On impact in the cups, the ions set up a very weak current that can be measured to determine the rate of impacts and the relative concentrations of different atoms in the beams. Mass spectrometry is a technique for separating ions by their mass-to-charge (m/z) ratios. ... The 1940s decade ran from 1940 to 1949. ... The 1950s decade refers to the years 1950 to 1959 inclusive. ... This article is about the electrically charged particle. ... A faraday cup is a metal (conductive) cup meant to recatch secondary particles. ...


The uranium-lead radiometric dating scheme is one of the oldest available, as well as one of the most highly respected. It has been refined to the point that the error in dates of rocks about three billion years old is no more than two million years. 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. ...


Uranium-lead dating is usually performed on the mineral "zircon" (ZrSiO4), though it can be used on other materials. Zircon incorporates uranium atoms into its crystalline structure as substitutes for zirconium, but strongly rejects lead. It has a very high blocking temperature, is resistant to mechanical weathering and is very chemically inert. Zircon also forms multiple crystal layers during metamorphic events, which each may record an isotopic age of the event. In situ micro-beam analysis can be achieved via laser ICP-MS or SIMS techniques [6] . For other uses, see Mineral (disambiguation). ... Zircon is a mineral belonging to the group of nesosilicates. ... General Name, Symbol, Number zirconium, Zr, 40 Chemical series transition metals Group, Period, Block 4, 5, d Appearance silvery white Standard atomic weight 91. ... ICP-MS (Inductively coupled plasma mass spectrometry) is a type of mass spectrometry that is highly sensitive and capable of the determination of a range of metals and several non-metals at concentrations below one part in 1012. ... The process known as secondary ion mass spectrometry (SIMS) involves bombarding the surface to be tested with a stream of ions. ...


One of its great advantages is that any sample provides two clocks, one based on uranium-235's decay to lead-207 with a half-life of about 700 million years, and one based on uranium-238's decay to lead-206 with a half-life of about 4.5 billion years, providing a built-in crosscheck that allows accurate determination of the age of the sample even if some of the lead has been lost.


Two other radiometric techniques are used for long-term dating. Potassium-argon dating involves electron capture or positron decay of potassium-40 to argon-40. Potassium-40 has a half-life of 1.3 billion years, and so this method is applicable to the oldest rocks. Radioactive potassium-40 is common in micas, feldspars, and hornblendes, though the blocking temperature is fairly low in these materials, about 125°C (mica) to 450°C (hornblende). Potassium-argon or K-Ar dating is a geochronological method used in many geoscience disciplines. ... Electron capture is a decay mode for isotopes that will occur when there are too many protons in the nucleus of an atom, and there isnt enough energy to emit a positron; however, it continues to be a viable decay mode for radioactive isotopes that can decay by positron... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... Rock with mica Mica sheet Mica flakes The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. ... This article does not cite any references or sources. ... Amphibole (Hornblende) Hornblende is a complex inosilicate series of minerals. ...


Rubidium-strontium dating is based on the beta decay of rubidium-87 to strontium-87, with a half-life of 50 billion years. This scheme is used to date old igneous and metamorphic rocks, and has also been used to date lunar samples. Blocking temperatures are so high that they are not a concern. Rubidium-strontium dating is not as precise as the uranium-lead method, with errors of 30 to 50 million years for a 3-billion-year-old sample. The rubidium-strontium dating method is a radiometric dating technique that geologists use to determine the age of rocks. ... General Name, Symbol, Number rubidium, Rb, 37 Chemical series alkali metals Group, Period, Block 1, 5, s Appearance grey white Standard atomic weight 85. ... General Name, Symbol, Number strontium, Sr, 38 Chemical series alkaline earth metals Group, Period, Block 2, 5, s Appearance silvery white metallic Standard atomic weight 87. ... Metamorphic rock is the result of the transformation of a pre-existing rock type, the protolith, in a process called metamorphism, which means change in form, derived from the Greek words meta, change, and morphe, form. The protolith is subjected to extreme heat (>150 degrees Celsius) and pressure causing profound...


Short-range dating techniques

There are a number of dating techniques that have short ranges and are so used for historical or archaeological studies. One of the best-known is the carbon-14 (C14) radiometric technique. Radiocarbon dating is a radiometric dating method that uses the naturally occurring isotope carbon-14 (14C) to determine the age of carbonaceous materials up to about 60,000 years. ...


Carbon-14 is a radioactive isotope of carbon, with a half-life of 5,730 years (very short compared with the above). In other radiometric dating methods, the heavy parent isotopes were synthesized in the explosions of massive stars that scattered materials through the Galaxy, to be formed into planets and other stars. The parent isotopes have been decaying since that time, and so any parent isotope with a short half-life should be extinct by now.


Carbon-14 is an exception. It is continuously created through collisions of neutrons generated by cosmic rays with nitrogen in the upper atmosphere. The carbon-14 ends up as a trace component in atmospheric carbon dioxide (CO2). Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ...


An organism acquires carbon from carbon dioxide during its lifetime. Plants acquire it through photosynthesis, and animals acquire it from consumption of plants and other animals. When an organism dies, it ceases to intake new carbon-14 and the existing isotope decays with a characteristic half-life (5730 years). The proportion of carbon-14 left when the remains of the organism are examined provides an indication of the time lapsed since its death. The carbon-14 dating limit lies around 58,000 to 62,000 years [1]. The leaf is the primary site of photosynthesis in plants. ...


The rate of creation of carbon-14 appears to be roughly constant, as cross-checks of carbon-14 dating with other dating methods show it gives consistent results. However, local eruptions of volcanoes or other events that give off large amounts of carbon dioxide can reduce local concentrations of carbon-14 and give inaccurate dates. The releases of carbon dioxide into the biosphere as a consequence of industrialization have also depressed the proportion of carbon-14 by a few percent; conversely, the amount of carbon-14 was increased by above-ground nuclear bomb tests that were conducted into the early 1960s. Also, an increase in the solar wind or the earth's magnetic field above the current value would depress the amount of carbon-14 created in the atmosphere. These effects are corrected for by the calibration of the radiocarbon dating scale. See the article on radiocarbon dating. Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... For other uses, see Biosphere (disambiguation). ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, in 1945 lifted nuclear fallout some 18 km (60,000 feet) above the epicenter. ... The 1960s decade refers to the years from 1960 to 1969. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... Magnetic field lines shown by iron filings Magnetostatics Electrodynamics Electrical Network Tensors in Relativity This box:      In physics, the magnetic field is a field that permeates space and which exerts a magnetic force on moving electric charges and magnetic dipoles. ... Radiocarbon dating is a radiometric dating method that uses the naturally occurring isotope carbon-14 (14C) to determine the age of carbonaceous materials up to about 60,000 years. ...


Another relatively short-range dating technique is based on the decay of uranium-238 into thorium-230, a substance with a half-life of about 80,000 years. It is accompanied by a sister process, in which uranium-235 decays into protactinium-231, which has a half-life of 34,300 years.


While uranium is water-soluble, thorium and protactinium are not, and so they are selectively precipitated into ocean-floor sediments, from which their ratios are measured. The scheme has a range of several hundred thousand years. This article is about the chemical element. ... General Name, Symbol, Number thorium, Th, 90 Chemical series Actinides Group, Period, Block n/a, 7, f Appearance silvery white Standard atomic weight 232. ... General Name, Symbol, Number protactinium, Pa, 91 Chemical series actinides Group, Period, Block n/a, 7, f Appearance bright, silvery metallic luster Standard atomic weight 231. ... This article or section cites very few or no references or sources. ...


Natural sources of radiation in the environment knock loose electrons in, say, a piece of pottery, and these electrons accumulate in defects in the material's crystal lattice structure. Heating the object will release the captured electrons, producing a luminescence. When the sample is heated, at a certain temperature it will glow from the emission of electrons released from the defects, and this glow can be used to estimate the age of the sample to a threshold of approximately 15 percent of its true age. The date of a rock is reset when volcanic activity remelts it. The date of a piece of pottery is reset by the heat of the kiln. Typically temperatures greater than 400 degrees Celsius will reset the "clock". This is termed thermoluminescence. Some mineral substances such as fluorite store energy when exposed to ultraviolet or other ionising radiation. ...


Finally, fission track dating involves inspection of a polished slice of a material to determine the density of "track" markings left in it by the spontaneous fission of uranium-238 impurities. Fission track dating is a radiometric dating technique based on analyses of the damage trails or tracks left by fission fragments in certain uranium bearing minerals and glass. ... Spontaneous fission (SF) is a form of radioactive decay characteristic of very heavy isotopes, and is theoretically possible for any atomic nucleus whose mass is greater than or equal to 100 amu (elements near ruthenium). ...


The uranium content of the sample has to be known, but that can be determined by placing a plastic film over the polished slice of the material, and bombarding it with slow neutrons. This causes induced fission of U-235, as opposed to the spontaneous fission of U-238. The fission tracks produced by this process are recorded in the plastic film. The uranium content of the material can then be calculated from the number of tracks and the neutron flux. A thermal neutron is a free neutron with a kinetic energy level of ca. ... flux in science and mathematics. ...


This scheme has application over a wide range of geologic dates. For dates up to a few million years micas, tektites (glass fragments from volcanic eruptions), and meteorites are best used. Older materials can be dated using zircon, apatite, titanite, epidote and garnet which have a variable amount of uranium content. Because the fission tracks are healed by temperatures over about 200°C the technique has limitations as well as benefits. The technique has potential applications for detailing the thermal history of a deposit. Rock with mica Mica sheet Mica flakes The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. ... A tektite Tektites (from Greek tektos, molten) are natural glass objects, up to a few centimeters in size, which — according to most scientists — have been formed by the impact of large meteorites on Earths surface, although a few researchers favor an origin from the Moon as volcanic ejecta. ... Zircon is a mineral belonging to the group of nesosilicates. ... Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, and chlorapatite, named for high concentrations of OH-, F-, or Cl- ions, respectively, in the crystal. ... Titanite Titanite or sphene is a calcium titanium nesosilicate mineral, CaTiSiO5. ... Epidote from Slovakia Epidote is a calcium aluminium iron sorosilicate mineral, Ca2(Al, Fe)3(SiO4)3(OH), crystallizing in the monoclinic system. ... Garnet is a group of minerals that have been used since the Bronze Age as gemstones and abrasives. ...


Large amounts of otherwise rare Cl-36 were produced by irradiation of seawater during atmospheric detonations of nuclear weapons between 1952 and 1958. The residence time of Cl-36 in the atmosphere is about 1 week. Thus, as an event marker of 1950s water in soil and ground water, Cl-36 is also useful for dating waters less than 50 years before the present. Cl-36 has seen use in other areas of the geological sciences, including dating ice and sediments. General Name, symbol, number chlorine, Cl, 17 Chemical series halogens Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ... Loess field in Germany Surface-water-gley developed in glacial till, Northern Ireland For the American hard rock band, see SOiL. For the System of a Down song, see Soil (song). ... Groundwater is any water found below the land surface. ...


Dating with shortlived extinct radionuclides

At the beginning of the solar system there were several relatively shortlived radionuclides like 26Al, 60Fe, 53Mn, and 129I present within the solar nebula. These radionuclides—possibly produced by the explosion of a supernova—are extinct today but their decay products can be detected in very old material such as meteorites. Measuring the decay products of extinct radionuclides with a mass spectrometer and using isochronplots it is possible to determine relative ages between different events in the early history of the solar system. Dating methods based on extinct radionuclides can also be calibrated with the U-Pb method to give absolute ages. Willamette Meteorite A meteorite is a natural object originating in outer space that survives an impact with the Earths surface without being destroyed. ... Mass spectrometry is a technique for separating ions by their mass-to-charge (m/z) ratios. ...


Types of radiometric dating

Argon-argon dating is a radiometric dating technique similar to that of Potasium-Argon. ... Fission track dating is a radiometric dating technique based on analyses of the damage trails or tracks left by fission fragments in certain uranium bearing minerals and glass. ... There are three daughter isotopes of Uranium and Thorium; they are 206Pb, 207Pb, and 208Pb. ... Optically Stimulated Luminescence or OSL Dating is a method of establishing the age of soil sediments. ... Potassium-argon or K-Ar dating is a geochronological method used in many geoscience disciplines. ... Radiocarbon dating is a radiometric dating method that uses the naturally occurring isotope carbon-14 (14C) to determine the age of carbonaceous materials up to about 60,000 years. ... Rhenium-Osmium dating is a form of radiometric dating based on the beta decay of the isotope187Re which has a half life of 41. ... The rubidium-strontium dating method is a radiometric dating technique that geologists use to determine the age of rocks. ... This article needs to be cleaned up to conform to a higher standard of quality. ... 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. ... 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. ... Uranium-uranium dating is a radiometric dating technique utilizing the comparison of two isotopes of uranium in a sample: uranium-238 and uranium-234. ...

See also

Absolute dating is the process of determining a specific archaeological date. ... Earth as seen from Apollo 17 Modern geologists consider the age of the Earth to be around 4. ... A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value. ... 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. ... Incremental dating techniques allow the construction of year-by-year annual chronologies, which can be fixed ( linked to the present day and thus calendar or sidereal time) or floating. ... Iscochron dating is a type of radiometric dating. ... Isotope geochemistry is an aspect of Geology based upon study of the relative and absolute concentrations of the elements and their isotopes in the Earth. ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... Radioactivity may mean: Look up radioactivity in Wiktionary, the free dictionary. ... Radiocarbon dating is a radiometric dating method that uses the naturally occurring isotope carbon-14 (14C) to determine the age of carbonaceous materials up to about 60,000 years. ... 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. ... Before the advent of absolute dating in the 20th century, archaeologists and geologists were largely limited to the use of Relative Dating techniques. ... Thermoluminescence (TL) dating is the determination by means of measuring the accumulated radiation dose of the time elapsed since material containing crystalline minerals was either heated (lava, ceramics) or exposed to sunlight (sediments). ... Superfamilies Alpheoidea Atyoidea Bresilioidea Campylonotoidea Crangonoidea Galatheacaridoidea Nematocarcinoidea Oplophoroidea Palaemonoidea Pandaloidea Pasiphaeoidea Procaridoidea Processoidea Psalidopodoidea Stylodactyloidea True shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. ... An isotopic signature (also isotopic fingerprint) is a ratio of stable or unstable isotopes of particular elements found in an investigated material. ...

References

  1. ^ International Union of Pure and Applied Chemistry. "radioactive dating". Compendium of Chemical Terminology Internet edition.
  2. ^ http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/decayRates.html
  3. ^ Georgia Perimeter College - Radiometric dating
  4. ^ U.S. Geological Survey - Radiometric Time Scale
  5. ^ University of South Carolina - Center for Science Education - Decay rates
  6. ^ SIMS ion micropobes able to achieve zircon analysis are SHRIMP or Cameca IMS 1270-1280. refer to Trevor Ireland, Isotope Geochemistry: New Tools for Isotopic Analysis, Science, December 1999, Vol. 286. no. 5448, pp. 2289 - 2290

IUPAC logo The International Union of Pure and Applied Chemistry (IUPAC) (Pronounced as eye-you-pack) is an international non-governmental organization established in 1919 devoted to the advancement of chemistry. ... Compendium of Chemical Terminology (ISBN 0-86542-684-8) is a book published by IUPAC containing internationally accepted definitions for terms in chemistry. ... Superfamilies Alpheoidea Atyoidea Bresilioidea Campylonotoidea Crangonoidea Galatheacaridoidea Nematocarcinoidea Oplophoroidea Palaemonoidea Pandaloidea Pasiphaeoidea Procaridoidea Processoidea Psalidopodoidea Stylodactyloidea True shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. ...

External links


  Results from FactBites:
 
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Radiometric dating provides numerical values for the age of an appropriate rock, usually expressed in millions of years.
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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.
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