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 60,000 years. Within archaeology it is considered an absolute dating technique. The technique was discovered by Willard Frank Libby and his colleagues in 1949 during his tenure as a professor at the University of Chicago. Libby estimated that the steady state radioactivity concentration of exchangeable 14C would be about 14 disintegrations per minute (dpm) per gram carbon (ca. 230 mBq/g). In 1960, Libby was awarded the Nobel Prize in chemistry for his method to use carbon-14 for age determination. 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. ... An isotope is any of several different forms of an element each having different atomic mass. ... Carbon-14 is the radioactive isotope of carbon discovered February 27, 1940, by Martin Kamen and Sam Ruben. ... This article belongs in one or more categories. ... Bold textSUCK ON THAT MUTHA FUCKA!!!!!!!!!!!!!!!!!!!!!!!!!!! Archaeology, archeology, or archæology (from the Greek words αρχαίος = ancient and λόγος = word/speech/discourse) is the study of human cultures through the recovery, documentation and analysis of material remains and environmental data, including architecture, artifacts, biofacts, human remains, and landscapes. ... Absolute dating is the process of determining a specific archaeological date. ... Willard Frank Libby (December 17, 1908 – September 8, 1980) was an American chemist, famous for his role in the development of radiocarbon dating, a process which revolutionized archaeology. ... The University of Chicago is a private university located principally in the Hyde Park neighborhood of Chicago. ... This is a list of Nobel Prize laureates in Chemistry from 1901 to the present day. ...

Furthering the technique and applications

Hessel de Vries, at the University of Groningen furthered the detection methods and applications to a variety of sciences. He has been called "the unsung hero of radiocarbon dating" (cf Willis). Front of the main building (Academiegebouw) of the University of Groningen The University of Groningen (Dutch: Rijksuniversiteit Groningen or RUG) is a university in Groningen, Netherlands. ...

Basic chemistry

Carbon has two stable, nonradioactive isotopes: carbon-12 (¹²C), and carbon-13 (¹³C). In addition, there are tiny amounts of the unstable isotope carbon-14 (¹⁴C) on Earth. Carbon-14 has a half-life of 5730 years and would have long ago vanished from Earth were it not for the unremitting cosmic ray impacts on nitrogen in the Earth's atmosphere, which forms more of the isotope. When cosmic rays enter the atmosphere, they undergo various transformations, including the production of neutrons. The resulting neutrons participate in the following reaction on one of the N atoms being knocked out of a Nitrogen (N₂) molecule in the atmosphere: General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... An isotope is any of several different forms of an element each having different atomic mass. ... Carbon 12 is a stable isotope of the element carbon. ... Carbon-13 is a stable isotope of carbon. ... Carbon-14 is the radioactive isotope of carbon discovered February 27, 1940, by Martin Kamen and Sam Ruben. ... Earth (IPA: , often referred to as the Earth, Terra, or Planet Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth largest. ... 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. ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... Layers of Atmosphere (NOAA) Air redirects here. ... This article or section does not cite its references or sources. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ...

¹n + ¹⁴N → ¹⁴C + ¹p

Atmospheric ¹⁴C, New Zealand[1] and Austria[2]. The New Zealand curve is representative for the Southern Hemisphere, the Austrian curve is representative for the Northern Hemisphere. Atmospheric nuclear weapon tests almost doubled the concentration of ¹⁴C in the Northern Hemisphere [3].

The highest rate of carbon-14 production takes place at altitudes of 9 to 15 km (30,000 to 50,000 ft), and at high geomagnetic latitudes, but the carbon-14 spreads evenly throughout the atmosphere and reacts with oxygen to form carbon dioxide. Carbon dioxide also permeates the oceans, dissolving in the water. For approximate analysis it is assumed that the cosmic ray flux is constant over long periods of time; thus carbon-14 could be assumed to be continuously produced at a constant rate and therefore that the proportion of radioactive to non-radioactive carbon throughout the Earth's atmosphere and surface oceans is constant: ca. 1 part per trillion (600 billion atoms/mole). For more accurate work, the temporal variation of the cosmic ray flux can be compensated for with calibration curves. If these curves are used, their accuracy and shape will be the limiting factors in the determination of the radiocarbon age range of a given sample. Image File history File links Radiocarbon_bomb_spike. ... Image File history File links Radiocarbon_bomb_spike. ... The cause of Earths magnetic field (the surface magnetic field) is not known for certain, but is possibly explained by dynamo theory. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ... The worlds oceans as seen from the South Pacific Ocean Oceans (from Okeanos in Greek, the ancient Greeks noticing the strong current that flowed off Gibraltar and assuming it was a great river) cover almost three quarters (71%) of the surface of the Earth, and nearly half of the... Parts per trillion (ppt) is a measure of concentration that is used where very low levels of concentration are significant. ...

Plants take up atmospheric carbon dioxide by photosynthesis, and are eaten by animals, so every living thing is constantly exchanging carbon-14 with its environment as long as it lives. Once it dies, however, this exchange stops, and the amount of carbon-14 gradually decreases through radioactive decay. The leaf is the primary site of photosynthesis in plants. ... Radioactive decay is the set of various processes by which unstable atomic nuclei emit subatomic particles (radiation). ...

¹⁴C → ¹⁴N + ⁰β

By emitting a β particle (Beta decay), carbon-14 is changed into stable (non-radioactive) nitrogen-14. This decay can be used to get a measure of how long ago a piece of once-living material died. However, aquatic plants obtain some of their carbon from dissolved carbonates which are likely to be very old, and thus deficient in the carbon-14 isotope, so the method is less reliable for such materials as well as for samples derived from animals with such plants in their food chain. 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. ... Nitrogen-14 is a stable, non-radioactive isotope of the nitrogen element. ... In inorganic chemistry, a carbonate is a salt of carbonic acid. ...

Measurements and scales

Measurements are traditionally made by counting the radioactive decay of individual carbon atoms by gas proportional counting or by liquid scintillation counting, but these are relatively insensitive and subject to relatively large statistical uncertainties for small samples (below about 1g carbon). If there is little carbon-14 to begin with, a half-life that long means that very few of the atoms will decay while their detection is attempted (4 atoms/s) /mol just after death, hence e.g. 1 (atom/s)/mol after 10,000 years). Sensitivity has since been greatly increased by the use of accelerator-based mass-spectrometric (AMS) techniques, where all the ¹⁴C atoms can be counted directly, rather than only those decaying during the counting interval allotted for each analysis. The AMS technique allows one to date samples containing only a few milligrams of carbon. Radioactive decay is the set of various processes by which unstable atomic nuclei emit subatomic particles (radiation). ... Properties For other uses, see Atom (disambiguation). ... A proportional counter is a measurement device to count particles of ionizing radiation and measure their energy. ... Liquid scintillation counting is a standard laboratory method in the life-sciences for measuring radiation from beta-emitting nuclides. ... 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. ... Basic schematic of a mass spectrometer Mass spectrometry (also know as mass spectroscopy (incorrect)[1] or in common speech mass-spec) is an analytical technique used to measure the mass-to-charge ratio of ions. ...

Raw radiocarbon ages (i.e., those not calibrated) are usually reported in years "before present" (BP). This is the number of radiocarbon years before 1950, based on a nominal (and assumed constant - see "calibration" below) level of carbon-14 in the atmosphere equal to the 1950 level. They are also based on a slightly off historic value for the half-life maintained for consistency with older publications (see "Radiocarbon half-life" below). See the Note, below, for the basis of the computations. Corrections for isotopic fractionation have not been included in the present note. Before Present (BP) years are the units of time (counted backwards to the past) used to report raw radiocarbon ages and dates referenced to the BP scale origin in the year AD 1950 (identical to 1950 CE). ... Raw radiocarbon measurements are usually reported as years before present (BP). ... 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 60,000 years. ... 1950 (MCML) was a common year starting on Sunday (link will take you to calendar). ... 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 60,000 years. ... There are three types of isotope fractionation: equilibrium fractionation kinetic fractionation mass-independent fractionation Categories: Physics stubs ...

Radiocarbon labs generally report an uncertainty, e.g., 3000±30BP indicates a standard deviation of 30 radiocarbon years. Traditionally this includes only the statistical counting uncertainty and some labs supply an "error multiplier" that can be multiplied by the uncertainty to account for other sources of error in the measuring process. Additional error is likely to arise from the nature and collection of the sample itself, e.g., a tree may accumulate carbon over a significant period of time. Such wood, turned into an artifact some time after the death of the tree, will reflect the date of the carbon in the wood. In probability and statistics, the standard deviation of a probability distribution, random variable, or population or multiset of values is defined as the square root of the variance. ... The coniferous Coast Redwood, the tallest tree species on earth. ...

The current maximum radiocarbon age limit lies in the range between 58,000 and 62,000 years. This limit is encountered when the radioactivity of the residual ¹⁴C in a sample is too low to be distinguished from the background radiation. Background radiation is the ionizing radiation emitted from a variety of natural and artificial radiation sources: sources in the Earth and from those sources that are incorporated in our food and water, which are incorporated in our body, and in building materials and other products that incorporate those radioactive sources...

Calibration

The need for calibration

Calibration curve for the radiocarbon dating scale. Data sources: Stuiver et al.[4]. Samples with a real date more recent than AD 1950 are dated and/or tracked using the N- & S-Hemisphere graphs. See preceding figure.

A raw BP date cannot be used directly as a calendar date, because the level of atmospheric ¹⁴C has not been strictly constant during the span of time that can be radiocarbon dated. The level is affected by variations in the cosmic ray intensity which is affected by variations caused by solar storms. In addition there are substantial reservoirs of carbon in organic matter, the ocean, ocean sediments (see methane hydrate), and sedimentary rocks. Changing climate can sometimes disrupt the carbon flow between these reservoirs and the atmosphere. The level has also been affected by human activities—it was almost doubled for a short period due to atomic bomb tests in the 1950s and 1960s and has been reduced by the release of large amounts of CO₂ from ancient organic sources where ¹⁴C is not present—the fossil fuels used in industry and transportation, known as the Suess effect. Image File history File links Radiocarbon_dating_calibration. ... Image File history File links Radiocarbon_dating_calibration. ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... A Solar Flare, courtesy NASA A solar flare is a violent explosion in the Suns atmosphere with an energy equivalent to tens of millions of hydrogen bombs. ... The worlds oceans as seen from the South Pacific Ocean Oceans (from Okeanos in Greek, the ancient Greeks noticing the strong current that flowed off Gibraltar and assuming it was a great river) cover almost three quarters (71%) of the surface of the Earth, and nearly half of the... Burning ice. Methane released by heating burns, water drips. ... Two types of sedimentary rock: limey shale overlaid by limestone. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 km (11 mi) above the epicenter. ... The 1950s was the decade spanning the years 1950 to 1959. ... The 1960s decade refers to the years from 1960 to 1969, inclusive. ... Coal rail cars in Ashtabula, Ohio Fossil fuels are hydrocarbons formed from the remains of dead plants and animals. ... Hans Eduard Suess (December 16, 1909 in Vienna - September 20, 1993) was an Austrian physical chemist and nuclear physicist. ...

Calibration methods

The raw radiocarbon dates, in BP years, are therefore calibrated to give calendar dates. Standard calibration curves are available, based on comparison of radiocarbon dates of samples that can be independently dated by other methods such as examination of tree growth rings (dendrochronology), ice cores, deep ocean sediment cores, lake sediment varves, coral samples, and speleothems (cave deposits). 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. ... Ice Core sample taken from drill. ... 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. ... A varve is an annual layer of sediment or sedimentary rock. ... Subclasses Alcyonaria Zoantharia See text for orders. ... 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. ...

The calibration curves can vary significantly from a straight line, so comparison of uncalibrated radiocarbon dates (e.g., plotting them on a graph or subtracting dates to give elapsed time) is likely to give misleading results. There are also significant plateaus in the curves, such as the one from 11,000 to 10,000 radiocarbon years BP, which is believed to be associated with changing ocean circulation during the Younger Dryas period. The accuracy of radiocarbon dating is lower for samples originating from such plateau periods. Three temperature records, the GRIP one clearly showing the Younger Dryas event at around 11 kyr BP The Younger Dryas stadial, named after the alpine / tundra wildflower Dryas octopetala, and also referred to as the Big Freeze [1], was a brief (approximately 1300 ± 70 years [1]) cold climate period following...

It has been noted that the plateau itself can be used as a time marker when it appears in a time series.

Radiocarbon half-life

Libby vs Cambridge values

Carbon dating was developed by a team led by Willard Libby. Originally a Carbon-14 half-life of 5568±30 years was used, which is now known as the Libby half-life. Later a more accurate figure of 5730±40 years was determined, which is known as the Cambridge half-life. However laboratories continue to use the Libby figure to avoid inconsistencies when comparing raw dates and when using calibration curves to obtain calendrical dates. Willard Frank Libby (December 17, 1908 – September 8, 1980) was an American chemist, famous for his role in the development of radiocarbon dating, a process which revolutionized archaeology. ... Carbon-14 is the radioactive isotope of carbon discovered February 27, 1940, by Martin Kamen and Sam Ruben. ... 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. ...

Examples

• Haraldskær Woman
• Thera eruption
• Vinland map
• Skeleton Lake
• Kennewick Man
• Shroud of Turin

Haraldskær Woman in glass covered coffin, Velje, Denmark The Haraldskær Woman (or Haraldskaer Woman) is a well-preserved Iron Age bog body naturally preserved in a bog in Jutland, Denmark. ... Satellite image of Thera The devastating volcanic eruption of Thera in the Bronze Age (dated to ca. ... The Vinland map. ... It has been suggested that this article or section be merged with Skeleton Lake. ... Kennewick Man is the name for the remains of a prehistoric man found on a bank of the Columbia River near Kennewick, Washington, on July 28, 1996. ... The first photo of the Shroud of Turin, taken in 1898, had the surprising feature that the image on the negative was clearer than the positive image. ...

See also

• Absolute dating
• Cosmogenic isotopes
• Environmental isotopes
• Radiometric dating
• Relative dating
• Discussion of half-life and average-life or mean-lifetime

Absolute dating is the process of determining a specific archaeological date. ... Cosmogenic isotopes are rare radioactive isotopes created when cosmic radiation interacts with an atomic nucleus. ... The environmental isotopes are a subset of the isotopes, both stable and radioactive, which are the object of Isotope geochemistry. ... 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. ... It has been suggested that half-life be merged into this article or section. ...

Note

Computations of ages and dates

The radioactive decay of carbon-14 follows an exponential decay. A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value. Symbolically, this can be expressed as the following differential equation, where N is the quantity and λ is a positive number called the decay constant: It has been suggested that half-life be merged into this article or section. ... Graph of a differential equation In mathematics, a differential equation is an equation in which the derivatives of a function appear as variables. ...

The solution to this equation is:

,

where C is the initial value of N.

For the particular case of radiocarbon decay, this equation is written:

,

where, for a given sample of carbonaceous matter:

N₀ = number of radiocarbon atoms at t = 0, i.e. the origin of the disintegration time,

N = number of radiocarbon atoms remaining after radioactive decay during the time t,

λ = radiocarbon decay or disintegration constant.

Two related times can be defined:

• half-life: time lapsed for half the number of radiocarbon atoms in a given sample, to decay,
• mean- or average-life: mean or average time each radiocarbon atom spends in a given sample until it decays.

It can be shown that:

t_{1 / 2} = = radiocarbon half-life = 5568 years (Libby value)

t_avg = = radiocarbon mean- or average-life = 8033 years (Libby value)

Notice that dates are customarily given in years BP which implies t(BP) = -t because the time arrow for dates runs in reverse direction from the time arrow for the corresponding ages. From these considerations and the above equation, it results:

For a raw radiocarbon date:

and for a raw radiocarbon age:

After replacing values, the raw radiocarbon age becomes any of the following equivalent formulae:

using logs base e and the average life:

and

using logs base 2 and the half-life:

References

• J. R. Arnold and W. F. Libby, "Age Determinations by Radiocarbon Content: Checks with Samples of Known Age", Science, Vol. 110 (1949).
• Bowman, Sheridan, Interpreting the Past: Radiocarbon Dating, University of California Press, 1990, ISBN 0-520-07037-2
• Currie, Lloyd. The Remarkable Metrological History of Radiocarbon Dating [II]. [5]
• Michael Friedrich, Sabine Remmele, Bernd Kromer, Jutta Hofmann, Marco Spurk, Klaus Felix Kaiser, Christian Orcel, Manfred Küppers: "The 12,460-Year Hohenheim Oak and Pine Tree-Ring Chronology from Central Europe—a Unique Annual Record for Radiocarbon Calibration and Paleoenvironment Reconstructions", Radiocarbon 46/3, S. 1111-1122 (2004).
• Harry E. Gove: From Hiroshima to the Iceman. The Development and Applications of Accelerator Mass Spectrometry. Bristol: Institute of Physics Publishing, 1999.
• Kovar, Anton J. Problems in Radiocarbon Dating at Teotihuacan. American Antiquity, Vol. 31, No. 3, Part 1 (Jan., 1966) , pp. 427-430 [6].
• Libby, W. F., Radiocarbon Dating, 2nd ed. (Univ. of Chicago Press, Chicago, Ill.,. 175 pp., 1955).
• Mook, Willem G and van der Plicht, Johannes (1999), "Reporting 14C activities and concentrations", Radiocarbon 41: 227–239. [7] [8]
• The Discovery of Global Warming, by Spencer Weart [9]
• Willis E.H. (1996), Radiocarbon dating in Cambridge: some personal recollections. A Worm's Eye View of the Early Days, [10]

External links

• Radiocarbon - The main international journal of record for research articles and date lists relevant to 14C
• C14dating.com - General information on Radiocarbon dating
• NOSAMS: National Ocean Sciences Accelerator Mass Spectrometry Facility at the Woods Hole Oceanographic Institution.
• Several calibration programs can be found at www.radiocarbon.org
• CalPal - Cologne Radiocarbon Calibration & Paleoclimate Research Package
• OxCal (Oxford Calibration) program
• Discussion of calibration
• Example of calibration
• CalPal Online
• Further basic information on radiocarbon dating (PDF)