query: radiocarbon dating is based on which decay process

pos: Radiocarbon dating plants by photosynthesis; animals then acquire by eating the plants. When the animal or plant dies, it stops exchanging carbon with its environment, and from that point onwards the amount of it contains begins to decrease as the undergoes radioactive decay. Measuring the amount of in a sample from a dead plant or animal such as a piece of wood or a fragment of bone provides information that can be used to calculate when the animal or plant died. The older a sample is, the less there is to be detected, and because the half-life of (the period of time

pos: Objections to evolution example, it is argued that radiometric dating technique of evaluating a material's age based on the radioactive decay rates of certain isotopes generates inconsistent and thus unreliable results. Radiocarbon dating based on the carbon-14 isotope has been particularly criticized. It is argued that radiometric decay relies on a number of unwarranted assumptions such as the principle of uniformitarianism, consistent decay rates, or rocks acting as closed systems. Such arguments have been dismissed by scientists on the grounds that independent methods have confirmed the reliability of radiometric dating as a whole; additionally, different radiometric dating methods and techniques have independently confirmed

pos: Geochronometry always rely on the phenomenon of radioactive decay. These alternative radiometric methods are: These methods, especially radiocarbon, are particularly reliable for recent samples, but are much less accurate for deep geologic time. More specifically, radiocarbon becomes unreliable already for samples >50000 years old. These methods are based on the building of incremental chronologies from a point of known age, which is usually the present. When a chronology is not tied to such a known age point, it is called a "floating chronology". Incremental dating methods include: A major achievement of geochronometry is the documentation of geologic time, as represented in

pos: Absolute dating of the radioactive atoms and their decayed daughter isotopes will be too small to measure within the uncertainty of the instruments. One of the most widely used and well-known absolute dating techniques is carbon-14 (or radiocarbon) dating, which is used to date organic remains. This is a radiometric technique since it is based on radioactive decay. Cosmic radiation entering the earth’s atmosphere produces carbon-14, and plants take in carbon-14 as they fix carbon dioxide. Carbon-14 moves up the food chain as animals eat plants and as predators eat other animals. With death, the uptake of carbon-14 stops. It takes 5,730

pos: Radiocarbon dating the technology being used. There are two types of testing technology: detectors that record radioactivity, known as beta counters, and accelerator mass spectrometers. For beta counters, a sample weighing at least is typically required. Accelerator mass spectrometry is much more sensitive, and samples containing as little as 0.5 milligrams of carbon can be used. For decades after Libby performed the first radiocarbon dating experiments, the only way to measure the in a sample was to detect the radioactive decay of individual carbon atoms. In this approach, what is measured is the activity, in number of decay events per unit mass

pos: Absolute dating materials with known dates (coins and written history). Techniques include tree rings in timbers, radiocarbon dating of wood or bones, and trapped-charge dating methods such as thermoluminescence dating of glazed ceramics. Coins found in excavations may have their production date written on them, or there may be written records describing the coin and when it was used, allowing the site to be associated with a particular calendar year. In historical geology, the primary methods of absolute dating involve using the radioactive decay of elements trapped in rocks or minerals, including isotope systems from very young (radiocarbon dating with ) to

pos: Radiocarbon dating the sample, the less will be left. The equation governing the decay of a radioactive isotope is: where "N" is the number of atoms of the isotope in the original sample (at time "t" = 0, when the organism from which the sample was taken died), and "N" is the number of atoms left after time "t". "λ" is a constant that depends on the particular isotope; for a given isotope it is equal to the reciprocal of the mean-life – i.e. the average or expected time a given atom will survive before undergoing radioactive decay. The mean-life, denoted by

pos: Radiocarbon dating is taken up by plants via photosynthesis. Animals eat the plants, and ultimately the radiocarbon is distributed throughout the biosphere. The ratio of to is approximately 1.25 parts of to 10 parts of . In addition, about 1% of the carbon atoms are of the stable isotope . The equation for the radioactive decay of is: By emitting a beta particle (an electron, e) and an electron antineutrino (), one of the neutrons in the nucleus changes to a proton and the nucleus reverts to the stable (non-radioactive) isotope . During its life, a plant or animal is in equilibrium

pos: Absolute dating a noble gas, is not commonly incorporated into such samples except when produced "in situ" through radioactive decay. The date measured reveals the last time that the object was heated past the closure temperature at which the trapped argon can escape the lattice. K–Ar dating was used to calibrate the geomagnetic polarity time scale. Thermoluminescence testing also dates items to the last time they were heated. This technique is based on the principle that all objects absorb radiation from the environment. This process frees electrons within minerals that remain caught within the item. Heating an item to 500 degrees Celsius

pos: Fact and theories that arise in the attempt to clarify the fundamental nature of scientific fact. Pertinent issues raised by this inquiry include: Consistent with the idea of confirmation holism, some scholars assert "fact" to be necessarily "theory-laden" to some degree. Thomas Kuhn points out that knowing what facts to measure, and how to measure them, requires the use of other theories. For example, the age of fossils is based on radiometric dating, which is justified by reasoning that radioactive decay follows a Poisson process rather than a Bernoulli process. Similarly, Percy Williams Bridgman is credited with the methodological position known

pos: Uranium–uranium dating between the ranges of Th/U (accurate up to ca. 450,000 years) and U–Pb dating (accurate up to the age of the solar system, but problematic on samples younger than about 2 million years). Uranium–uranium dating Uranium–uranium dating is a radiometric dating technique which compares two isotopes of uranium (U) in a sample: uranium-234 (U) and uranium-238 (U). It is one of several radiometric dating techniques exploiting the uranium radioactive decay series, in which U undergoes 14 alpha and beta decay events on the way to the stable isotope Pb. Other dating techniques using this decay series include uranium–thorium dating and

pos: Uranium–uranium dating Uranium–uranium dating Uranium–uranium dating is a radiometric dating technique which compares two isotopes of uranium (U) in a sample: uranium-234 (U) and uranium-238 (U). It is one of several radiometric dating techniques exploiting the uranium radioactive decay series, in which U undergoes 14 alpha and beta decay events on the way to the stable isotope Pb. Other dating techniques using this decay series include uranium–thorium dating and uranium–lead dating. U, with a half-life of about 4.5 billion years, decays to U through emission of an alpha particle to thorium-234 (Th), which is comparatively unstable with a half-life of just 24

pos: K–Ar dating K–Ar dating Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in geochronology and archaeology. It is based on measurement of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar). Potassium is a common element found in many materials, such as micas, clay minerals, tephra, and evaporites. In these materials, the decay product is able to escape the liquid (molten) rock, but starts to accumulate when the rock solidifies (recrystallizes). The amount of argon sublimation that occurs is a function of the purity of the sample, the composition of the mother material,

pos: Radiocarbon dating plants by photosynthesis; animals then acquire by eating the plants. When the animal or plant dies, it stops exchanging carbon with its environment, and from that point onwards the amount of it contains begins to decrease as the undergoes radioactive decay. Measuring the amount of in a sample from a dead plant or animal such as a piece of wood or a fragment of bone provides information that can be used to calculate when the animal or plant died. The older a sample is, the less there is to be detected, and because the half-life of (the period of time

pos: K–Ca dating K–Ca dating Potassium–calcium dating, abbreviated K–Ca dating, is a radiometric dating method used in geochronology. It is based upon measuring the ratio of a parent isotope of potassium (K) to a daughter isotope of calcium (Ca). This form of radioactive decay is accomplished through beta decay. Calcium is common in many minerals, with Ca being the most abundant naturally occurring isotope of calcium (96.94%), so use of this dating method to determine the ratio of daughter calcium produced from parent potassium is generally not practical. However, in minerals with low calcium content (under 1/50th of the potassium content), this dating

pos: K–Ca dating is also most effective, comparatively, at providing major element abundances for crustal magma sources, if used with high precision. K–Ca dating Potassium–calcium dating, abbreviated K–Ca dating, is a radiometric dating method used in geochronology. It is based upon measuring the ratio of a parent isotope of potassium (K) to a daughter isotope of calcium (Ca). This form of radioactive decay is accomplished through beta decay. Calcium is common in many minerals, with Ca being the most abundant naturally occurring isotope of calcium (96.94%), so use of this dating method to determine the ratio of daughter calcium produced from parent potassium

pos: Uranium–lead dating Uranium–lead dating Uranium–lead dating, abbreviated U–Pb dating, is one of the oldest and most refined of the radiometric dating schemes. It can be used to date rocks that formed and crystallised from about 1 million years to over 4.5 billion years ago with routine precisions in the 0.1–1 percent range. The dating method is usually performed on the mineral zircon. The mineral incorporates uranium and thorium atoms into its crystal structure, but strongly rejects lead. Therefore, one can assume that the entire lead content of the zircon is radiogenic, i.e. it is produced solely by a process of radioactive decay

neg: Radiometric dating dating technique is based on the decay of uranium-234 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 32,760 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. A related method is ionium–thorium dating, which measures the ratio of ionium (thorium-230) to thorium-232 in ocean sediment. Radiocarbon dating is also simply called Carbon-14 dating.

neg: Thorium to fissile U by neutron capture and subsequent beta decay. Two radiometric dating methods involve thorium isotopes: uranium–thorium dating, based on the decay of U to Th, and ionium–thorium dating, which measures the ratio of Th to Th. These rely on the fact that Th is a primordial radioisotope, but Th only occurs as an intermediate decay product in the decay chain of U. Uranium–thorium dating is a relatively short-range process because of the short half-lives of U and Th relative to the age of the Earth: it is also accompanied by a sister process involving the alpha decay of

neg: Geochronology 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. More slowly decaying isotopes are useful for longer periods of time, but less accurate in absolute years. With the exception of the radiocarbon method, most of these techniques are actually based on measuring an increase in the abundance of a radiogenic isotope, which is the decay-product of the radioactive parent isotope. Two or more radiometric methods can be used in concert to achieve

neg: Radiocarbon dating Radiocarbon dating Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon. The method was developed in the late 1940s by Willard Libby, who received the Nobel Prize in Chemistry for his work in 1960. It is based on the fact that radiocarbon () is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting combines with atmospheric oxygen to form radioactive carbon dioxide, which is incorporated into

neg: Weak interaction phenomena involving the weak interaction include beta decay, and the fusion of hydrogen into helium that powers the Sun's thermonuclear process. Most fermions will decay by a weak interaction over time. Such decay makes radiocarbon dating possible, as carbon-14 decays through the weak interaction to nitrogen-14. It can also create radioluminescence, commonly used in tritium illumination, and in the related field of betavoltaics. During the quark epoch of the early universe, the electroweak force separated into the electromagnetic and weak forces. In 1933, Enrico Fermi proposed the first theory of the weak interaction, known as Fermi's interaction. He suggested that

neg: Calibration of radiocarbon dates Calibration of radiocarbon dates Radiocarbon dating measurements produce ages in "radiocarbon years", which must be converted to calendar ages by a process called calibration. Calibration is needed because the atmospheric / ratio, which is a key element in calculating radiocarbon ages, has not been constant historically. Although Willard Libby, the inventor of radiocarbon dating, had pointed out as early as 1955 the possibility that the / ratio might have varied over time, it was not until discrepancies began to accumulate between measured ages and known historical dates for artefacts that it became clear that a correction would need to be

neg: Radiocarbon dating or minus 250 years. These results were published in "Science" in 1949. Within 11 years of their announcement, more than 20 radiocarbon dating laboratories had been set up worldwide. In 1960, Libby was awarded the Nobel Prize in Chemistry for this work. In nature, carbon exists as two stable, nonradioactive isotopes: carbon-12 (), and carbon-13 (), and a radioactive isotope, carbon-14 (), also known as "radiocarbon". The half-life of (the time it takes for half of a given amount of to decay) is about 5,730 years, so its concentration in the atmosphere might be expected to reduce over thousands of

neg: Surface exposure dating other means, such as radiocarbon dating, thermoluminescence, or optically stimulated luminescence. The excess relative to natural abundance of cosmogenic nuclides in a rock sample is usually measured by means of accelerator mass spectrometry. Cosmogenic nuclides such as these are produced by chains of spallation reactions. The production rate for a particular nuclide is a function of geomagnetic latitude, the amount of sky that can be seen from the point that is sampled, elevation, sample depth, and density of the material in which the sample is embedded. Decay rates are given by the decay constants of the nuclides. These equations can

neg: Accelerator mass spectrometry Be, an isotope widely used in geology. Soon the accelerator technique, since it was more sensitive by a factor of about 1,000, virtually supplanted the older “decay counting” methods for these and other radioisotopes. The applications are many. AMS is most often employed to determine the concentration of C, e.g. by archaeologists for radiocarbon dating. An accelerator mass spectrometer is required over other forms of mass spectrometry due to their insufficient suppression of molecular isobars to resolve CH and CH from radiocarbon. Because of the long half-life of C decay counting requires significantly larger samples. Be, Al, and Cl are

neg: Radiocarbon dating of the Shroud of Turin traces in her study of the shroud. Harry E. Gove helped to invent radiocarbon dating and was closely involved in setting up the shroud dating project. He also attended the actual dating process at the University of Arizona. Gove has written (in the respected scientific journal Radiocarbon) that: "Another argument has been made that the part of the shroud from which the sample was cut had possibly become worn and threadbare from countless handlings and had been subjected to medieval textile restoration. If so, the restoration would have had to be done with such incredible virtuosity as to render it

neg: Radiocarbon dating of the Shroud of Turin stated that his analysis showed: "The radiocarbon sample contains both a gum/dye/mordant coating and cotton fibers. The main part of the shroud does not contain these materials." He speculated that these products may have been used by medieval weavers to match the colour of the original weave when performing repairs and backing the shroud for additional protection. Based on this comparison Rogers concluded that the undocumented threads received from Gonella did not match the main body of the shroud, and that in his opinion: "The worst possible sample for carbon dating was taken." As part of the testing process in

neg: Biblical manuscript means known for determining the age of a manuscript. Script groups belong typologically to their generation; and changes can be noted with great accuracy over relatively short periods of time. Dating of manuscript material by a radiocarbon dating test requires that a small part of the material be destroyed in the process. Both radiocarbon and paleographical dating only give a range of possible dates, and it is still debated just how narrow this range might be. Dates established by radiocarbon dating can present a range of 10 to over 100 years. Similarly, dates established by paleography can present a range

neg: Radiocarbon dating in the late 19th century. Conversely, nuclear testing increased the amount of in the atmosphere, which attained a maximum in about 1965 of almost twice what it had been before the testing began. Measurement of radiocarbon was originally done by beta-counting devices, which counted the amount of beta radiation emitted by decaying atoms in a sample. More recently, accelerator mass spectrometry has become the method of choice; it counts all the atoms in the sample and not just the few that happen to decay during the measurements; it can therefore be used with much smaller samples (as small as individual

neg: Bridge of the Gods (land bridge) landslide have evolved as more investigators have studied it and as more modern dating techniques have become available. Early work based on dendrochronology and radiocarbon dating suggested the landslide occurred between AD 1060 and 1180 or between 1250 and 1280. The year 1100 has often been cited as the date of the Bonneville landslide. More recent work using radiocarbon dating and lichenometry has suggested dates between 1500 and 1760 or between 1670 and 1760. These younger radiocarbon ages permitted a possible link to the 1700 Cascadia earthquake. However, more recent investigations using radiocarbon dating and dendrochronology show the landslide occurred

neg: Monrepos (archaeology) Palaeolithic and Mesolithic hunter-gatherers. Since the mid-1980s, Monrepos has been involved in the construction and improvement of an absolute chronology of the European Palaeolithic. In this process, comprehensive dating programs of the Upper Palaeolithic were initiated Innovative methods of radiocarbon calibration were developed by Olaf Jöris (Monrepos) and Bernhard Weninger (University of Cologne). These methods became constantly better and made precise calibration of increasingly older radiocarbon dates possible by the connection with high-resolution climate data sets. The calibration program CalPal is based on this approach and was first created by Olaf Jöris and Bernhard Weninger in the mid-1990s. Hunting of

neg: Before Present "raw") and "calibrated" (also called "Cambridge") dates. "Uncalibrated" radiocarbon dates should be clearly noted as such by "uncalibrated years BP", because they are not identical to calendar dates. This has to do with the fact that the level of atmospheric radiocarbon (carbon-14 or C) has not been strictly constant during the span of time that can be radiocarbon-dated. Uncalibrated radiocarbon ages can be converted to calendar dates by means of calibration curves based on comparison of raw radiocarbon dates of samples independently dated by other methods, such as dendrochronology (dating on the basis of tree growth-rings) and stratigraphy (dating on

neg: Before Present dates established by means other than radiocarbon dating, such as stratigraphy. This usage differs with the recommendation by van der Plicht & Hogg, followed by the "Quaternary Science Reviews", both of which requested that publications should use the unit "a" for year and reserve the term "BP" for radiocarbon estimations. Some archaeologists use the lowercase letters "bp", "bc" and "ad" as terminology for uncalibrated dates for these eras. The Centre for Ice and Climate at the University of Copenhagen has proposed "b2k" as "years before AD 2000", based on the Greenland Ice Core Chronology 2005 (GICC05) time scale. Radiocarbon dating

neg: Radiocarbon dating re-use, is that of lengthy use, or delayed deposition. For example, a wooden object that remains in use for a lengthy period will have an apparent age greater than the actual age of the context in which it is deposited. Archaeology is not the only field to make use of radiocarbon dating. The ability to date minute samples using AMS has meant that palaeobotanists and palaeoclimatologists can use radiocarbon dating on pollen samples. Radiocarbon dates can also be used in geology, sedimentology, and lake studies, for example. Dates on organic material recovered from strata of interest can be used to

neg: Fringe theories about the Shroud of Turin of the shroud. Prof H E Gove, former professor emeritus of physics at the University of Rochester and former director of the Nuclear Structure Research Laboratory at the University of Rochester, helped to invent radiocarbon dating and was closely involved in setting up the shroud dating project. He also attended the actual dating process at the University of Arizona. Gove has written (in the respected scientific journal Radiocarbon) that: "Another argument has been made that the part of the shroud from which the sample was cut had possibly become worn and threadbare from countless handlings and had been subjected to

neg: Shroud of Turin Jesus, based on disciplines ranging from chemistry to biology and medical forensics to optical image analysis. In 1988, three radiocarbon dating tests dated a corner piece of the shroud from the Middle Ages, between the years 1260 and 1390. Some shroud researchers have challenged the dating, arguing the results were skewed by the introduction of material from the Middle Ages to the portion of the shroud used for radiocarbon dating. However, all of the hypotheses used to challenge the radiocarbon dating have been scientifically refuted, including the medieval repair hypothesis, the bio-contamination hypothesis and the carbon monoxide hypothesis. The image

neg: Radiocarbon dating to be too young. Multiple papers have been published both supporting and opposing the criticism. Soon after the publication of Libby's 1949 paper in "Science", universities around the world began establishing radiocarbon-dating laboratories, and by the end of the 1950s there were more than 20 active research laboratories. It quickly became apparent that the principles of radiocarbon dating were valid, despite certain discrepancies, the causes of which then remained unknown. The development of radiocarbon dating has had a profound impact on archaeologyoften described as the "radiocarbon revolution". In the words of anthropologist R. E. Taylor, " data made a "world"

neg: Timeline of natural history Carbon-14 "aka" radiocarbon dating works for organic materials that are less than about 50,000 years old. For older periods, the potassium-argon dating process is more accurate. Radiocarbon dating is carried out by measuring how much of the carbon-14 and nitrogen-14 isotopes are found in a material. The ratio between the two is used to estimate the material's age. Suitable materials include wood, charcoal, paper, fabrics, fossils and shells. It is assumed that rock exists in layers according to age, with older beds below later ones. This is the basis of stratigraphy. The ages of more recent layers are calculated primarily

neg: Radiocarbon dating and . With the development of AMS in the 1980s it became possible to measure these isotopes precisely enough for them to be the basis of useful dating techniques, which have been primarily applied to dating rocks. Naturally occurring radioactive isotopes can also form the basis of dating methods, as with potassium–argon dating, argon–argon dating, and uranium series dating. Other dating techniques of interest to archaeologists include thermoluminescence, optically stimulated luminescence, electron spin resonance, and fission track dating, as well as techniques that depend on annual bands or layers, such as dendrochronology, tephrochronology, and varve chronology. Radiocarbon dating Radiocarbon dating

neg: Thomas Athol Rafter bones and ash showers from volcanos on the North Island of New Zealand. After difficulties with the process published by Willard Libby, radiocarbon dating’s American pioneer, Rafter worked with DSIR physicist Gordon Fergusson and their team to perfect a new and reliable method of radiocarbon dating using carbon dioxide gas rather than solid carbon. In 1959, Rafter was appointed the inaugural director of the DSIR’s Institute of Nuclear Sciences, in Gracefield, New Zealand. In his new position, Rafter encouraged research into natural variations in radiocarbon levels, in the process discovering a link between atmospheric nuclear weapons tests and rising levels

neg: Radiocarbon dating with its surroundings by exchanging carbon either with the atmosphere, or through its diet. It will therefore have the same proportion of as the atmosphere, or in the case of marine animals or plants, with the ocean. Once it dies, it ceases to acquire , but the within its biological material at that time will continue to decay, and so the ratio of to in its remains will gradually decrease. Because decays at a known rate, the proportion of radiocarbon can be used to determine how long it has been since a given sample stopped exchanging carbon – the older

neg: Radiocarbon dating levels in a stratigraphic sequence, Bayesian analysis can be used to evaluate dates which are outliers, and can calculate improved probability distributions, based on the prior information that the sequence should be ordered in time. When Bayesian analysis was introduced, its use was limited by the need to use mainframe computers to perform the calculations, but the technique has since been implemented on programs available for personal computers, such as OxCal. Several formats for citing radiocarbon results have been used since the first samples were dated. As of 2014, the standard format required by the journal "Radiocarbon" is as follows.

neg: Radiocarbon dating of the Shroud of Turin some technical concerns that have been raised about radiocarbon dating of the Shroud, no radiocarbon-dating expert has asserted that the dating is unreliable. The idea of scientifically dating the shroud had first been proposed in the 1960s, but permission had been refused because the procedure at the time would have required the destruction of too much fabric (almost 0.05 sq m ≅ 0.538 sq ft). The development in the 1970s of new techniques for radio-carbon dating, which required much lower quantities of source material, prompted the Catholic Church to found the "Shroud of Turin Research Project" (S.Tu.R.P.), which involved about

neg: Before Present was first used in 1940. Beginning in 1954, metrologists established 1950 as the origin year for the BP scale for use with radiocarbon dating, using a 1950-based reference sample of oxalic acid. According to scientist A. Currie Lloyd: The year 1950 was chosen because it was the standard astronomical epoch at that time. It also marked the publication of the first radiocarbon dates in December 1949, and 1950 also antedates large scale atmospheric testing of nuclear weapons, which altered the global ratio of carbon-14 to carbon-12. Dates determined using radiocarbon dating come in two kinds: "uncalibrated" (also called "Libby" or

neg: Radiocarbon dating Egyptologists. This was possible because although annual plants, such as corn, have a / ratio that reflects the atmospheric ratio at the time they were growing, trees only add material to their outermost tree ring in any given year, while the inner tree rings don't get their replenished and instead start losing through decay. Hence each ring preserves a record of the atmospheric / ratio of the year it grew in. Carbon-dating the wood from the tree rings themselves provides the check needed on the atmospheric / ratio: with a sample of known date, and a measurement of the value

neg: Luminescence dating al. discovered that OSL and radiocarbon dates agreed in some samples, but the radiocarbon dates were up to 5800 years older in others. The sediments with disagreeing ages were determined to be deposited by aeolian processes. Westerly winds delivered an influx of -deficient carbon from adjacent soils and Paleozoic carbonate rocks, a process that is also active today. This reworked carbon changed the measured isotopic ratios, giving a false older age. However, the wind-blown origin of these sediments were ideal for OSL dating, as most of the grains would have been completely bleached by sunlight exposure during transport and burial.

neg: Ancient footprints of Acahualinca radiocarbon dating to determine the age of soil humates, from a buried soil directly underlying the footprints, to 5,945±145 radiocarbon years Before Present. Based upon this date, he estimated that the footprints dated to about 5,000 Before Present. But, later dating of the volcanic deposits in which they occur, known as the Masaya Triple Layer, demonstrated that the fossil tracks are only about 2,120 ± 120 years old. In 1978, the Nicaraguan researcher Jorge Espinosa continued the excavation near the termination of the original excavation. He uncovered more footprints at a depth of 4 meters. The track is believed to

neg: Radiocarbon dating after which half of a given sample will have decayed) is about 5,730 years, the oldest dates that can be reliably measured by this process date to around 50,000 years ago, although special preparation methods occasionally permit accurate analysis of older samples. Research has been ongoing since the 1960s to determine what the proportion of in the atmosphere has been over the past fifty thousand years. The resulting data, in the form of a calibration curve, is now used to convert a given measurement of radiocarbon in a sample into an estimate of the sample's calendar age. Other corrections must

neg: Dendroarchaeology between Irish and English chronologies, but individual ring patterns tend to match better against their local chronologies. Hence, this strong geographical component of tree ring chronologies can be used to source timber samples at archaeological sites to uncover trade routes required for the site construction. Dendrochronology can also be used in concert with radiocarbon dating to allow for more accurate date measurements using radiocarbon dating on archaeological sites. It is known that the concentration of carbon-14 in the atmosphere is not constant. By performing radiocarbon dating on timber samples in a known chronology, radiocarbon dates can be plotted against real

neg: Radiocarbon dating samples Radiocarbon dating samples Samples used for radiocarbon dating must be handled carefully to avoid contamination. Not all material can be dated by this method; only samples containing organic matter can be tested: the date found will be the date of death of the plants or animals from which the sample originally came. Samples for dating need to be converted into a form suitable for measuring the content; this can mean conversion to gaseous, liquid, or solid form, depending on the measurement technique to be used. Before this can be done, however, the sample must be treated to remove any contamination

neg: Radiocarbon dating of the Shroud of Turin Radiocarbon dating of the Shroud of Turin The Shroud of Turin, a linen cloth that tradition associates with the crucifixion and burial of Jesus, has undergone numerous scientific tests, the most notable of which is radiocarbon dating, in an attempt to determine the relic's authenticity. In 1988, scientists at three separate laboratories dated samples from the Shroud to a range of 1260–1390 AD, which coincides with the first certain appearance of the shroud in the 1350s and is much later than the burial of Jesus in 30 or 33 AD. Aspects of the 1988 test continue to be debated. Despite

neg: Source criticism being studied may have important consequences for how sources are selected, interpreted and used. Feminist scholars may, for example, select sources made by women and may interpret sources from a feminist perspective. Epistemology should thus be considered a part of source criticism. It is in particular related to "tendency analysis". In archaeology, radiocarbon dating is an important technique to establish the age of information sources. Methods of this kind were the ideal when history established itself as both a scientific discipline and as a profession based on "scientific" principles in the last part of the 1880s (although radiocarbon dating is

neg: Hessel de Vries his death, he might have shared in the 1960 Nobel Prize in Chemistry, which was awarded to Libby for his radiocarbon-dating method. Hessel de Vries Hessel de Vries (November 15, 1916 in Annen – December 23, 1959 in Groningen), was a Dutch physicist and professor at the University of Groningen who furthered the detection methods and applications of radiocarbon dating to a variety of sciences. But for his untimely death, he might have been a Nobel laureate. He has been called "the unsung hero of radiocarbon dating" by Eric Willis, the first director of the radiocarbon-dating laboratory at the University

neg: Superflare ammonium and other chemical indicators of combustion. There is no evidence that nitrate concentrations can be used as indicators of historic solar activity. When energetic protons enter the atmosphere they create isotopes by reactions with the major components; the most important of these is carbon-14 (C), which is created when secondary neutrons react with nitrogen. C, which has a half-life of 5,730 years, reacts with oxygen to form carbon dioxide which is taken up by plants; dating wood by its C content is the basis of radiocarbon dating. If wood of known age is available the process can be reversed.

neg: Serpent Mound three of these unknown factors of when designed, when built, and by whom. Recently the dating of the site has been brought into question. While it has long been thought to be an Adena site based on slim evidence, a couple of radiocarbon dates from a small excavation raise the possibility that the mound is no more than a thousand years old. Middle Ohio Valley people of the time were not known for building large earthworks, however; they did display a high regard for snakes as shown by the numerous copper serpentine pieces associated with them. Radiocarbon dating of charcoal

neg: Radiocarbon dating of the Shroud of Turin radiocarbon test suggests the presence of contamination in some of the samples. They conclude that: "The effect is not large over the sampled region; … our estimate of the change is about two centuries." In December 2010, Timothy Jull, a member of the original 1988 radiocarbon-dating team and editor of the peer-reviewed journal "Radiocarbon", coauthored an article in that journal with Rachel A Freer-Waters. They examined a portion of the radiocarbon sample that was left over from the section used by the University of Arizona in 1988 for the carbon dating exercise, and were assisted by the director of the

neg: Paleoclimatology intact wood that has escaped decay can extend the time covered by the record by matching the ring depth changes to contemporary specimens. By using that method, some areas have tree-ring records dating back a few thousand years. Older wood not connected to a contemporary record can be dated generally with radiocarbon techniques. A tree-ring record can be used to produce information regarding precipitation, temperature, hydrology, and fire corresponding to a particular area. On a longer time scale, geologists must refer to the sedimentary record for data. Within climatic geomorphology one approach is to study relict landforms to infer ancient

neg: Flood geology six day creation from the Earth to the entire universe, and said that death and decay had only begun with the Fall of Man, which had therefore introduced entropy and the second law of thermodynamics. He proposed that a vapor canopy, before providing water for the Flood, created a mild even climate and shielded the Earth from cosmic rays so radiocarbon dating would not work. He cited Clifford L. Burdick's testimony that some of the Paluxy River dinosaur trackways overlapped human footprints, but Burdick failed to confirm this and the section was removed from the third edition. In a 1957

neg: Radiocarbon dating time during World War II, Willard Libby, who was then at Berkeley, learned of Korff's research and conceived the idea that it might be possible to use radiocarbon for dating. In 1945, Libby moved to the University of Chicago where he began his work on radiocarbon dating. He published a paper in 1946 in which he proposed that the carbon in living matter might include as well as non-radioactive carbon. Libby and several collaborators proceeded to experiment with methane collected from sewage works in Baltimore, and after isotopically enriching their samples they were able to demonstrate that they contained .

neg: Minze Stuiver Hessel de Vries and received a Ph.D. in Biophysics in 1958 with a thesis on the Biophysics of the Sense of Smell. Shortly thereafter he began working in the rapidly developing field of radiocarbon dating with de Vries, who found variations in the concentration of radiocarbon in the atmosphere which challenged the assumptions of the radiocarbon dating method. In 1959, together with his wife, Anneke, Minze went to Yale University for a one-year fellowship position but was called back to Groningen to take over as director of the radiocarbon facility when De Vries died. However Minze chose to remain in

neg: Radiocarbon dating plant seeds), and gives results much more quickly. The development of radiocarbon dating has had a profound impact on archaeology. In addition to permitting more accurate dating within archaeological sites than previous methods, it allows comparison of dates of events across great distances. Histories of archaeology often refer to its impact as the "radiocarbon revolution". Radiocarbon dating has allowed key transitions in prehistory to be dated, such as the end of the last ice age, and the beginning of the Neolithic and Bronze Age in different regions. In 1939, Martin Kamen and Samuel Ruben of the Radiation Laboratory at Berkeley

neg: Raised beach often correlated to marine oxygene isotopic stages (MIS) (e.g. Johnson, M. E.; Libbey, L. K. 1997) and can also be roughly dated using their stratigraphic position. There are various methods for the direct dating of marine terraces and their related materials including C radiocarbon dating, which is the most common one. E.g. this method has been used on the North Island of New Zealand to date several marine terraces. It utilizes terrestrial biogenic materials in coastal sediments such as mollusc shells analyzing the C isotope. In some cases dating based on the Th/U ratio was applied though in case of

neg: Radiocarbon dating radiocarbon ages also requires the value of the half-life for . In Libby's 1949 paper he used a value of 5720 ± 47 years, based on research by Engelkemeir et al. This was remarkably close to the modern value, but shortly afterwards the accepted value was revised to 5568 ± 30 years, and this value was in use for more than a decade. It was revised again in the early 1960s to 5,730 ± 40 years, which meant that many calculated dates in papers published prior to this were incorrect (the error in the half-life is about 3%). For consistency

neg: Fission track dating is the only isotope with a decay rate that is relevant to the significant production of natural fission tracks; other isotopes have fission decay rates too slow to be of consequence. The fragments emitted by this fission process leave trails of damage (fossil tracks or ion tracks) in the crystal structure of the mineral that contains the uranium. The process of track production is essentially the same by which swift heavy ions produce ion tracks. Chemical etching of polished internal surfaces of these minerals reveals spontaneous fission tracks, and the track density can be determined. Because etched tracks are relatively

neg: Radiocarbon dating considerations between the sample and the environment, depleting the sample's content. Radiocarbon dating considerations The variation in the / ratio in different parts of the carbon exchange reservoir means that a straightforward calculation of the age of a sample based on the amount of it contains will often give an incorrect result. There are several other possible sources of error that need to be considered. The errors are of four general types: In the early years of using the technique, it was understood that it depended on the atmospheric / ratio having remained the same over the preceding few thousand years.

neg: Radiocarbon dating considerations Radiocarbon dating considerations The variation in the / ratio in different parts of the carbon exchange reservoir means that a straightforward calculation of the age of a sample based on the amount of it contains will often give an incorrect result. There are several other possible sources of error that need to be considered. The errors are of four general types: In the early years of using the technique, it was understood that it depended on the atmospheric / ratio having remained the same over the preceding few thousand years. To verify the accuracy of the method, several artefacts that

neg: Hearth deposited atop the hearth. Unlined hearths, which are less easily identified, may also include these materials. Because of the organic nature of most of these items, they can be used to pinpoint the date the hearth was last used via the process of radiocarbon dating. Although carbon dates can be negatively affected if the users of the hearth burned old wood or coal, the process is typically quite reliable. This was the most common way to cook, and to heat interior spaces in cool seasons. In the Byzantine Empire a tax on hearths known as "kapnikon" was first explicitly mentioned

neg: Topper Site dating of the carbonized remains at Topper, arguing that 1) the stain represented the result of a natural fire, and 2) 50,000 years is the theoretical upper limit of effective radiocarbon dating, meaning that the stratum is radiocarbon dead, rather than dating to that time period. Goodyear discovered the objects by digging 4 meters deeper than the Clovis artifacts readily found at the site. Before discovering the oldest lithics, he had discovered other objects which he claimed were tools dating around 16,000 years old, or about 3,000 years before Clovis. According to Dean Snow, this assertion of 3,000 years is

neg: Radiocarbon dating in Hawaii radiocarbon methods in the 1980s on identified samples started to lend considerable support to the "short chronology" of settlement, whereby the central archipelagoes of Eastern Polynesia did not begin to be colonized until after AD 800 or later. By the early 1990s “chronometric hygiene” radiocarbon dating aka, high-precision radiocarbon dating approach of samples also started to be employed causing further reconsideration of old orthodoxies. Using chronometric hygiene, previous samples from all around Hawai'i were retested. On the lowest calibration of testing the retested samples returned dates of between 1100–1200 AD, with some samples from Kaua'i going back to around 1000

neg: Peștera cu Oase samples), University of Oxford (AMS radiocarbon dating on 8 bone/tooth samples), Max Planck Institute (stable isotope analysis and ancient DNA on 37 bone/tooth samples), University of Vienna (AMS radiocarbon dating on 25 bone/tooth samples). A skull found in Peștera cu Oase in 2004/5 bears features of both modern humans and Neanderthals. According to a paper by Erik Trinkaus and others, published in the Proceedings of the National Academy of Sciences in January, 2007, this finding suggests that the two groups interbred thousands of years ago. Radiocarbon dating indicates that the skull is 37,800 years old, making it amongst the oldest

neg: Radiocarbon dating factors affect all trees in an area, so examining tree-ring sequences from old wood allows the identification of overlapping sequences. In this way, an uninterrupted sequence of tree rings can be extended far into the past. The first such published sequence, based on bristlecone pine tree rings, was created by Wesley Ferguson. Hans Suess used this data to publish the first calibration curve for radiocarbon dating in 1967. The curve showed two types of variation from the straight line: a long term fluctuation with a period of about 9,000 years, and a shorter term variation, often referred to as "wiggles",

neg: Radiocarbon dating more objects at an archaeological site? It frequently happens that a sample for radiocarbon dating can be taken directly from the object of interest, but there are also many cases where this is not possible. Metal grave goods, for example, cannot be radiocarbon dated, but they may be found in a grave with a coffin, charcoal, or other material which can be assumed to have been deposited at the same time. In these cases a date for the coffin or charcoal is indicative of the date of deposition of the grave goods, because of the direct functional relationship between the

neg: Stave church direct eye-movement, suggest spatial enclosure, create patterning, permit transparency and establish continuity with landscape." Stave churches can be dated in various ways: by historical records or inscriptions, by stylistic means using construction details or ornaments, or by dendrochronology and radiocarbon dating. Often historical records or inscriptions will point to a year when the church is known to have existed. Archaeological excavations can yield finds which can provide relative dating for the structure, whereas absolute dating methods such as radiocarbon dating and dendrochronology can provide a more exact date. One drawback of dendrochronology is that it tends to overlook the possibility

neg: Radiocarbon dating varied significantly and as a result the values provided by the equation above have to be corrected by using data from other sources. This is done by calibration curves (discussed below), which convert a measurement of in a sample into an estimated calendar age. The calculations involve several steps and include an intermediate value called the "radiocarbon age", which is the age in "radiocarbon years" of the sample: an age quoted in radiocarbon years means that no calibration curve has been used − the calculations for radiocarbon years assume that the atmospheric / ratio has not changed over time. Calculating

neg: Radiocarbon dating of the Shroud of Turin of the three laboratories were mutually compatible, and that, on the evidence submitted, none of the mean results was questionable." Although the quality of the radiocarbon testing itself is unquestioned, criticisms have been raised regarding the choice of the sample taken for testing, with suggestions that the sample may represent a medieval repair fragment rather than the image-bearing cloth. It is hypothesised that the sampled area was a medieval repair which was conducted by "invisible reweaving". Since the C14 dating at least four articles have been published in scholarly sources contending that the samples used for the dating test may

neg: Ecosystem decay had declined to six. Ecosystem decay Ecosystem decay is a term coined by Thomas Lovejoy to define the process of which species become extinct locally based on habitat fragmentation. This process is what led to the extinction of several species, including the Irish Elk. Ecosystem decay can be mainly attributed to population isolation, leading to inbreeding, leading to a decrease in the population of local species. Another factor is the absence of competition, preventing the mechanisms of natural selection to benefit the population. This leads to a lack of a skill set for the animal to adjust and adapt to

neg: Ecosystem decay Ecosystem decay Ecosystem decay is a term coined by Thomas Lovejoy to define the process of which species become extinct locally based on habitat fragmentation. This process is what led to the extinction of several species, including the Irish Elk. Ecosystem decay can be mainly attributed to population isolation, leading to inbreeding, leading to a decrease in the population of local species. Another factor is the absence of competition, preventing the mechanisms of natural selection to benefit the population. This leads to a lack of a skill set for the animal to adjust and adapt to a new environment. Although

neg: Rhenium–osmium dating Rhenium–osmium dating Rhenium-Osmium dating is a form of radiometric dating based on the beta decay of the isotope Re to Os. This normally occurs with a half-life of 41.6 × 10 y, but studies using fully ionised Re atoms have found that this can decrease to only 33 y. Both rhenium and osmium are strongly siderophilic (iron loving), while Re is also chalcophilic (sulfur loving) making it useful in dating sulfide ores such as gold and Cu-Ni deposits. This dating method is based on an isochron calculated based on isotopic ratios measured using N-TIMS (Negative – Thermal Ionization Mass Spectrometry).

neg: Radiocarbon dating be made to account for the proportion of in different types of organisms (fractionation), and the varying levels of throughout the biosphere (reservoir effects). Additional complications come from the burning of fossil fuels such as coal and oil, and from the above-ground nuclear tests done in the 1950s and 1960s. Because the time it takes to convert biological materials to fossil fuels is substantially longer than the time it takes for its to decay below detectable levels, fossil fuels contain almost no , and as a result there was a noticeable drop in the proportion of in the atmosphere beginning

neg: Radiocarbon dating be measured with the same error term of 80 years. Radiocarbon dating is generally limited to dating samples no more than 50,000 years old, as samples older than that have insufficient to be measurable. Older dates have been obtained by using special sample preparation techniques, large samples, and very long measurement times. These techniques can allow measurement of dates up to 60,000 and in some cases up to 75,000 years before the present. Radiocarbon dates are generally presented with a range of one standard deviation (usually represented by the Greek letter sigma as 1σ) on either side of the mean.

neg: Radiocarbon dating By contrast, methane created from petroleum showed no radiocarbon activity because of its age. The results were summarized in a paper in "Science" in 1947, in which the authors commented that their results implied it would be possible to date materials containing carbon of organic origin. Libby and James Arnold proceeded to test the radiocarbon dating theory by analyzing samples with known ages. For example, two samples taken from the tombs of two Egyptian kings, Zoser and Sneferu, independently dated to 2625 BC plus or minus 75 years, were dated by radiocarbon measurement to an average of 2800 BC plus

neg: Radiocarbon dating ideas with them. As radiocarbon dates began to prove these ideas wrong in many instances, it became apparent that these innovations must sometimes have arisen locally. This has been described as a "second radiocarbon revolution", and with regard to British prehistory, archaeologist Richard Atkinson has characterized the impact of radiocarbon dating as "radical ... therapy" for the "progressive disease of invasionism". More broadly, the success of radiocarbon dating stimulated interest in analytical and statistical approaches to archaeological data. Taylor has also described the impact of AMS, and the ability to obtain accurate measurements from very small samples, as ushering in

neg: Megalithic Temples of Malta an eminent Maltese archaeologist of the late nineteenth century, had dated the Neolithic temples to 2800 BC and the Tarxien Bronze Age culture to 2000 BC. These dates were considered "considerably too high" by scholars, who proposed a reduction of half a millennium each. However, radiocarbon testing favoured Żammit’s dating. A theory that the temple art was connected with an Aegean-derived culture collapsed with this proof of the temples' elder origins. The development of the chronological phases, based on recalibrated radiocarbon dating, has split the period up to the Bronze Age in Malta into a number of phases. The first

neg: Santorini eruption occurred during the "Late Minoan IA" period at Crete and the "Late Cycladic I" period in the surrounding islands. Archaeological evidence, based on the established chronology of Bronze Age Mediterranean cultures, dates the eruption to around 1500 BC. These dates, however, conflict with radiocarbon dating which indicates that the eruption occurred at about 1645–1600 BC. For those, and other, reasons, the date of the eruption is disputed. For discussion, see Minoan eruption#Eruption dating. Santorini remained unoccupied throughout the rest of the Bronze Age, during which time the Greeks took over Crete. At Knossos, in a LMIIIA context (14th century

neg: Lake Tauca dates between 12,360 ± 120 and 10,640 ± 280 BP for the highest deposits at Salar de Coipasa and Salar de Uyuni, and 10,020 ± 160 and 10,380 ± 180 BP for deposits which formed shortly before the lake dried. The reliability of the dates was questioned in 1990, and a later estimate was set at 13,000 to 10,000 BP. In 1990, Rondeau proposed ages of 14,100 to 11,000 BP based on radiocarbon dating and 7,000 to 14,800 BP based on uranium-thorium dating. In 1993 it was suggested that Lake Tauca had an earlier phase, with water levels reaching ,

neg: Key Marco Because of the limited knowledge of the archaeological discipline at the time, no record of the stratification of the objects was kept. They cannot be placed in sequence. There is no sign of European trade goods or influence in the finds. Radiocarbon dating did not exist at the time of excavation. Radiocarbon dating of objects which have been handled and stored away from their original environment for long periods may not be reliable. In the 1960s an attempt to radiocarbon date some objects yielded a date of 1670 AD. A second attempt in 1975 using five different objects yielded dates

neg: Point Rosee the result of natural processes. The 2016 documentary film "Vikings Unearthed" included information about the 2015 excavation and the radiocarbon dating of two berries from the site, which returned dates between the 1600s and the 1800s. In the film Parcak commented that this was inconsistent with the archaeology of the site, and concluded that the samples must have been intrusive. Bolender added that the preservation of organics on the site was poor and that he did not think that it had good potential for radiocarbon dating. Carbon residue scraped from the cracked boulder was later radiocarbon dated to between 800

neg: Radiocarbon dating AD ± 12 years by wiggle-matching. The wiggles also mean that reading a date from a calibration curve can give more than one answer: this occurs when the curve wiggles up and down enough that the radiocarbon age intercepts the curve in more than one place, which may lead to a radiocarbon result being reported as two separate age ranges, corresponding to the two parts of the curve that the radiocarbon age intercepted. Bayesian statistical techniques can be applied when there are several radiocarbon dates to be calibrated. For example, if a series of radiocarbon dates is taken from different

neg: Noble gas the atom, helium cannot be retained by the Earth's gravitational field. Helium on Earth comes from the alpha decay of heavy elements such as uranium and thorium found in the Earth's crust, and tends to accumulate in natural gas deposits. The abundance of argon, on the other hand, is increased as a result of the beta decay of potassium-40, also found in the Earth's crust, to form argon-40, which is the most abundant isotope of argon on Earth despite being relatively rare in the Solar System. This process is the basis for the potassium-argon dating method. Xenon has an unexpectedly

neg: Radiocarbon dating considerations it would have led to an increase in the / ratio of only a few per cent, but the immediate effect was to almost double the amount of in the atmosphere, with the peak level occurring in about 1965. The level has since dropped, as the "bomb carbon" (as it is sometimes called) percolates into the rest of the reservoir. Photosynthesis is the primary process by which carbon moves from the atmosphere into living things. Two different photosynthetic processes exist: the C3 pathway and the C4 pathway. About 90% of all plant life uses the C3 process; the remaining plants

neg: Radiometric dating 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 that which constitutes meteorites. By measuring the decay products of extinct radionuclides with a mass spectrometer and using isochronplots, it is possible to determine relative ages of 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. Thus both the approximate age and a high time resolution can be obtained. Generally a shorter half-life

neg: Happisburgh footprints have lived on an island in the estuary that provided safety from predators, and were travelling from their island base to the shore at low tide. The Happisburgh site is too old to date using radiocarbon dating, which is not suitable for sites older than approximately 50,000 years. Dating the site has instead been based upon stratigraphy, palaeomagnetism, and the evidence of fossil flora and fauna in the sediments. The combined evidence suggests that the sediments were laid down at the end of a period of reversed magnetism between 780,000 and 1 million years ago. The exact date of the

neg: Christopher Bronk Ramsey Christopher Bronk Ramsey Christopher Bronk Ramsey is a British physicist, mathematician and specialist in radiocarbon dating. He is a professor at the University of Oxford and is the incumbent Director of the Oxford Radiocarbon Accelerator Unit (ORAU), a post he has held since 2003. He is a member of Merton College, Oxford and a Bodley Fellow. His doctorate, completed in 1987, included the first successful implementation of carbon dioxide gas as a target for radiocarbon dating via accelerator mass spectrometry. In the early 1990s, Bronk Ramsey became interested in the application of Bayesian statistics to the analysis of radiocarbon data.

neg: Radiocarbon dating machines also measure the sample's , for use in calculating the sample's radiocarbon age. The use of AMS, as opposed to simpler forms of mass spectrometry, is necessary because of the need to distinguish the carbon isotopes from other atoms or molecules that are very close in mass, such as and . As with beta counting, both blank samples and standard samples are used. Two different kinds of blank may be measured: a sample of dead carbon that has undergone no chemical processing, to detect any machine background, and a sample known as a process blank made from dead carbon

neg: Ancient protein Abelson (1968) conducted another pioneering analysis on shells and found out that amino acids degrade or change their internal L to D configuration progressively over time, and that this could thus be used as dating tool, in what is called amino acid dating or amino acid racemization. This dating approach was later shown to be a very capable tool for dating periods extending further back than the limits of radiocarbon at ca. 50.000 years. Palaeoproteomics is an emerging neologism used to describe the application of mass spectrometry (MS)-based approaches to the study of ancient proteomes. As with palaeogenomics (the study

neg: Calculation of radiocarbon dates Calculation of radiocarbon dates Radiocarbon dating methods produce data that must then be further manipulated in order to calculate a resulting "radiocarbon age". The calculations to be performed on the measurements taken depend on the technology used, since beta counters measure the sample's radioactivity, whereas accelerator mass spectrometers (AMS) determine the ratio of the three different carbon isotopes in the sample. The calculations to convert measured data to an estimate of the age of the sample require the use of several standards. One of these, the standard for normalizing values, is Pee Dee Belemnite (PDB), a fossil which has a

neg: Willard Libby at the UCLA Medical Center in Los Angeles on September 8, 1980, from a blood clot in his lung complicated by pneumonia. His papers are in the Charles E. Young Research Library at the UCLA. Seven volumes of his papers were edited by Leona and Rainer Berger and published in 1981. Willard Libby Willard Frank Libby (December 17, 1908 – September 8, 1980) was an American physical chemist noted for his role in the 1949 development of radiocarbon dating, a process which revolutionized archaeology and palaeontology. For his contributions to the team that developed this process, Libby was awarded the

neg: Chicanná Chicanná are Structures I and II. Structures I and II are both temples situated within the main plaza and have been interpreted to be aligned with solar movements for calendar-keeping purposes. Based on radiocarbon dating of charcoal and other organic materials at the site, both Structures I and II are dated to the Late Classic period. Chicanná was built in multiple phases. Structure XI, positioned adjacent to Structure X, was assembled first based on the ceramic sequence of materials found. Ceramic analysis also supports the radiocarbon data that suggests Structures I and II were built sometime later during the Late

neg: Carolina bay bays. Additional radiocarbon dates have been obtained from organic matter collected from the undisturbed sediments filling Carolina bays by Bliley and Burney, Mixon and Pilkey, Thom, and Kaczorowski. Many radiocarbon dates, which were obtained from organic matter preserved within undisturbed sediments are greater than 14,000 BP radiocarbon in age. The finite radiocarbon dates range in age from 440 ± 50 to 27,700 ±2,600 BP radiocarbon in age. Some samples are so old, they contained insufficient radiocarbon for dating, which results in "greater than" dates. For example, samples from sediments filling Carolina bays have been dated at greater than 38,000 to

neg: Radiocarbon dating that is processed into target material in exactly the same way as the sample which is being dated. Any signal from the machine background blank is likely to be caused either by beams of ions that have not followed the expected path inside the detector, or by carbon hydrides such as or . A signal from the process blank measures the amount of contamination introduced during the preparation of the sample. These measurements are used in the subsequent calculation of the age of the sample. The calculations to be performed on the measurements taken depend on the technology used, since