Archeological carbon dating

Another tracer technique was introduced for carbon dating of archeological specimens. Accelerator mass spectometry (AMS) is based on measuring atomic weight ratios of atoms in extremely small samples. 

Ammo acid racemization (Section 27 2) A method for dating archeological samples based on the rate at which the stereo chemistry at the a carbon of ammo acid components is ran domized It is useful for samples too old to be reliably dated by decay... 

AMS is used for the dating of archeological artifacts because the carbon composing living organisms has a 14C/12C ratio determined by the 14C levels in the... 

Archeological records chronicle the ancient association of man with the plant genus Cannabis, of the plant family Cannabaceae. The use of cannabis fibers for the production of hemp has been dated to 4000 b.c. using carbon-14 methods. Seeds and pollen of the plant have been found in tombs, their leaves painted on funerary urns. The plant has been so well cultivated that a wild variant no longer exists. 

Olives appeared in Israel about 45,000 years ago (1). Charred pieces of olive wood have been found in excavations at Lower Boker-Har Hanegev in layers dating to 42,980 B.c. Both charred wood and carbonized stones have been found in many archeological sites in Israel dating from 8000 b.c. onward, and indirect evidence suggests the use of wild olives O. oleaster) by humans as early as the seventh millennium b.c. (3). It is not known whether the carbonized stones and charred wood obtained from Chalcolithic (fourth millennium b.c.) and Early Bronze Age (2900-2700 B.c.) sites represented cultivated or wild olives. 

In archeology and forensics, carbon-14 (half-life of 5,700 years) dating has been used extensively, since living things absorb carbon, but when they die, no new carbon is absorbed and the rate of decay of the absorbed carbon gives a good measure to the time of death. This can be used only for a certain length of time (about 60,000 years), but other isotopes, such as potassium-40 (half-life... 

Archeology uses nuclear chemistry for radiometric dating. The most commonly used nuclide for this technique is Carbon-14. C-14 is mostly synthesized in the upper atmosphere where extraterrestrial radiation interacts with other molecules to produce neutrons used in the reaction ... 

Besides the most abundant isotope (98.89%) there are also the isotope C (1.11%) and the radioactive C (traces). The molar weight of carbon (12.011 gmol ) results from this isotopic composition. " C is employed to determine the age of archeological objects (radiocarbon dating). The stable isotope is a valuable tool for molecular structure elucidation by NMR spectroscopy because its nuclear-spin quantum number is I =... 

Many elements exist in nature as two or more isotopes, and a number of isotopes have been prepared artificially for all elements. Some elements have more than 20 naturally occurring isotopes. The predominant naturally occurring forms of carbon (at. no. 6) are of mass 12 CiQ and 13 ( gC) in the proportion of 98.9 to 1.1. Another isotope, is formed from nitrogen by the action of cosmic rays, and is radioactive its application in the dating of archeological material is discussed later in this chapter. 

Brigham Young researcher Scott Woodward takes a bone sample for carbon-14 dating at an archeological site In Egypt. 

A wooden object from an archeological site is subjected to radiocarbon dating. The activity due toi-t is measured to be 11.6 disintegrations per second. The activity of a carbon sample of equal mass from fresh wood is 15.2 disintegrations per second. The half-life of is 5715 yr. What is the age of the archeological sample ... 

The initial activity is a known constant through the past 70,000 years independent of passing time and with a value independent of geographical location and the species of dead plant or animal from which the relevant tissues are taken. It is assumed that the sample to be dated was not contaminated by modern radiocarbon and that its observed activity is unaffected by radioactive impurities. Research has shown that the initial carbon-14 activity of modern plant and animal tissues is constant to a first approximation and also that the radiocarbon activity in archeological materials of known age is measurable with sufficient precision to provide radiocarbon dates that agree satisfactorily with the known historical ages. 

Describe in general terms how an archeological artifact is dated using carbon-14. 

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