Radioactive dating artifacts
Shells of known age collected prior to nuclear testing have also been dated ( to ascertain the effects of old carbon (i.e., local marine reservoir effects). However, the most common materials dated by archaeologists are wood charcoal, shell, and bone. In brief, radiocarbon dating measures the amount of radioactive carbon 14 (14C) in a sample.Radiocarbon analyses are carried out at specialized laboratories around the world (see a list of labs at: When a biological organism dies, the radioactive carbon in its body begins to break down or decay.Alone, or in concert, these factors can lead to inaccuracies and misinterpretations by archaeologists without proper investigation of the potential problems associated with sampling and dating.To help resolve these issues, radiocarbon laboratories have conducted inter-laboratory comparison exercises (see for example, the August 2003 special issue of Radiocarbon), devised rigorous pretreatment procedures to remove any carbon-containing compounds unrelated to the actual sample being dated, and developed calibration methods for terrestrial and marine carbon. Radiocarbon dating can be used on either organic or inorganic carbonate materials.To obtain a truly absolute chronology, corrections must be made, provided by measurements on samples of know age.The most suitable types of sample for radiocarbon dating are charcoal and well-preserved wood, although leather, cloth, paper, peat, shell and bone can also be used.Desmond Clark (1979:7) observed that without radiocarbon dating "we would still be foundering in a sea of imprecisions sometime bred of inspired guesswork but more often of imaginative speculation." And as Colin Renfrew (1973) aptly noted over 30 years ago, the "Radiocarbon Revolution" transformed how archaeologists could interpret the past and track cultural changes through a period in human history where we see among other things the massive migration of peoples settling virtually every major region of the world, the transition from hunting and gathering to more intensive forms of food production, and the rise of city-states.However, as with any dating technique there are limits to the kinds of things that can be satisfactorily dated, levels of precision and accuracy, age range constraints, and different levels of susceptibility to contamination.
Green plants absorb the carbon dioxide, so the population of carbon-14 molecules is continually replenished until the plant dies.Shell may succumb to isotopic exchange if it interacts with carbon from percolating ground acids or recrystallization when shell aragonite transforms to calcite and involves the exchange of modern calcite.The surrounding environment can also influence radiocarbon ages.Radiocarbon dating: radioactive carbon decays to nitrogen with a half-life of 5730 years.In dead material, the decayed 14C is not replaced and its concentration in the object decreases slowly.