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Radiocarbon dating reservoir effects and calibration

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Working with several collaboraters, Libby established the natural occurrence of radiocarbon by detecting its radioactivity in methane from the Baltimore sewer.In contrast, methane made from petroleum products had no measurable radioactivity.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 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.

This discovery meant that there are three naturally occurring isotopes of carbon: Whereas carbon-12 and carbon-13 are stable isotopes, carbon-14 is unstable or radioactive.

Carbon-14 is produced in the upper atmosphere when cosmic rays bombard nitrogen atoms.

In contrast to relative dating techniques whereby artifacts were simply designated as "older" or "younger" than other cultural remains based on the presence of fossils or stratigraphic position, 14C dating provided an easy and increasingly accessible way for archaeologists to construct chronologies of human behavior and examine temporal changes through time at a finer scale than what had previously been possible.

The application of Accelerator Mass Spectrometry (AMS) for radiocarbon dating in the late 1970s was also a major achievement.