Cross dating in archaeology

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Derivative methods may only be used for dating if their results can be related to a time-scale or reference curve that has been established by absolute dating methods.

The strength of resonance reflects the number of electrons that have become trapped since the crystals were formed.Cores extracted from ocean floor deposits reveal variations in oxygen isotopes in the shells and skeletal material of dead marine creatures, which reflect fluctuations in global temperature and the volume of the ocean.Sections cut through lake beds in glacial regions reveal a regular annual pattern of coarse and fine layers, known as varves.Radiocarbon dating was one peaceful by-product of accelerated wartime research into atomic physics and radioactivity in the 1940s.The rate of decay of 14C, which has a half-life of 5730 (40) years, is long enough to allow samples of carbon as old as 70,000 years to contain detectable levels of radioactive emissions, but short enough for samples from periods since the late Stone Age to be measured with reasonable precision.

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