Thorium uranium dating

A piece of uranium 238 must originally have had no lead or other daughter products in it. Uranium-lead dating techniques has also been applied to other minerals such as calcite/aragonite and other carbonate minerals.

As corals grow, they incorporate significant seawater uranium and virtually no thorium into their skeletons.

U at the time of sample formation must be known or calculated.

Instead, the uranium-thorium technique calculates an age from the degree to which secular equilibrium has been restored between the radioactive isotope thorium-230 and its radioactive parent uranium-234 within a sample.

Thorium is not soluble in natural waters under conditions found at or near the surface of the earth, so materials grown in or from these waters do not usually contain thorium.

Calibration of the 14C timescale over the past 30,000 years using mass spectrometric U-Th ages from Barbados corals.

Uranium series dating of impure carbonates: an isochron technic using total sample dissolution.

This will give us the precise measure of time that has elapsed since the disruption.

The basic principle of uranium – thorium series dating in corals is that uranium in oxygenated environments is about ten thousand times more soluble in seawater than thorium is.

With time, Thorium 230 accumulates in the sample through radiometric decay.

The sample age is based on the difference between the initial ratio of U with the environment (i.e., that it is a closed system.) The method is used for samples that can retain Uranium and Thorium, such as carbonate sediments, bones and teeth.

Thorium-230 is itself radioactive with a half-life of 75,000 years, so instead of accumulating indefinitely (as for instance is the case for the uranium-lead system), thorium-230 instead approaches secular equilibrium with its radioactive parent uranium-234.

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