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This method has a couple of advantages over sediment traps.
First, it is quicker: it doesn't take long to obtain a sediment core sample, whereas a sediment trap has to be left in place for at least a year to produce useful results.
The methods discussed in this article each require two isotopes: a parent isotope which is soluble (or the commonly occurring compounds of which are soluble) and a radioactive daughter isotope which is not soluble.
The table below shows three such systems together with the half-life of the daughter isotope, since this is the crucial figure.
) is most commonly used, other minerals such as monazite (see: monazite geochronology), titanite, and baddeleyite can also be used.
Where crystals such as zircon with uranium and thorium inclusions do not occur, uranium-lead dating techniques have also been applied to other minerals such as calcite/aragonite and other carbonate minerals.
However, use of a single decay scheme (usually Pb) leads to the U-Pb isochron dating method, analogous to the rubidium-strontium dating method.
Finally, ages can also be determined from the U-Pb system by analysis of Pb isotope ratios alone. Clair Cameron Patterson, an American geochemist who pioneered studies of uranium-lead radiometric dating methods, is famous for having used it to obtain one of the earliest accurate estimates of the age of the Earth.
It can be used to date rocks that formed and crystallised from about 1 million years to over 4.5 billion years ago with routine precisions in the 0.1–1 percent range. This mineral incorporates uranium and thorium atoms into its crystal structure, but strongly rejects lead when forming.This damage is most concentrated around the parent isotope (U and Th), expelling the daughter isotope (Pb) from its original position in the zircon lattice.In areas with a high concentration of the parent isotope, damage to the crystal lattice is quite extensive, and will often interconnect to form a network of radiation damaged areas.Uranium-lead dating is usually performed on the mineral zircon (Zr Si O), though it can be used on other minerals.Zircon incorporates uranium and thorium atoms into its crystalline structure, but strongly rejects lead.