Uranium Lead

The uranium-lead technique has been used the longest; it was introduced in 1907. There is more than one useful uranium-lead dating sequence. Natural uranium consists of two isotopes, U-235 and U-238.

As shown in the chart on page 47, these two isotopes decay at different rates to produce lead-207 and lead-206, respectively. Because of this, it is possible to get two age estimates for each sample. Because U-235 has a half-life of 704 million years and U-238 has a half-life of 4.5 billion years, each sample can be cross-checked, ensuring greater accuracy. Sometimes, however, it is hard to keep uranium and lead in many minerals in which they are found. Because of this, the uranium-lead dating technique can be less reliable than other measures.

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