The uranium-lead dating method relies on two separate decay chains , the uranium series from 238U to 206Pb , with a half-life of 4.47 billion years and the actinium series from 235U to 207Pb , with a half-life of 704 million years .
The method relies on two separate decay chains , the uranium series from 238U to 206Pb , with a half-life of 4.47 billion years and the actinium series from 235U to 207Pb , with a half-life of 704 million years .