Pub. date: 2006 | Online Pub. Date: September 15, 2007 | DOI: 10.4135/9781412952453 | Print ISBN: 9780761930297 | Online ISBN: 9781412952453| Publisher:SAGE Publications, Inc.About this encyclopedia
L. A. Pavlish
The Uranium-Lead (U-Pb) Dating is a method that encompasses several techniques that are employed in determining the geological age of both terrestrial and extraterrestrial (for example, meteorites) rocks. The method was first suggested by Boltwood in 1907 when he postulated lead to be the decay product of uranium. The method has a dating range from 4.55 × 10 9 years ago to approximately 5 × 10 4 years ago, and takes advantage of the long decay chains of the radioactive parent atoms such as 238 U, which spontaneously decays through 13 transitional stages until it reaches 206 Pb, which is stable and is termed the daughter. 238 U has a half-life of 4.47 × 10 9 years; the transitional stages have an accumulated decay time of 0.0073% of the primary half-life permitting the parent-daughter comparison for chronometric purposes if a closed system with accompanying equilibrium conditions exists. More recently, Figure ...