40Ar/39Ar dating in paleoanthropology and archeology

✍ Scribed by Alan L. Deino; Paul R. Renne; Carl C. Swisher III

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 271 KB
• Volume: 6
• Category: Article
• ISSN: 1060-1538
• DOI: 10.1002/(sici)1520-6505(1998)6:2<63::aid-evan4>3.0.co;2-x

✦ Synopsis

HISTORICAL DEVELOPMENT AND BASIC PRINCIPLES

The K-Ar method is based on the quantitative accumulation of the isotope 40 Ar* ('*' denotes radiogenic) generated by the radioactive decay of naturally occurring 40 K (about 0.01% of all potassium, and having a half-life of 1.250 billion years 1,2 ) in suitable geologic materials. In an archeological or paleoanthropological context, suit-

The potassium-argon (K-Ar) dating method has been widely used over the past 40 years to provide radioisotopic age control of hominid/hominoid evolutionary time scales. The wide appeal of the technique to paleoanthropology and archeology has been, in part, a result of its broad time range of applicability, from materials as young as a few thousand years old to an essentially unbounded upper age limit. Another reason for its appeal is the many geological circumstances in which datable materials are found. Beginning about two decades ago and accelerating into this decade, however, the conventional K-Ar technique has given way to Ar/ 39 Ar dating as the method of preference. This technique is not only more precise and accurate when dating ideal materials, but also permits excellent ages to be obtained from situations that often stymie the conventional K-Ar technique, such as dating of contaminated tuffs and altered rocks.