Amino Acid Dating

G. H. Miller, D. S. Kaufman, S. J. Clarke

Research output: Chapter in Book/Report/Conference proceedingChapter

17 Scopus citations


The racemization of amino acids preserved in biominerals belongs to the chemical family of dating methods, with an age range that spans the past 105 to ~107 years. Chemical methods differ from radioactive dating techniques in that their reaction rate depends on one or more environmental parameters, whereas radioactive decay remains constant regardless of most environmental conditions. Amino acids, derived from indigenous protein residues protected by the skeletal hardparts of organisms, survive in most environments for thousands to millions of years. The extent of racemization of these amino acids is dependent primarily on the time elapsed since death of the organism and the integrated thermal history experienced by the biominerals since death, and to a lesser extent on vital effects unique to each taxon. Amino acid geochronology (often referred to as simply amino acid racemization (AAR)) relies on the chiral nature of most amino acids. Chiral molecules are not superimposable on their mirror image. All but the simplest protein amino acid can exist in either a 'left-' or 'right-' handed configuration. When an organism dies and its biomineral hardparts are archived, nearly all of the amino acids stored within the biomineral are of the l-configuration. Over time, the indigenous amino acids racemize to their d-configuration, providing a clock. At cold sites (-10°C), racemization requires ≫106 years to reach equilibrium; at hot sites (~25°C), equilibrium is reached in just over 105 years. Selecting appropriate samples and following strict preparation methods increases the temporal accuracy of AAR.

Original languageEnglish (US)
Title of host publicationEncyclopedia of Quaternary Science
Subtitle of host publicationSecond Edition
PublisherElsevier Inc.
Number of pages12
ISBN (Electronic)9780444536433
ISBN (Print)9780444536426
StatePublished - Jan 1 2013


  • Amino acid racemization
  • Aminostratigraphy
  • Effective diagenetic temperature

ASJC Scopus subject areas

  • General Earth and Planetary Sciences


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