Marine sediments: dating by the racemization of amino acids.

Isoleucine has been found to undergo a slow racemization reaction in a 5-meter sediment core taken from the Atlantis fracture zone (water depth, 4014 meters; actual location, 30 degrees 15.7'N, 43 degrees 18.9'W). The amount of racemization increases with increasing depth below the sediment-seawater interface. This isoleucine racemization reaction was used to calculate an age of 1.23 million years for the bottom of the core.