Amino acid racemization dating of a 140 000 year old tephra‐loess‐palaeosol sequence on the Mamaku Plateau near Rotorua, New Zealand

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Abstract
The degree of racemization of aspartic acid released by 6 mol/L HCI hydrolysis of peptides contained in a rhyolitic tephra‐loess‐palaeosol sequence in North Island, New Zealand, increases rapidly with depth and also with age as defined by radiocarbon and fission‐track dating and by tephrochronology. D/L values for aspartic acid released from peptides still remaining in the stratigraphic materials after being subject to this procedure and only released after subsequent treatment with hydrofluoric acid also showed an increase to a depth of 5.5 m, but to a much lesser degree. The ages determined largely agree with previous estimates from tephrochronology. This technique may form a basis for dating of airfall deposits and palaeosols beyond the range of the radiocarbon method.