AMINO-ACID RACEMIZATION DATING OF A 140000 YEAR-OLD TEPHRA-LOESS-PALEOSOL SEQUENCE ON THE MAMAKU PLATEAU NEAR ROTORUA, NEW-ZEALAND

The degree of racemization of aspartic acid released by 6 mol/L HCl hy drolysis of peptides contained in a rhyolitic tephra-loess-palacosol s equence 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 peptid es still remaining in the stratigraphic materials after being subject to this procedure and only released after subsequent treatment with hy drofluoric 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 es timates from tephrochronology. This technique may form a basis for dat ing of airfall deposits and palaeosols beyond the range of the radioca rbon method.