Amino acid analysis of indigenous protein preserved in fossil marine bivalves from Plio-Pleistocene sediments in the Wanganui Basin, North Island, New Zealand has provided an aminostratigraphy. D-alloisoleucine/L-isoleucine (D-aIle/L-Ile) ratios were measured in the venerid marine bivalves Tawera spissa and Austrovenus stutchburyi that show progressively increasing D-aIle/L-Ile ratios with increasing stratigraphical age. When calibrated by magnetostratigraphy, fission-track dating, radiocarbon dating, and coccolith biostratigraphy, these relative D-aIle/L-Ile ages range up to c. 1 Ma. The aminostratigraphy provides a framework of correlation and dating for other sites in the New Zealand area where other methods of dating are unavailable, as well as facilitating correlation with oxygen isotope stratigraphy. This is the first calibrated aminostratigraphical sequence from a long sequence of sediments that cover a significant proportion of the Pleistocene.