Quaternary marine terrace chronology, North Canterbury, New Zealand, using amino acid racemization and infrared-stimulated luminescence

Extensive marine terraces along the North Canterbury coast of the South Island of New Zealand record uplift in this tectonically active area. Although the terraces have been studied previously, applications of Quaternary geochronological techniques to the region have been limited. We use infrared-stimulated luminescence (IRSL), amino acid racemization (AAR), and radiocarbon to determine ages of terraces at three locations—Glenafric, Motunau Beach, and Haumuri Bluff. We develop an AAR calibration curve for the mollusk species Tawera spissa from sites of known age, including the sedimentary sequence of the Whanganui Basin. Bayesian model averaging of the results is used to estimate ages of marine shells from the North Canterbury terraces. By using both IRSL and AAR, we are able to confirm ages using two independent dating methods and to identify one IRSL result that is likely in error. We develop new age estimates for the marine terraces of North Canterbury and propose correlations between sites. This terrace chronology differs significantly from most previous studies, highlighting the importance of numerical dating. The most extensive terraces are from marine isotope stages (MISs) 5a and 5c, with partial reoccupation of one terrace during MIS 3, whereas MIS 5e terraces are notably lacking among those dated.