Optical dating of paleosols bracketing the widespread Rotoehu tephra, North Island, New Zealand

Optical dating of the fine-grained mineral fraction of paleosols developed on, or within, loess bracketing the widespread Rotoehu tephra at two sites in central North Island, New Zealand, was undertaken using infrared excitat ion of potassium feldspars. Optical ages suggest that Rotoehu tephra was de posited at ca 45 ka, and support several previous age determinations. Our o ptical ages are also consistent with individual K-Ar ages from bracketing l ava flows, though inconsistent with the currently preferred age for the tep hra (64 +/- 4 ka) which is the weighted mean of them. Our data also suggest s that the age of two other important time-stratigraphic markers, Tihoi and Tahuna tephras, estimated to have been deposited at 46 and 43 ka, respecti vely, may have instead been formed between 25 and 35 ka. In the light of th is, the chronology of other North Island tephra beds older than 30 ka may h ave to be revised. (C) 2000 Elsevier Science Ltd. All rights reserved.