MULTIMETHOD DATING COMPARISON FOR MID-PLEISTOCENE RANGITAWA-TEPHRA, NEW-ZEALAND

The Rangitawa Tephra, a widespread mid-Pleistocene marker in the New Z ealand region, is dated by fission-track, thermoluminescence (TL), inf rared stimulated luminescence (IRSL), K/Ar and single crystal laser fu sion (SCLF) Ar-40/Ar-39 methods, as well as by matching to the astrono mical timescale via oxygen isotope stratigraphy in deep sea cores. Fif ty one independent numerical age estimates for Rangitawa Tephra range from 173 to 456 ka. However, only 15 of these results are considered t o be reliable: five zircon fission-track results, four isothermal plat eau fission-track (ITPFT) age estimates on glass shards, four SCLF Ar- 40/Ar-39 results, and two astronomically calibrated age estimates from deep sea cores. The weighted mean of the nine reliable fission-track age determinations is 345+/-12 ka, in excellent agreement with the wei ghted mean of 340+/-7 ka for the two reliable astronomically calibrate d age estimates. The weighted mean of the four reliable Ar-40/Ar-39 re sults (302+/-8 ka) is significantly younger, and further Ar/Ar dating is recommended to investigate this difference. Since the TL and IRSL d ating methods are experimental for sediments beyond 200 ka, we have ex cluded these from the group of reliable age results. TL and IRSL resul ts on dunesand appear to be systematically younger than TL results on loess, and loess results depend upon analytical procedures. Copyright (C) 1996 Elsevier Science Ltd