Mount Curl Tephra, a 230000-year-old implications for quaternary chronology marker bed in New Zealand, and its

Abstract

The rhyolitic Mount Curl Tephra, probably erupted from the central region of the North Island of New Zealand, is inferred to be the product of a single major eruption, possibly associated with an ignimbrite. From potassium-argon and fission track age determinations, it is considered to be 230 000 years old. It mantles ancient land surfaces that pre-date the three youngest raised marine benches of interglacial origin in the south-western North Island. From stratigraphic relations between the tephra and the loess and aggradation alluvium underlying it, and the dune sand, other tephra and loess overlying it, it is inferred that the tephra fell at the beginning of the penultimate interglacial—the interglacial during which the third youngest (Brunswick) marine bench was cut. Using the age inferred for the Mount Curl Tephra together with overseas radiometric dates, and assuming constant rates of uplift of the south-western North Island marine benches, it is considered that the Brunswick marine bench began forming at 230 000 years B.P., and stopped forming at or more recently than 190 000 years B.P., and that the second youngest (Ngarino) marine bench stopped forming at or more recently than 115 000 years B.P. The marine bench sequence can be correlated satisfactorily with raised coral reef sequences on Barbados and New Guinea. The times of interglacials implied by the Wanganui marine bench sequence appear to correlate better with those implied by the Barbados and New Guinea sequences, than with those inferred by Emiliani & Rona (1969) from ocean core sequences.