HAVE LOCAL STAGES OUTLIVED THEIR USEFULNESS FOR THE NEW-ZEALAND PLIOCENE-PLEISTOCENE

Stratigraphic subdivision of the New Zealand Pliocene-Pleistocene has its historical basis in biostratigraphy, especially in the shallow mar ine strata in the Wanganui and East Coast basins, North Island. Intern ationally, an astronomically calibrated, high resolution timescale is now well established for the Pliocene-Pleistocene, based on predominan tly precession-controlled sedimentary cycles in the Mediterranean regi on, and the mainly obliquity-controlled, high resolution, deep-sea, be nthonic oxygen isotope record. Naish and others have recently provided a similar Milankovitch-frequency cyclostratigraphy for the Pliocene-P leistocene of New Zealand (last 3.6 m.y.), based on the Wanganui Basin record. This cyclostratigraphic record allows numeric ages to be esti mated for at least 114 stratigraphic horizons in Wanganui Basin, which are not otherwise dated. Based on this record, we propose new definit ions for the boundaries between New Zealand Pliocene-Pleistocene stage s. The new boundaries respect traditional biostratigraphic indicators, but are based upon objective markers, mainly magnetic polarity revers als. The Mo exceptions are the base-Marahauan (equated with the intern ational Pliocene-Pleistocene boundary, at 1.81 Ma) and the base-Hawera n (equated with the base of the Rangitawa Tephra, at 0.34 Ma). The rev ised positions and ages for the age/stage and subage/substage boundari es, from older to younger, are: base-Opoitian Stage, base-Thvera subch ron, 5.25 Ma; base-Waitotarran Stage (= base-Waipipian Substage), Gaus s/Gilbert boundary, 3.60 Ma; base-Mangapanian Substage, top-Kaena Subc hron, 3.03 Ma; base-Nukumaruan Stage (= base-Hautawan Substage), Matuy ama/Gauss boundary, 2.58 Ma; base-Marahauan Substage, Pliocene-Pleisto cene boundary, 1.81 Ma; base-Castlecliffian Stage (= base-Okehuan Subs tage), base-Jaramillo Subchron, 1.07 Ma; base-Putikian Substage, Brunh es/Matuyama boundary, 0.78 Ma; base-Haweran Stage, base-Rangitawa Teph ra, 0.34 Ma.