Geological and Nuclear Sciences, New Zealand

Ocean Drilling Program Sites 1123 and 1124 provide an unprecedented 12 m.y. record of major rhyolitic eruptions from the Coromandel and Taupo volcanic zones of New Zealand. Macroscopic tephras (n = 197) were dated using magnetostratigraphy, supplemented by geochemical correlation with subaerial tephra, isothermal plateau fission-track ages, and orbitally tuned stable isotope data. Eruptions began in the Coromandel volcanic zone ca. 12 Ma, approximately 1.6-1 m.y. earlier than previously known. Thereafter, volcanism was fairly continuous with a tempo and intensity that increased through the late Miocene-Pliocene and into the Quaternary, when the Taupo volcanic zone formed. The transition from the Coromandel to the Taupo zone, previously placed as ca. 4-2 Ma, was seamless, without obvious breaks or changes in ash composition. This well-dated history of long-lived and productive volcanism allows for more confident correlation with other circum-Pacific tephra records, thus helping confirm the occurrence of widespread coeval eruptions throughout the region.