Late Quaternary tephrostratigraphy from the southern Havre Trough ‐ Bay of Plenty, northeast New Zealand

Abstract

A number of late Quaternary subaerial silicic tephra erupted from the Taupo Volcanic Zone are dispersed at least 230 km to the northeast of New Zealand, and are deposited as predominantly airfall vitric ash; other tephra are recognised as reworked ash turbidites. Tephra occurring as both megascopic and nonmegascopic ash within three piston cores from the Bay of Plenty ‐ southern Havre Trough are used to establish a c. 55 ka old marine tephrostratigraphy. On the basis of core stratigraphy, 14C dating, glass chemistry, and ferromagnesian mineralogy, the Kaharoa, Taupo, Mamaku, Waiohau, ?Okareka, Kawakawa, Omataroa, Hauparu, Tahuna, and ?Rotoehu Tephras are identified between 160 and 350 km from source. Peralkaline tephra from previously unrecognised Mayor Island eruptions are identified at c. 30 and 55 ka, and possibly 11.5 ka. Other tephra comprising pumiceous ash‐lapilli, and low SiO2 silicic glass, are also identified, but cannot be reliably correlated to a volcanic centre source. Occasional shards of andesitic and dacitic composition are probably largely derived from White Island eruptions. Provisional northerly seaward limits of airfall dispersal are presented for nine late Quaternary silicic tephra. Within the Bay of Plenty region, the c. 36 ka Hauparu Tephra has an extensive distribution comparable to that of the c. 22.6 ka Kawakawa Tephra, and hence forms an important offshore late Quaternary stratigraphic horizon.