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dc.contributor.authorBuck, M.D.
dc.contributor.authorBriggs, Roger M.
dc.contributor.authorNelson, Campbell S.
dc.date.accessioned2011-01-13T00:58:28Z
dc.date.available2011-01-13T00:58:28Z
dc.date.issued1981
dc.identifier.citationBuck, M.D., Briggs, R.M. & Nelson, C.S. (1981). Pyroclastic deposits and volcanic history of Mayor Island. New Zealand Journal of Geology and Geophysics, 24, 449-467.en_NZ
dc.identifier.urihttps://hdl.handle.net/10289/4927
dc.description.abstractThe emergent summit of Mayor Island, Bay of Plenty, New Zealand, is a peralkaline rhyolite volcano constructed by: a sequence of lava flows, the Tutaretare Rhyolite Formation new; and pyroclastic deposits, the Oira Pyroclastite Formition (new). These 2 formations constitute the Mayor Island Group new. The pyroclastic deposits mantle most of the outer slopes of the island, in places exceeding 100 m in thickness, and also occur interbedded with lava flows of the main cone. The pyroclastics have been informally assigned on the basis of their compositional, welding and textural, and sedimentary structural characteristics to one or other of 15 lithotypes which may be related to particular modes of eruption and emplacement, of both airfall (phreatic, phreatomagmatic, phreatoplinian, and plinian types) and pyroclastic flow (ignimbrite, nuée ardente, and base surge types origins). A sixteenth lithotype comprises epiclastic deposits formed possibly by catastrophic overspill from an ancestral crater lake. Two new radiocarbon dates on logs from the pyroclastic deposits are recorded: (Wk105) 8000 ± 70 years B.P., and (Wk77) 6340 ± 190 years B.P. Recognition of the calcalkaline Rotoehu and possibly Rotoma Ashes on Mayor Island, together with the new radiocarbon dates, enables definition of 8 phases of major volcanic activity, each separated by relatively quiescent periods with erosion and paleosol formation. Volcanism commenced sometime prior to 42 000 years ago and has continued intermittently up to the eruption of the young dome lavas, possibly less than 1000 years ago. At present, only I Mayor Island-derived tephra has been identified on the mainland of the North Island, namely the Tuhua Tephra dated (Wk77) at source as 6340 ± 190 years B .P. However, the character and magnitude of several of the pyroclastic units on Mayor Island is such that recognition of other peralkaline tephras is anticipated in northern North Island.en_NZ
dc.format.mimetypeapplication/pdf
dc.language.isoen
dc.relation.urihttp://www.royalsociety.org.nz/publications/journals/nzjg/en_NZ
dc.rightsThis article is published in New Zealand Journal of Geology and Geophysics. © 1981 the Royal Society of New Zealand.en_NZ
dc.subjectpyroclasticsen_NZ
dc.subjectvolcanologyen_NZ
dc.subjectvolcanoesen_NZ
dc.subjectradiocarbon datingen_NZ
dc.subjectMayor Islanden_NZ
dc.subjectMayor Island Groupen_NZ
dc.subjectTutaretare Rhyolite Formationen_NZ
dc.subjectOira Pyroclastite Formationen_NZ
dc.subjectOtura Faulten_NZ
dc.subjectnew stratigraphic namesen_NZ
dc.titlePyroclastic deposits and volcanic history of Mayor Islanden_NZ
dc.typeJournal Articleen_NZ


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