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dc.contributor.authorNelson, Campbell S.en_US
dc.contributor.authorLee, Daphne E.en_US
dc.contributor.authorMaxwell, Phillipen_US
dc.contributor.authorMaas, Rolanden_US
dc.contributor.authorKamp, Peter J.J.en_US
dc.contributor.authorCooke, Steveen_US
dc.date.accessioned2008-03-19T05:10:06Z
dc.date.available2007-04-18en_US
dc.date.available2008-03-19T05:10:06Z
dc.date.issued2004-12-01en_US
dc.identifier.citationNelson, C.S., Lee, D., Maxwell, P., Maas, R., Kamp, P. J. J., & Cooke, S. (2004). Strontium isotope dating of the New Zealand Oligocene. New Zealand Journal of Geology and Geophysics. 47(4), 719-730.en_US
dc.identifier.urihttps://hdl.handle.net/10289/175
dc.description.abstractOne of the least well resolved portions of the New Zealand Cenozoic time-scale is that centred on and about the Oligocene Epoch, internationally regarded as spanning c. 10 m.y. from 33.7 to 23.8 Ma. We have determined the 87Sr/86Sr ratios and derived absolute ages for 77 macrofossil samples collected from several biostratigraphically dated mid-Tertiary sections in the South Auckland (North Island) and North Otago/South Canterbury (South Island) regions. While the site-specific stratigraphic significance of our ages remains to be assessed, we present them here to foster wider consideration and discussion in relation to evolving absolute age schemes for the New Zealand Oligocene biostratigraphic stages. Initial results suggest: (1) The approximate boundary ages for the mid-Tertiary Stages are: Runangan/Whaingaroan, 34.8 Ma; early Whaingaroan/late Whaingaroan, 31.0 Ma; Whaingaroan/Duntroonian, 28.5 Ma; Duntroonian/Waitakian, 25.5 Ma; Waitakian/Otaian, 22.2 Ma. These values are mainly older than ages assigned over the past decade.(2) The early Whaingaroan Stage, traditionally held to be entirely within the Oligocene, and to define its base, extends back across the Eocene/Oligocene boundary at 33.7 Ma into the late Eocene by up to 1.1 m.y., as previously suspected by Morgans et al. (1996) on biostratigraphic grounds.(3) There has been considerable uncertainty about placement of the Waitakian Stage over the past two decades, whether entirely in the Miocene, entirely in the Oligocene, or straddling both epochs. Our Sr dating shows that the Oligocene/Miocene boundary (23.8 Ma) lies about midway through the Waitakian Stage, in agreement with Graham et al. (2000).(4) The Whaingaroan/Duntroonian boundary approximates the international early-late Oligocene one (28.5 Ma).Comparisons with recently published Oligocene stable oxygen isotope records suggest that ?18O maxima and attendant sea-level lowering, with possibly significant unconformity development, may be anticipated on three occasions in the early Whaingaroan, two or three in the late Whaingaroan, two in the Duntroonian, and at least two in the Waitakian. The unconformities bounding formations and members in the Oligocene successions may relate to these sea-level changes, and so be regionally correlatable, including the well publicised Marshall Paraconformity of latest Whaingaroan (c. 29 Ma) age.en_US
dc.format.mimetypeapplication/pdf
dc.language.isoen
dc.publisherSIR Publishingen_NZ
dc.relation.urihttp://www.rsnz.org/publish/nzjgg/2004/052.phpen_US
dc.rightsThis article has been published in the New Zealand Journal of Geology and Geophysics. (c) 2004 Royal Society of New Zealand.en_US
dc.subjectNew Zealanden_US
dc.subjectOligoceneen_US
dc.subjectWhaingaroan Stageen_US
dc.subjectDuntroonian Stageen_US
dc.subjectWaitakian Stageen_US
dc.subjectabsolute ageen_US
dc.subjectstrontium isotope datingen_US
dc.subjectfossilsen_US
dc.titleStrontium isotope dating of the New Zealand Oligoceneen_US
dc.typeJournal Articleen_US
dc.identifier.doi10.1080/00288306.2004.9515085en_NZ
dc.relation.isPartOfNew Zealand Journal of Geology & Geophysicsen_NZ
pubs.begin-page719en_NZ
pubs.elements-id30418
pubs.end-page730en_NZ
pubs.issue4en_NZ
pubs.volume47en_NZ


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