Integrated stratigraphy of the Waitakian-Otaian Stage boundary stratotype, Early Miocene, New Zealand

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dc.contributor.authorMorgans, Hugh E.G.
dc.contributor.authorEdwards, A.R.
dc.contributor.authorScott, G.H.
dc.contributor.authorGraham, I.J.
dc.contributor.authorKamp, Peter J.J.
dc.contributor.authorMumme, T.C.
dc.contributor.authorWilson, G.J.
dc.contributor.authorWilson, Gary S.
dc.date.accessioned2009-12-15T00:28:03Z
dc.date.available2009-12-15T00:28:03Z
dc.date.issued1999
dc.description.abstractThe base of the type section of the Otaian Stage at Bluecliffs, South Canterbury, is recognised as the stratotype for the boundary between the Waitakian and Otaian Stages. Principal problems with the boundary are the restriction of existing bioevent proxies to shelf and upper slope environments and its uncertain age. These topics are addressed by a multidisplinary study of a 125 m section about the boundary, which examines its lithostratigraphy, depositional setting, biostratigraphy, correlation, and geochronology. The lower siltstone lithofacies (0-38.5 m) was deposited at upper bathyal depths (200-600 m) in a marginal basin which was partially sheltered from fully oceanic circulation by a submarine high and islands. The site was covered by cool-temperate water and was probably adjacent to the Subtropical Convergence. This unit is succeeded by the banded lithofacies (38.5-106 m) and the upper siltstone lithofacies (basal 19 m studied). Paleodepth probably declined up-sequence, but deposition at shelf depths is not definitely indicated. A cyclic pattern of abundance spikes in benthic and planktonic foraminifera commences 9 m above base and extends to 73 m in the banded lithofacies. Oxygen isotope excursions (up to 2.08%) in Euuvigerina miozea and Cibicides novozelandicus are greatest within the interval containing the abundance spikes. The stage boundary occurs in the banded lithofacies at the highest abundance spike (73 m). Although condensed intervals might affect the completeness of the section, they are not associated with sedimentary discontinuities, and we consider that the section is suitable as a biostratigraphic reference. Spores, pollens, dinoflagellates, calcareous nannofossils, foraminifera, bryozoans, and ostracods are preserved near the boundary, but molluscs principally occur higher, in the shallower upper siltstone lithofacies. Siliceous microfossils are rare. There is considerable scope for further biostratigraphic research. The primary event marking the boundary at 73 m is the appearance of the benthic foraminifer Ehrenbergina marwicki. This is a distinctive and widely distributed event but is restricted to shelf and upper bathyal environments. Supplementary events in planktonic foraminifera and calcareous nannofossils were researched. Highest occurrences of Globigerina brazieri and G. euapertura are recorded at 47 and 58 m. There is a marked decline in relative abundance of Paragloborotalia spp. at 62 m. Helicosphaera carteri becomes more abundant than H. euphratis between 56 and 87 m. These events are not exact proxies for the boundary but they may usefully indicate proximity to it. They occur in the interval of prominent spikes in foraminiferal abundance. The Waitakian-Otaian boundary is dated at 21.7 Ma by strontium isotopes. Stable primary remanence could not be determined in a pilot paleomagnetic study of Bluecliffs specimens. However, specimens trended towards reversed polarity, and remagnetisation great circle analysis will allow directions to be calculated in future collections.en
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dc.identifier.citationMorgans, H. E. G., Edwards, A. R., Scott, G. H., Graham, I. J., Kamp, P. J. J., Mumme, T. C., … Wilson, G. S. (1999). Integrated stratigraphy of the Waitakian-Otaian Stage boundary stratotype, Early Miocene, New Zealand. New Zealand Journal of Geology, 42, 581-614.en
dc.identifier.doi10.1080/00288306.1999.9514864en_NZ
dc.identifier.urihttps://hdl.handle.net/10289/3491
dc.language.isoen
dc.relation.isPartOfNew Zealand Journal of Geology and Geophysicsen_NZ
dc.relation.urihttp://www.royalsociety.org.nz/Site/publish/Journals/nzjgg/1999/38.aspxen
dc.rightsThis article has been published in the journal: New Zealand Journal of Geology. © 1999 The Royal Society of New Zealand.en
dc.subjectOligoceneen
dc.subjectMioceneen
dc.subjectWaitakianen
dc.subjectOtaianen
dc.subjectstage boundary stratotypeen
dc.subjectlithostratigraphyen
dc.subjectbiostratigraphyen
dc.subjectgeochronologyen
dc.subjectintegrated stratigraphyen
dc.subjectBluecliffs Silten
dc.subjectOtekaike Limestoneen
dc.subjectplanktonic foraminiferaen
dc.subjectbenthic foraminiferaen
dc.subjectcalcareous nannofossilsen
dc.subjectMolluscaen
dc.subjectpalynofloraen
dc.subjectdinoflagellatesen
dc.subjectRadiolariaen
dc.subjectoxygen isotopesen
dc.subjectcarbon isotopesen
dc.subjectcarbon isotopesen
dc.titleIntegrated stratigraphy of the Waitakian-Otaian Stage boundary stratotype, Early Miocene, New Zealanden
dc.typeJournal Articleen
pubs.begin-page581en_NZ
pubs.elements-id41001
pubs.end-page614en_NZ
pubs.issue4en_NZ
pubs.volume42en_NZ
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