Abstract The Mangaone Subgroup is a sequence of 14 plinian tephra beds erupted from the Okataina Volcanic Centre in North Island, New Zealand, that are bracketed between the regional marker beds of Rotoehu Tephra (50–60 ka) and Oruanui Tephra (26 ka). The Mangaone Subgroup tephra beds are separated by thin paleosols in ascending stratigraphic order: unit A, unit B, unit C, Pupuwharau Tephra (new), Pongakawa Tephra (new), Maketu, Te Mahoe, Hauparu, unit G, unit H, Mangaone, Awakeri, Omataroa, and unit L. Geochemical fingerprinting of the glass and phenocryst phases allows clear subdivision of the Mangaone Subgroup into two stratigraphic intervals. Units A‐G are rhyodacites and low‐SiO2 rhyolites (71–75.5 wt% SiO2 glass; 68–71 wt% SiO2 whole rock), clinopyroxene bearing, with calcic plagioclase (An40–60) and magnesian orthopyroxene (En60–70), and they display high eruption temperatures (870–940°C) and oxygen fugacities (‐logfO2= 11.66–10.40). Some of these units are compositionally heterogeneous in the glass phase (SiO2 range up to 8 wt%), especially unit A, Ngamotu, Te Mahoe, and Hauparu tephra beds. Units A‐G can easily be distinguished from other Taupo Volcanic Zone tephra erupted in the last c. 60 000 yr. Units H‐L are high SiO2 rhyolites (76–78 wt% SiO2glass; 71.5–75 wt% SiO2 whole rock), which contain sodic plagioclase (An30–40), low‐Mg orthopyroxene (En50–60), and display lower eruption temperatures (755–830°C) and oxygen fugacities (‐log?O2 = 14.7–12.93). Compositional differences in titanomagnetite and ilmenite can also be used to distinguish them from older units. The two compositional groups also form distinct T‐?O2 trends. The shift in chemical affinity follows the large volume Hauparu eruption, and coincides with the likely geographic shift in vent location to the eastern margin of the caldera complex. Tephra beds that both predate and postdate the Mangaone Subgroup also reflect changes in magma type and vent location. The distinctive geochemical character of tephra in the Mangaone Subgroup makes them valuable stratigraphic markers in the central North Island and surrounding oceans.

Phenocryst

10.1080/00288306.2002.9514969

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Citations (39)

A Late Quaternary Record of Natural Change and Human Impact from Rangihoua Bay, Bay of Islands, Northern New Zealand

Journal of Coastal Research (2007)

Mark Horrocks Scott Nichol Donna D’Costa Paul Augustinus Tatjana Jacobi

A multiproxy analysis of back-dune sediment cores from Rangihoua Bay, northern New Zealand, provides an environmental history of the Late Quaternary, placing human impacts on the site into a geomorphological and ecological context. The inferred paleoecological significance of the trends is generally coeval between proxies. The history commences with a Late Pleistocene deposit that formed part of a river terrace during lower sea level. The dryland vegetation at that time was dominated by Fuscospora forest. The record recommences at ca. 7400 YBP, by which time Fuscospora had been replaced by podocarp-hardwood forest, comprising mainly Dacrydium and Prumnopitys taxifolia emerging through a Metrosideros canopy. One of the core sites was a lagoon fringed with mainly Cyperaceae, Leptospermum, and Dodonaea. Redox-sensitive elements reflect phases of anoxia related to variation in lagoon depth. Transition from lagoon to peat swamp, due to natural infilling and/or climate change, occurred after ca. 5500 YBP. Human impacts were of high magnitude and include deforestation of the catchment and drainage of the wetland by early Polynesians. Errors in the radiocarbon and tephra chronologies preclude an accurate date for this. Microfossils of introduced Polynesian plants and a thick gravel bed in one of the cores suggest that parts of the wetland were used for prehistoric horticulture.

Swamp

10.2112/04-0182.1

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Citations (17)

Tephrostratigraphy, Magnetostratigraphy and Geochronology of Some Early and Middle Pleistocene Deposits in New Zealand

Phil Shane

<p>Numerous early Pleistocene silicic tephras are exposed in long sedimentary sequences in the East Coast and Wanganui basin regions in southern North Island of New Zealand, some 150-250 km south of the Taupo Volcanic Zone. They provide time planes that can be correlated between different facies and basins. Individual tephras can often be distinguished on the basis of major and trace element glass chemistry, and Fe-Ti oxide composition. Approximately 51 different eruptive events may be recorded in the interval from ca. 1.7 Ma to 0.5 Ma. Early Pleistocene tephras in deep-sea sediments of the Southern Pacific Ocean at latitudes >60 degrees S were previously considered to have been sourced in the TVZ. However, their alkalic compositions are compatible only with volcanoes of Western Antarctica and the Ross Sea region. Most of the tephras examined here are reworked, and many have been emplaced as catastrophic flood deposits in overbank settings of braid plains in the East Coast region. Their mode of emplacement and the presence of ignimbrites in the sequences indicate early Pleistocene transport routes through the site of the present main Axial Ranges, and suggest substantial tectonic uplift in the last 0.8 Ma. Long sequences spanning the Jaramillo Subchron (0.99-1.07 Ma) and older Matuyama Chron are recognised at Mangatewaiiti and Mangatewainui in the East Coast region, and Rewa Hill in the Rangitikei Valley. Numerical age control is provided by 40Ar/39Ar single crystal laser fusion ages from plagioclase in key tephra horizons. This new chronology indicates the tephras are nearly twice as old as several previous studies have suggested, thus requiring a major revision of the New Zealand Pleistocene stratigraphy. By integrating isotopic, paleomagnetic and geochemical data, 3 widespread tephras can be correlated between basins of the East Coast and Wanganui: Pakihikura Tephra (ca. 1.6 Ma), Potaka Tephra (1.00 Ma), and Kaukatea Tephra (ca. 1 Ma). These tephras and others provide a chronological framework for much of the early Pleistocene in southern North Island. Potaka Tephra is particularly widespread, allowing correlation between marine strata of the Castlecliffian (local early Pleistocene stage) type section at the Wanganui coast, and marine strata elsewhere in the Wanganui basin, as well as with fluvial and lacustrine strata in the East Coast. The tephra occurs as an ignimbrite and as a catastrophic flood deposit in the East Coast and as a fallout ash in North Canterbury, South Island (ca. 600 km from source). Potaka Tephra (normal polarity) and Kaukatea Tephra (reversed polarity) bracket the top of the Jaramillo Subchron and constrain its age to ca. 1 Ma. This is in accord with the astronomical calibration of the Pleistocene geomagnetic time scale, but older than previous determinations using the 'chronogram' method on K-Ar data. The precise source vents for the distal early Pleistocene tephras are uncertain, however their ages indicates they are coeval with dated proximal ignimbrite sheets from the Mangakino Caldera in the SW part of TVZ. The large number of distal tephras would imply a greater frequency of eruptions from this source than previously expected.</p>

Early Pleistocene

Geochronology

Overbank

Magnetostratigraphy

Diachronous

10.26686/wgtn.16958836.v1

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Citations (1)

All Toba Tephra Occurrences across Peninsular India Belong to the 75,000 yr B.P. Eruption

Quaternary Research (1998)

John A. Westgate Phil Shane Nicholas J.G. Pearce William T. Perkins Ravi Korisettar

A controversy currently exists regarding the number of Toba eruptive events represented in the tephra occurrences across peninsular India. Some claim the presence of a single bed, the 75,000-yr-old Toba tephra; others argue that dating and archaeological evidence suggest the presence of earlier Toba tephra. Resolution of this issue was sought through detailed geochemical analyses of a comprehensive suite of samples, allowing comparison of the Indian samples to those from the Toba caldera in northern Sumatra, Malaysia, and importantly, the sedimentary core at ODP Site 758 in the Indian Ocean—a core that contains several of the earlier Toba tephra beds. In addition, two samples of Toba tephra from western India were dated by the fission-track method. The results unequivocally demonstrate that all the presently known Toba tephra occurrences in peninsular India belong to the 75,000 yr B.P. Toba eruption. Hence, this tephra bed can be used as an effective tool in the correlation and dating of late Quaternary sedimentary sequences across India and it can no longer be used in support of a middle Pleistocene age for associated Acheulian artifacts.

Caldera

Sequence (biology)

10.1006/qres.1998.1974

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Citations (161)

Eruption recurrence rates in a basaltic volcanic field based on tephra layers in maar sediments: Implications for hazards in the Auckland volcanic field

Geological Society of America Bulletin (2009)

Catherine Molloy Phil Shane Paul Augustinus

Research Article| November 01, 2009 Eruption recurrence rates in a basaltic volcanic field based on tephra layers in maar sediments: Implications for hazards in the Auckland volcanic field Catherine Molloy; Catherine Molloy 1 School of Geography, Geology & Environmental Science, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand Search for other works by this author on: GSW Google Scholar Phil Shane; Phil Shane 1 School of Geography, Geology & Environmental Science, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand †E-mail: pa.shane@auckland.ac.nz Search for other works by this author on: GSW Google Scholar Paul Augustinus Paul Augustinus 1 School of Geography, Geology & Environmental Science, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand Search for other works by this author on: GSW Google Scholar Author and Article Information Catherine Molloy 1 School of Geography, Geology & Environmental Science, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand Phil Shane 1 School of Geography, Geology & Environmental Science, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand Paul Augustinus 1 School of Geography, Geology & Environmental Science, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand †E-mail: pa.shane@auckland.ac.nz Publisher: Geological Society of America Received: 08 Apr 2008 Revision Received: 05 Oct 2008 Accepted: 09 Oct 2008 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2009 Geological Society of America GSA Bulletin (2009) 121 (11-12): 1666–1677. https://doi.org/10.1130/B26447.1 Article history Received: 08 Apr 2008 Revision Received: 05 Oct 2008 Accepted: 09 Oct 2008 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Catherine Molloy, Phil Shane, Paul Augustinus; Eruption recurrence rates in a basaltic volcanic field based on tephra layers in maar sediments: Implications for hazards in the Auckland volcanic field. GSA Bulletin 2009;; 121 (11-12): 1666–1677. doi: https://doi.org/10.1130/B26447.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Long-term eruption recurrence rates in monogenetic basaltic volcanic fields are difficult to assess because of low eruption frequencies, but they are important because of the spread of human infrastructure into such fields. Auckland City, New Zealand, is built on the Auckland volcanic field, a young (<250 ka) basaltic volcanic field. In the absence of abundant material for radiocarbon and isotopic dating, an eruptive chronology based on basalt tephra layers deposited in maar lakes was developed. Interbedded, well-dated tephra layers from silicic volcanoes some 220–270 km to the south were used as age constraints. The basalt tephra layers reveal a pattern of activity not evident from the temporal-spatial distribution of volcanic landforms. Twenty-four basalt tephra layers over the last 80 k.y. represent an average frequency of one per 3.5 k.y. Recurrence times vary from <0.5 k.y. to 20 k.y. and show no temporal trend. The tephra record shows a major "flare-up" in explosive activity at 32 ± 2 ka during heightened activity at 34–24 ka. This was related to a period of simultaneous eruptions from several volcanoes across the field revealed by paleomagnetic and isotopic ages. In contrast, the field has been relatively quiet during the last 20 k.y., punctuated by the construction of a shield volcano at 0.7 ka. Thus, the surface manifestation of magmatism varies greatly with time, complicating long-term volcanic hazard forecasting. Despite the high risk from future basalt activity because of proximity, ash fall from distant andesite volcanoes is the most frequently occurring volcanic hazard in Auckland City. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

10.1130/b26447.1

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Citations (119)

Volcanic Stratigraphy and Geochemistry of the Soufrière Volcanic Centre, Saint Lucia with Implications for Volcanic Hazards

AGUFM (2012)

Jan M. Lindsay Axel K. Schmitt Robert B. Trumbull Daniel F. Stöckli Phil Shane

Volcanic hazards

Source

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Citations (0)

Glass chemistry, paleomagnetism, and correlation of middle Pleistocene tuffs in southern North Island, New Zealand, and Western Pacific

New Zealand Journal of Geology and Geophysics (1991)

Phil Shane P. C. Froggatt

Abstract New Zealand middle Pleistocene (Castlecliffian) rhyolitic tuffs older than 0.5 Ma are characterised on the basis of glass chemistry and paleomagnetism for the purpose of correlation. Of the tuffs examined, Rewa Pumice (c. 0.74 Ma), Potaka Pumice (c. 0.64 Ma), and Lower Te Muna Tephra (c. 0.75 Ma) are particularly widespread marker horizons. Their proven proximity to the Brunhes‐Matuyama paleomagnetic reversal provides a useful framework for correlation and absolute age control between regions in southern North Island— Wanganui, Wairarapa, and Hawke's Bay—and with deep‐sea cores from the Western Pacific. The tuffs allow correlation between a diverse range of sedimentary facies including marine, freshwater, and terrestrial, and provide absolute age control for thick sequences of unfossiliferous strata in Wairarapa and Hawke's Bay. The characterisation and correlation of the tuffs has a number of implications for Castlecliffian paleoclimatic, tectonic, and stratigraphic studies. The Rewa Pumice is contained in periglacial facies, and we assign it to oxygen isotope stage 20. Some tuffs in Hawke's Bay contain charcoal and are considered to be derived from ignimbrites. Their presence implies that the main axial ranges in Hawke's Bay were uplifted after 0.6 Ma. Previous lithostratigraphic correlations from the Castlecliffian stratotype along the Wanganui coast to sections across the Wanganui Basin, which contain radiometrically dated tuffs, are not sustainable, suggesting greater facies variations than hitherto assumed. The sequence of strata in the Rangitikei section containing the Rewa and Potaka Pumices is not a correlative of Kaimatira Pumice Sand at the coast section. Previous tuff correlations were made on the basis of age and mineralogy. Only the integrated use of glass chemistry and paleomagnetism allows correlation of tuffs in this time interval.

Pumice

Tephrochronology

Volcanic glass

Radiometric dating

10.1080/00288306.1991.9514458

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Citations (44)

The prevalence of plagioclase antecrysts and xenocrysts in andesite magma, exemplified by lavas of the Tongariro volcanic complex, New Zealand

Contributions to Mineralogy and Petrology (2019)

Phil Shane Kate Cocker Alisha Coote Claudine H. Stirling Malcolm Reid

Phenocryst

Basaltic andesite

10.1007/s00410-019-1626-y

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Citations (22)