Mineralogical and textural discrimination of loess derived from a tephra near Rotorua, New Zealand

Benny, LA; Kennedy, N. M.; Kirkman, J. H.; Stewart, R. B.

doi:10.1071/sr9880301

Cited by 7 publications

(5 citation statements)

References 18 publications

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“…In New Zealand, anomalous thicknesses associated with tephra distribution patterns in sequences of last-glacial age led to the recognition of tephric loess overlying primary tephras (Vucetich and Pullar, 1969). An aeolian origin for such material both in New Zealand and elsewhere has been supported subsequently by grain-size, mineralogical, and quartz isotopic analyses (e.g., Benny et al, 1988;Mizota et al, 1990;Alloway et al, 1992;Yoshinga et al, 1992). Rain flushing through ash clouds may also lead to locally-overthickened tephra deposits (e.g., Kobayashi et al, 2005).…”

Section: Reworking Of Tephras and Taphonomic Considerationsmentioning

confidence: 96%

Tephrochronology and its application: A review

Lowe

2011

Quaternary Geochronology

643

535

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Tephrochronology (from tephra, Gk "ashes") is a unique stratigraphic method for linking, dating, and synchronizing geological, palaeoenvironmental, or archaeological sequences or events. As well as utilizing the Law of Superposition, tephrochronology in practise requires tephra deposits to be characterized (or "fingerprinted") using physical properties evident in the field together with those obtained from laboratory analyses. Such analyses include mineralogical examination (petrography) or geochemical analysis of glass shards or crystals using an electron microprobe or other analytical tools including laser-ablation-based mass spectrometry or the ion microprobe. The palaeoenvironmental or archaeological context in which a tephra occurs may also be useful for correlational purposes. Tephrochronology provides greatest utility when a numerical age obtained for a tephra or cryptotephra is transferrable from one site to another using stratigraphy and by comparing and matching inherent compositional features of the deposits with a high degree of likelihood. Used this way, tephrochronology is an age-equivalent dating method that provides an exceptionally precise volcanic-event stratigraphy. Such age transfers are valid because the primary tephra deposits from an eruption essentially have the same short-lived age everywhere they occur, forming isochrons very soon after the eruption (normally within a year).As well as providing isochrons for palaeoenvironmental and archaeological reconstructions, tephras through their geochemical analysis allow insight into volcanic and magmatic processes, and provide a comprehensive record of explosive volcanism and recurrence rates in the Quaternary (or earlier) that can be used to establish time-space relationships of relevance to volcanic hazard analysis.The basis and application of tephrochronology as a central stratigraphic and geochronological tool for Quaternary studies are presented and discussed in this review. Topics covered include principles of tephrochronology, defining isochrons, tephra nomenclature, mapping and correlating tephras from proximal to distal locations at metre-through to sub-3 millimetre-scale, cryptotephras, mineralogical and geochemical fingerprinting methods, numerical and statistical correlation techniques, and developments and applications in dating including the use of flexible depositional age-modelling techniques based on Bayesian statistics.Along with reference to wide-ranging examples and the identification of important recent advances in tephrochronology, such as the development of new geoanalytical approaches that enable individual small glass shards to be analysed near-routinely for major, trace, and rare-earth elements, potential problems such as miscorrelation, erroneous-age transfer, and tephra reworking and taphonomy (especially relating to cryptotephras) are also examined. Some of the challenges for future tephrochronological studies include refining geochemical analytical methods further, improving understanding of cryptotephra dis...

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Section: Reworking Of Tephras and Taphonomic Considerationsmentioning

confidence: 96%

Tephrochronology and its application: A review

Lowe

2011

Quaternary Geochronology

643

535

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“…Some loess on the North Island has formed by aeolian reworking of tephras. These volcanic or tephric loess deposits are best developed in central North Island generally close to source volcanoes (Lowe, 1986;Alloway et al, 1988;Benny et al, 1988;Kennedy, 1988).…”

Section: Loessmentioning

confidence: 99%

Towards a climate event stratigraphy for New Zealand over the past 30 000 years (NZ‐INTIMATE project)

Alloway

Lowe

Barrell

et al. 2006

J Quaternary Science

307

288

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“…Because the Okareka eruption was also followed by continuing wind erosion and redeposition of tephric loess (Benny et al 1988), most measurements of Okareka Ash thickness are probably overestimates (Pullar 1973). Data from N. Kennedy (pers.…”

Section: Okareka Ashmentioning

confidence: 99%

“…(Wilson et al 1988). However, no further details of the Te Rere and Okareka eruptions have been published, apart from a study of the tephric loess which overlies the Okareka Ash (Benny et al 1988). The present paper records new data collected on the Te Rere and Okareka eruptive episodes, mostly obtained during regional mapping of the Okataina Volcanic Centre (Nairn 1981(Nairn ,1989.…”

Section: Introduction and Previous Workmentioning

confidence: 99%

The Te Rere and Okareka eruptive episodes — Okataina Volcanic Centre, Taupo Volcanic Zone, New Zealand

Nairn

1992

New Zealand Journal of Geology and Geophysics

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The Te Rere and Okareka eruptive episodes occurred within the Okataina Volcanic Centre at c. 21 000 and 18 000 yr B.P., respectively. The widespread rhyolitic pumice fall deposits of Te Rere Ash (volume 5 km 3 ) and Okareka Ash (6 km 3 ) are only rarely exposed in near-source areas, and locations of their vent areas have been uncertain. New exposures and petrographic and chemical analyses show that the Te Rere episode eruptions occurred from multiple vents, up to 20 km apart, on the Haroharo linear vent zone. The Okareka episode eruptions occurred from vents since buried beneath the Tarawera volcanic massif. Eruption of the rhyolitic Okareka pumice fall was immediately preceded by a small basaltic scoria eruption, apparently from vents close to those for the following rhyolite eruptions. Dacitic mixed pumices scattered within the rhyolite pumice layers immediately overlying the scoria were formed by mixing of the basalt and rhyolite magmas. The Te Rere and Okareka pyroclastic eruptions were both followed by extrusion of voluminous rhyolite lavas. These eruptive episodes mark the commencement of growth of the present-day Haroharo and Tarawera volcanic complexes.

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Mineralogical and textural discrimination of loess derived from a tephra near Rotorua, New Zealand

Cited by 7 publications

References 18 publications

Tephrochronology and its application: A review

Tephrochronology and its application: A review

Towards a climate event stratigraphy for New Zealand over the past 30 000 years (NZ‐INTIMATE project)

The Te Rere and Okareka eruptive episodes — Okataina Volcanic Centre, Taupo Volcanic Zone, New Zealand

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