Correlation Techniques in Tephra Studies

Westgate, John A.; Gorton, Michael P.

doi:10.1007/978-94-009-8537-7_5

Cited by 128 publications

(101 citation statements)

References 31 publications

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“…Fe-Ti oxide compositions, determined in various ways, have proved useful in tephra correlation studies in New Zealand and elsewhere (e.g., Kohn 1970;Topping & Kohn 1973;Westgate & Gorton 1981;King et al 1982;Hogg & McCraw 1983). Kohn & Neall (1973) demonstrated that Tongariro tephras could be distinguished from those of Egmont by titanomagnetite chemistry as measured by emission spectrographic analysis.…”

Section: Fe-ti Oxidesmentioning

confidence: 99%

“…Because the EMP is a grain-discrete method, mixed populations in samples may be readily detected (e.g., Kohn 1979;Westgate & Gorton 1981;Hogg & McCraw 1983). Assuming that the above differences in Crp3 and MnO concentrates in the titanomagnetites are reliable indicators of a Tongariro or Egmont source, the analyses showed that some samples may contain admixed Tongariro and Egmont derived grains.…”

Section: Fe-ti Oxidesmentioning

confidence: 99%

See 1 more Smart Citation

Stratigraphy, age, composition, and correlation of late Quaternary tephras interbedded with organic sediments in Waikato lakes, North Island, New Zealand

Lowe

1988

New Zealand Journal of Geology and Geophysics

139

203

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Cores from 14 peaty lakes in the central Waikato region, northern North Island, contain a sequence of 41 well-preserved, mainly macroscopic, occasionally bedded, ash and lapilli layers ranging in thickness from c. 2 to 110 mm and interbedded with fine-grained organic lake sediment. The layers, whose field and compositional properties are described in detail, are distal airfall tephras that were erupted between c. 17 000 and c. 1800 1 4 C years ago from six rhyolitic and andesitic volcanic centres located c. 70-200 km from the Waikato sites: Taupo (5 tephras), Okataina (7), Maroa (1) (rhyolitic); Mayor Island (2) (peralkaline); Tongariro (11), and Egmont (15) (andesitic).These sources were distinguished using the tephras' mineralogical assemblages and glass and mineral compositions (determined by electron microprobe). The tephras were correlated with named proximal eruptives using their strati graphic relationships and radiometric ages (based on multiple 14C dates on enclosing lake sediment) in combination with the mineralogical and chemical criteria. The correlated tephras associated with each source (listed youngest to oldest) are: Taupo- Taupo,

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Section: Fe-ti Oxidesmentioning

confidence: 99%

Section: Fe-ti Oxidesmentioning

confidence: 99%

Stratigraphy, age, composition, and correlation of late Quaternary tephras interbedded with organic sediments in Waikato lakes, North Island, New Zealand

Lowe

1988

New Zealand Journal of Geology and Geophysics

139

203

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“…This tephra resembles Mazama tephra, based on electron microprobe analysis of glass-encased titanomagnetites and glass shard morphology (BEAUDOIN, 1984;BEAUDOIN and KING, 1986). The Mazama tephra in the western Cordillera is dated at 6700 yr BP (WESTGATE and GORTON, 1981). Dates for intermediate parts of the record are estimated by assuming constant sedimentation rates between the dated layers.…”

Section: Methodsmentioning

confidence: 99%

Using Picea/Pinus Ratios from the Wilcox Pass Core, Jasper National Park, Alberta, to Investigate Holocene Timberline Fluctuations

Beaudoin¹

2007

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Holocene timberline fluctuations are investigated using Picea/Pinus ratios from the tephra and radiocarbon-dated Wilcox Pass Core (52°14'N, 117°13'W). Timberline elevations are calibrated by comparing Picea/Pinus ratios from the core with modern ratios obtained in surface samples of a transect from alpine vegetation in Wilcox Pass into subalpine forest in adjacent Sunwapta Pass. Ratios higher than present ratios from the site imply higher-than-present timberline elevation. The Picea/Pinus ratios imply higher-than-present timberline between ca. 6540-1480 yr BP, with a minimum about 4210 yr BP, while timberline was lower than present between ca. 1480 - 540 yr BP and increased in elevation after 540 yr BP. This record substantially agrees with other palaeoenvironmental records from the region. The main limitation on the technique is that it can only be applied since similar-to-present vegetation became established in the area. Hence, Piceal Pinus ratios from the Wilcox Pass core prior to ca. 6540 yr BP cannot readily be interpreted by this method.On a pu évaluer les différentes altitudes de la limite des arbres en comparant les taux de Picea et de Pinus présents dans la carotte, qui a été datée au radiocarbone et par tephrochronologie, avec les taux actuels enregistrés dans des échantillons de surface le long d'un tracé qui s'étend de Wilcox Pass, en végétation alpine, jusqu'à Sunwapta Pass tout près, en forêt subalpine. Les plus forts taux de pollen observés dans la carotte que dans les échantillons de surface démontrent que la limite des arbres était à une altitude supérieure entre environ 6540 et 1480 BP que maintenant, avec un minimum vers 4210 BP. Par contre, la limite des arbres était inférieure à maintenant entre environ 1480 et 540 BP, pour s'élever de nouveau après 540 BP. Ces observations concordent en grande partie avec d'autres études paléoenvironnementales effectuées dans la région. La technique ne peut toutefois s'appliquer qu'à partir du moment où le même type de végétation que celui que l'on trouve aujourd'hui s'est déjà manifesté. Pour cette raison, les taux de Picea et de Pinus enregistrés dans la carotte de Wilcox Pass avant 6540 BP environ ne peuvent être interprétés à l'aide de cette méthode.Die Fluktuationen der Baumgrenze im Holozàn werden unter Nutzung der Picea/Pinus-Anteile des mittels Tephra und Radiokarbon datierten Wilcox Pass-Probe (117°13'W, 52°14'N) untersucht. Die verschiedenen Hôhen der Baumgrenze wurden kalibriert, indem man Picea/Pinus-Anteile der Probe verglich mitgegenwârtigen Anteilen, welche aus Oberflàchenproben entlang einem Làngsschnitt gewonnen wurden, der von der alpinen Vegetation im Wilcox Pass bis zum subalpinen WaId im angrenzenden Sunwapta Pass reicht. Hôhere Anteile als die gegenwàrtigen von dieser Stelle bedeuten, daB die Baumgrenze hôher war als gegenwàrtig. Die Picea/Pinus-Anteile lassen fur die Zeit zwischen etwa 6540 — 1480 Jahren v.u.Z. auf eine hôhere Baumgrenze als gegenwàrtig schliepen mit einem Minimum vor etwa 4210 Jahren v.u.Z., als die Baumgrenze niedri...

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“…As well as studies on distal tephra deposits preserved in sediments, and in soils or palaeosols, new laboratory methods for characterizing the glass-shard and crystal (mineral) components of tephra deposits were being developed in a period of substantial technical advancement (e.g. Kohn 1970;Sarna-Wojcicki 1976;Westgate & Gorton 1981;Beaudoin & King 1986). These methods included the innovative use of the electron microprobe, developed mainly through the 1970s and 1980s, to obtain major element compositions of individual glass shards rather than bulk samples (Smith & Westgate 1968;Froggatt 1983Froggatt , 1992Hunt & Hill 1996).Its advent in 1968 a stroke of brilliance, the microprobe method for glass analysis, initially criticised by some 'traditional' volcanic petrologists and geo-analysts, has been widely adopted today as the cornerstone analytical technique in tephra studies used alongside stratigraphic, chronological, and mineralogical data to help enable correlations to be made (Froese et al 2008a;Lowe 2011).…”

Section: Tephrochronological Advancesmentioning

confidence: 99%

Marine tephrochronology: a personal perspective

Lowe

2014

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IntroductionThis special volume on marine tephrochronology is remarkable, and timely, because it marks a concerted step towards what might be informally termed 'phase 3' of a revolution in Quaternary geosciences that began around 40 years ago. The ten articles collectively represent a re-focussed examination of tephras and cryptotephras preserved in ocean sediments at various locations and the authors describe their significance for a range of subdisciplines. Eight provide a new understanding of the origin, distribution, and ages of various tephra and cryptotephra deposits and their stratigraphic inter-relationships; how the terrestrial ages of the tephra/crypotephra deposits relate to those of enclosing sediments and inform the ongoing development of the marine radiocarbon time-scale; mechanisms for the emplacement, remobilisation, or bioturbation of the tephras or cryptotephras; and volcanic eruption history. Two further articles document the characterization of tephra-derived glass shards using microbeam techniques to analyse 3040 elements from individual shards as small as 10 µm in diameter. The collection thus provides snapshots of many aspects of the latest developments and directions in tephra studies -volcanology, primary and secondary dispersal, stratigraphy, single-grain characterization, chronology -through the medium of marine sediments. My personal perspective reflects briefly on how this point was reached and identifies a few of the important milestones on the way from 'phase 1' to 'phase 3'. I am privileged to write it.3

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Correlation Techniques in Tephra Studies

Cited by 128 publications

References 31 publications

Stratigraphy, age, composition, and correlation of late Quaternary tephras interbedded with organic sediments in Waikato lakes, North Island, New Zealand

Stratigraphy, age, composition, and correlation of late Quaternary tephras interbedded with organic sediments in Waikato lakes, North Island, New Zealand

Using Picea/Pinus Ratios from the Wilcox Pass Core, Jasper National Park, Alberta, to Investigate Holocene Timberline Fluctuations

Marine tephrochronology: a personal perspective

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