Norwegian Sea tephrostratigraphy of marine isotope stages 4 and 5: Prospects and problems for tephrochronology in the North Atlantic region

Brendryen, Jo; Haflidason, Haflidi; Sejrup, Hans Petter

doi:10.1016/j.quascirev.2009.12.004

Cited by 80 publications

(123 citation statements)

References 42 publications

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“…(5) lack of recognition that tephra desposits from one eruption episode may have "multiple fingerprints" temporally and spatially because of magmatic changes during their eruption (e.g., Shane et al, 2008a), or because of the presence of small mineral micro-inclusions chiefly in andesitic or basaltic glasses (described further below); (6) by tephras having closely similar and therefore ambiguous compositions -i.e., non-unique "fingerprints" (e.g., Brendryen et al, 2010); (7) by inappropriate geochemical analysis leading to faulty or inadequate characterization so that analytical data are compromised (e.g., Pearce et al, 2004b;Denton and Pearce, 2008); (8) by reworking of a tephra (or dispersal of cryptotephric glass shards or crystals) to a different stratigraphic position (e.g., Boygle, 1999;Dugmore et al, 2004;Gehrels et al, 2006;Shane et al, 2006;Payne and Gehrels, 2010;Pyne-O'Donnell, in press);…”

Section: Miscorrelation and Erroneous-age Transfermentioning

confidence: 99%

Tephrochronology and its application: A review

Lowe

2011

Quaternary Geochronology

649

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: Miscorrelation and Erroneous-age Transfermentioning

confidence: 99%

Tephrochronology and its application: A review

Lowe

2011

Quaternary Geochronology

649

535

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“…The purpose of this study was not, however, to obtain accurate concentration data for individual layers, but rather to identify relative downcore changes in compositions that might reflect variable abundance of volcanic material. In this context, XRF core-scanning is useful as it is a rapid, non-destructive and high-resolution technique that has, for example, previously been used in palaeoclimate (Palike et al, 2001) and tephrostratigraphy studies (Vogel et al 2010, Brendryen et al 2010Kylander et al 2012). …”

Section: Xrf-core Scanningmentioning

confidence: 99%

Construction of volcanic records from marine sediment cores: A review and case study (Montserrat, West Indies)

Cassidy

Watt

Palmer

et al. 2014

Earth-Science Reviews

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Detailed knowledge of the past history of an active volcano is crucial for the prediction of the timing, frequency and style of future eruptions, and for the identification of potentially at-risk areas. Subaerial volcanic stratigraphies are often incomplete, due to a lack of exposure, or burial and erosion from subsequent eruptions. However, many volcanic eruptions produce widelydispersed explosive products that are frequently deposited as tephra layers in the sea. Cores of marine sediment therefore have the potential to provide more complete volcanic stratigraphies, at least for explosive eruptions. Nevertheless, problems such as bioturbation and dispersal by currents affect the preservation and subsequent detection of marine tephra deposits.Consequently, cryptotephras, in which tephra grains are not sufficiently concentrated to form layers that are visible to the naked eye, may be the only record of many explosive eruptions.Additionally, thin, reworked deposits of volcanic clasts transported by floods and landslides, or during pyroclastic density currents may be incorrectly interpreted as tephra fallout layers, leading to the construction of inaccurate records of volcanism. This work uses samples from the volcanic island of Montserrat as a case study to test different techniques for generating volcanic eruption records from marine sediment cores, with a particular relevance to cores sampled in relatively proximal settings (i.e. tens of kilometres from the volcanic source) where volcaniclastic material may form a pervasive component of the sedimentary sequence. Visible volcaniclastic deposits identified by sedimentological logging were used to test the effectiveness of potential alternative volcaniclastic-deposit detection techniques, including point counting of grain types (component analysis), glass or mineral chemistry, colour spectrophotometry, grain size measurements, XRF core scanning, magnetic susceptibility and X-radiography. This study demonstrates that a set of time-efficient, non-destructive and high-spatial-resolution analyses (e.g. XRF core-scanning and magnetic susceptibility) can be used effectively to detect potential cryptotephra horizons in marine sediment cores. Once these horizons have been sampled, microscope image analysis of volcaniclastic grains can be used successfully to discriminate between tephra fallout deposits and other volcaniclastic deposits, by using specific criteria Page | 3 related to clast morphology and sorting. Standard practice should be employed when analysing marine sediment cores to accurately identify both visible tephra and cryptotephra deposits, and to distinguish fallout deposits from other volcaniclastic deposits.

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“…Tephra particles may sink through soft organic-rich sediments and occur lower in a core than its original stratigraphic position as described for the lake deposits (e.g., Beierle and Bond 2002). Tephra also can be deposited from icebergs with some delay and thus occur higher in the section (Brendryen et al 2010). In case of PL2 tephra in the core SO201-2-77KL, however, none of these complications seem likely because the PL2 ash (though bioturbated) forms quite a distinct layer (Dullo et al 2009), the axis of the distal ash coincides with that for the terrestrial PL2 tephra (Fig 11a), and the glaciers did not reach the coast in early Holocene, so iceberg formation at this time is unlikely (Melekestsev et al 1974).…”

Section: Marker Tephra Layers From Ploskymentioning

confidence: 99%