Magnetic characterisation and correlation of a Younger Dryas tephra in North Atlantic marine sediments

Peters, C.; Austin, William E. N.; Walden, John; Hibbert, Fiona D.

doi:10.1002/jqs.1320

Cited by 20 publications

(24 citation statements)

References 48 publications

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“…Measurements of magnetic susceptibility and other magnetic parameters such as isothermal remanent magnetization have been used successfully as correlation tools in tephra-related studies (e.g., Palmer and Pillans, 1996;Gonzalez et al, 1999;Newnham et al, 1999b;Xia et al, 2007;Peters et al, 2010;Venuti and Verosub, 2010). Wagner et al (2008) warned that high magnetic susceptibility values in lake sediments in their European study related to detrital magnetic minerals rather than tephra or cryptotephra layers, however, a finding echoed in part by Veres et al (2008).…”

Section: Magnetostratigraphymentioning

confidence: 96%

“…Techniques used to detect and map cryptotephras or thin, visible tephras include field or ship-board instruments such as core scanners and magnetic susceptibility meters (e.g., Vogel et al, 2009;Brendryen et al, 2010;Peters et al, 2010). Some techniques are destructive, others are not (Gehrels et al, 2008).…”

Section: Cryptotephrasmentioning

confidence: 99%

“…A technique central to most cryptoephra studies is the enumeration of glass-shard concentrations (e.g., van den Bogaard et al, 1994;Dugmore et al, 1995;Hall and Pilcher, 2002;Turney et al, 2004;Gehrels et al, 2006;Kristjánsdóttir et al, 2007;Peters et al, 2010;Pyne-O"Donnell, in press). Such counting of shards (or crystals) requires the use of concentration techniques including ashing (burning) or step-wise acid or alkali digestion to remove enclosing organic matter such as by NaOH treatment (e.g., Rose et al, 1996;Hall and Pilcher, 2002), density separation by flotation to separate material (usually <2.5 g cm -3 unless basaltic) (Turney, 1998), or magnetic separation (e.g., Froggatt and Gosson, 1982;Mackie et al, 2002;O"Donnell, in press).…”

Section: Cryptotephrasmentioning

confidence: 99%

“…Glass-shard concentrations may be recorded as the number of shards counted (using a polarizing microscope and point counter) in either a set volume of wet sediment (usually 1 cm 3 ), or in a gram or milligram of dry sediment, hence resulting in units of shards per gram (or milligram) dry weight (e.g., Gehrels et al, 2006;Wastegård and Davies, 2009;Payne and Gehrels, 2010;Peters et al, 2010), or shards per cubic centimetre (Pyne-O"Donnell, in press).…”

Section: Cryptotephrasmentioning

confidence: 99%

See 3 more Smart Citations

Tephrochronology and its application: A review

Lowe

2011

Quaternary Geochronology

636

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: Magnetostratigraphymentioning

confidence: 96%

Section: Cryptotephrasmentioning

confidence: 99%

Section: Cryptotephrasmentioning

confidence: 99%

Section: Cryptotephrasmentioning

confidence: 99%

See 2 more Smart Citations

Tephrochronology and its application: A review

Lowe

2011

Quaternary Geochronology

636

535

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“…Gehrels et al (2008) reviewed several non-destructive approaches for detecting tephra in peat cores including: spectrophotometry, x-radiography, magnetic susceptibility, and X-ray fluorescence (XRF). Others have tried to use magnetic properties (Peters et al 2010), X-ray diffraction (Andrews et al 2006), and instrumental neutron activation analysis (Lim et al 2008). De Vleeschouwer et al (2008) applied petrography, scanning electron microscopy, and scanning XRF to resin-impregnated peat columns.…”

Section: Introductionmentioning

confidence: 99%

Investigating the Use of Scanning X-Ray Fluorescence to Locate Cryptotephra in Minerogenic Lacustrine Sediment: Experimental Results

Balascio

Francus

Bradley

et al. 2015

Micro-XRF Studies of Sediment Cores

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Methods to isolate and analyze low concentrations of tephra-cryptotephra-are destructive, time consuming, and can be prohibitive when sample size is limited, when looking for tephra over long stratigraphic intervals, or when sediments are minerogenic. Therefore, a more rapid, non-destructive approach to detecting cryptotephra would allow for wider application of tephrochronology and for more complete evaluation of tephra content within sedimentary profiles. In this experiment, we test the ability of scanning X-ray fluorescence to detect tephra glass shards with different composition, concentration, and grain-size in minerogenic lacustrine sediment. Synthetic sediment cores spiked with tephra were created in centrifuge tubes, which provided a simple means to introduce tephra in known positions and to replicate the process of analyzing real sediment cores. Background sediment was added incrementally and spun in a centrifuge to create a series of 20 laminations in 4 synthetic cores. Rhyolitic and basaltic tephra were added between laminations with different concentrations and using two grain-size ranges (< 53 µm and 105-177 µm). The synthetic cores were split and analyzed on an XRF core scanner, which produced a signal of element composition every 100 µm. Ti, Mn, and Si produced the strongest response to the rhyolitic tephra, and Ti, Mn, Fe, and Cu were most diagnostic of the basaltic tephra. Element ratios were also used to accentuate the difference in composition between tephra and the background sediment. We were able to identify a distinct elemental response across a few cryptotephra horizons, but in general the signal of tephra attenuated quickly with decreasing concentration. Comparison of the signal between different tephra grain-size fractions showed that grain-size was inversely related to the strength of the elemental response. We also compared these experimental results to XRF scans of a lake sediment core where basaltic and rhyolitic cryptotephra layers had previously been identified using conventional methods. The rhyolitic tephra did not produce a distinct elemental response, but the basaltic tephra was identified in the XRF data. These experiments provide new perspectives on the application and limitations of scanning XRF for cryptotephra studies.

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Identifying cryptotephra units using correlated rapid, nondestructive methods: VSWIR spectroscopy, X‐ray fluorescence, and magnetic susceptibility

McCanta

Hatfield

Thomson

et al. 2015

Geochem Geophys Geosyst

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Understanding the frequency, magnitude, and nature of explosive volcanic eruptions is essential for hazard planning and risk mitigation. Terrestrial stratigraphic tephra records can be patchy and incomplete due to subsequent erosion and burial processes. In contrast, the marine sedimentary record commonly preserves a more complete historical record of volcanic activity as individual events are archived within continually accumulating background sediments. While larger tephra layers are often identifiable by changes in sediment color and/or texture, smaller fallout layers may also be present that are not visible to the naked eye. These cryptotephra are commonly more difficult to identify and often require timeconsuming and destructive point counting, petrography, and microscopy work. Here we present several rapid, nondestructive, and quantitative core scanning methodologies (magnetic susceptibility, visible to shortwave infrared spectroscopy, and XRF core scanning) which, when combined, can be used to identify the presence of increased volcaniclastic components (interpreted to be cryptotephra) in the sedimentary record. We develop a new spectral parameter (BDI1000VIS) that exploits the absorption of the 1 mm nearinfrared band in tephra. Using predetermined mixtures, BDI1000VIS can accurately identify tephra layers in concentrations >15-20%. When applied to the upper $270 kyr record of IODP core U1396C from the Caribbean Sea, and verified by traditional point counting, 29 potential cryptotephra layers were identified as originating from eruptions of the Lesser Antilles Volcanic Arc. Application of these methods in future coring endeavors can be used to minimize the need for physical disaggregation of valuable drill core material and allow for near-real-time recognition of tephra units, both visible and cryptotephra.

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Magnetic characterisation and correlation of a Younger Dryas tephra in North Atlantic marine sediments

Cited by 20 publications

References 48 publications

Tephrochronology and its application: A review

Tephrochronology and its application: A review

Investigating the Use of Scanning X-Ray Fluorescence to Locate Cryptotephra in Minerogenic Lacustrine Sediment: Experimental Results

Identifying cryptotephra units using correlated rapid, nondestructive methods: VSWIR spectroscopy, X‐ray fluorescence, and magnetic susceptibility

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