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| Titel |
Paleointensity study on obsidians of Pleistocene Age from Armenia |
| VerfasserIn |
Sandra Frank, Annika Ferk, Uwe Kirscher, Roman Leonhardt, Khachatur Meliksetian, Kai-Uwe Hess, Donald Dingwell, Valerian Bachtadse |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250099736
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| Publikation (Nr.) |
 EGU/EGU2014-15552.pdf |
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| Zusammenfassung |
| Volcanic glass is often considered an ideal recording material for paleointensities.
Experiments to determine the ancient field intensity are time consuming and mostly have low
success rates. Studies have shown that the usage of glassy samples can increase success rates
very much as the remanence carriers are in or close to the single domain range. However, it
was found that hydration and/or devitrification may falsify the results and maybe hard to
identify. Here we investigate up to ~6 myr old subaerial obsidians of rhyolitic composition
from Armenia to examine time dependencies in such processes and to obtain high
quality field records. We present data from 60 subaerial obsidian samples from
nine volcanic structures of Armenia. Almost all samples show a linear directional
component which trends towards the origin of projection in both thermal and alternating
field demagnetization experiments. The 1.75 and ~6myr old glasses are inversely
magnetized while all other samples show normal polarity. Titanomagnetites with
varying titanium content and Curie temperatures at 190 to 270°C and 530° to 570°C,
respectively, were revealed to be the remanence carriers. Almost all thermomagnetic
curves are reversible underlining the thermal stability of the material. Thellier-type
experiments with alteration and tail checks were used to determine paleointensities.
Virtual axial dipole moments of 4.6*1022 Am2 (0.5Ma), 8.6*1022 Am2 (0.65Ma),
9.4*1022 Am2 (1.5Ma), 6.9*1022 Am2 and 7.3*1022 Am2 (~6 Ma) were found
which agrees well with published reference data (Channell et al., 2009). The thermal
stability, low alteration and good accordance with other data support the suitability
of glassy materials for geomagnetic field studies and also shows the potential of
subaerial obsidian to identify the source areas of prehistoric obsidian artefacts. |
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