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| Titel |
The use of luminescence for dating young volcanic eruptions |
| VerfasserIn |
Christoph Schmidt, Maria Schaarschmidt, Thomas Kolb, Daniel Richter, Jean Pierre Tchouankoue, Ludwig Zöller |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250138254
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| Publikation (Nr.) |
 EGU/EGU2017-1222.pdf |
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| Zusammenfassung |
| Reliable chronologies of volcanic eruptions are vital for hazard analysis, but dating of
Holocene and Late Pleistocene volcanism poses a major challenge. Established techniques
such as 40Ar/39Ar are often problematic due to the long half-life of 40K or the absence of
datable materials. In this context, luminescence dating methods are an alternative since they
are applicable to Earth’s most common minerals and to a range of different datable
events.
Luminescence signal resetting during volcanic activity can be caused by heat (lava,
contact to lava), light (disintegration of ejecta) or (temperature-assisted) pressure in the
course of phreatomagmatic explosions. While volcanogenic minerals assembling basalt
or other volcanic rocks are less suitable for luminescence dating due to so-called
anomalous fading, the signal of volcanogenically heated or fragmented country rock
actually relates to the time of eruption as well and further provides reproducible
results.
This contribution aims to illustrate the potential of this latter approach by presenting two
case studies. The first refers to two Late Pleistocene scoria cones in the Westeifel Volcanic
Field (WEVF), Germany, of which the Wartgesberg locality was dated by 40Ar/39Ar and 14C,
while the closeby Facher Höhe is chronologically poorly constrained (Mertz et al. 2015; pers
comm. Luise Eichhorn, 2016). The former locality allows testing the accuracy of various
luminescence techniques (thermoluminescence, TL, optically stimulated luminescence, OSL,
infrared stimulated luminescence, IRSL) applied to quartz and feldspar against independent
age control. The other study site is the monogenetic Lake Nyos Maar as part of the Cameroon
Volcanic Line, having killed 1,700 people in 1986 following the release of large
amounts of CO2. Previous dating efforts of the last explosive activity are inconsistent
and yielded age estimates ranging from 400 a (14C) to >350 ka (K-Ar) (Aka et al.
2008).
Our results demonstrate that multiple luminescence methods (TL, OSL) yield equally
valid age estimates averaging to 33.6 ± 2.4 ka for the Wartgesberg site, in good agreement
with 40Ar/39Ar and 14C results. The Facher Höhe, however, is much younger than previously
expected with an average TL age of 15.5 ± 1.1 ka. This southeastern part of the WEVF thus
hosts many of the most recent eruption sites, which has important implications for studying
the causes of Eifel volcanism but also for assessing future eruption locations. Preliminary
findings suggest that the phreatomagmatic explosion of the Nyos Maar was capable of
completely resetting the inherited luminescence signal and indicate a significant
overestimation by K-Ar.
References
Aka, F.T., Yokoyama, T., Kusakabe, M., Nakamura, E., Tanyileke, G., Ateba, B., Ngako,
V., Nnange, J., Hell, J., 2008. U-series dating of Lake Nyos maar basalts, Cameroon (West
Africa): Implications for potential hazards on the Lake Nyos dam. Journal of Volcanology
and Geothermal Research 176, 212-224.
Mertz, D.F., Löhnertz, W., Nomade, S., Pereira, A., Prelevic, D., Renne, P.R., 2015.
Temporal–spatial evolution of low-SiO2 volcanism in the Pleistocene West Eifel volcanic
field (West Germany) and relationship to upwelling asthenosphere. Journal of Geodynamics
88, 59-79. |
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