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| Titel |
A Holocene speleothem record from Morocco, NW Africa |
| VerfasserIn |
Jasper Wassenburg, Jan Fietzke, Detlev Richter, Adrian Immenhauser |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250040849
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| Zusammenfassung |
| A well dated Holocene speleothem (stalagmite) from the Middle Atlas Mountains in
Morocco has been investigated for its continental climate record. The aim is to compile an
improved understanding of the climatically complex triple point of the North Atlantic,
Mediterranean and Saharan / Monsoonal climate realms in NW Africa. At present, only few
studies concerning continental climate reconstructions from NW Africa have been published
(Lamb et al. 1995, Cheddadi et al. 1998, Genty et al. 2006). Given the significance of this
region, this lack of data forms a strong motivation for additional, well dated climate
records.
The speleothem (GP2) was sampled in the “Grotte de Piste” (ca 800 m above sea level),
mean annual precipitation is about 930 mm (mainly falling in the winter season) and the
mean annual temperature is about 13Ë C. GP2 is 60 cm tall and grew – based on U/Th
MC-ICP-MS data – continuously between 11.5 kyr BP (early Holocene) and 2.9 kyr BP
(late Holocene). X-Ray Diffraction data indicate a mainly aragonitic mineralogy.
”Hendy tests” suggest that CaCO3 precipitation was close to isotopic equilibrium with
respect to oxygen isotopes, however kinetic effects might have influenced carbon
isotopes.
Carbon and oxygen isotope data have been measured along a transect with increments of
approximately 1 mm representing a resolution of about 15 yrs. Highly covariant oscillations
in δ13C and δ18O with an average cyclicity of about 410 yrs. are observed. These oscillations
coincide with macroscopically visible high density and low density layers, possibly
reflecting a higher or lower amount of inclusions and perhaps higher and lower growth
rates.
Geochemical analysis of speloan aragonite is accompanied by cave monitoring that has
started in November 2009. Parameters quantified include: drip water parameters, cave air
humidity, pCO2 and cave air temperature. Precipitation experiments using watch glasses will
also be performed.
References
Cheddadi, R., Lamb, H. F., Guiot, J., van der Kaars, S. 1998: Holocene climatic change in
Morocco: a quantitative reconstruction from pollen data. Climate Dynamics, 14,
883-890
Genty, D., Blamart, D., Ghaleb, B., Plagnes, V., Causse, Ch., Bakalowicz, M., Zouari, K.,
Chikr, N., Hellstrom, J., Wainer, K., Bourges, F. 2006: Timing and dynamics of the last
deglaciation from European and North African delta C-13 stalagmite profiles – comparison
with Chinese and South Hemisphere stalagmites. Quaternary Science Reviews, 25,
2118-2142
Lamb, H. F., Gasse, F., Benkaddour, A., El Hamouti, N., van der Kaars, S., Perkins, W. T.,
Pearce, N. J., Roberts, C. N. 1995: Relation between century-scale Holocene arid intervals in
tropical and temperate zones. Nature, 373, 134-137 |
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