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| Titel |
Interpreting δ18O and δ13C of two co-eval calcite and aragonite speleothems supported by cave monitoring from Grotte de Piste, Morocco |
| VerfasserIn |
Jasper A. Wassenburg, Christoph Spoetl, Hai Cheng, Klaus Peter Jochum, Andrea Niedermayr, Detlev K. Richter, Adrian Immenhauser, Denis Scholz |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250135719
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| Publikation (Nr.) |
 EGU/EGU2016-16618.pdf |
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| Zusammenfassung |
| Interpreting speleothem δ18O and δ13C records can be challenging. Although these proxies
can be affected by various processes taking place within the cave environment, δ18O values
commonly reflect local and regional atmospheric and hydrological processes, whereas δ13C
values are rather controlled by local processes only, such as type of vegetation (C3 versus
C4), soil CO2 production, cave air circulation, and drip rate. In order to relate speleothem
stable isotope data to the exterior climate, monitoring of the local meteoric rainfall and
drip water isotope composition, and temperature is necessary. In the case of δ18O
values, it is important to assess whether the speleothem reflects the δ18O value
of meteoric precipitation or whether there are significant isotope effects due to
evapo-transpiration and/or other processes occurring within the karst environment. In
addition, net infiltration is commonly restricted to a particular season, and speleothem
growth may be seasonal. Hence speleothem δ18O values may be biased to a specific
season.
Here we present the results of two years (2011-2012) of monitoring of the δ18O values of
spring water, meteoric rainfall and cave drip water in Grotte de Piste, NW Middle Atlas,
Morocco. Watch glass experiments were performed at the monitored drip sites
that correspond to an actively growing calcite stalagmite (GP7) and an actively
growing aragonite stalagmite (GP5). This enabled us to assess the link between
the δ18O values of the rainfall, the drip water, the associated CaCO3 precipitates
and the stalagmite δ18O values of both polymorphs. In addition, δ18O and δ13C
values of both stalagmites were analyzed at 5-year or higher resolution for the last
600 years. As expected, a systematic isotopic offset between the calcite and the
aragonite stalagmite can be observed. This is approximately 0.86 ‰ for δ18O and 0.88
‰ for δ13C. However, both stalagmites show similar trends in their δ18O and δ13C
records, even though speleothem growth rates differ considerably. This replication test
increases the confidence that these stalagmites recorded an environment signal. |
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