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Stable isotopes: Development of a paleohumidity proxy from oxygen isotopes in Ca-sulfate hydration water

Research areas: Geochemistry, Climate research

Principal investigators: Dr. Daniel Herwartz, Prof. Dr. Michael Staubwasser


Project Info

This study seeks to systematically investigate aqueous isotope exchange of 16O-17O-18O and H-D between crystal water of hydrated Ca-sulphates (gypsum, bassanite) and principal types of Atacama desert water (water vapor, fog water, salt lakes and plant water). The purpose of this study is to determine if humidity- a key environmental parameter in deserts - can be directly inferred from the isotopic composition of gypsum hydration water (GHW) and plant water. 

After determination of the respective fractionation factors we aim to conduct experiments on possible exchange dynamics between gypsum powder and fog water. Selected transects and profiles will be investigated to test the theoretical and experimental constraints. We hypothesize that the purely mass dependent variation in 17O-excess can be used as a paleo humidity proxy.

In our pilot study we discovered that not only SO4 but also gypsum crystal water can carry a massindependent (MIF) 17O signature. This water carries a low δD signature (-100‰) implying that some crystal water in the Atacama is of stratospheric origin. In this project we aim to quantify the proportion of this stratospheric water (and thus gypsum) within natural samples and to determine how resistant this 17O enriched crystal water is to isotopic exchange. Such MIF water is probably only preserved under hyper arid conditions and may serve as a tool to identify (paleo-) hyper arid conditions.

Finally we suggest to analyze plant water to test (1) if plants utilize GHW as a water source and (2) if humidity can be inferred from the 17O-excess in leaf and stem water.

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Prof. Dr. Tibor J. Dunai
Institute of Geology and Mineralogy | University of Cologne
Zülpicher Str. 49b | 50674 Cologne
+49 (0)221 470-3229 | tdunai@uni-koeln.de
  Managing Director:
Christian Tiede
Institute of Geology and Mineralogy | University of Cologne

Zülpicher Str. 49b | 50674 Cologne
+49 (0)221 470-89833 | christian.tiede@uni-koeln.de
  Deputy Speaker:
Prof. Dr. Martin Melles
Institute of Geology and Mineralogy | University of Cologne

Zülpicher Str. 49a | 50674 Cologne
+49 (0)221 470-2262 | mmelles@uni-koeln.de
Tim Schlüter
Institute of Geography | University of Cologne

Otto-Fischer-Str. 4 | 50674 Cologne
+49 (0)221 470-3735 | webmaster@sfb1211.de
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