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Dating of Evaporites

Research areas: Geochemistry, Geochronology

Principal investigators: Prof. Dr. Carsten Münker, Dr. Daniel Herwartz


Project Info

Understanding the chronology of arid and hyperarid environments is of pivotal importance in order to constrain the coupled evolution of biosphere and Earth surface processes through time. The Atacama Desert, chosen as natural laboratory for this CRC initiative, apparently belongs to the oldest deserts on Earth, with a proposed >23 Ma history of aridity. Direct dating of aridity in the Atacama Desert has so far relied on cosmogenic nuclide dating of preserved surfaces and on K-Ar dating of supergene minerals in ore deposits, both only providing indirect age estimates for the onset of aridity.

Here we present a novel geochronological approach to date the evolution of aridity in the Atacama desert, by employing 176Lu-176Hf and 238U-230Th chronometry to evaporite minerals, the formation of which directly dates the onset of (hyper)arid conditions and intermittent humid events. Our study will largely focus on carbonates, gypsum, bassanite and anhydrite, all being widespread in the Atacama Desert. Employing the two chronometers to these minerals was long hampered by their extremely low abundances of U-Th-Lu-Hf. The advent of new analytical protocols with increased sensitivity, namely Multicollector ICP Mass Spectrometry (MC-ICPMS), now enables sufficiently precise and accurate isotope ratio measurements of for as little as 1 ng of element and even less. Following the development of suitable analytical protocols, we will apply for the first time 176Lu-176Hf chronometry and also isochron-based 238U-230Th disequilibrium dating to evaporites. Our approach will be complemented by petrology, trace element geochemistry and XRD measurements. The 176Lu-176Hf chronometer (half life 37 Ga) can cover age ranges older than 1 million years, whereas 238U-230Th disequilibrium dating covers an age range up to ca. 0.4 Ma. The combination of the both chronometers will therefore permit to date formation of evaporites over virtually the complete age range proposed for the duration of aridity and possible intermittent humid periods in the Atacama Desert.

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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
© 2018 CRC1211 - Earth - Evolution at the Dry Limit