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  Geochemical proxies for water-soil interactions in the hyperarid Atacama Desert, Chile

Arens, F. L., Airo, A., Feige, J., Sager, C., Wiechert, U., Schulze-Makuch, D. (2021): Geochemical proxies for water-soil interactions in the hyperarid Atacama Desert, Chile. - Catena, 206, 105531.
https://doi.org/10.1016/j.catena.2021.105531

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Arens, Felix L.1, Autor
Airo, Alessandro1, Autor
Feige, Jenny1, Autor
Sager, Christof1, Autor
Wiechert, Uwe1, Autor
Schulze-Makuch, Dirk2, Autor              
Affiliations:
1External Organizations, ou_persistent22              
23.7 Geomicrobiology, 3.0 Geochemistry, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum, ou_146043              

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Schlagwörter: Gypsum Anhydrite Stable isotopes Pedogenesis Hyperarid Atacama Desert
 Zusammenfassung: The Atacama Desert is the oldest and driest non-polar desert on Earth. Millions of years of hyperaridity enabled salt accumulations through atmospheric deposition. These salts can serve as proxies to decipher the interaction between water and soil as well as to understand the habitability with changing environmental settings. Therefore, we investigated four soil profiles regarding their mineralogy, salt abundance, and sulfate stable isotopic composition. The profiles were located along an elevation transect in the hyperarid region southeast of Antofagasta, Chile. The two lower sites situated on the distal parts of inactive alluvial fan deposits were subject to occasional fog occurrences. The upper steeper-sloped sites experienced no fog but are subject to minimal erosion. In all soil profiles, sulfates are the dominant salts showing a downward transition from gypsum to anhydrite that is accompanied by an increase of highly soluble salts and a decrease of sulfate δ34S and δ18O values. These trends are consistent with downward directed water infiltration during rare rain events causing salt dissolution followed by precipitation within the deeper soil column. This conclusion is also supported by our Rayleigh fractionation model. We attribute the presence of anhydrite at > 40 cm depth to the cooccurrence of nitrate and chloride salts, which decreases water activity during sulfate precipitation and therefore drives anhydrite formation. Along the elevation transect, the total salt inventories of each profile show a trend for nitrates and chlorides concentration decreasing with elevation. This observation together with the sulfate stable isotopes indicates a fog-independent source and suggests remobilization of soluble salts through enhanced washout from hillslopes to alluvial fans. These findings are essential for assessing the long-term regional habitability of hyperarid environments and have also relevance for Mars.

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 Datum: 20212021
 Publikationsstatus: Final veröffentlicht
 Seiten: -
 Ort, Verlag, Ausgabe: -
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 Art der Begutachtung: -
 Identifikatoren: DOI: 10.1016/j.catena.2021.105531
GFZPOF: p4 T5 Future Landscapes
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Titel: Catena
Genre der Quelle: Zeitschrift, SCI, Scopus
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Ort, Verlag, Ausgabe: -
Seiten: - Band / Heft: 206 Artikelnummer: 105531 Start- / Endseite: - Identifikator: CoNE: https://gfzpublic.gfz-potsdam.de/cone/journals/resource/journals65
Publisher: Elsevier