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Gypsum desert & atmospheric deposition

Research areas: Geochemistry, Mineralogy and Crystallography

Principal investigators: Prof. Dr. Petra Becker-Bohatý, Prof. Dr. Tibor J. Dunai, Prof. Dr. Sandro Jahn, Prof. Dr. Michael Staubwasser

Gypsum is the most dominant mineral in hyperarid Atacama soils. CaSO4 ⋅2H2O (and other compounds CaSO4 ⋅ xH2O, x = 0...2), together with other water-soluble minerals such as nitrates, play an essential role concerning weathering of soil and rocks, water penetration and trapping in the soil and soil dynamics.

In the Atacama prominent features include landscape-draping by powdery gypsum blankets, gypsum crust formation and disintegration and polygon fissure formation, which we hypothesize to be key to the understanding of the evolution of landscape in the Atacama Desert, and likely also for Martian geomorphology.

The main objectives of this project are to explore the origin and deposition rates of CaSO4 ⋅ xH2O compounds and highly water-soluble minerals, e.g. nitrates; their pedogenic and geomorphologic distribution and preservation and processes affecting these minerals after deposition, i.e. transformation of phases CaSO4 ⋅ xH2O under variable conditions of temperature, relative humidity and chemical environs.

In this context the project will address the question of the present and long-term gypsum deposition rates and the relative contribution of marine, continental and atmospheric sulfates to gypsum deposition across the coastal and central regions of the Atacama from the South to the hyper-arid core in the North. Here, also the contents and spatial distributions (regionally across the coastal and central regions of the Atacama Desert) of highly soluble salts, i.e. minerals that are more soluble than gypsum, will be considered. Besides the regional spatial distribution of salts also their local distribution in the soil column, caused by either descending or ascending water in soils, which trace the present and/or past hydrological regimes will be regarded.

A central topic of the project will also be the investigation of transformation processes of phases CaSO4 ·xH2O, i.e. processes of dehydration of gypsum CaSO4 ·2H2O to subhydrates or soluble anhydrite and a rehydration, particularly concerning their occurrence and velocity under environmental conditions in in the Atacama, concerning the involved subhydrate phases and concerning the influence of further chemical components besides CaSO4 ⋅ x H2O (x = 0...2) in the soil on the kinetics of formation (crystallization) of the different phases of the system CaSO4 – H2O (and transformation between them). From these investigations more insight is expected into processes that are assumed to contribute to surficial gypsum crust formation and preservation in the Atacama, and, since CaSO4 ⋅ xH2O phase transitions imply in part substantial volume changes, into the geomorphic effects (e.g. haloturbation) of these phase changes. This includes in particular surface and near-surface features, such as nodules, wedges and the widespread soil-polygons, and their potential impact on surface modification in the Atacama will be studied.

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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 2634 | tduanai@uni-koeln.de
Dr. Maximilian Müller
Institute of Geography | University of Cologne

Otto-Fischer-Str. 4 | 50674 Cologne
+49-(0)221-470 2241 | maximilian.mueller@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
© 2017 CRC1211 - Earth - Evolution at the Dry Limit

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