Titel
Pedogenesis at the coastal arid-hyperarid transition deduced from a Late Quaternary chronosequence at Paposo, Atacama Desert
Autor*in
Melanie Bartz
Institute of Earth Surface Dynamics, University of Lausanne
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Abstract
Under hyperarid climate conditions, pedogenesis is driven by the atmospheric deposition and subsequent accumulation of easily to moderately soluble salts forming extreme types of Aridisols. In contrast, the processes and timescales of soil formation in coastal desert environments are as yet not well understood. Therefore, a soil chronosequence at the arid-hyperarid transition in the south-central coastal Atacama Desert is investigated. We measured physicochemical soil parameters of shallow soil profiles on four generations of a multi-stage alluvial fan system, assisted by micromorphological analysis, allowing to deduce the soil-forming processes. We further established a geochronological framework by applying 10Be cosmogenic nuclide exposure dating on the abandoned surface generations, which allowed to infer the timescales for soil formation. The results indicate initial yet clearly identifiable pedogenesis occurring since MIS 5e–c. Along the Late Quaternary chronosequence, physicochemical soil properties show decreasing trends with growing age for the median grain size, salinity, long-term pH development, and CaCO3 contents. Contrarily, organic carbon, the ratio of organic to total phosphorus, the redness, and the contents of total and poorly crystalline pedogenic iron oxides tend to increase with age. This provides evidence for soil formation under an arid to hyperarid coastal climate characterized by (i) redistribution of salts by leaching causing topsoil desalinization; (ii) decalcification coupled with (iii) dealkalinization in totally decalcified horizons; (iv) accumulation of soil organic matter; (v) initial rubification through formation of pedogenic iron oxides (i.e. hematite); and (vi) initial loamification that, in turn, might have impeding effects on the translocation of soil constituents on timescales larger than 105 a. Furthermore, in situ pedogenesis might be superimposed considerably by aeolian dust influx. At Atacama’s south-central coast, the state of pedogenic alteration scales with the cumulative precipitation received throughout the entire Late Quaternary, yet evolved strongest between MIS 5 and the MIS 4/3-transition.
Stichwort
South AmericaPacific CoastDesert soilsPedogenic processesChronosequencesExposure age
Objekt-Typ
Sprache
Englisch [eng]
Persistent identifier
phaidra.univie.ac.at/o:2008721
Erschienen in
Titel
CATENA
Band
228
ISSN
0341-8162
Erscheinungsdatum
2023
Publication
Elsevier BV
Erscheinungsdatum
2023
Zugänglichkeit
Rechteangabe
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