Assessing soil formation under coastal hyperaridity since the Mid-Pleistocene using a chronosequence dated by in situ cosmogenic 10Be at Paposo, Atacama Desert (N Chile)

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Title:Main Title: Assessing soil formation under coastal hyperaridity since the Mid-Pleistocene using a chronosequence dated by in situ cosmogenic 10Be at Paposo, Atacama Desert (N Chile)
Description:Abstract: Soil formation under hyperaridity is governed by the limited availability of water, biotic activity, and unfavourable soil properties, which results in a group of taxa subsumed under Aridisols according to the USDA soil taxonomy. In the Atacama Desert, previous investigations have focussed on the hyperarid core of the desert, describing and identifying soils with salic, gypsic, or nitric characteristics. Contrarily, and although also classified as hyperarid, the coastal sector of the Atacama Desert receives much larger amounts of moisture, mainly due to the orographic blocking of advective fog by the Coastal Cordillera between ~500 and ~1,200 m above sea level. Adapted to this conditions by being able to comb out precipitation equivalents of several hundreds of mm/a, Loma vegetation populates the western Coastal Cordillera and coastal plain. Despite the large climatic contrast to the core of the desert, neither the soil properties, the pedogenic processes nor the timescales on which the coastal soils evolved have as yet been studied. We therefore assessed the physical and chemical parameters of a soil catena at an alluvial fan system at Paposo, composed of four morphostratigraphic units over minimal spatial and thus climatic variation. From each alluvial fan surface generation, we sampled four upper soil profiles. On the one hand, examining the soil physicochemical parameters across the chronosequence allows to deduce the pedogenic processes that are active under coastal hyperaridity. On the other hand, we established an absolute morphochronology based on exposure dating of the depositional surfaces using in situ cosmogenic 10Be, which enables us to indirectly assess rates of soil formation. The results show mostly monotonic relationships of physicochemical soil properties with increasing time since abandonment of the first fan surface in the Mid-Pleistocene. Contrary to the expectation, a trend towards desalinization seems to prevail. Moreover, complete decalcification of the oldest soils is closely related to a drop of pH values from slightly alkaline to neutral and slightly acid conditions. Spectrophotometric analysis of the soil colour as well as the geochemistry of pedogenic iron oxides indicates that rubification is a major pedogenic process active under coastal hyperaridity. The combined effects of soil-forming and weathering processes on the soil texture are reflected by a continuous fining towards older soils. Strong indication for in situ formation of clay-sized particles and colloids is provided by the difference of the grain size distributions calculated between two optical laser diffraction models. However, different proxies derived from bulk geochemistry do not support a relevant role of hydrolytic feldspar weathering. In contrast, a significant cumulative effect of biotic activity becomes apparent in the organic carbon content as well as the concentrations of colloidal plant nutrients, both featuring a high temporal and spatial variability.
Identifier:https://doi.org/10.5194/egusphere-egu22-7889 (DOI)
Responsible Party
Creators:Janek Walk (Author), Christopher Tittmann (Author), Philipp Schulte (Author), Ramona Mörchen (Author), Xiaolei Sun (Author), Melanie Bartz (Author), Steven Binnie (Author), Georg Stauch (Author), Roland Bol (Author), Helmut Brückner (Author), Frank Lehmkuhl (Author)
Funding Reference:Deutsche Forschungsgemeinschaft (DFG): CRC 1211: Earth - Evolution at the Dry Limit
Publisher:EGU
Publication Year:2022
Topic
CRC1211 Topic:Surface
Related Subproject:C2
Subjects:Keywords: Geomorphology, Biogeochemistry of Soils, Geochronology, Cosmogenic Nuclides, Landscape Evolution, Arid Zone
Geogr. Information Topic:Environment
File Details
Filename:Walk_et_al_2022_EGU22-7889-print.pdf
Data Type:Text - Event Paper
File Size:293 KB
Date:Submitted: 12.01.2022
Mime Type:application/pdf
Data Format:PDF
Language:English
Status:Completed
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Download Permission:Free
General Access and Use Conditions:According to the CRC1211DB data policy agreement. © Author(s) 2022. CC Attribution 4.0 license.
Access Limitations:According to the CRC1211DB data policy agreement. © Author(s) 2022. CC Attribution 4.0 license.
Licence:[Creative Commons] Attribution 4.0 International (CC BY 4.0)
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Specific Information - Publication
Publication Status:Published
Review Status:Not peer reviewed
Publication Type:Event Paper
Issue:7889
Volume:EGU22
Number of Pages:2 (1 - 2)
Event:EGU General Assembly 2022
Event Type:Conference
Event Location:Vienna, Austria
Event Duration:23rd of May, 2022 - 27th of May, 2022
Metadata Details
Metadata Creator:Janek Walk
Metadata Created:29.06.2022
Metadata Last Updated:29.06.2022
Subproject:C2
Funding Phase:2
Metadata Language:English
Metadata Version:V50
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