Coupled controls of climate, geology, and biota on late Pleistocene alluvial fan morphodynamics along the coast of the hyperarid Atacama Desert

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Title:Main Title: Coupled controls of climate, geology, and biota on late Pleistocene alluvial fan morphodynamics along the coast of the hyperarid Atacama Desert
Description:Abstract: I n the hyperarid environment of the Atacama Desert, alluvial fans are the principle fluvial geoarchive reflecting variations in climate and tectonics in their architecture. While they have been studied in the core of the desert to reconstruct long-term palaeoenvironmental changes from the Oligocene to the Quaternary and, in particular, to constrain the onset of hyperaridity, alluvial fans along the coast (20.5°S – 25.5°S) are younger and show a much higher activity; thus, they can serve as archives during the Pleistocene to Holocene evolution. However, past and recent morphodynamics of the coastal alluvial fans (CAF) are yet poorly reconstructed so that the understanding of an interplay between climatic, geologic, and biotic controls is still challenging. We related climatic, lithologic, and tectonic source-area characteristics to geomorphometric parameters of the CAF and their catchments. Geomorphometric analyses were conducted based on the 12.5 m TanDEM‑X WorldDEM™, lithological and tectonic data were extracted from regional geological maps, and the frequency of heavy rainfall events derived from a regional Weather Research and Forecasting (WRF) model was used as a climate parameter. We further combined luminescence dating, cosmogenic nuclide exposure dating, and existing chronological data to constrain the timing of Pleistocene alluvial fan deposition as well as the ages of interbedded marine terraces. Results indicate a primary climatic control on CAF dynamics shown in the functional relationships with catchment hydromorphometrics that mirror a high susceptibility to debris-flows as well as in the temporal pattern of CAF activity. Distinct phases of CAF activity occurred during the late Pleistocene (95–80 ka, 60–45 ka, and 35-20 ka) and the Holocene – driven by atmospheric changes from the Pacific Ocean. The primary source of precipitation is reflected along the latitudinal gradient: frontal systems and cut-off lows mainly originating from the extratropics. Towards the south, an increasing density of Loma vegetation can be observed so that also possible feedback mechanisms of biota on sediment supply need to be considered. While source-area lithology is of negligible relevance for CAF morphodynamics, an important long-term influence of tectonics can be seen in the regional uplift, which in turn controls the catchment shape and relief. From the numerical dating of the marine terraces, uplift rates ranging between ~0.06 and ~0.57 m/ka were derived for the late Pleistocene period.
Responsible Party
Creators:Janek Walk (Author), Melanie Bartz (Author), Georg Stauch (Author), Mark Reyers (Author), Steven Binnie (Author), Dominik Brill (Author), Paulina Vásquez (Author), Fernando Sepúlveda (Author), Dirk Hoffmeister (Author), Helmut Brückner (Author), Frank Lehmkuhl (Author)
Funding Reference:Deutsche Forschungsgemeinschaft (DFG): CRC 1211: Earth - Evolution at the Dry Limit
Publisher:EGU
Publication Year:2020
Topic
CRC1211 Topic:Surface
Related Subproject:C2
Subjects:Keywords: Geomorphology, Landscape Evolution, Remote Sensing, Geochronology, Climate Models , Arid Zone
Geogr. Information Topic:Environment
File Details
Filename:Walk_et_al_2020_EGU2020-7461.pdf
Data Type:Text - Event Paper
File Size:294 KB
Date:Submitted: 14.01.2020
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) 2020. CC Attribution 4.0 license.
Access Limitations:According to the CRC1211DB data policy agreement. © Author(s) 2020. CC Attribution 4.0 license.
Licence:[Creative Commons] Attribution 4.0 International (CC BY 4.0)
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Publication Status:Published
Review Status:Not peer reviewed
Publication Type:Event Paper
Proceedings Title:Geophysical Research Abstracts
Issue:EGU2020-7461
Volume:22
Number of Pages:2 (1 - 2)
Event:EGU2020: Sharing Geoscience Online
Event Type:Conference
Event Location:Vienna, Austria (online)
Event Duration:4th of May, 2020 - 8th of May, 2020
Metadata Details
Metadata Creator:Janek Walk
Metadata Created:08.04.2020
Metadata Last Updated:29.06.2022
Subproject:C2
Funding Phase:1
Metadata Language:English
Metadata Version:V50
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