The origins and implications of paleochannels in hyperarid, tectonically active regions: The northern Atacama Desert, Chile

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Title:Main Title: The origins and implications of paleochannels in hyperarid, tectonically active regions: The northern Atacama Desert, Chile
Description:Abstract: Preserved remnants of fluvial activity in deserts constitute evidence for changing boundary conditions. The Atacama Desert of northern Chile is the global end-member for aridity, so the history of relict stream networks in this region is a record of how landscapes develop under extreme conditions. On Pampa de Tana in northern Chile (19.4°S), a series of channel forms that are presently inactive but in the past flowed westward are incised into the surface of a fault bounded, topographically elevated portion of the El Diablo Formation, a regionally extensive, relict pediment. We measure cosmic-ray produced 10Be, 26Al and 21Ne in fluvial deposits to date the timing of abandonment of three channels and couple this with topographic profile information from a SPOT-6 derived, 2m resolution digital elevation model. We find two of the channels were abandoned approximately>5.6 Myr and 2.0 Myr ago. One channel is still capable of flow and has ages suggesting it was fluvially active within the last few hundred thousand years. Using the paleochannel ages measured here and published ages for the end of aggradation of the El Diablo Formation we estimate the rates of fluvial channel incision before channel abandonment, and uplift rates on the faults after channel abandonment. Maximum uplift rates of ~12 m/Myr over the last 2 Myr are found. In general, while rates of uplift are relatively low they are several-fold more rapid than the rates of fluvial incision prior to channel abandonment. This implies that westward channel flow was interrupted by uplift of topography above a blind NW-SE striking reverse fault that affects the Central Depression, an alluvial forearc basin. We consider also that shrinkage of the upstream catchment area by stream capture, promoted via headward erosion and lateral expansion of adjacent canyons (quebradas) could be a factor in the abandonment of the channels on Pampa de Tana. Our results highlight the polygenetic nature of this landscape and show that relatively minor amounts of fault displacement in hyperarid regions can have implications for stream network evolution. Even subtle topographic uplift upstream should be taken into account when fluvial deposits are used as proxies for long-term environmental conditions.
Identifier:https://doi.org/10.1016/j.gloplacha.2019.103083 (DOI)
Citation Advice:Binnie, S.A. et al., 2020, in press, The origins and implications of paleochannels in hyperarid, tectonically active regions: The northern Atacama Desert, Chile, Global and Planetary Change, 103083, https://doi.org/10.1016/j.gloplacha.2019.103083
Responsible Party
Creators:Steven Binnie (Author), Klaus Reicherter (Author), Pia Victor (Author), Gabriel González (Author), Ariane Binnie (Author), Karin Niemann (Author), Finlay Stuart (Author), Christoph Lenting (Author), Stefan Heinze (Author), Stewart Freeman (Author), Tibor Dunai (Author)
Publisher:Elsevier
Publication Year:2019
Topic
CRC1211 Topic:Surface
Related Subproject:C5
Subjects:Keywords: Geomorphology, Cosmogenic Nuclides, Tectonics
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Filename:Binnie_2020_in_press.pdf
Data Type:Text - Article
File Size:4.8 MB
Date:Available: 26.11.2019
Mime Type:application/pdf
Data Format:PDF
Language:English
Status:Completed
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Publication Status:Accepted
Review Status:Peer reviewed
Publication Type:Article
Article Type:Journal
Source:Global and Planetary Change
Number of Pages: ( - )
Metadata Details
Metadata Creator:Steven Binnie
Metadata Created:26.11.2019
Metadata Last Updated:26.11.2019
Subproject:C5
Funding Phase:1
Metadata Language:English
Metadata Version:V50
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