Large-scale Cenozoic Wind Erosion in the Puna Plateau: The Salina del Fraile Depression. McMillan, M. and Schoenbohm, L., M. Journal of Geophysical Research: Earth Surface, 2020.
Large-scale Cenozoic Wind Erosion in the Puna Plateau: The Salina del Fraile Depression [pdf]Paper  abstract   bibtex   5 downloads  
Wind erosion is integral to the evolution of arid landscapes on Earth and Mars, but the nature of long-term wind erosion of bedrock is poorly understood. Here we describe the Salina del Fraile (SdF) depression in the Puna Plateau of the Central Andes, NW Argentina, as a landform excavated by wind over several million years. New structural cross-sections and a compilation of chronostratigraphic ages rule out the hypothesis that the depression was created by transtensional tectonics. Dated remnant lacustrine and alluvial deposits in the floor of the depression constrain the rate and timing of erosion. Late Oligocene-Miocene compressional folding uplifted friable strata that were preferentially eroded, resulting in the high-relief (900 m) depression. Up to 1.95 km and an average of 1.05 km of strata were eroded during the last 8.2 to 17 Ma, at rates of 0.06 to 0.23 mm/yr. These rates are similar to long-term average wind erosion rates reported in other regions. Coarse-grained eolian megaripples, yardangs, and elongated ridges indicate ongoing eolian abrasion and deflation, aided by salt weathering, of the floor of the depression. Megaripple migration across stony lag surfaces exposes fresh bedrock to continued erosion. The SdF also contains kilometer-scale mesas and ridges that we interpret as erosional remnants. These landforms are similar to megayardangs and erosional topography identified on the lower flanks of Mount Sharp, Gale crater, Mars. In such hyperarid landscapes characterized by lithologic heterogeneities, high relief landforms can be generated and sustained by wind erosion, without significant fluvial or glacial incision. Plain Language Summary We investigated the origin of a large topographic depression in the arid Puna Plateau of the Central Andes, NW Argentina. Previous research interpreted the depression as formed by faulting, but we found that it is likely formed by wind erosion. While rivers and glaciers are usually responsible for erosion on Earth, there is no evidence for river or glacier action in the Salina del Fraile. Rather, much like the surface of Mars, wind was primarily responsible for forming the depression and surrounding landscape over several million years. We show that wind was able to excavate the depression because tectonic folding brought fine-grained rocks close to the surface, where they were exposed to strong winds and breakdown by salt weathering. Wind erosion was active for the last 8.2 to 17 million years, and, as evidenced by large dust storms originating from this region, is ongoing today. Wind is lowering the surface at an average rate of 0.06 to 0.23 mm/yr, similar to previous studies. The Salina del Fraile can help researchers understand the long-term effects of wind erosion on Earth and Mars.
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 title = {Large-scale Cenozoic Wind Erosion in the Puna Plateau: The Salina del Fraile Depression},
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 abstract = {Wind erosion is integral to the evolution of arid landscapes on Earth and Mars, but the nature of long-term wind erosion of bedrock is poorly understood. Here we describe the Salina del Fraile (SdF) depression in the Puna Plateau of the Central Andes, NW Argentina, as a landform excavated by wind over several million years. New structural cross-sections and a compilation of chronostratigraphic ages rule out the hypothesis that the depression was created by transtensional tectonics. Dated remnant lacustrine and alluvial deposits in the floor of the depression constrain the rate and timing of erosion. Late Oligocene-Miocene compressional folding uplifted friable strata that were preferentially eroded, resulting in the high-relief (900 m) depression. Up to 1.95 km and an average of 1.05 km of strata were eroded during the last 8.2 to 17 Ma, at rates of 0.06 to 0.23 mm/yr. These rates are similar to long-term average wind erosion rates reported in other regions. Coarse-grained eolian megaripples, yardangs, and elongated ridges indicate ongoing eolian abrasion and deflation, aided by salt weathering, of the floor of the depression. Megaripple migration across stony lag surfaces exposes fresh bedrock to continued erosion. The SdF also contains kilometer-scale mesas and ridges that we interpret as erosional remnants. These landforms are similar to megayardangs and erosional topography identified on the lower flanks of Mount Sharp, Gale crater, Mars. In such hyperarid landscapes characterized by lithologic heterogeneities, high relief landforms can be generated and sustained by wind erosion, without significant fluvial or glacial incision. Plain Language Summary We investigated the origin of a large topographic depression in the arid Puna Plateau of the Central Andes, NW Argentina. Previous research interpreted the depression as formed by faulting, but we found that it is likely formed by wind erosion. While rivers and glaciers are usually responsible for erosion on Earth, there is no evidence for river or glacier action in the Salina del Fraile. Rather, much like the surface of Mars, wind was primarily responsible for forming the depression and surrounding landscape over several million years. We show that wind was able to excavate the depression because tectonic folding brought fine-grained rocks close to the surface, where they were exposed to strong winds and breakdown by salt weathering. Wind erosion was active for the last 8.2 to 17 million years, and, as evidenced by large dust storms originating from this region, is ongoing today. Wind is lowering the surface at an average rate of 0.06 to 0.23 mm/yr, similar to previous studies. The Salina del Fraile can help researchers understand the long-term effects of wind erosion on Earth and Mars.},
 bibtype = {article},
 author = {McMillan, Mitchell and Schoenbohm, Lindsay M.},
 journal = {Journal of Geophysical Research: Earth Surface}
}
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