Large‐Scale Cenozoic Wind Erosion in the Puna Plateau: The Salina del Fraile Depression

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.

Late Cenozoic Extensional Formation of the Antofalla Depression, Southern Puna Plateau, Argentina: An Effect of Lithospheric Foundering?

“…We compared the topographic slopes of the linear escarpments to the slopes of erosive, curving escarpments in the same area thought to result from Miocene to Quaternary wind erosion (Figures 4a and 4f; McMillan & Schoenbohm, 2020) to determine whether the linear escarpments have oversteepened slopes suggestive of active faulting (e.g., Hanks et al, 1984). Linear escarpments associated with faulting attain surface slopes of up to ∼20°, whereas the curving, non-fault-related escarpments attain surface slopes of 20°-40° (Figure 4f).…”

Source‐To‐Sink Aeolian Fluxes From Arid Landscape Dynamics in the Lut Desert

“…This approach is now expanding for a variety of morpho‐sedimentary systems in glacial (Jaeger & Koppes, 2016), lacustrine (Bouton et al., 2020), submarine (Liu et al., 2016; Salles et al., 2018), and aeolian environments (Fitzsimmons et al., 2020; Nicoll et al., 2020; Shao et al., 2011), not only on Earth but also on other planetary bodies (Boazman et al., 2021; Day & Kocurek, 2016). However, works dedicated to aeolian‐dominated landscapes often remain qualitative or limited to a single component of the sediment budget such as erosion or accumulation, dust or sand (East et al., 2015; McMillan & Schoenbohm, 2020; Pastore et al., 2021; Sun, 2002; Zender et al., 2004). Hence, the potential of source‐to‐sink methods is still to be exploited to bring new quantitative information on aeolian sediment‐routing systems and associated landforms.…”

Eocene to Quaternary Deformation of the Southern Puna Plateau: Thermochronology, Geochronology, and Structural Geology of an Andean Hinterland Basin (NW Argentina)

“…For metasedimentary and igneous lithologies, which represent the majority of our samples, we specify an initial high-temperature constraint (with a minimum bound greater than the maximum temperature of the AFT PAZ and an age of approximately twice the oldest measured AFT age) representing metamorphism or igneous emplacement, during which AFT were reset (Table S5 in Supporting Information S1). We also impose a constraint at 0 Ma representing mean annual temperatures of ∼0-15 °C (McMillan & Schoenbohm, 2020), reflecting the fact that all samples were collected at the surface. We use track-pit diameter, D par , as a proxy for chemical composition annealing behavior.…”

“…The Salina del Fraile is an erosional depression formed by Miocene to Recent wind erosion (McMillan & Schoenbohm, 2020) that exposes Permian strata, Triassic intrusive volcanics, Jurassic strata, and Cenozoic strata (Adelmann, 2001; Voss, 2002).…”

“…Within the Salina del Fraile depression, subhorizontal Late Miocene to Pliocene terrace deposits unconformably overlie the Quiñoas Formation (e.g., at Location L, Figure 8). Mapped by Voss (2002) as “Salina beds,” these 20–100‐m thick layers of alluvial sandstones and conglomerates and lacustrine sediments represent remnants of basin‐floor deposits that have been eroded by NW‐prevailing winds, often into streamlined forms such as yardangs (McMillan & Schoenbohm, 2020).…”