Abstract:Dating of extensive alluvial fan surfaces and fluvial features in the hyperarid core of the Atacama Desert, Chile, using cosmogenic nuclides provides unrivalled insights about the onset and variability of aridity. The predominantly hyperarid conditions help to preserve the traces of episodic climatic and/or slow tectonic change. Utilizing single clast exposure dating with cosmogenic 10Be and 21Ne, we determine the termination of episodes of enhanced fluvial erosion and deposition occurring at ~19, ~14, ~9.5 Ma… Show more
“…The studied clay pan (21° 32.5″S, 69° 54.8″W) is located at the northern end of an endorheic basin (Fig. 1C), which was formed by tectonic drainage displacement by reverse faulting (Adamito or Auguire fault) 29–31 . The clay pan at its terminus has a maximum surface area of 640 by 1000 m, and a catchment area of 560 km 2 (Fig.…”
Section: Site Informationmentioning
confidence: 99%
“…south of 21°30′S), whereas comparable features are largely absent further to the north.Figure 1( A ) Colour shaded digital elevation model (derived from SRTM-data, created using ArcGIS 10.5.1) with isohyets 1 after Ritter, et al . 31 . Dashed white line indicates the border between winter-rain dominated areas in the SW and summer-rain dominated areas in the 1 .…”
Paleoclimate records from the Atacama Desert are rare and mostly discontinuous, mainly recording runoff from the Precordillera to the east, rather than local precipitation. Until now, paleoclimate records have not been reported from the hyperarid core of the Atacama Desert (<2 mm/yr). Here we report the results from multi-disciplinary investigation of a 6.2 m drill core retrieved from an endorheic basin within the Coastal Cordillera. The record spans the last 215 ka and indicates that the long-term hyperarid climate in the Central Atacama witnessed small but significant changes in precipitation since the penultimate interglacial. Somewhat ‘wetter’ climate with enhanced erosion and transport of material into the investigated basin, commenced during interglacial times (MIS 7, MIS 5), whereas during glacial times (MIS 6, MIS 4–1) sediment transport into the catchment was reduced or even absent. Pelagic diatom assemblages even suggest the existence of ephemeral lakes in the basin. The reconstructed wetter phases are asynchronous with wet phases in the Altiplano but synchronous with increased sea-surface temperatures off the coasts of Chile and Peru, i.e. resembling modern El Niño-like conditions.
“…The studied clay pan (21° 32.5″S, 69° 54.8″W) is located at the northern end of an endorheic basin (Fig. 1C), which was formed by tectonic drainage displacement by reverse faulting (Adamito or Auguire fault) 29–31 . The clay pan at its terminus has a maximum surface area of 640 by 1000 m, and a catchment area of 560 km 2 (Fig.…”
Section: Site Informationmentioning
confidence: 99%
“…south of 21°30′S), whereas comparable features are largely absent further to the north.Figure 1( A ) Colour shaded digital elevation model (derived from SRTM-data, created using ArcGIS 10.5.1) with isohyets 1 after Ritter, et al . 31 . Dashed white line indicates the border between winter-rain dominated areas in the SW and summer-rain dominated areas in the 1 .…”
Paleoclimate records from the Atacama Desert are rare and mostly discontinuous, mainly recording runoff from the Precordillera to the east, rather than local precipitation. Until now, paleoclimate records have not been reported from the hyperarid core of the Atacama Desert (<2 mm/yr). Here we report the results from multi-disciplinary investigation of a 6.2 m drill core retrieved from an endorheic basin within the Coastal Cordillera. The record spans the last 215 ka and indicates that the long-term hyperarid climate in the Central Atacama witnessed small but significant changes in precipitation since the penultimate interglacial. Somewhat ‘wetter’ climate with enhanced erosion and transport of material into the investigated basin, commenced during interglacial times (MIS 7, MIS 5), whereas during glacial times (MIS 6, MIS 4–1) sediment transport into the catchment was reduced or even absent. Pelagic diatom assemblages even suggest the existence of ephemeral lakes in the basin. The reconstructed wetter phases are asynchronous with wet phases in the Altiplano but synchronous with increased sea-surface temperatures off the coasts of Chile and Peru, i.e. resembling modern El Niño-like conditions.
“…This precipitation threshold is likely >1 and <20 mm/yr, because at >20 mm/yr CaCO 3 starts to accumulate in these soils (Ewing et al, 2006). Furthermore, the lack of CaCO 3 in the form of Bk horizons in all the test sites, including T1 which is 5 Ma, is evidence that this part of the Atacama has been predominantly hyperarid for millions of years (Hartley and Chong, 2002;Hartley, 2003;Dunai et al, 2005;Ewing et al, 2006;Rech et al, 2006;Garreaud et al, 2010;Amundson et al, 2012;Jordan et al, 2014;Ritter et al, 2018).…”
Section: The Nature Of Pavements In the Atacamamentioning
A distinct feature of many of the earliest archaeological sites (13,000-11,200 cal yr BP) at the core of the Atacama Desert is that they lie at or just below the surface, often encased in desert pavements. In this study, we compare these sites and undisturbed desert pavements to understand archaeological site formation and pavement development and recovery. Our results indicate these pavements and their soils are poorly developed regardless of their age. We propose that this is because of sustained lack of rain and extreme physical breakdown of clasts by salt expansion. Thus, the core of the Atacama provides an example of the lower limits of rainfall (<50 mm/yr) needed to form desert pavements. At site Quebrada Maní 12 (QM12), humans destroyed the pavement. After abandonment, human-made depressions were filled with eolian sands, incorporating artifacts in shallow deposits. Small and medium-sized artifacts preferentially migrated upwards, perhaps due to earthquakes and the action of salts. These artifacts, which now form palimpsests at the surface, helped – along with older clasts - to restore surface clast cover. Larger archaeological features remained undisturbed on top of a deeper Byzm horizon. The vesicular A horizons (Av horizons) have not regenerated on the archaeological sites due to extreme scarcity of rainfall during the Holocene.
“…If PD by itself was to be considered in the future as an indicator for conservation by any local or global organization, then the deserts present in the three studies could appear as areas of low conservation priority compared to neighboring regions. Geologically, hot deserts are relatively recent with origins ranging from Oligocene to Miocene times (35 to 5 million years ago [Ma]; Fujioka et al, 2009; Graham, 2011; Ritter et al, 2018). By contrast, other major formations such as tropical rainforests originated around 100 Ma (Couvreur and Baker, 2013).…”
Section: Phylogeny‐based Measures Of Diversity In Hot Desertsmentioning
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