Antiquity of aridity in the Chilean Atacama Desert

Clarke, Jonathan

doi:10.1016/j.geomorph.2005.06.008

Cited by 239 publications

(187 citation statements)

References 45 publications

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“…However, estimates of onset, origin, and intensity of Atacama aridity have been largely debated (e.g., Dunai et al, 2005; Hartley & Chong, 2002). Long‐term estimates based on evaporitic deposits suggest at the very least intermittent semiarid conditions since as early as 200 Ma (Clarke, 2005) though a decrease to arid (<200 mm/yr) and subsequently hyperarid (<20–50 mm/yr) conditions is generally agreed to have occurred since the Miocene (e.g., 19–13 Ma; Jordan et al, 2014; Rech et al, 2006). Repeated onset of hyperaridity since 14 Ma may be further responsible for ambiguous records and interpretations (Jordan et al, 2014).…”

Section: Field Settingmentioning

confidence: 99%

Slow Long‐Term Exhumation of the West Central Andean Plate Boundary, Chile

2018

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We present a regional analysis of new low‐temperature thermochronometer ages from the Central Andean fore arc to provide insights into the exhumation history of the western Andean margin. To derive exhumation rates over 10 million‐year timescales, 38 new apatite and zircon (U‐Th)/He ages were analyzed along six ~500‐km long near‐equal‐elevation, coast parallel, transects in the Coastal Cordillera (CC) and higher‐elevation Precordillera (PC) of the northern Chilean Andes between latitudes 18.5°S and 22.5°S. These transects were augmented with age‐elevation profiles where possible. Results are synthesized with previously published thermochronometric data, corroborating a previously observed trenchward increase in cooling ages in Peru and northern Chile. One‐dimensional thermal‐kinematic modeling of all available multichronometer equal‐elevation samples reveals mean exhumation rates of <0.2 km/Myr since ~50 Ma in the PC and ~100 Ma in the CC. Regression of pseudovertical age‐elevation transects in the CC yields comparable rates of ~0.05 to ~0.12 km/Myr between ~40 and 80 Ma. Differences between the long‐term mean 1‐D rates and shorter‐term age‐elevation‐derived rates indicate low variability in the exhumation history. Modeling results suggest similar background exhumation rates in the CC and PC; younger ages in the PC are largely a function of increased heat flow and consequently an elevated geothermal gradient near the arc. Slow exhumation rates are suggestive of semiarid conditions across the region since at least the Eocene and deformation and development of the Andean fore arc around this time.

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Section: Field Settingmentioning

confidence: 99%

Slow Long‐Term Exhumation of the West Central Andean Plate Boundary, Chile

2018

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“…In northern Chile, the annual precipitation and resulting fluvial dissection decline rapidly westward, with annual rainfall ranging from $20 cm/a at higher elevations to <0.1 cm/a near the coast (Houston and Hartley, 2003;Houston, 2006;Strecker et al, 2007;García et al, 2011). Long-term semiarid to hyperarid climates, arguably since the late Triassic (Clarke, 2006) or late Jurassic (Hartley et al, 2005), has combined with rapid uplift of the Andes since the Miocene (when the rain shadow and aridity were enhanced) to create a landscape in which tectonic features are unusually well expressed on the surface (Gregory-Wodzicki, 2000;Rech et al, 2006).…”

Section: Regional Settingmentioning

confidence: 99%

“…The study sites are in the Atacama Desert of northern Chile (Fig. 2), which has arguably experienced more prolonged and severe aridity than any other region on Earth (Hartley et al, 2005;Dunai et al, 2005;Clarke, 2006). Hoke et al (2004) inferred a groundwater sapping origin for three theater-headed quebradas (i.e., valleys or canyons, although the Spanish word does not necessarily imply a theater headscarp) that cross the desert from the Andes westward to the Pacific Ocean (18-19.5°S) or to enclosed basins (>19.5°S) (Fig.…”

Section: Introductionmentioning

confidence: 99%

Origin and development of theater-headed valleys in the Atacama Desert, northern Chile: Morphological analogs to martian valley networks

Irwin

Tooth

Craddock

et al. 2014

Icarus

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a b s t r a c tUnderstanding planetary landforms, including the theater-headed valleys (box canyons) of Mars, usually depends on interpreting geological processes from remote-sensing data without ground-based corroboration. Here we investigate the origin and development of two Mars-analog theater-headed valleys in the hyperarid Atacama Desert of northern Chile. Previous workers attributed these valleys to groundwater sapping based on remote imaging, topography, and publications on the local geology. We evaluate groundwater sapping and alternative hypotheses using field observations of characteristic features, strength measurements of strata exposed in headscarps, and estimates of ephemeral flood discharges within the valleys. The headscarps lack evidence of recent or active seepage weathering, such as spring discharge, salt weathering, alcoves, or vegetation. Their welded tuff caprocks have compressive strengths multiple times those of the underlying epiclastic strata. Flood discharge estimates of cubic meters to tens of cubic meters per second, derived using the Manning equation, are consistent with the size of transported clasts and show that the ephemeral streams are geomorphically effective, even in the modern hyperarid climate. We interpret that headscarp retreat in the Quebrada de Quisma is due to ephemeral flood erosion of weak Miocene epiclastic strata beneath a strong welded tuff, with erosion of the tuff facilitated by vertical jointing. The Quebrada de Humayani headscarp is interpreted as the scar of a giant landslide, maintained against substantial later degradation by similar strong-over-weak stratigraphy. This work suggests that theater-headed valleys on Earth and Mars should not be attributed by default to groundwater sapping, as other processes with lithologic and structural influences can form theater headscarps.Published by Elsevier Inc.

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“…4 The Atacama Desert in northern Chile is such an extreme habitat and is acknowledged to be the driest place on earth due to the rainshadow in front of the Andes mountains. 5 It is the oldest continuously arid desert, which has experienced extreme hyper-aridity for at least 150 million years of climatic stability. 6,7 Drees and coworkers 8 has shown that the hyper-arid soils of the Atacama Desert are not sterile but harbor a rich source of culturable bacteria, the majority of which were members of the phylum Actinobacteria.…”

Section: Introductionmentioning

confidence: 99%

Atacamycins A–C, 22-membered antitumor macrolactones produced by Streptomyces sp. C38

et al. 2011

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Three new 22-membered macrolactone antibiotics, atacamycins A-C, were produced by Streptomyces sp. C38, a strain isolated from a hyper-arid soil collected from the Atacama Desert in the north of Chile. The metabolites were discovered in our HPLC-diode array screening and isolated from the mycelium by extraction and chromatographic purification steps. The structures were determined by mass spectrometry and NMR experiments. Atacamycins A, B and C exhibited moderate inhibitory activities against the enzyme phosphodiesterase (PDE-4B2), whereas atacamycin A showed a moderate antiproliferative activity against adeno carcinoma and breast carcinoma cells. INTRODUCTIONThe phylum Actinobacteria and particularly the genus Streptomyces is an excellent and in-exhausted source for the discovery of novel secondary metabolites with diverse biological activities based on unique pharmacophores. 1,2 High-quality isolates are a pre-requisite to prevent the rediscovery of known compounds as well as new sources for strain isolation. 3 Our focus for strain isolation is based on poorly studied habitats within the extremobiosphere. 4 The Atacama Desert in northern Chile is such an extreme habitat and is acknowledged to be the driest place on earth due to the rainshadow in front of the Andes mountains. 5 It is the oldest continuously arid desert, which has experienced extreme hyper-aridity for at least 150 million years of climatic stability. 6,7 Drees and coworkers 8 has shown that the hyper-arid soils of the Atacama Desert are not sterile but harbor a rich source of culturable bacteria, the majority of which were members of the phylum Actinobacteria.In a recently published study, the isolation of novel members of the order Actinomycetales from Atacama Desert soils was reported. 9 In this study, samples were collected at El Tatio (4300 m, geyser field), the Salar de Atacama (2300 m, salt flat hyper-arid) and the Valle de la Luna (2450 m, extreme hyper-arid). In all, 16 selected actinomycete isolates were added to our HPLC-diode array screening program to detect the production of novel secondary metabolites. In all, 3 of them

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Antiquity of aridity in the Chilean Atacama Desert

Cited by 239 publications

References 45 publications

Slow Long‐Term Exhumation of the West Central Andean Plate Boundary, Chile

Slow Long‐Term Exhumation of the West Central Andean Plate Boundary, Chile

Origin and development of theater-headed valleys in the Atacama Desert, northern Chile: Morphological analogs to martian valley networks

Atacamycins A–C, 22-membered antitumor macrolactones produced by Streptomyces sp. C38

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