Salar de Punta Negra

Coordinates: 24°35′42″S 68°58′12″W / 24.595°S 68.970°W / -24.595; -68.970
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Western Cordillera. These dry valleys, from mountains such as the Llullaillaco volcano, carry water only occasionally. More permanent sources of water, in the form of springs
, also exist at Salar de Punta Negra.

At the beginning of the

archeological sites. Copper
mining presently takes place in the region.

Geography and geomorphology

The Salar de Punta Negra lies in the eastern

lava flow on the eastern side of Salar de Punta Negra that was erupted during the Late Pleistocene.[3]

The Salar has a surface of 230 square kilometres (89 sq mi),

saltwater.[4] The salt deposits consist mainly of gypsum, halite and ulexite,[5] they form crenulated rims[6] and pressure ridges in some points.[7] The playa appears to be somewhat asymmetric, lower in the northwest, probably a consequence of faulting.[8]

Salar de Punta Negra lies at the centre of a converging drainage network[9] and is surrounded by a bajada which often becomes steep where it meets the playa and is itself crisscrossed by channels that originate in dry valleys at the top of the bayada. Of these dry valleys, four of these in the Western Cordillera carry water seasonally[10] and are known as Quebrada Zorros, Quebrada Zorritos, Quebrada Tocomar (or Toconar[11]) and Quebrada Llullaillaco. These are often subject to flash floods which occasionally reach the playa surface in the form of mudflows.[12] Additional valleys are the Quebrada El Salto and the Quebrada El Salado.[13] The Río Frio enters the Salar from the south and gets its water from the Cordillera Domeyko.[14] Most of the drainages do not carry water all the way to Salar de Punta Negra; the water seeps underground before reaching the Salar.[15] Finally, fault-controlled springs such as Barrancas Blancas and water seeps at the eastern margin of Salar de Punta Negra discharge water.[11]

It is part of a 77 kilometres (48 mi) long and 30 kilometres (19 mi) wide basin between the

block faulting and was then filled by Cenozoic deposits.[10] In the Western Cordillera, the volcano Llullaillaco reaches a height of 6,725 metres (22,064 ft) while the average elevation of the depression amounts to 3,000 metres (9,800 ft);[1] Llullaillaco is one of the highest volcanoes in the world.[11] The basin has a surface area of about 4,263 square kilometres (1,646 sq mi);[18] to the east of Salar de Punta Negra lie the Pampa El Salado, the Pampa San Eulogio and the Pampa del Chino.[19] North of Punta Negra lies the smaller Salar de Imilac.[15]

Supposed paleolake

It was once believed that Salar de Punta Negra at one time contained a large

shorelines and lacustrine terraces have been found.[21] During the latest Pleistocene-Holocene, the Quebrada de las Zorras conveyed water from the mountains around Llullaillaco to Salar de Punta Negra.[22] The lake eventually overflowed first into the Salar de Imilac farther north and then through the Quebrada de Agua Colorada into the Salar de Atacama;[23] archeological findings have been made in proximity to the overflow pathways.[20]

Later research indicated that there is no firm evidence of such a lake such as either lacustrine sediments[24] or former shorelines, with supposed shorelines being instead berms formed by subsidence and faults. Likewise, typical fine sediments associated with water are only found on the eastern side of Salar de Punta Negra, where springs are active. The absence of a lake in Salar de Punta Negra is consistent with the fact that paleolakes with clear shorelines in the region only occur at elevations of over 3,500 metres (11,500 ft).[25] Farther south, the Salar de Aguas Calientes and the Salar de Pajonales feature clear evidence of former lakes.[26]

Geology

The Central Andes in Chile consist of five separate geological domains. From east to west these are the

Cordillera de Domeyko, the Central Depression and finally the Cordillera de la Costa. With the exception of the Salar de Atacama, the geology of the Pre-Andean Depression is usually poorly known, as most geological research is focused on the eastern side of the Andes where oil reserves are suspected and on the copper-bearing domains of the western Andes.[27]

The area is largely covered by

plutons, the Triassic sediment-volcanic Sierra Guanaco and the fluvial-lacustrine Sierra de Varas and the marine Rhaetian-Jurassic Profeta Formation.[28] Finally, there are Paleogene deposits of mostly sedimentary or volcanic origin such as the Naranja Formation and the Pampa de Mulas Formation.[29] Large fault systems such as the Escondida-Punta Negra fault delimit the Salar de Punta Negra basin to the west and the east; some eastern faults offset recent deposits.[30]

Climate and biology

The area has a

cold desert climate with average temperatures of 18–8 °C (64–46 °F) and average annual rainfall of 14 millimetres per year (0.55 in/year)[18]-30 millimetres per year (1.2 in/year);[1] precipitation diminishes from 50–150 millimetres per year (2.0–5.9 in/year) in the Western Cordillera to almost zero in the Cordillera Domeyko[1] and occurs mostly during the summer months, leading to episodic flows in the dry valleys.[18] Diurnal temperature variation reaches 30 °C (54 °F)[1] and the region is windy, with winds reaching up to 90 kilometres per hour (56 mph) and an average of 14 kilometres per hour (8.7 mph).[18]

There is virtually no vegetation close to Salar de Punta Negra today,

calibrated radiocarbon years ago.[39]

Human activity

While the

arid again, the lakes and many of these wetlands disappeared again.[40][41]

The latest

calibrated radiocarbon,[45] although most earlier sites had been abandoned. This is consistent with the so-called "archeological silence" of this period in the Salar de Atacama area.[46]

At the Pleistocene/Holocene sites of Salar de Punta Negra,

groundwater depletion and the drying of remnant wetlands, leading to legal restrictions in 2005 on groundwater exploration[34] and a complaint by the Chilean State Defence Council in 2020.[57] The results of groundwater depletion at Salar de Punta Negra induced local communities to fight similar water exploration projects in the Salar de Atacama.[58]

References

  1. ^ a b c d e f van Overmeeren & Staal 1976, p. 196.
  2. ^ a b Lynch 1986, p. 145.
  3. ^ a b Craig 1997, p. 65.
  4. ^ van Overmeeren & Staal 1976, p. 1976.
  5. ^ van Overmeeren & Staal 1976, p. 199.
  6. ^ Stoertz & Ericksen 1974, p. 40.
  7. ^ Stoertz & Ericksen 1974, p. 50.
  8. ^ Stoertz & Ericksen 1974, p. 15.
  9. ^ Craig 1997, p. 63.
  10. ^ a b van Overmeeren & Staal 1976, p. 197.
  11. ^ a b c Quade et al. 2017, p. 345.
  12. ^ van Overmeeren & Staal 1976, p. 201.
  13. ^ Quade et al. 2017, p. 344.
  14. ^ Lynch 1986, p. 148.
  15. ^ a b c Souza et al. 2021, p. 3.
  16. ^ a b Martínez et al. 2018, p. 189.
  17. ^ Martínez et al. 2018, p. 334.
  18. ^ a b c d e Loyola et al. 2018, p. 208.
  19. ^ a b Martínez et al. 2018, p. 337.
  20. ^ a b Lynch 1986, p. 151.
  21. ISSN 0169-555X
    .
  22. ^ Grosjean, Núñez & Cartajena 2005, p. 2.
  23. ^ Lynch 1986, p. 146.
  24. ^ Grosjean & Núñez 1994, p. 275.
  25. ^ Quade et al. 2017, p. 352.
  26. ^ Lynch 1990, pp. 201–202.
  27. ^ Martínez et al. 2018, p. 188.
  28. ^ Martínez et al. 2018, p. 190.
  29. ^ Martínez et al. 2018, pp. 190–191.
  30. ^ Martínez et al. 2018, p. 338.
  31. ^ Quade et al. 2017, p. 347.
  32. S2CID 247542012
    .
  33. PMID 17061807
    .
  34. ^
    ISSN 1035-8811
    .
  35. ^ a b Souza et al. 2021, p. 4.
  36. ^ Quade et al. 2017, p. 353.
  37. S2CID 244146814
    .
  38. S2CID 244146814
    .
  39. ^ a b Quade et al. 2017, p. 355.
  40. ^
    ISSN 0718-1043. Archived
    from the original on 2019-02-26. Retrieved 2018-11-18.
  41. ^ Loyola et al. 2018, p. 207.
  42. ^ Loyola et al. 2018, p. 206.
  43. ^ Souza et al. 2021, p. 8.
  44. ^ Souza et al. 2021, p. 17.
  45. ^ Grosjean, Núñez & Cartajena 2005, p. 5.
  46. ^ Grosjean & Núñez 1994, p. 282.
  47. ^ Lynch 1986, p. 153.
  48. ^ Lynch 1986, p. 155.
  49. ^ Grosjean & Núñez 1994, p. 280.
  50. ^ Lynch 1986, p. 159.
  51. ^ Grosjean, Núñez & Cartajena 2005, p. 8.
  52. ISSN 0716-1182. Archived
    from the original on 2018-11-15. Retrieved 2018-11-18.
  53. ^ Lynch 1990, p. 214.
  54. ^ Lynch 1990, p. 216.
  55. ISSN 0717-7356
    .
  56. ^ Lynch 1990, p. 224.
  57. S2CID 242738341
    .
  58. S2CID 158330163
    .

Sources

24°35′42″S 68°58′12″W / 24.595°S 68.970°W / -24.595; -68.970

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