Salar de Pajonales
Salar de Pajonales seen from space, north on the left
Map showing location Salar de Pajonales in Chile
Map showing location Salar de Pajonales in Chile
Salar de Pajonales
Coordinates25°08′40″S 68°49′12″W / 25.14444°S 68.82000°W / -25.14444; -68.82000
Primary inflowsRío San Eulogio
Catchment area1,984 square kilometres (766 sq mi)
Basin countriesChile
Surface area104 square kilometres (40 sq mi)
Surface elevation3,537 metres (11,604 ft)
References[1]

Salar de Pajonales is a playa in the southern Atacama Region of Chile and the third-largest in that country, behind Salar de Punta Negra and Salar de Atacama. It consists mostly of a gypsum crust; only a small portion of its area is covered with water. During the late Pleistocene, Salar de Pajonales formed an actual lake that has left shoreline features.

The climate in the region is arid and windy, with high insolation and low atmospheric pressure. The extreme environmental conditions have drawn comparisons to Mars, and Salar de Pajonales has been used as an analogue for Martian environments.

Geography and hydrology

The salar lies at the margin of the hyperarid Atacama Desert,[2] on the Altiplano-Puna high plateau[3] at 3,537 metres (11,604 ft) elevation. It covers an area of 104 square kilometres (40 sq mi), making it the third-largest in the region behind Salar de Atacama and Salar de Punta Negra.[1] It has roughly the shape of a square, with three peninsulas jutting in on the northeastern and southeastern corners;[4] this shape may be due to fault activity.[5] Several islands are found in the north-central and south-central area of the salar.[6] Only about 1.4 square kilometres (0.54 sq mi) of Salar de Pajonales are actually covered with water[1] in the form of ponds and lagoons,[7] mostly on the margins and at the centre of the salar.[8] A road crosses the salar.[3]

The principal salt has variously been stated to be either halite[9] or gypsum in the form of selenite.[10] There are minor amounts of calcium chloride, elemental sulfur[11] and ulexite.[12] The salts form a thick, brine-filled salt formation[13] with domes, mounds,[14] ridges, polygonal cracks,[2] tumuli[10] (an area covered with numerous domes is called "Dome Field"[9]) and a rough crust.[15] A raised area at the eastern end of the salar features small holes draped in gypsum[16] that appear to be produced by degassing.[17] Water at Salar de Pajonales is extremely salty,[18] with calcium chloride and calcium sulfate being the main components.[2] There is evidence of ongoing dissolution of the salt,[7] which has left deep pits[19] and cavities reaching 1–2 metres (3 ft 3 in – 6 ft 7 in) height.[20] The dissolution may be caused by salt draining into groundwater.[21] Salt deposition is influenced by the activity of cyanobacteria and sulfur-oxidizing bacteria,[22] which precipitate gypsum that may entomb microorganisms.[12]

Its catchment covers an area of 1,984 square kilometres (766 sq mi),[1] but lacks permanent surface drainages. Its waterbodies, which are inhabited by flamingos, are sustained by underground water.[23] In the north, there is intermittent discharge in the San Eulogio River, Quebrada La Pena and in other nameless streams from Cerro La Pena, Cerro Pajonales and Pampa San Eulogio.[24][8] The terrain is formed mostly by volcanic rocks consisting of andesite and rhyolite; there are active hot springs.[25] The Lazufre uplift, an area where the ground is rising, lies in close proximity to Salar de Pajonales.[26]

Prehistoric lake

Around the last glacial maximum, water levels in Salar de Pajonales rose by about 50 metres (160 ft), covering an area of about 205 square kilometres (79 sq mi).[27] The lake left clear shorelines[28] with terraces,[29] river deltas and wavecut platforms and notches.[30] Islands in the salar were cut in or even flattened by wave erosion.[31] This lake level highstand may be correlated to the Lake Tauca episode on the Bolivian Altiplano, which took place shortly after the last glacial maximum when water levels rose in the regional lakes. Archaeological sites found at Pajonales and neighbouring Aguas Calientes may be correlated to a former lake highstand.[32] The present-day gypsum deposits formed underwater during this highstand.[10] The climatic conditions may have resembled these of Mars during the Hesperian period.[33]

Climate and vegetation

The mean temperature at Salar de Pajonales is 5 °C (41 °F) and annual precipitation ranges 80–150 millimetres (3–6 in). Annual potential evaporation reaches 1,350 millimetres (53 in).[1] Precipitation occurs mostly during summer from the east and in winter from the west.[25]

The vegetation of the area consists of matorral formed by Fabiana bryoides and Phacelia pinnatifida[34] and steppe dominated by Stipa frigida.[35] Other plant species recorded are Cistanthe minuscula[36] and Cristaria andicola.[37]

Microbialites and stromatolites grow in the salar,[2] and former stromatolites form mounds and small domes on the crust of Salar de Pajonales.[38] Maximum development has variously been found either in the central parts of the salar and the deeper lagoons,[39] or around the islands.[6] There are also diatoms at Salar de Pajonales.[12]

Human use

Salar de Pajonales lies in the southern part of the Llullaillaco National Park.[40] There are prehistoric shelters, pircas, in the area.[41] The European Large Southern Array observatory project placed instruments at Salar de Pajonales in 1997,[42] before moving them to Llano de Chajnantor the following year.[43]

Owing to its extreme conditions, like the low atmospheric pressure,[10] extreme salinity and aridity, large day-night temperature differences and high UV radiation,[3] Salar de Pajonales has been used as an analogue for environments on Mars where life may persist to this day.[2] Traces of such life can be preserved by sediments and sulfate-chloride salts.[2] Models of how life-bearing environments may appear from remote imaging have been developed on the basis of the appearance of Salar de Pajonales.[44]

References

  1. 1 2 3 4 5 Alonso, Risacher & Salazar 1999, p. 285.
  2. 1 2 3 4 5 6 Warren-Rhodes et al. 2023, p. 2.
  3. 1 2 3 Phillips 2022, p. 1.
  4. ↑ Ercilla Herrero 2019, p. 213.
  5. ↑ Stoertz & Ericksen 1974, p. 15.
  6. 1 2 Ercilla Herrero 2019, p. 216.
  7. 1 2 Ruch et al. 2012, p. 123.
  8. 1 2 Pontificia Universidad Católica de Chile 2008, p. 33.
  9. 1 2 Phillips et al. 2023, p. 2.
  10. 1 2 3 4 Hinman et al. 2017, p. 1.
  11. ↑ Tebes-Cayo et al. 2021, p. 145.
  12. 1 2 3 Tebes et al. 2019, p. 1.
  13. ↑ Risacher, Alonso & Salazar 2003, p. 271.
  14. ↑ Hofmann et al. 2023, p. 1.
  15. ↑ Ercilla Herrero 2019, p. 214.
  16. ↑ Hofmann et al. 2023, p. 5.
  17. ↑ Hofmann et al. 2023, p. 12.
  18. ↑ Risacher, Alonso & Salazar 2003, p. 253.
  19. ↑ Risacher, Alonso & Salazar 2003, p. 256.
  20. ↑ Bishop et al. 2021, p. 2.
  21. ↑ Ruch et al. 2012, p. 124.
  22. ↑ Tebes-Cayo et al. 2021, p. 146.
  23. ↑ CONAF 1999, p. 11.
  24. ↑ CONAF 1999, p. 12.
  25. 1 2 Warren-Rhodes et al. 2023, p. 7.
  26. ↑ Hofmann et al. 2023, p. 7.
  27. ↑ Huber, Bugmann & Reasoner 2005, p. 96.
  28. ↑ Quade et al. 2008, p. 352.
  29. ↑ Lynch 1990, p. 203.
  30. ↑ Lynch 1990, p. 202.
  31. ↑ Lynch 1990, p. 204.
  32. ↑ Lynch 1990, p. 205.
  33. ↑ Warren-Rhodes et al. 2023, pp. 5–6.
  34. ↑ Peñaloza et al. 2013, p. 46.
  35. ↑ Peñaloza et al. 2013, p. 48.
  36. ↑ Peñaloza et al. 2013, p. 132.
  37. ↑ Peñaloza et al. 2013, p. 138.
  38. ↑ Ercilla Herrero 2019, p. 220.
  39. ↑ Tebes-Cayo et al. 2021, p. 460.
  40. ↑ Peñaloza et al. 2013, p. 26.
  41. ↑ Lynch 1990, p. 214.
  42. ↑ Radford & Nyman 2001, p. 7.
  43. ↑ Radford & Nyman 2001, p. 8.
  44. ↑ Warren-Rhodes et al. 2023, p. 4.

Bibliography

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