Wikipedia

Sajsi

Sajsi is the name of an ancient lake in the Andes

The existence of ancient lakes in the Altiplano was proposed as early as 1882. At first, a Lake Minchin was identified with ages of 30,000 years or older; later additional lake cycles were recognized.[1] The minor ones include Inca Huasi, Salinas and Coipasa. The major ones include Lake Tauca and Ouki.[2] Because of this, it was proposed that Lake Minchin was actually a combination of several different ancient lakes.[3]

This lake occupied the area of the current Salar de Uyuni;[4] it also covered the Salar de Coipasa but it is not clear whether and how it extended in the Lake Poopo.[5] Its waters reached altitudes of 3,670 metres (12,040 ft) and its depth did not exceed 17 metres (56 ft).[6] A sample dated 23,700 ± 2,600 years ago by uranium-thorium dating indicates that lake levels at that point were about 15 metres (49 ft) deep in the Uyuni basin.[7] Water levels subsequently decreased to less than 5 metres (16 ft) above the present day levels before Lake Tauca formed,[8] however both the timing and the history of water levels are uncertain.[9] The surface area of the lake may have been 21,000 square kilometres (8,100 sq mi) during the highstand.[10] By 19,900 ± 900 - 18,700 ± 200 years ago, the Lake Tauca was beginning to form.[7] The so-called "L2" unit in drill cores in Salar de Uyuni may correspond to both the Sajsi and the later Lake Tauca cycle.[11] Sr isotope data indicate that about 41% of the water in Sajsi came from Lake Poopo and 4% from Lake Titicaca.[12]

Radiocarbon dates have been obtained for Sajsi-age ooids and tufa, uncalibrated they range from 17,080 ± 720 to 20,830 ± 140 years ago.[13] Later dates indicated that the lake existed between 25,000 and 19,000 years ago and reached its maximum depth 23,000 years ago.[7] The existence of this lake coincides with the Last Glacial Maximum. Earlier, lakes had formed in the Laguna Blanca, the Salar de Atacama,[4] as well as the Pozuelos Basin in northwest Argentina.[14] Given the small size of the glacial Sajsi and Inca Huasi paleolakes, it is likely that the Last Glacial Maximum was accompanied by a dry climate on the Altiplano[8] and indeed climate modelling shows that only a small precipitation increase - or none at all - would be needed to create the Sajsi lake.[15] Glacier expansion is recorded at that time in Northwest Argentina.[16] The second Heinrich event seems to coincide with the Sajsi lake period.[17]

A maximum in local insolation about 21,000 years ago coincides with the existence of the Sajsi lake but was probably not responsible for the lake's existence.[18] Farther south, precipitation in the drainage area of the Rio Salado had increased by 10 millimetres per year (0.39 in/year) during the Sajsi time,[19] lakes formed within the Western Cordillera[20] and the Bolivian Chaco likewise shows evidence of increased precipitation.[21] The Sajsi lake was apparently followed by Lake Tauca, but evidence is lacking.[22] Another theory postulates that Sajsi was simply a sub-phase of Lake Tauca,[23] an interpretation applied in particular to data taken from drill cores.[24]

References [ edit ]

  1. ^ Sánchez-Saldías, Andrea; Fariña, Richard A. (March 2014). "Palaeogeographic reconstruction of Minchin palaeolake system, South America: The influence of astronomical forcing". Geoscience Frontiers. 5 (2): 250. doi:10.1016/j.gsf.2013.06.004.
  2. ^ Placzek, Quade & Patchett 2006, p. 520.
  3. ^ Placzek, Quade & Patchett 2006, p. 528.
  4. ^ a b Torres, Gonzalo R.; Lupo, Liliana C.; Kulemeyer, Julio J.; Pérez, Claudio F. (May 2016). "Palynological evidence of the geoecological belts dynamics from Eastern Cordillera of NW Argentina (23° S) during the Pre-Last Glacial Maximum". Andean Geology. 24 (2): 151. doi:10.5027/andgeoV43n2-a01. ISSN 0718-7106. Retrieved 9 October 2016.
  5. ^ Placzek, Quade & Patchett 2013, p. 102.
  6. ^ Placzek, Quade & Patchett 2006, p. 524.
  7. ^ a b c Blard et al. 2011, p. 3984.
  8. ^ a b Placzek, Quade & Patchett 2006, p. 531.
  9. ^ Blard et al. 2011, p. 3974.
  10. ^ Placzek, Quade & Patchett 2013, p. 103.
  11. ^ Placzek, Quade & Patchett 2006, p. 529.
  12. ^ Placzek, Christa J.; Quade, Jay; Patchett, P. Jonathan (January 2011). "Isotopic tracers of paleohydrologic change in large lakes of the Bolivian Altiplano". Quaternary Research. 75 (1): 239. doi:10.1016/j.yqres.2010.08.004.
  13. ^ Placzek, Quade & Patchett 2006, p. 519.
  14. ^ McGlue et al. 2013, p. 653.
  15. ^ Vargo, L.J.; Galewsky, J.; Rupper, S.; Ward, D.J. (April 2018). "Sensitivity of glaciation in the arid subtropical Andes to changes in temperature, precipitation, and solar radiation". Global and Planetary Change. 163: 87. doi:10.1016/j.gloplacha.2018.02.006. ISSN 0921-8181.
  16. ^ Zech, Jana; Zech, Roland; Kubik, Peter W.; Veit, Heinz (December 2009). "Glacier and climate reconstruction at Tres Lagunas, NW Argentina, based on 10Be surface exposure dating and lake sediment analyses". Palaeogeography, Palaeoclimatology, Palaeoecology. 284 (3–4): 180. doi:10.1016/j.palaeo.2009.09.023.
  17. ^ Placzek, Quade & Patchett 2013, p. 106.
  18. ^ Quade, Jay; Rech, Jason A.; Betancourt, Julio L.; Latorre, Claudio; Quade, Barbra; Rylander, Kate Aasen; Fisher, Timothy (May 2008). "Paleowetlands and regional climate change in the central Atacama Desert, northern Chile". Quaternary Research. 69 (3): 358. doi:10.1016/j.yqres.2008.01.003.
  19. ^ Latorre, Claudio; Betancourt, Julio L.; Arroyo, Mary T.K. (May 2006). "Late Quaternary vegetation and climate history of a perennial river canyon in the Río Salado basin (22°S) of Northern Chile". Quaternary Research. 65 (3): 462. doi:10.1016/j.yqres.2006.02.002.
  20. ^ Pfeiffer, Marco; Latorre, Claudio; Santoro, Calogero M.; Gayo, Eugenia M.; Rojas, Rodrigo; Carrevedo, María Laura; McRostie, Virginia B.; Finstad, Kari M.; Heimsath, Arjun; Jungers, Matthew C.; De Pol-Holz, Ricardo; Amundson, Ronald (October 2018). "Chronology, stratigraphy and hydrological modelling of extensive wetlands and paleolakes in the hyperarid core of the Atacama Desert during the late quaternary". Quaternary Science Reviews. 197: 237. doi:10.1016/j.quascirev.2018.08.001. ISSN 0277-3791.
  21. ^ May, Jan-Hendrik; Zech, Roland; Veit, Heinz (June 2008). "Late Quaternary paleosol–sediment-sequences and landscape evolution along the Andean piedmont, Bolivian Chaco". Geomorphology. 98 (1–2): 47. doi:10.1016/j.geomorph.2007.02.025.
  22. ^ Broecker, Wally; Putnam, Aaron E. (December 2012). "How did the hydrologic cycle respond to the two-phase mystery interval?". Quaternary Science Reviews. 57: 20. doi:10.1016/j.quascirev.2012.09.024.
  23. ^ McPhillips, Devin; Bierman, Paul R.; Crocker, Thomas; Rood, Dylan H. (December 2013). "Landscape response to Pleistocene-Holocene precipitation change in the Western Cordillera, Peru: Be concentrations in modern sediments and terrace fills". Journal of Geophysical Research: Earth Surface. 118 (4): 2490. doi:10.1002/2013JF002837.
  24. ^ McGlue et al. 2013, p. 652.

Sources [ edit ]

  • Blard, P.-H.; Sylvestre, F.; Tripati, A.K.; Claude, C.; Causse, C.; Coudrain, A.; Condom, T.; Seidel, J.-L.; Vimeux, F.; Moreau, C.; Dumoulin, J.-P.; Lavé, J. (December 2011). "Lake highstands on the Altiplano (Tropical Andes) contemporaneous with Heinrich 1 and the Younger Dryas: new insights from 14C, U–Th dating and δ18O of carbonates". Quaternary Science Reviews. 30 (27–28): 3973–3989. doi:10.1016/j.quascirev.2011.11.001.
  • McGlue, Michael M.; Cohen, Andrew S.; Ellis, Geoffrey S.; Kowler, Andrew L. (December 2013). "Late Quaternary stratigraphy, sedimentology and geochemistry of an underfilled lake basin in the Puna plateau (northwest Argentina)". Basin Research. 25 (6): 638–658. doi:10.1111/bre.12025.
  • Placzek, C.; Quade, J.; Patchett, P. J. (8 May 2006). "Geochronology and stratigraphy of late Pleistocene lake cycles on the southern Bolivian Altiplano: Implications for causes of tropical climate change". Geological Society of America Bulletin. 118 (5–6): 515–532. doi:10.1130/B25770.1.
  • Placzek, C.J.; Quade, J.; Patchett, P.J. (February 2013). "A 130ka reconstruction of rainfall on the Bolivian Altiplano". Earth and Planetary Science Letters. 363: 97–108. doi:10.1016/j.epsl.2012.12.017.

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