Ouki

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Ouki was an ancient lake in the Bolivian

uranium-thorium dating
yielding different dates spanning the time between 28,200 and 125,990 ± 9,580 years ago.

Whether Ouki existed is a subject of controversy. In 2011, scientists claimed that the lake did not exist outside of the

Lake Poopo
basin. The formation of Ouki is associated with a major glaciation and was probably caused by increased precipitation, which has also been observed elsewhere.

General characteristics

Ouki may have reached a water level of approximately 3,735 metres (12,254 ft)

Coipasa basins may rather have been filled by a separate postulated lake, Lake Salinas.[5] Estimates of the surface area depend on the assumed lake levels and whether the lake covered only the Lake Poopó basin or also the Uyuni/Coipasa basins. Estimates range from 10,400–46,500 square kilometres (4,000–18,000 sq mi).[6]

The Ouki lake is one of the so-called deep lake cycles, along with Lake Tauca, from which it may have separated during a period when water levels dropped below 3,700 metres (12,100 ft) altitude. At a locality called Vinto, it has left characteristic tufa deposits which have shapes of inverted cones.[7] The depth of the lake did not exceed c. 80 metres (260 ft). The subsequent Salinas lake cycle may simply be a shrinking stage of the Ouki lake.[8] Likewise, the existence of Lake Minchin may be in part based on misattributing deposits left by Ouki.[2] The Ouki lake cycle may be subdivided into individual phases in the future.[9]

The Ouki lake may have been populated by species such as

ostracodes and the Biomphalaria andecola snail.[10] Waters had a high concentration of strontium.[11] While one model inferred from strontium isotope data assumes that most of the Ouki water was contributed by the Poopó basin, another called "Ouki B" assumes a 69% contribution by waters from Lake Titicaca and no contribution from the Coipasa and Uyuni basins, which is less likely.[12] Waters from the Poopó basin would have spilled into the Uyuni/Coipasa basin.[13] The drying of the lake left deposits containing amphibole, illite, plagioclase feldspar, potassium feldspar, kaolinite, pyroxene, quartz and smectite.[14]

Dating

Various radiometric dates have been obtained for the postulated Ouki paleolake from tufa, wood and fossils of

North Atlantic,[17] lternatively, if radiocarbon dates of 44,609 ± 927 to 33,422 ± 1937 are attributed to Ouki, sediments in the Uyuni basin attributed to Lake Minchin would instead belong to Ouki.[18]

Context

Lake Ouki's formation may have been caused by an increase in precipitation,

La Nina-like conditions.[20] The increase of precipitation may have amounted to 50–100%.[21]

The Ouki lake cycle occurred during a major

Lomas de Lachay in Peru also coincide with the Ouki humid period.[32]

Controversy

The existence of this lake was questioned in 2011, based on the lack of evidence for such a lake in drill cores of Salar de Uyuni.[33] It is unknown whether the Poopó basin lake extended to the Uyuni/Coipasa basins as well.[5] The sill separating the Poopó and Uyuni/Coipasa basins may not have been breached until 80,000–60,000 years ago.[34] In 2013, it was suggested that the "L4" lacustrine stage, which has been identified in drill cores taken from Salar de Uyuni, may be the Ouki/Salinas lake phase.[35]

References

  1. ^ Baker & Fritz 2015, p. 40.
  2. ^ a b Placzek, Quade & Patchett 2006, p. 528.
  3. S2CID 134780354
    .
  4. ^ Placzek, Quade & Patchett 2011, p. 240.
  5. ^ a b Placzek, Quade & Patchett 2011, p. 242.
  6. ^ Placzek, Quade & Patchett 2013, p. 103.
  7. ^ a b Placzek, Quade & Patchett 2006, p. 520.
  8. ^ a b Placzek, Quade & Patchett 2006, p. 523.
  9. ^ a b Placzek, Quade & Patchett 2011, p. 233.
  10. ^ a b Placzek, Quade & Patchett 2006, p. 521.
  11. ^ Placzek, Quade & Patchett 2011, p. 236.
  12. ^ Placzek, Quade & Patchett 2011, p. 239.
  13. ^ Placzek, Quade & Patchett 2011, p. 241.
  14. ^ Placzek et al. 2006, p. 11.
  15. ^ Placzek, Quade & Patchett 2006, p. 518.
  16. ^ Zech et al. 2017, p. 712.
  17. ^ a b Placzek, Quade & Patchett 2013, p. 106.
  18. ^ Gosling et al. 2008, pp. 45–46.
  19. ^ Placzek, Quade & Patchett 2006, p. 530.
  20. ^
    doi:10.1016/j.palaeo.2009.09.023
    .
  21. ^ Placzek, Quade & Patchett 2013, p. 104.
  22. ^ Zech et al. 2017, p. 714.
  23. S2CID 134780354
    .
  24. ISSN 0277-3791
    .
  25. ^ Gosling et al. 2008, p. 45.
  26. S2CID 59381972
    .
  27. hdl:2445/98248
    .
  28. S2CID 189986799
    .
  29. doi:10.1016/j.jsames.2022.103824
    .
  30. hdl:2097/34092
    .
  31. S2CID 134540130
    .
  32. S2CID 214164504
    .
  33. doi:10.1016/j.palaeo.2011.03.002
    .
  34. ^ Baker & Fritz 2015, p. 41.
  35. ^ Placzek, Quade & Patchett 2013, p. 101.

Sources

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