Ouki was an ancient lake in the Bolivian Altiplano. Its existence was postulated in 2006 by a group of scientists who had subdivided the Lake Minchin lake cycle into several lake phases. The Lake Minchin cycle had been previously identified in 1904 as a now disappeared lake in the central Altiplano.[1] Sediments attributed to Lake Minchin may rather be part of Ouki. The dating is uncertain, with radiocarbon and 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.