Late Quaternary glacier advances and palaeolake highstands in the Bolivian Altiplano

Recent study of late Quaternary moraines and 'pluvio'-lacustrine features around the southern Altiplano of Bolivia suggests they developed more or less synchronously during the last glacial cycle. The stratigraphy of lacustrine and deltaic sediments can be linked to outwash and moraines on glaciated massifs, e.g. Cerro Condor Iquiña, Cerro Azanaques and Cerro Tunupa, which border the Poopo, Uyuni and Coipasa salt basins. Uranium-series and radiometric dating of lake carbonates by previous workers, suggests that major palaeolakes developed during the intervals 72-68 ka BP, 44-34 ka BP and 15.4-9.5 ka BP. Radiocarbon dating of peat associated with glacifluvial and glacial sediments indicates that the most extensive glacier advance of the later part of the last glacial cycle culminated after 13.3 ka BP and that a smaller readvance may have occurred between 12 and 10 ka BP. As the highest palaeolake stand (the Tauca phase) has been dated to ca. 13.8 ka BP, it is concluded that increased effective moisture and cool climatic conditions during the interval ca. 14-13 ka BP, forced the simultaneous expansion of glaciers and lakes in and around the southern Altiplano. A palaeolake may have been present on the southern Altiplano for much of the interval ca. 15.4-9.5 ka BP, its surface reaching different levels at different times.