LATE QUATERNARY GLACIER ADVANCES AND PALAEOLAKE HIGHSTANDS IN THE BOLIVIAN ALTIPLANO

Recent study of late Quaternary moraines and 'pluvio'-lacustrine featu res around the southern Altiplano of Bolivia suggests they developed m ore or less synchronously during the last glacial cycle. The stratigra phy of lacustrine and deltaic sediments can be linked to outwash and m oraines on glaciated massifs, e.g. Cerro Condor Iquina, Cerro Azanaque s and Cerro Tunupa, which border the Poopo, Uyuni and Coipasa salt bas ins. Uranium-series and radiometric dating of lake carbonates by previ ous workers, suggests that major palaeolakes developed during the inte rvals 72-68 ka BP, 44-34 ka BP and 15.4-9.5 ka BP. Radiocarbon dating of pear associated with glacifluvial and glacial sediments indicates t hat the most extensive glacier advance of the later part of the last g lacial 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 s tand (the Tauca phase) has been dated to ca. 13.8 ka BP, it is conclud ed that increased effective moisture and cool climatic conditions duri ng 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 interv al ca. 15.4-9.5 ka BP, its surface reaching different levels at differ ent times. Copyright (C) 1996 INQUA/Elsevier Science Ltd.