Timing and extent of Late Pleistocene glaciation in the arid Central Andes of Argentina and Chile (26°-41°S)

JANA ZECH; ROLAND ZECH; CARLA M. TERRIZZANO; EZEQUIEL GARCIA MORABITO

Cuadernos de Informacion Geografica

Universidad de La Rioja

Año: 2017 vol. 43 p. 697 - 718

0211-6820

Thearid Central Andes are a key site to study changes in intensity andmovement of the threemain atmospheric circulation systems over South America: the SouthAmerican Summer Monsoon(SASM),the Westerlies and the El Niño Southern Oscillation (ENSO). In thissemi-arid to arid region glaciersare particularly sensitive to precipitation changes and thus thetiming of past glaciation is stronglylinked to changes in moisture supply. Surface exposure ages fromstudy sites between 41° and 22°Ssuggest that glaciers advanced: i) prior to the global Last GlacialMaximum (gLGM) at ~40 ka in themid (26°- 30°S) and southern Central Andes (35°-41°S), ii) inphase with the gLGM in the northern andsouthern Central Andes and iii) during the late glacial in thenorthern Central Andes. Deglaciation startedsynchronous with the global rise in atmospheric CO2 concentration andincreasing temperature startingat ~18 ka. The pre-gLGM glacial advances likely document enhancedprecipitation related to the SouthernWesterlies, which shifted further to the North at that time thanpreviosuly assumed. During the gLGMglacial advances were favored by decreased temperatures incombination with increased humidity dueto a southward shifted Intertropical Convergence Zone (ITCZ) andSASM. During the late-glacial a substantialincrease in moisture can be explained by enhanced upper troposphericeasterlies as response toan intensified SASM and sustained La Niña-like conditions over theeastern equatorial Pacific that lead toglacial advances in the northern Central Andes and the lake levelhighstand Tauca (18-14 ka) on the Altiplano.In the southernmost Central Andes at 39º-41°S, further north at31°S and in the northernmost CentralAndes at 22°S glacial remnants even point to precipitation drivenglaciations older than ~115 ka and260 ka.