Glacier and climate reconstruction at Tres Lagunas, NW Argentina, based on 10Be surface exposure dating and lake sediment analyses

We present 35 10Be surface exposure ages from quartzite moraine boulders at Tres Lagunas in the Sierra de Santa Victoria, NW Argentina. Additionally, an ~ 8 m sediment core from a glacial lake was investigated to provide independent radiocarbon age control. The oldest and most extensive glaciation occurred ≥ 116.3 ka and likely coincides with the lake transgression phase Ouki on the Altiplano. Maximum glaciation in phase with the global Last Glacial Maximum (LGM) is dated to 22–25 ka and documents a glacial mass-balance response to substantially lower temperatures and minor precipitation increase in phase with the Sajsi lake transgression phase. After initial deglaciation and formation of a small paleolake at Tres Lagunas, a glacial readvance is documented by an outwash diamict in the sediment core and radiocarbon dated to 19–17 ka, as well as by a moraine surface exposure dated to ~ 17 ka. The most prominent moraine was deposited at ≥ 14.5 ka coinciding with the lake transgression phase Tauca on the Altiplano. This Late Glacial advance reflects the massive intensification of the South American Summer Monsoon (SASM) in response to northern hemispheric cooling during Heinrich I and the resultant southward shift of the intertropical convergence zone (ITCZ) and La Niña like conditions in the eastern equatorial Pacific. Rapid deglaciation started after ~ 14.5 ka, interrupted only by minor glacial still stands at ~ 13.8 ± 1.5 ka and 12.0 ± 1.5 ka, the latter one correlating with the Coipasa transgression phase on the Altiplano and the Younger Dryas.