Late Quaternary glacier advances in the Andes of Santiago, central Chile, and paleoclimatic implications

Andean mountain glaciers in central Chile are in a transitional zone between the seasonal influence of the mid-latitude westerlies and subtropical semiarid conditions to the north. Long-term glacial dynamics for these glaciers and their relationship with the paleoclimate during the late Quaternary are poorly known despite their relevancy. We estimate here the timing and extent of late Pleistocene-early Holocene glaciers in the Andes of Santiago (33 degrees 50 ' S) from geomorphological and geochronological analyses. Our observations evidence that a glacial stage occurred before the Last Glacial Maximum (ELGM) at the San Gabriel drift (1,300 m a.s.l.), dated as similar to 46-36 ka. Glacial stages during the latest Pleistocene-early Holocene transition period, partially concomitant with the Antarctic Cold Reversal (ACR) and with the Younger Dryas (YD) chronozones, were identified and dated at La Engorda drift (2,450-2,570 m a.s.l.) at similar to 15-10 ka. We propose that the San Gabriel drift represents a prolonged glacial advance driven by increased precipitation and cold conditions off central Chile during glacial times. In La Engorda drift, late glacial advances occurred associated with increased regional precipitation, in the context of a transition from humid to arid climate in central Chile, concomitantly with a general warming trend of sea surface temperatures offshore in the southeastern Pacific and with reduced austral summer insolation. The results support the sensitivity of the Andean mountain glaciers to precipitation and paleoclimate conditions, most possibly associated with periods of increased northward influence of the mid-latitude westerlies during glacial and late glacial times, in addition to the El Nino/Southern Oscillation (ENSO) impact since the mid-Holocene, driving late Quaternary glacier advances in central Chile. We estimate a maximum variation of similar to 1,200 m in the position of the late Quaternary Equilibrium Line Altitude (ELA), inferred at similar to 3,400 m and similar to 3,600 m a.s.l. at the time of the San Gabriel and La Engorda drifts, respectively, with respect to its modern location close to 4,600 m a.s.l.

Automated summary

The Andean mountain glaciers in central Chile are influenced by the mid-latitude westerlies and subtropical semiarid conditions. The glacial dynamics during the late Pleistocene-early Holocene period were mainly driven by precipitation and paleoclimate conditions, with multiple advances and retreats identified.