Was the Late-glacial advance at ~14.0 ka B.P. in Torres del Paine (Patagonia, 51S) the most extensive glacial pulse of Oxygen Isotope Stage 2?

Uncovering the timing and spatial extent of glaciers and associated climate changes in the southern hemisphere provide key foundations in the understanding of the origin and termination of ice ages and new insights regarding the Milankovitch model of ice ages. Here, we discuss paleoclimatological implications from our preliminary 10Be-dating program of moraines in Torres del Paine National Park (TDP), in southern Chilean Patagonia (51S). Four main moraine belts (TDP I-IV, from outer to inner) expose geomorphological evidence for ice extent and fluctuations during the last glacial cycle in Torres del Paine. We collected 24 boulders embedded in the outer two moraines (TDP I-II moraines) for 10Be cosmogenic-exposure dating to reconstruct the Quaternary glacial and climate history. The 10Be exposure data show that the mean ages of TDP I moraine, at least in Laguna Azul basin, is about 40 ka BP (n=5) (ka BP= 1,000 years before present) and TDP II is about 14 ka BP. Although most of the 10Be glacial records in Patagonia have documented that the local Last Glacial Maximum (LGM) occurred between 25-17.5 ka BP, in Torres del Paine the maximum extent of the Southern Patagonian Icefield during the last glacial cycle may have occurred as early as ~40 ka BP. This is one of the first lines of (moraine-based) evidence that suggests the existence of an early LGM in Patagonia. The apparent age of the TDP II moraine dating to the late-glacial seems to imply that there are no distinct moraines in Torres del Paine dating to the time of the global LGM, a unique case revealed here. Scattered boulders from TDP II moraine dates to the late LGM and seems to suggest that late-glacial ice overrode the LGM moraines in Torres del Paine. Both glacial pulses at 40 ka BP and 14 ka BP in Torres del Paine occurred during stadial phases in West Antarctica suggesting the existing of an Antarctic climate control on southern Patagonian during the last glacial cycle. Physical mechanisms allowing climate teleconnections between Antarctica and southern Patagonia may be tied to the location of the Antarctic Front Zone and associated Polar Vortex and the Westerly wind belt.