Late glacial and holocene palaeolake history of the Última Esperanza region of southern Patagonia

• Published in: Frontiers in Earth Science
• Main Authors: Roberts, Stephen J., McCulloch, Robert D., Emmings, Joseph F., Davies, Sarah J., Van Nieuwenhuyze, Win, Sterken, Mieke, Heirman, Katrien, Van Wichelen, Jeroen, Díaz Prado, Carolina, Van de Vyver, Evelien, Whittle, Alex, Vyverman, Win, Hodgson, Dominic A., Verleyen, Elie
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI 2022
• Subjects: Last glacial maximum (LGM); Palaeoclimate; Palaeolimnology; Glaciation; Lake-level changes; Patagonia; Southern hemisphere westerly winds (SWW); Antarctic; Esperanza; Paine; Antarc*
• Online Access: https://doi.org/10.3389/feart.2022.813396; https://repositorio.uchile.cl/handle/2250/186466

We undertook multi-proxy analyses on two sediment cores from Lago Pato, a small lake basin at 51 degrees S topographically separated from Lago del Toro in Torres del Paine (TdP), to provide insights into glacier dynamics and lake-level change in the TdP and ultima Esperanza region over the last similar to 30,000 cal a BP (30 ka). Lago Pato is situated in a region overridden by the Southern Patagonian Ice Field during the Last Glacial and in a transitional climatic zone of Southern Patagonia sensitive to seasonal- to millennial-scale changes in the Southern Hemisphere Westerly Winds (SWW). Results show that a deep ice-dammed and enlarged palaeolake encompassed Lago del Toro and Lago Pato c. 30-20 ka after the ice had retreated from local-Last Glacial Maximum (l-LGM) limits at c. 48-34 ka and during the build-up to the global-Last Glacial Maximum (g-LGM), c. 26-19 ka. Gaps in both sediment records between c. 20-13.4 ka and c. 20-10 ka suggest hiatuses in sediment accumulation during the g-LGM and Antarctic Cold Reversal (ACR) readvances and/or removal by lake lowering or flushing during the Late Glacial-early Holocene. The palaeolake level dropped from >100 m a.s.l. to similar to 40-50 m a.s.l. towards the end of the ACR c. 13.4-13.0 ka, creating a shallower glaciolacustrine environment dammed by an ice tongue in the Estancia Puerto Consuelo-ultima Esperanza fjord. Further lowering of the enlarged palaeolake level occurred when the ice thinned to <40 m a.s.l., eventually isolating Lago Pato from Lago del Toro and glaciogenic sediment input at c. 11.7 ka. After isolation, the ecology and water levels in Lago Pato became sensitive to regional climate shifts. The shallow, stable, and highly anoxic environment that developed after c. 11.7 ka is associated with weaker (or poleward shifted) SWW at 51 degrees S and was replaced at c. 10 ka by an increasingly productive shallow-littoral lake with a variable lake-level and periodic shifts in anoxic-oxic bottom water conditions and ratios of benthic-planktonic ...