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Southeastern Patagonia's (49° S) post‐glacial history inferred from high Andean lake sediments provides new insights regarding Late Pleistocene and Holocene vegetation dynamics at the eastern margin of the Southern Patagonian Icefield. The fossil records of pollen, charcoal and geochemical data from tephra layers from Laguna Chiquita and Laguna Gemelas Este were analysed to reveal past landscape dynamics related to vegetation changes, fire and volcanic events from ca. 15 200 cal a bp to the present. Nothofagus forest expanded over shrubland communities sometime between 15 200 and 4600 cal a bp, along with at least three disturbance sources related to the volcanic eruptions of Lautaro, Aguilera and Hudson, important local fire episodes, and neoglacial advances. Major charcoal deposition reveals moderate fire activity during the Late Pleistocene related to an open landscape characterised by a grass/shrub steppe. Local glacier advances may have affected the Laguna Gemelas Este sedimentation. Tephra deposition events do not correlate to vegetation changes inferred from the Laguna Gemelas Este and Laguna Chiquita pollen records. Late Holocene eastern Andean forest changes and fire activity at 49° S match other southern palaeoenvironmental records (50–52° S) suggesting that changes in the Southern Westerly Wind latitudinal position and intensity drove major palaeovegetation and fire dynamics before the European settlement. In the last centuries, fire and vegetation changes have been closely related to an increase in local ignition sources and the introduction of alien species. [ABSTRACT FROM AUTHOR]

Holocene environmental changes in Patagonia were mostly shaped by fluctuating ice cover recession. Consequently, environmental reconstructions are largely based on discontinuous moraine chronologies from valley deposits. Here, we present a 3 m long continuous sediment record recovered from Laguna Meseta (LME), a lake located on Meseta Chile Chico. Its altitude and location relative to the North Patagonian Icefield provide a unique opportunity to reconstruct the glacial history and related environmental dynamics. Our radiocarbon chronology constrains sedimentation to the last ∼10000 years and provides a minimum age for postglacial ice-free lacustrine conditions, due to a westward retreat of the ice cap. Lacustrine productivity reached its maximum at the start of the lake phase and decreased afterwards. Between 5500 and 4600 cal yr BP, a major shift towards allochthonous sediment accumulation occurred, caused by an abrupt increase in clastic deposition from basaltic lithologies of the Meseta Chile Chico. This episode correlates with the precipitation-driven Mid-Holocene glacier advance of Patagonian glaciers and suggests that conditions were colder and/or wetter on Meseta Chile Chico at that time. After 4600 cal yr BP, these conditions continued to supply LME with clastic sediments until a stepped decrease around 900 cal yr BP. Thereupon, lacustrine productivity distinctly increased and stabilized around 300 cal yr BP. Our findings indicate that changes in sedimentation on Meseta Chile Chico were mainly controlled by regional variability in the precipitation. Furthermore, strong correlation between our records and available proxies for oscillations of the Southern Hemisphere Westerly Winds suggest a pronounced climatic control by this prominent wind system for central west Patagonia during the last 10 000 years. [ABSTRACT FROM AUTHOR]