Integrated reconstruction of Holocene millennial-scale environmental changes in Tierra del Fuego, southernmost South America

• The recovery of a complete lacustrine archive sensitive to paleoclimate changes
• The first record of diatom and terrestrial flora from Lago Fagnano
• Fluctuations in lacustrine algae may indicate small-scale lake-level oscillations.
• Changes in the pollen record relate to temporal changes in humidity.
• Humidity changes through time relate to southern westerlies latitudinal variations.

This study presents new paleoenvironmental data obtained from sedimentary cores from Lago Fagnano, an elongated lake located at 54°S in southernmost South America. Data from palynomorphs (pollen, spores and algae) and associated palynofacies as well as from diatom taxa retrieved from these cores compared with other regional proxies contribute to evaluate the similarities and differences in the climate patterns based on different proxies from southernmost Patagonia. The pollen analysis reveals that a grass steppe environment existed during the early Holocene (11,300–~ 8000 cal a BP) followed by a major vegetation change characterized by development of forest-steppe ecotone communities between ~ 8000 and ~ 6500 cal a BP, under more humid conditions. Between ~ 6500 and ~ 4000 cal a BP, expansion and colonization by Nothofagus forests reflect an increase in effective moisture levels, while openness in the forest communities characterizes the region after ~ 1100 cal a BP. The palynological organic matter combined with the algal content reflects hydrological changes occurring in the lake and its nutrient status, probably in close relation with past climate oscillations. All these past ecological changes are closely related to oscillations in precipitation and temperature as a response to the variations in the latitudinal position and/or strength of the Southern Westerlies wind belt during the Holocene.