Paleolimnological response to climate variability during Late Glacial and Holocene times: A record from Lake Arturo, located in the Fuegian steppe, southern Argentina

Last Glacial Maximum and Holocene environmental conditions are reconstructed from a lacustrine core obtained from Lake Arturo, located in the Fuegian steppe of southern Argentina. Proxies include diatoms, ostracods, plants remains, organic matter content and sedimentological studies, and they suggest that Lake Arturo experienced climate-related variations in the water level, hydrological balance and temporal stability throughout the last 23,200 cal yr BP. The Late Glacial period, which ended about 15,400 cal yr BP, is characterized by a few low-diversity diatom assemblages dominated by benthic and small-celled fragilarioid taxa. Between the Pleistocene-Holocene transition and the mid-Holocene, Lake Arturo was a shallow, fresh-to-brackish lake with relatively high organic productivity. Around 6200 cal yr BP, the diatom Surirella tuberosa replaced Thalassiosira patagonica, and diatom species richness fell to its lowest level in the records. Together with the presence of the ostracod Limnocythere rionegroensis, which lives in ephemeral environments, this suggests that the lake was very shallow and experienced negative hydrological balance, with hydrochemical and biological conditions that were similar to those of today. Data from other sites in southern Tierra de Fuego suggest that, around 5000 cal yr BP until 800 cal yr BP the rainfall increased and the temperature decreased as a result of an intensification of the Southern Westerlies. By that time, the Lake Arturo record indicates the existence of an ephemeral, shallow, highly saline water body. This suggests an antiphase response to the atmospheric circulation pattern between the southern humid forest and the northern steppe during the middle to late Holocene.