CONICET | Buscador de Institutos y Recursos Humanos

A soil profile from the southern margin of Colhue Huapi Lake, at La Campanita site (45º38? S, 68º37? W), was analysed for pollen and algae content to know the past vegetation communities and to infer changes in lake water level occurred during the Late Holocene. Samples were dated by AMS 14C methods. Radiocarbon ages were of 1711 ± 35 14C yr BP at the base, 95cm depth, and another of 979 ± 42 14C yr BP at 40cm depth. The record was dominated by no arboreal taxa, Chenopodiaceae being the principal shrub taxon and Cyperaceae the herbaceous one. Changes in the pollen record occurred mainly at a local scale and few differences were observed in the input of regional and extra regional pollen. From 1711 ± 35 14C yr BP until ca. 1212 yr BP, a high lake water level was indicated by the low representation of Cyperaceae associated with few shallow areas available to be colonized and high percentages of Pediastrum and Botryococcus algae. Between ca. 1212 and 414 yr BP a period of changes with several fluctuations in water depth developed. This trend would modify at 979 ± 42 14C yr BP with a decrease in the waters reflected by the expansion of Cyperaceae and algal reduction. From ca. 414 yr BP until 195 yr BP lake water level continued falling with a less fluctuating and net trend as indicated by the highest percentage of Cyperaceae in the sequence and a low algal representation. The subsequent reduction in Cyperaceae percentage and the moderate increase in the algae would indicate a recovery of the lake water level for the last ca. 195 yr BP. Additionally La Campanita sequence was statistically compared with a sequence obtained from the north-western margin of the lake. Both sites registered a similar trend before 979 ± 42 14C yr BP.