A similar to 6000 yr diatom record of mid- to late Holocene fluctuations in the level of Lago Winaymarca, Lake Titicaca (Peru/Bolivia)

摘要

A multidecadal-scale lake-level reconstruction for Lago Winaymarca, the southern basin of Lake Titicaca, has been generated from diatom species abundance data. These data suggest that similar to 6500 cal yr BP Lago Winaymarca was dry, as indicated by a sediment unconformity. At similar to 4400 cal yr BP, the basin began to fill, as indicated by the dominance of shallow epiphytic species. It remained somewhat saline with extensive wetlands and abundant aquatic plants until similar to 3800 cal yr BP, when epiphytic species were replaced by planktic saline-indifferent species, suggesting a saline shallow lake. Winaymarca remained a relatively shallow lake that fluctuated on a multidecadal scale until similar to 1250 cal yr BP, when freshwater planktic species increased, suggesting a rise in lake level with a concomitant decrease in salinity. The lake became gradually fresher, dominated by deep, freshwater species from similar to 850 cal yr BP. By similar to 80 cal yr BP, saline-tolerant species were rare, and the lake was dominated by freshwater planktic diatoms, resembling the fresh and deep lake of today. These results reveal a more dynamic and chronologically specific record of lake-level fluctuations and associated ecological conditions that provide important new data for paleoclimatologists and archaeologists, to better understand human-environmental dynamics during the mid- to late Holocene.