Quaternary non-marine ostracods of Runtuyoc lake, northern Argentina: New taxonomic descriptions and the implication for Holocene paleoenvironment

摘要

We performed an ostracod taxonomic analysis on samples from a shallow lake (Runtuyoc Lake) in north-western Argentina in order to contribute to the understanding of the evolution of this water body through the last 5000 years. The ostracod assemblages consist of 15 species, two species exclusively from modern samples (Herpetocypris helenae and Chlamydotheca incisa), 8 exclusively from Quaternary samples (Limnocythere jujunensis sp. nov., L. titicaca, L. alexanderi, L. aff. staplini, Cyprideis salebrosa, Penthesilenula incae, Cypridopsis vidua, Sarscypridopsis aculeata) and 5 from both, modern and Quaternary samples (Ilyocypris natural, Potamocypris smaragdina, Heterocypris incongruens, Heterocypris similis, Candona sp.). The lake is located in the Miraflores river course and is characterized nowadays by freshwater conditions, but a saline past is evident as it went through different periods of desiccation. From 5500 to 3000 cal a BP, the lake was absent, probably related to extreme dry conditions. Then, water inputs into the lake produced a saline shallow lake until to reach modern setting as a freshwater body basin. Runtuyoc lake records, supports the regional environmental trending change for the Argentinian northwest, with wetter conditions in the early and late Holocene, and arid for the middle Holocene at least from 5500 to 3000/2500 cal a BP.