From open and fresh to closed and alkaline: a history of transforming basins recorded in lacustrine carbonates
Final Report Abstract
Lake Van, the largest alkaline lake in the world, belongs to a canon of closed basins famous for their sensitive reactions to environmental change. Isotopic composition of lacustrine carbonates often provides the key to the local paleohydrological conditions. However, in case of ICDP PALEOVAN data, the oxygen isotope record of the bulk carbonate fraction was random and inconsistent with other environmental proxies. Additionally, initial data suggested that early Lake Van had a different hydrological regime than its modern equivalent. The mentioned interpretative conundrum and possibility of documenting changes in a basin undergoing a substantial transformation from freshwater to alkaline sparked the motivation for two parallel projects, a proxy-validation study focussing on the 0-147 ka window, and the documentation of ecological and geochemical changes in the early Lake Van, with the overall aim of pinpointing the freshwater/open to alkaline/closed transition focussing on the ca 280-640 ka window. The current project benefited significantly from findings of the previous one. Among others, we have found no evidence of early diagenetic changes reported from the younger sediments of alkaline Lake Van. The presence of deformed unit hindered the exact identification of hydrological transition but based on our data we hypothesise that the Lake Van remained an open and predominantly freshwater basin throughout the MIS13 to MIS15. A manuscript collating data gendered here and in the parallel project is in preparation.
