Fig. 1

Location map of saline lakes. Blue lines in the top panel show reconstructed limits of the West Siberian sea in different stages of the Palaeogene [18]: Latest Selandian-early Thanetian (a), Late Thanetian–Ypresian (b), Lutetian (c), and Bartonian-Priabonian (d). The panel below shows simplified geology. 1 Pre-Quaternary clay silt, clay, and loess, including those building the hills; 2,3 Lower-Middle Pleistocene lacustrine-fluvial clay silt, or less often silt and sand (2) and loess and lake sand, silt, and clay silt (3); 4 Middle-Upper Pleistocene lacustrine and fluvial sand, silt, clay silt, often muddy; 5–7 Upper Pleistocene-Holocene lacustrine clay silt (often muddy), silt, and sand (5), alluvium and slope wash (6), and lacustrine-bog peat, muddy clay silt, and sapropel (7); 8 Freshwater (a) and saline (b) lakes; 9 Sampling sites