Analysis of a fragmentary diatom record from Lake Van (Turkey) reveals substantial lake-level variability during previous interglacials MIS7 and MIS5e

Ancient lake sediments provide opportunities to reconstruct aquatic ecosystems during previous interglacials. In the summer of 2010, the ICDP project PALEOVAN drilled a complete succession of the lacustrine sedimentary sequence deposited during the last *600,000 years in Lake Van, eastern Anatolia (Turkey). Previous palaeolimnological analysis of the Lake Van sediment record has shown diatoms to be absent over most of the sequence apart from a short interval during the Holocene. Here, we demonstrate the preservation of additional fragmentary diatom records during Marine Isotope Stage (MIS) 7 (243,000–191,000 years ago; Lisiecki and Raymo in Paleoceanography 20:PA1003, 2005; Jouzel et al. in Science 317:793–796, 2007) and MIS5e (130,000–116,000 years ago; Lisiecki and Raymo 2005; Jouzel et al. 2007), each spanning no more than a few thousand years. Although brief, the presence of contrasting diatom assemblages between these two interglacials provide a snapshot of varying water depth and, by inference, climate. Analysis of MIS7e samples suggests that lake water levels were low after a period when the lake was open (i.e., high lake levels with the presence of an outflow present), resulting in higher salinities and possibly less stable bottom waters, which switched between anoxic and oxic states more frequently. By contrast, the diatom assemblages Electronic supplementary material The online version of this article (doi:10.1007/s10933-017-9973-z) contains supplementary material, which is available to authorized users. S. M. North (&) Department of Life Sciences, Imperial College London, Silwood Park Campus, London SL5 7PY, UK e-mail: [email protected] M. Stockhecke Geological Institute, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland M. Stockhecke Large Lakes Observatory, University of Minnesota, Duluth, MN, USA Y. Tomonaga Department of Water Resources and Drinking Water, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland Y. Tomonaga Institute of Geological Sciences, University of Bern, Baltzerstrasse 1?3, 3012 Bern, Switzerland A. W. Mackay Environmental Change Research Centre, Department of Geography, UCL, London, UK