Groundwater discharge to a Gobi desert lake during Mid and Late Holocene dry periods Steffen Mischke a, * , Dieter Demske a , Bernd Wu ¨ nnemann b , Michael E. Schudack a a Institute of Geological Sciences, Freie Universita ¨t Berlin, Malteserstr. 74-100, Haus D, 12249 Berlin, Germany b Institute of Geographical Sciences, Freie Universita ¨t Berlin, Malteserstr. 74-100, Haus L, 12249 Berlin, Germany Received 19 August 2001; received in revised form 28 September 2004; accepted 25 May 2005 Abstract High levels of Lake Eastern Juyanze and a wetter climate in the Gobi desert (NW China) were recorded between 5100 and 4100 cal. year BP from ostracod distribution, shell geochemistry, sedimentology and palynological data. After about 4100 cal. year BP lake levels decreased and groundwater discharge became dominant source of water during short-term regressive events at about 4000, 3800 and 3500 cal. year BP as suggested by a significant difference in modern river water and groundwater chemistry and the geochemical signal of fossil ostracod shells. The overall trend towards lower lake levels culminated in repeated episodes of desiccation of Lake Eastern Juyanze between 3200 and 2900 cal. year BP. Individual regressive events as well as the rapid environmental fluctuations of Lake Eastern Juyanze at about 3000 cal. year BP were likely caused by Mid to Late Holocene temperature fluctuations, recorded by the Dunde ice core [Yao, T., Thompson, L.G., 1992. Trends and features of climatic changes in the past 5000 years recorded by the Dunde ice core. Annals of Glaciology 16, 21–24] and shifts of the southeastern Asian monsoon. D 2005 Elsevier B.V. All rights reserved. Keywords: Ostracods; Shell chemistry; Palaeoclimate; Holocene; Gobi desert; China 1. Introduction Large lakes covered vast areas in the Chinese Gobi desert during the Late Quaternary but few studies of environmental reconstruction and palaeo- climate are in existence until recently (Pachur et al., 1995; Rhodes et al., 1996; Wu ¨nnemann et al., 1998; Chen et al., 1999). Late Pleistocene and Holocene lake sediments from the Tibetan Plateau in the south of the Gobi desert (e.g. Kashiwaya et al., 1991; Lister et al., 1991; Gu et al., 1993; Gasse et al., 1996) and from northern Mongolia (e.g. Dorofeyuk and Tarasov, 1998; Grunert et al., 2000) have received more attention. This is especially unsatis- factory considering that the Gobi desert region was probably sensitive to past shifts of the southeastern Asian monsoon, which is the main moisture source 0031-0182/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2004.10.022 * Corresponding author. Fax: +49 30 83870745. E-mail address: smischke@web.de (S. Mischke). Palaeogeography, Palaeoclimatology, Palaeoecology 225 (2005) 157– 172 www.elsevier.com/locate/palaeo