187 Journal of Paleolimnology 22: 187–204, 1999. © 1999 Kluwer Academic Publishers. Printed in the Netherlands. Late Quaternary palaeohydrology of the Konya Basin, Turkey, based on isotope studies of modern hydrology and lacustrine carbonates* Melanie J. Leng 1 , Neil Roberts 2 **, Jane M. Reed 2 *** & Hilary J. Sloane 1 1 NERC Isotope Geosciences Laboratory, Keyworth, Nottingham, NG12 5GG, UK (E-mail: M.Leng@nigl.nerc.ac.uk; H.Sloane@nigl.nerc.ac.uk) 2 Department of Geography, Loughborough University, Loughborough, LE11 3TU, UK (E-mail: C.N.Roberts@lboro.ac.uk; J.M.Reed@lboro.ac.uk) Current addresses: **Department of Geographical Sciences, University of Plymouth, Plymouth, PL4 8AA, UK (E-mail: C.N.Roberts@plymouth.ac.uk) ***Department of Geography, University of Newcastle, Newcastle-upon-Tyne, NE1 7RU (E-mail: Jane.Reed@newcastle.ac.uk) Received 21 November 1997; accepted 16 September 1998 Key words: stable isotopes, authigenic carbonate, ostracods, palaeolimnology, Konya Basin, Turkey Abstract The Konya plain in south central Anatolia, Turkey, which is now largely dry, was occupied around the time of the Last Glacial Maximum by a fresh-oligosaline lake covering more than 4000 km 2 . Sediment cores from three residual water bodies (Pinarba-i, Akgöl and Süleymanhaci) within the larger Pleistocene lake basin, have been analysed using a multidisciplinary approach. The sediment sequences are dated as spanning the last > 50 Ka years, although breaks in sedimentation mean that there is only partial chronological overlap between them. Carbon and oxygen isotope analyses on lacustrine carbonate from the three cores give contrasting isotope profiles which reflect the different ages and independent hydrological behaviour of different sub-basins through the late Quaternary. Distinguishing changes that are regional from local effects is aided by modern isotope hydrology studies and by comparing the carbonate δ 13 C and δ 18 O values to diatom and other analyses undertaken on the same cores. *This paper was presented at the 7th International Symposium on Palaeolimnology (1997), held at Heiligkreuztal, Germany. Introduction Stable isotope analysis of lacustrine authigenic and biogenic carbonates provide a valuable indicator of past climatic change in a range of different hydrological contexts. In long residence time terminal lakes the dominant control on the 18 O/ 16 O ratios of the water is evaporative fractionation which is controlled largely by the temperature and relative humidity. δ 18 O records from lakes in arid and semi-arid environments have consequently been interpreted in terms of past changes in the precipitation/evaporation balance of the lake catchment (e.g. Hillaire-Marcel & Casanova, 1987; Gasse & Fontes, 1989). By contrast, evaporation is less significant in short residence-time open lake systems with both inflow and outflow. Assuming no major change in the source, amount, or seasonality of precipitation, authigenic carbonates precipitated in these types of lakes record the changing isotopic composition of the inflowing water and variations in the lake epiliminetic summer temperatures. For example, carbonates from alpine foreland lakes often show abrupt changes in δ 18 O values during the last glacial-interglacial transition. These match closely with co-stratigraphic changes in pollen assemblages