Age limit and age underestimation using different OSL signals from lacustrine quartz and polymineral fine grains

As part of a systematic palaeohydrological reconstruction of lake level fluctuations during the Last Glacial Maximum, a transect of cores from ancient Lake Xinias in central Greece has already been studied with respect to pollen, sediment and mineral magnetic analyses. The chronology was based on ¹⁴C AMS dating of terrestrial plant macrofossil remains from peat and clayey peat (Palaeogeog. Palaeoclimatol. Palaeoecol. 158 (2000) 65). This site thus provides an opportunity for the comparison of fine grain optically stimulated luminescence (OSL) ages of water–lain sediments with an independent chronology. We present here infrared (IR), post-IR blue and blue OSL characteristics of the fine grain sediments from Lake Xinias and a preliminary comparison with independent ages. The equivalent doses based on the IR results are about 40% of those based on post-IR blue stimulation, which in turn are 10–15% below those based on quartz OSL. We discuss the ages derived from the 3 signals in terms of the independent chronology, and draw conclusions about initial bleaching of the quartz and feldspar components, and the reliability of the post-IR blue signal as a chronometer.