Combined IRSL/OSL Dating on Fine Grains from Lake Baikal Sediments

In this work we present luminescence dating results obtained for samples taken from a gravity core of sediments of the Lake Baikal. The initial attempts to date coarse quartz grains failed because such grains were very sparse and dim. Fine grain quartz was also relatively dim and only IRSL signal from fine grain polymineral fraction was sufficient to obtain absorbed dose estimates. We made the measurements on 6-12 μm fraction extracted by differential precipitation in a water column. Samples were collected from the sediment depth range between 80-750 cm which, basing on paleomagnetic data, were expected to cover the period up to ca. 150 ka. The equivalent absorbed doses measured by means of OSL grow with depth down to 350 cm where they reach about 100-120 Gy and then apparently saturate. For the depth range 80-350 cm IRSL ages also grow almost linearly from 11 to 50 ka. Calibrated radiocarbon ages obtained for micro samples of pollen from the same site yielded an average sedimentation rate of 6.86±0.21 cm/ka for the period between 15-1 ka BP. This is in good agreement with the sedimentation rate deduced from IRSL dating (6.15±0.55).