Geochronological and Sedimentological Interpretation of Interglacial Aquatic Sediments based on TL Dating

For the first time sedimentological interpretation of absolute ages obtained by thermoluminescence method on aquatic interglacial sediments was made. The analyzed size fractions of quartz grains were 160-250, 125-160, 100-125, 80-100 and 63-80 μm. The youngest and most reliable ages from 22 analyzed samples were obtained from the following quartz grain size granulometric fractions: 160-250 μm - 3 cases, 125-160 μm - 7, 100-125 μm - 6, 80-100 μm - 3 and 63-80 μm - 2 cases. Therefore, it may be concluded that the most suitable fractions for thermoluminescence dating are 125-160 μm and 100-125 μm. While evaluating the results of thermoluminescence dating it is necessary to take into account the procedure of sampling from layers of interest, their lithological composition, first of all granulometric, sedimentary environment, including sources of material, the material getting to the load flows, transportation mode and basin differentiation. From all the granulometric fractions of a sample, age of fine-grained fraction (63-80 μm) may be explained by the input of aeolian dust to a basin and sedimentation along with clasts brought to a lake by water flows. Aeolian sand storms performed precise multigenetic sedimentation that was active during that time. Bimodality of granulometric composition is defined by input of material from various sources of different composition. Older ages were obtained in the case of positive granulometric asymmetry. After sedimentological interpretation of thermoluminescence (TL) dating we can state that formation of aquatic fine-grained sands occurred 83.6±10 - 116.1±13 and 130.2±15 - 276.4±32 thousand years (ky) ago. Those geochronological zones coincide with interg lacial periods of Merkine (75.5-114 ky) and Snaigupele (180-280 ky) in Lithuania.