Luminescence dating of bottom sediments from Lake Hovsgol,Mongolia(HDP-08)

To understand the past environmental change using geological archives（e.g.,core of sediments or ice）,establishing the reliable chronology is one of the most important key issues.Luminescence dating is a powerful mediod due to its applicability to quartz,which is common mineral found in various kinds of environment,and the datable age range being from present to 100 cal ka.A core of;8 m in length were obtained in 2008 from Lake Hovsgol,Mongolia（HDP-08） for the purpose of reconstructing the climate-forcing environmental fluctuation in the central continent with high altitude.In this study,optically stimulated luminescence（OSL） from quarts and red thermoluminescence（RTL） from carbonate were measured to estimate depositional ages the sediments.The 16 samples were collected every 10 cm from the core using squire stainless tubes（1 cm × 1 cm） with the length of 4 cm.The surface part,which was exposed to light during core dividing procedures,was then removed in a dark room.After chemical treatment to extract fine grained quarts,OSL were measured.RTL were measured on the bulk sediments based on the thermoluminescence colour images of particular components of sediment.Luminescence was measured by MOSL-11 or MOSL-22 with x-ray source（MEDEC）.When the Des estimated from OSL and RTL are compared,they are identical for eleven samples within the error range.To estimate annual dose,concentrations of radioisotopes(;U,;U,;Th and;Rb) were measured by laser ablation- inductively coupled plasma- mass spectrometry（LA-ICPMS）.Potassium concentration was measured by X-ray fluorescence spectrometry（XRF）.The OSL ages increase from（6.8 ± 3.7） ka to（72.4 ± 13.6） ka along with the depth,but are smaller than C ages.This may be caused by either or both of underestimation of water content in estimation of annual dose and overestimation of C ages due to reservoir effect.