| Aqueous deposits,such as alluvial sediments, diluvial-deposits, lacustrine sediments and fluvioglacial deposits of Late Quaternary sediments are widely distributed in the North, Northeast and Northwest of China, especially in plains, hills and the mountain front. The lithology and lithofacies of alluvial sediments directly reflect the characteristics of the sedimentary environments, and information about regional climate and environmental change are rich in the sedimentary strata.It is significant for human production and economic development to carry out chronological study of regional climate evolution and create a chronological framework so as to predict future environmental changes. Quaternary workers think highly of OSL dating for its unique advantages in dating of loose deposits. Taking Hutuo-river alluvial-diluvial sediments for example, Pre-treatment experiment,the possibility of Re-OSL dating with fine-grained quartz for water-deposited sediments and the environmental change of the Hutuo-river alluvial area has been studied in this paper.The results are as follows.1.The fine-grained quartz samples have been divided into 7 different groups of the same amount. Silicon fluoride acid etching experiments have been conducted in each group through controlling of time and concentration respectively. The results show that we should choose corresponding pre-treatment methods for different samples, because of the complex sedimentary environment, the various of mineral composition, and different sources of the water sediments,especially for the alluvial sediments.2.By the experiments of etching the coarse particles with heavy liquid and 12 amine to purify quartz, the comparative study of X-diffraction and quartz OSL signal attenuation implies that samples by 12 amine flotation still contain 10.5% impurities. Samples which are separated by the heavy liquid contain quartz up to 98%. Therefore, heavy liquid separation can purify quartz better than other methods.3.There are TT-OSL signals in the fine-grained quartz both of alluvial sediments of Hutuo-river and lacustrine sediments of Yangyuan area,The OSL signals of the fluvial sediments does not increase gradually with depth while the lacustrine does; The recovery dose experiment reveal that dose value can not be restored of the alluvial sediments; Comparing the multiple aliquots fine-grained quartz SMAR and Re-OSL dating results of the same lacustrine sediments, the result shows that the Re-OSL dating for lacustrine sediments is feasible to some range of time.4. Through OSL dating of alluvial sediments of Hutuo-river since late pleistocene and comparing the sample age with the pollen analysis, the chronological framework of paleoclimatic evolution since late Pleistocene of the study area was reconstructed. It can be divided into four stages. Before 146±8.1ka B.P., the climate was moderate and dry. The vegetation environment was desert and steppe type; From 146±8.1 ka B.P. to 80±4.5ka B.P.,the climate became warm and wet and the vegetation changed into mixed forests of coniferous and latifoliate and grassland; From 80±4.5ka B.P. to 18±2.5ka B.P.,the climate was dry and cold and the vegetation was mainly desert and steppe with steppe-woodland in part of the region; Since 18±2.5ka B.P. the climate has been alternate with cold and warm and the vegetation has become steppe-woodland.
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