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Optically Stimulated Luminescence Dating of the Chengdu Clay in the West Sichuan Basin
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摘要


     West of Sichuan basin is the western part of the very large Sichuan basin,in the Southwest China,lies just to the south of the Loess Plateau and to the east of the Tibetan Plateau.Chengdu clay which is silty clay sediment widely distributed in the basin surfaces,intrabasinal river terraces and surrounding mountains at different altitudes,it covered in the Early and Middle Pleistocene vermiculated red soil or Mesozoic strata.It has a general thickness of 2-7m with a maximum thickness of greater than 10m.Geological and geochemical evidencespatial variation of thickness and grain size,distributive features,common and trace elements,REE,surface textures of quartz particles,etc.have demonstrated that the Chengdu clay in western Sichuan basin is eolian,it record important information for reconstructing the Pleistocene environments.However,Chengdu clay has not been dated by modern dating techniques,this hampers paleoenvironment significance discussion.In this study,six optically stimulated luminescenceOSLsamples of Chengdu clay were taken at different section,fine quartz particles4-11μmwere chosen for OSL dating,following the combined pretreatment methods of Lu et al.1988and Aitken1998.Luminescent signals were excited by blue laser47±5nmand measured on a Daybreak 2200 at the State Key Laboratory of Crustal Dynamics,Institute of Crustal Dynamics,China Earthquake Administration,Beijing.The results show that Chengdu clay age is 74.67±9.59ka-18.60±0.33ka,suggesting that it accumulated during the Last Glaciation in Late Pleistocene,correspond to Malan loess on the Chinese Loess Plateau.Dry and cool conditions has provided abundant sources for aeolian deposits in the Last Glaciation in Late Pleistocene,thus accumulated Chengdu clay in west Sichuan basin.

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