Sedimentary characteristics of Wuwei Basin since Late Mid-Pleistocene——Based on OSL chronological study of the wv3 core
Objectives:A series of Cenozoic basins are formed in the Hexi Corridor in the northeast of Qilian Mountains.Clarifying the sedimentary history of these Cenozoic basins is of great significance for understanding the tectonic growth process and dynamic mechanism and the sedimentary evolution history of the Wuwei Basin since the late Middle Pleistocene in the northeast margin of Qinghai—Xizang(Tibetan)plateau.Methods:This paper takes investigated the wv3 borehole core in the middle—lower reaches of Shiyang River in the Wuwei Basin,in the eastern part of Hexi Corridor.The OSL dating and grain size testing were employed for reconstructing the chronological framework and the sedimentary characteristics of sediments at the top 17 m in wv3 borehole since late Middle Pleistocene.Results and Conclusions:The results of 19 two-step PIR200IR290s and 2 multi-step MET-pIRIR dating were obtained,and the OSL dating framework of sediments at the top 17 m in wv3 borehole since late Middle Pleistocene was established.The results show that the two-step pIR200IR290 and multi-step MET-pIRIR test ages are consistent within the margin of errors.During the period of 220～128 ka,the deposition rate was the lowest,0.35 mm/ka,and the hydrodynamic conditions were strong.During the 128～108 ka(MIS 5d,MIS 5e)period,the sedimentation rate was 1.94 mm/ka,and the sediment grain size changed from coarse to fine,indicating that the hydrodynamic conditions changed from strong to weak.From the last glacial maximum to the early Holocene(19～9 ka),the deposition rate was 2.78 mm/ka,and the sediment grain size was relatively fine,indicating that the hydrodynamic conditions were weak at this time and the deposition rate was maximum.The neotectonic movement is relatively active in this area,and there are thrusting activities during the last interglacial to the last glacial maximum.This study is of great significance for revealing the sedimentary characteristics of the Shiyang River Basin on north eastern Qilian Mountains since late Middle Pleistocene.
late Middle PleistoceneWuwei BasinShiyang RiverOSL datingsedimentary evolution
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