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六盘地脊东方麓泾河下流河流动阶地的结合丁代

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  Liupanshan is the key region to research the uplift and tectonic deformation of the northeastern Tibet-an Plateau.Jinghe River terraces at the eastern piedmont are geomorphology carriers to record tectonic uplift process of Liupanshan since the Quaternary.The detailed study of profiles of the upper Jinghe River terraces shows that Jinghe River mainly developed 5 river terraces,i.e.T5 -T1.Terraces of T5,T4 and T3 in Liu-shugou are accumulation terraces,and T2 and T1 are pedestal terraces;terraces in Gaojiashan are erosional terraces or pedestal terraces.Trough dating results of OSL and ESR and combined with loess-paleosol sequences the ages of 5-level terraces were defined as 541 ka B.P.,477 ka B.P.,279 ka B.P.,60 ka B.P.and 8 ka B.P.,respectively.The morphological types of terraces and the relationship between age of terraces and cli-mate change indicate that the upper Jinghe River terraces are mainly driven by tectonic uplift while the effects of climate change are complementary.During 541 ka B.P.to 279 ka B.P.,Liushugou region is accumulation area and the accumulation rate is 0.31m /ka,correspondingly,the incision rate of Jinghe River in Gaojiashan is averaged as 0.37 m /ka,which is located in tectonic uplift region,and the accumulation rate is almost equal to the incision rate,indicating the thick gravel layers in T5,T4 and T3 related to Liupanshan rapid uplift.In 279 ka B.P.,Liushugou transforms to an erosion area under sustained uplift in Liupanshan,resulting the incision rate in T1 and T2 increasing to be 1.13 m /ka,indicating eastward extrusion uplifting under the background of expansive uplift of the northeastern Tibetan Plateau.The study provides a new evidence for the cognition that the Tibetan Plateau expands in a way of area and volume.

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