On the north piedmont of Tianshan Mountains, China, the Kuytun River and Manas River transverse the Dushanzi and Manas folds, resulted in 7-level and 6-level pedestal terraces, respectively, which are the tectonomorph...On the north piedmont of Tianshan Mountains, China, the Kuytun River and Manas River transverse the Dushanzi and Manas folds, resulted in 7-level and 6-level pedestal terraces, respectively, which are the tectonomorphic marks of folding and uplift of the Dushanzi and Manas anticlines since the late Quaternary. We have collected samples from deposits of all terraces for OSL （optically stimulated luminescence） geological dating using the SMAR （single-multiple-aliquot-regeneration） method on fine grains. We have also performed dating using the ~4C method on the samples from the deposit of terrace T1 along the Kuy- tun River. The results show that all these deposits are of the later phase of the late Pleistocene. Comparison of terrace dating and climate change since 200 ka suggests that the terraces TI, T2, T3, T4 and T5 along the Manas River formed in 6, 8.5, 10, 14 and 32 ka, respectively. The incision time of Kuitun River＇s T1, T2, T3, T4, T5, T6 and T7 terraces were 1.7, 14, 20, 25, 32 50 and 100 ka years ago, respectively. The terrace T4 along the Manas River and T2 along the Kuytun River were formed dur- ing the late part of the late Pleistocene, i.e., 14 ka. Since 14 ka, the incision of the Manas River has generated three levels of pedestal terraces, while that of the Kuytun River has only produced one level of such terraces. The latest folding and uplift of the Dushanzi anticline took place in 1.7 ka, while that of the Manas anticline occurred in 5 ka. Since 14ka or the later time of the late Pleistocene, the Dushanzi and Manas anticlines have risen by 40 and 95 m, respectively, implying uplift rates 2.7 and 6.8 mm/a for each.展开更多
The Altyn Tagh Fault and the Altyn Mountain define respectively the tectonic and geographical northern edges of the Tibetan Plateau, and figure prominently in the growth and rising mechanism of the plateau. The rhombu...The Altyn Tagh Fault and the Altyn Mountain define respectively the tectonic and geographical northern edges of the Tibetan Plateau, and figure prominently in the growth and rising mechanism of the plateau. The rhombus-shaped Altyn Mountain has long been thought to have an intimate relation with the Altyn Tagh Fault; however, its formation mechanism remains unclear and debatable. In this paper, we focus on the EW-trending uplifts in the Altyn Mountain, and investigated three Cenozoic sedimentary sections in the vicinity of the EW-trending uplifts located along the southern side of the central segment of the Altyn Tagh Fault. Magnetostratigraphy and pollen analysis were used to constrain ages of the sediments. Clast composition of conglomerate and paleocurrents obtained from clast imbrications were applied to determine the provenance. We also established a geological section parallel to the Altyn Tagh Fault on sedimentary facies across the northwestern Qaidam Basin. The results indicate that these en-echelon EW-trending uplifts formed as early as ca. 36 Ma and were preferred to be under the control of basal shear of the Altyn Tagh Fault in the middle-lower crust, symbolizing the early uplift of the Altyn Mountain during the Cenozoic. Left-slip along the Altyn Tagh Fault occurring during the Miocene and afterwards displaced and altered these uplifts, shaping the Altyn Mountain to its present fabric.展开更多
基金supported by National Natural Science Foundation of China (Grant No. 40572126)Special Project of Seismological Community (Grant No. 200808013)
文摘On the north piedmont of Tianshan Mountains, China, the Kuytun River and Manas River transverse the Dushanzi and Manas folds, resulted in 7-level and 6-level pedestal terraces, respectively, which are the tectonomorphic marks of folding and uplift of the Dushanzi and Manas anticlines since the late Quaternary. We have collected samples from deposits of all terraces for OSL （optically stimulated luminescence） geological dating using the SMAR （single-multiple-aliquot-regeneration） method on fine grains. We have also performed dating using the ~4C method on the samples from the deposit of terrace T1 along the Kuy- tun River. The results show that all these deposits are of the later phase of the late Pleistocene. Comparison of terrace dating and climate change since 200 ka suggests that the terraces TI, T2, T3, T4 and T5 along the Manas River formed in 6, 8.5, 10, 14 and 32 ka, respectively. The incision time of Kuitun River＇s T1, T2, T3, T4, T5, T6 and T7 terraces were 1.7, 14, 20, 25, 32 50 and 100 ka years ago, respectively. The terrace T4 along the Manas River and T2 along the Kuytun River were formed dur- ing the late part of the late Pleistocene, i.e., 14 ka. Since 14 ka, the incision of the Manas River has generated three levels of pedestal terraces, while that of the Kuytun River has only produced one level of such terraces. The latest folding and uplift of the Dushanzi anticline took place in 1.7 ka, while that of the Manas anticline occurred in 5 ka. Since 14ka or the later time of the late Pleistocene, the Dushanzi and Manas anticlines have risen by 40 and 95 m, respectively, implying uplift rates 2.7 and 6.8 mm/a for each.
基金supported by Chinese National Key Scientific and Technological Projects (Grant Nos. 2011ZX05009-001 and2011ZX05003-002)
文摘The Altyn Tagh Fault and the Altyn Mountain define respectively the tectonic and geographical northern edges of the Tibetan Plateau, and figure prominently in the growth and rising mechanism of the plateau. The rhombus-shaped Altyn Mountain has long been thought to have an intimate relation with the Altyn Tagh Fault; however, its formation mechanism remains unclear and debatable. In this paper, we focus on the EW-trending uplifts in the Altyn Mountain, and investigated three Cenozoic sedimentary sections in the vicinity of the EW-trending uplifts located along the southern side of the central segment of the Altyn Tagh Fault. Magnetostratigraphy and pollen analysis were used to constrain ages of the sediments. Clast composition of conglomerate and paleocurrents obtained from clast imbrications were applied to determine the provenance. We also established a geological section parallel to the Altyn Tagh Fault on sedimentary facies across the northwestern Qaidam Basin. The results indicate that these en-echelon EW-trending uplifts formed as early as ca. 36 Ma and were preferred to be under the control of basal shear of the Altyn Tagh Fault in the middle-lower crust, symbolizing the early uplift of the Altyn Mountain during the Cenozoic. Left-slip along the Altyn Tagh Fault occurring during the Miocene and afterwards displaced and altered these uplifts, shaping the Altyn Mountain to its present fabric.
