Abstract:

Abstract:  The interaction zone between southwest Tianshan and Tarim is located on the northeast side of Pamir; it is a region with several rows of active reverse faults and active fold zones, and the Artux anticline is one of the active folds. The Boguzi River originated from a glacier in Tianshan Mountains incises the middle segment of Artux active fold. Six pedestal terraces formed in the Late Quaternary had developed along the both banks of the Boguzi River at the site of Artux anticline. These terraces had been folded since its formation. The longitudinal profiles of the terraces have been measured at the Boguzi River by differential GPS. It is found that the terrace surfaces of T1, T2 and T4 dip north on the north limb of the Artux anticline and its slope direction is opposite to the flow direction of the Boguzi River. On the south limb of the Artux anticline, the terrace surfaces of T1, T2 and T5 dip south. The average slope angles of the terrace surfaces of T1, T2 and T5 are 09°, 1.2°, and 1.8°, respectively. These slope angles are larger than the average slope angle of presentday river bed (0.5°). Using the optically stimulated luminescence dating of finegrained quartz and finegrained mixed minerals by the “DoubleSMAR” procedure, we found out that the formation ages of T1, T2, T3, T4 and T5 terraces are about 25.0±2.6, 42.7±4.4, 63.1±6.3, 96.9±9.9 and 120±10 ka BP, respectively. The incision rates of the Boguzi River are nonuniform at different periods in the Late Quaternary. The incision rates of T3 and T4 terraces are 0.49 and 0.44 mm/a, respectively. The incision rates of T1, T2 and T5 terraces are 1.2 mm/a, 1.69 mm/a, and 1.36 mm/a, respectively. The three times of strong incision of the Boguzi River occurred at different periods of time which are (120±10)～(96.9±9.9) ka、(42.7±4.4)～(25.0±2.6) kaka and(25.0±2.6) ka to present, respectively. The accelerated incision may have been caused by the quickly uplifting of the Artux anticline at the corresponding period.

Key words: Key words: Tianshan; river terrace; OSL dating; active fold; tectonic uplift