Formation of the Yazi Spring Stream and its significance on tectonics-climate on the northern slope of Kunlun Mountains

The sequences of fluvial terraces in the Yazi Spring Stream are signs of the stepwise uplift of the Kunlun Mountains in the northern part of the Tibetan Plateau since the Late Pleistocene. Geomorphic and sedimentary features of the terraces reveal that they have resulted from the phased tectonic uplift and the consequent river incision in the northern plateau. Using the method of Single-aliquot Regenerative-dose (SAR) Protocol and Radiocarbon (14)c dating, the deposit ages of three-grade terraces were obtained, which are 57.5, 12.8 and 5.7 kaBP, respectively. The features and ages of terraces reveal that the incision rate of the stream accelerated at the beginning of the Holocene. The incision rate changed suddenly at 12.8 KaBP, from 0.43 +/- 0.07 mm/a to 1.59 +/- 0.55 mm/a. This implicates that uplift of the Kunlun Mountains is intensive at the first onset of the Holocene, corresponding to the obvious change of slip-rate on the Alyn Tagh Fault. But its uplift rate is much lower than that of the latter, which suggests that growth of the northern margin of the Tibetan Plateau is stronger than its interior.