Alternating Wind and Fluvial Erosion during the Quaternary in the Qaidam Basin (NE Tibetan Plateau) and its tectonic and climatic significance

Abstract:

The Qaidam Basin is located in the NE Tibetan Plateau, and trapped by the Altyn Tagh Fault system to the northwest, the Qilian Mts. to the northeast and the East Kunlun Mts. – Qiman Tagh to the south. It forms one of the driest regions on earth with severe wind erosion since ca. 3.0 Ma (Heermance et al., 2013).

Whether the Qaidam Basin is one of the major sources of the Chinese Loess Plateau is still debating: study on U-Pb ages of zircon crystals favored the positive answer (Pullen et al., 2011), whereas chemical and mineralogical analysis (Sun, 2002), together with observation on dust storms over the past 50 years (Sun et al., 2001), preferred the negative one. Kapp et al. (2011) reconciled the two contrasting viewpoints by numerical modeling based on the assumption that the Qaidam Basin underwent strong wind erosion during glacial periods but weak wind erosion even fluvial deposition during interglacial periods. However, no geological evidences have been found to back up the assumption. In this contribution, we reported geological evidence indicating that alternating wind erosion and fluvial deposition do exist in the western Qaidam Basin. The evidence consists of an isolated alluvial fan overlying old yardangs forming prior to the fan. The fan, as well as the underlying old yardangs, is now tens of meters higher than adjacent area which is full of young yardangs, suggesting that the fan was deposited between the two wind erosion events. We obtained high resolution (<10cm) DEM data of the fan and adjacent area by terrestrial LiDAR scanning and the age of the fan by ¹⁰Be exposure dating (test in process). We will use the results to calculate the long-term wind erosion rate in the Qaidam Basin, which is the first wind erosion rate obtained from accurate geological evidence. We believe that the result is significant to evaluate the impact of wind erosion on folding inside the basin, and of the global glacial – interglacial cycles on surface processes in the northeastern Tibetan Plateau.

References:

Heermance, R.V. et al., 2013. GSA Bulletin, 125(5-6): 833-856.

Kapp, P. et al., 2011. GSA Today, 21(4-5): 4-10.

Pullen, A. et al., 2011. Geology, 39(11): 1031-1034.

Sun, J., 2002. 203(3): 845 - 859.

Sun, J., Zhang, M. and Liu, T., 2001. Journal of Geophysical Research: Atmospheres, 106(D10): 10325-10333.