第九届青年地学论坛

The Headwater Region of the Yellow River (HRYR) is located in the northeastern Tibetan Plateau at an altitude higher than 4000 m above sea level. Modern aeolian sandy land is widely distributed in the HRYR, and the reactivation of paleo aeolian sediments under the disturbance of climate change and human activities has become a hot issue since the past decades. However, the chronology of paleo aeolian sediments in this region remains poorly understood. In this study, 22 samples of aeolian sediments were collected from six sections and dated using optical stimulated luminescence (OSL). Combining the OSL data with 15 previously published OSL ages from three sections in the HRYR, the following results were obtained. The oldest aeolian sand sediments in the HRYR are dated at 7.12 ± 0.39 ka. The remaining aeolian sediments were deposited in the late Holocene, ranging between 3.29 ± 0.42 ka and 0.18 ± 0.01 ka. In the late Holocene, phases of intensifying aeolian activities were recorded by clusters of OSL ages at 2.12–1.81 ka, 1.30–1.26 ka, and the Little Ice Age. In our dataset (37 OSL ages), 27 ages correspond to the past millennium and the aeolian activity phases mainly occurred in the Little Ice Age. The relatively scarce aeolian sand deposits in the early Holocene is likely due to the existence of Maduo Paleolake, which maintained a high water stand, inhibiting the availability of sediments for wind erosion. The absence of mid-Holocene aeolian sediments in this region is attributed to the optimum climate during this period although the HRYR had opened around 7.0 ka BP. Coupled with the drier and cooler climate, the exposure of lacustrine sediments during the endorheic-exorheic drainage transition (EEDT) of the HRYR ultimately triggered enhanced aeolian activities in the late Holocene.

aeolian desertification; OSL dating; hydrological geomorphology; Maduo Paleolake