Environmental changes during the late Pleistocene and the Holocene in the Gonghe Basin, north-eastern Tibetan Plateau

摘要

Different types of aeolian sediments are widespread in Gonghe Basin on the north-eastem Tibetan Plateau. Despite that individual sections are often discontinuous, the analysis of a large number of individual sections distributed in the entire basin provides a valuable archive for the reconstruction of environmental changes since the late Pleistocene. This study presents 43 new OSL (optical stimulated luminescence) ages and combines them with 39 previously published ages from the Gonghe Basin for the last 16 ka. From around 15 to 14 ka onwards an increase in moisture facilitated the formation of a vegetation cover and the fixation of loess sediments on the northern and southern side of the basin. After enhanced mobility of aeolian sediments during the dry Younger Dryas greater than before precipitation fixated also the sands in the lower parts of the basin. The increase in moisture can be attributed to the strengthening of the Asian summer monsoon. A comparison with the timing of aeolian sediment accumulation in the neighbouring basins probably indicates a time-transgressive strengthening of the monsoon on the north-eastern Tibetan Plateau. Aeolian sands were first permanently stored from around 17 ka at the Qinghai Lake in the north-east of the area and at 10.5 ka at the Donggi Cona in the south-west. The Gonghe Basin is located in an intermediate position. Highest moisture values occurred during the mid-Holocene from around 7.5 until probably 2.5 ka in the Gonghe Basin. In most parts of the basin aeolian activity was low during this time. In the central part of the basin aeolian sand movement occurred sporadically. Since 2.5 ka aeolian activity in most parts of the basin resumed due to the late Holocene weakening of the Asian summer monsoon. However, the parallel accumulation of aeolian sands and silts indicates an increased human influence. (C) 2016 Elsevier B.V. All rights reserved.