Aeolian sediments on the north-eastern Tibetan Plateau

Abstract

Aeolian sediments on the Tibetan Plateau are an important archive of palaeoclimatic information. This study presents a detailed analysis of sediments from the Donggi Cona catchment on the north-eastern part of the Tibetan Plateau. Long- and short-distance sediment transport leads to a complex pattern of aeolian sediment deposition that depends on climatic changes as well as on the availability of sediments. Based on the largest dataset of OSL datings (51) from a single catchment on the Tibetan Plateau so far, different periods of increased sediment transport have been reconstructed. Increased aeolian deposition in this high elevation environment started in the early Holocene with the accumulation of sands from around 10.5 to 7 ka. Loess sediments have been preserved from a period from 10.5 to 7.5 ka. Both archives are related to the strengthening of the Asian summer monsoons characterized by wetter and warmer climate. This change in climate supported the trapping of aeolian sediments. Under full monsoon conditions from around 9 ka onwards fluvial processes resulted in erosion of the aeolian archives and the formation of colluvial sediments until 6 ka. A dry and cooler climate resulted in the reactivation of dune sands from 3 ka to present, possibly in combination with stronger human influence. Aeolian sediments on the Tibetan Plateau therefore indicate two different climatic modes. During the early Holocene wetter conditions were favourable to retain aeolian sediments. The reactivation of sediment in the late Holocene due to small-scale disturbances in the vegetation cover, points to a cooler and drier climate.