A multiproxy record of Asian monsoon variations during the last 15,000 years from Peiku Co, Tibetan plateau.

Abstract

Knowledge of Asian monsoon variations will help extend our understanding of global atmospheric circulation. Numerous studies on the Tibetan Plateau have demonstrated the great potential of lake sediment records as indicators of monsoon induced climatic changes during the Holocene. This study focuses on a multi-proxy record from Peiku Co, including XRF elemental composition, carbon isotopes of biomarkers, and GDGT indicies (TEX86, BIT, MBT/CBT), providing a paleoenvironmental history of this region on the southern Tibetan Plateau. The study shows that the climate of the Peiku basin transitioned to wetter conditions after 15 ka BP, but the wetter phase was followed by an arid event between 13 ka and 11.5 ka BP that likely correlated to the Younger Dryas. The early- to mid-Holocene climate was wetter, while drier climate prevailed after 6.7 ka BP. The climate of the late- Holocene returned to wetter conditions, probably due to stronger SW monsoons. The cold event at 8.2 ka BP and a widespread event at 4.2 ka BP could not be distinctively identified in all the proxy records from Peiku Co. The application of the BIT index indicated a constantly high amount of soil organic matter input to the lake, which biased the mean annual lake surface temperature as reconstructed by TEX86. Most Tibetan lakes are greatly influenced by riverine supply, resulting in high BIT values. Further study of the GDGT distribution in soil, water column and lake sediments are needed for a better regional calibration of lake surface temperature and air temperature.