Lake Qinghai is the largest interior plateau lake in North China and has long been sensitive to climate change and the environmental effects of Tibetan Plateau uplift. 

Long, continuous, terrestrial lacustrine sedimentary records are extremely rare but an almost continuous 626 m long sediment core of ancient Lake Qinghai have been obtained from an in-filled part of the southern lake basin, which documents both the age of the origin of the lake and the evolution of the East Asian monsoon during the Late Cenozoic.

A new study presents a high-resolution magnetostratigraphy work which provides a chronology back to about 5.1 million years ago. Analysis of lithofacies and depositional environments reveal that the change from eolian to lacustrine facies occurred ~4.63 million years ago, corresponding to a shift from an arid/semi-arid to a more humid climate, which resulted in the origin of Lake Qinghai.

Changes in sediment lithology and mean grain-size indicate that the lake level fluctuated considerably, superimposed on a long-term trend from higher to lower levels in response to variations in the East Asian Monsoon.

This archive is a significant additional source of information on regional and global environmental change, complementing the existing records from North China which are mainly based on analysis of loess deposits. 

Paper: Chaofeng Fu et al., State Key Laboratory of Loess and Quaternary Geology, Institute of Earth and Environment, CAS, Xi'an, Shaanxi, 710075, China; and Key Laboratory of Western Mineral Resources and Geological Engineering, Ministry of Education of China&Chang'an university, Xi'an, Shaanxi, 710054, China. DOI10.1130/G34418.1.