A 60 000-year loess-paleosol record of millennial-scale summer monsoon instability from Lanzhou, China

The 28-m high-resolution Shajinping loess section in Lanzhou on the Chinese western Loess Plateau records a detailed history of millennial Asian summe r monsoon change since the earlier last glaciation. Summer monsoon proxies of soil magnetic susceptibility, carbonate content and soil color show that Asian summer monsoon experienced a series of rapid episodic pulse enhancem ents spanning only ca, 1-2 ka and have sub-Milankovitch cycles of progressi ve weakening in low frequency domain since ca. 60 kaBP. Soil formation resp onds to these by deepening colors, accumulating organic matter, increasing biological channels and leaching certain carbonates. The pedogenic degree g enerally increases with the degree of enhancement of summer monsoon. These may reflect the impact of the last glacial fast climatic change in the Nort h Atlantic region on Asian summer monsoon.