A MID-HOLOCENE DRY INTERVAL IN CENTRAL CHINA: EVIDENCE FROM LAKE SEDIMENT LITHOLOGIES AND ECOLOGICAL PROXIES

In China, the mid-Holocene is traditionally thought to be a warm and humid magathermal period with a strong summer monsoon. Here we present high resolution pollen data and lacustrine lithological evidence from the margin of the present summer monsoon on the western inner Mongolian Plateau. The data shows that present lakes and wetlands in the Tengger Desert experienced desertification in the mid-Holocene around 5000-7000 cal years ago. Forest vegetation declined in the mountains along the northern margin of the Tibetan Plateau during the same period. These proxies suggest the dry climate of this interval was due to the failure of the Asian summer monsoon. This mid-Holocene drying episode is documented in a number of lakes in the middle latitudes of North China, indicating the impact of the event was quite wide spread. These results suggest the dry 5-7000 cal yr BP interval in north central China is related to a mid-Holocene decline in global monsoon circulation. We suggest the failure of the monsoon may be the result of the rapid cooling of the Tibetan Plateau and is ultimately related to a decrease in solar radiation.