Radiocarbon constraints on the Holocene flood deposits of the Ning-Zhen Mountains, lower Yangtze River area of China

Lying athwart both the temperate and subtropical zones, the Ning-Zhen Mountains are particularly prone to extreme floods in the summer months when cold fronts collide with the subtropics-derived warm airmasses. The Holocene flood deposits in the region may provide a long-term perspective on hydrographical change and its palaeoclimatic implications. Radiocarbon dates on carbonised wood preserved in flooding sediments reveal that the region has experienced a number of catastrophic floods throughout the middle Holocene. These extreme flooding events cluster into three periods: (i) 9200-8200 cal. yr BP, (ii) 7600-5800 cal. yr BP and (iii) 5200-4000 cal. yr BP, corresponding to the times when the East Asian monsoon has been intensified under warm conditions. The significant falls in flooding frequency around 8200 cal. yr BP, 5800 cal. yr BP and 4000 cal. yr BP may have resulted from Substantial reduction in regional precipitation, probably associated with meridional displacement of the planetary frontal system. Copyright (C) 2003 John Wiley Sons, Ltd.