Extreme drought event in AD 1637–1643 in North China: New insight from pollen records in Kaifeng City

Abstract. Long-lasting droughts usually result in water shortage and famine and even hinder the progress of human civilization. This paper presents the first study to identify the "Chong Zhen drought" event during the Late Ming Dynasty (AD 1637–1643) in a region with alluvial sediment. Using AMS14C dating, grain size and historical documents, we determined the formation age of the sediment. Pollen records at 5–7.8 m, with the highest values for mesoxerophyte and xerophyte taxa such as Chenopodiaceae, Nitraria and Ephedra pollen, were found to provide evidence for the "Chong Zhen drought" event. Other pollen percentages were almost the lowest value of the entire core. However, sediment at 5–6.7 m also had a very high value of Pinus, which was mainly caused by fluvial transport and depositional processes. Chenopodiaceae, Artemisia and Asteraceae pollen are always transported and deposited together with coarser sediment during the flood running stage, while pollen with thinner extine and air-sacs are always deposited in slow flow or hydrostatic conditions during the flood falling stage. In addition, pollen transported by wind from local and regional areas deposited on the ancient ground are always mixed with the sediment during the flood running stage with coarser until it covered by next flood. Our work helps shed light on the interpretation of the ancient vegetation and past climate based on pollen in alluvium, but it is important to make allowances for flood processes and sedimentary facies.