PALEOCLIMATIC CHANGES AROUND MEDIEVAL WARM PERIOD IN LEIZHOU PENINSULA,CHINA

Huguangyan Maar Lake is located in Leizhou Peninsula,Guangdong Province.The Chronology of its lake sediments is determined by the methods of ¹³⁷Cs,AMS and ¹⁴C,and Organic carbon(TOC),nitrogen(TN) and inorganic carbon(TIC) are analyzed.In this hydrologically closed lake,TIC variations may reflect changes in the precipitation/evaporation ratio.TOC and TN in the sediments are proxy indicators of lake productivity and nutrient input.In this tropical area,where surface water temperatures are high year-round,temperature is probably a less important factor controlling algai productivity.Therefore,increased rainfall may be responsible for the observed increase in TOC,TN and TOC/TN.
High TIC content correlates with low concentrations of TOC and TN,and indicates two drought episodes dated to AD 670~760 and AD 880~1260 in the sediments of lake Huguangyan.The drought Medieval Warm Period indicted by geochemical proxy in Huguangyan Maar Lake is temporally correlated with the drought period from diatom and pollen data in Longgan Lake,Anhui Province.They may imply that thereis a drought in Medieval Warm Period in south China.