Chinese Science Bulletin © 2008 SCIENCE IN CHINA PRESS Springer www.scichina.com | csb.scichina.com | www.springerlink.com Chinese Science Bulletin | January 2008 | vol. 53 | no. 2 | 262-266 Study of the varve record from Erlongwan maar lake, NE China, over the last 13 ka BP YOU HaiTao 1,2† , LIU JiaQi 1 , LIU Qiang 1 , CHU GuoQiang 1 , Patrick RIOUAL 1 & HAN JingTai 1 1 Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; 2 College of Earth Sciences, Jilin University, Changchun 130061, China In a sediment sequence from Erlongwan maar lake that spans the last 13 ka BP, two main varve types can be recognized: biogenic varves (from the present to ~11.2 ka BP, 0 632 cm) and clastic varves (from ~11.2 to ~12.7 ka BP, 632 700 cm). Based on the dominant types of algae contained in the sediment, the biogenic varves can be classified into dinocyst-biogenic varves (0 63 cm) and mixed (dinocyst and diatom)-biogenic varves (214 632 cm). In this paper, the formation process and com- ponents of the varve are described, the possible reason for the types of varve changing throughout the record is discussed and a high-resolution varve chronology is established spanning the last 13 ka BP. Although further varve counting and error assessment are needed, the results presented here repre- sent a solid foundation for studying the palaeoclimate record of Erlongwan maar lake. biogenic varve, clastic varve, dinocyst, varve chronology In the context of palaeoclimatic and palaeoenvironmen- tal research in continental settings, lake sediment re- cords, especially annually laminated (varved) lake sedi- ments, are important geological archives. This is be- cause they commonly provide a large variety of high-resolution proxy data and offer the possibility to establish precise time scales in calendar year by varve counting if the seasonal character and the components of the varves can be identified [1 8] . A varve is defined as a layer or series of layers of sediment deposited in one year. By extension, a varved sediment is a rhythmic se- quence of sediments deposited in annual cycles in a lake [5] . Research on varved sediments has over a 100-year long history [9] . According to their different formation processes and components, lacustrine varves can be classified into three main types, i.e. biogenic varves, clastic varves and chemical varves. In addition, varve subtypes have also been recognized [6,10 12] . In China, annually laminated sediments have been recognized at widespread geographic locations, however, only few laminated sediment records have been found and thoroughly investigated [1,8] . Annual laminations have been found to be preserved in the sediment records of several small maar lakes from the Longgang Volcanic Field, NE China. Thanks to quite a large initial depth combined with the small area, maar lakes often have large aspect ratio which indicates that only little energy from the wind field is available for water column deep mixing. This creates favorable conditions for the forma- tion and preservation of varves. These sediment se- quences therefore represent high-resolution geological archives [1] . In this paper, we study the laminations ob- served in a 7-m long sediment section taken from one of these lakes, the Erlongwan maar lake. 1 Site location, core recovery and methods The dimictic Erlongwan maar lake (126°21.4 ′ E, Received May 2, 2007; accepted June 5, 2007 doi: 10.1007/s11434-007-0448-x † Corresponding author (email: haitao_you1003@yahoo.com.cn) Supported by CAS Key Project (Grant No. KZCX3-SW-145) and the National Natu- ral Science Foundation of China (Grant No. 4032014043)