*Masanobu Yamamoto¹, Takafumi Kikuchi¹, Hiromichi Sakurai¹, Ryoma Hayashi², Osamu Seki¹, Takafumi Omori³, Abdullah Sulaiman⁴, Hasrizal Shaari⁵, Lulie Melling⁶ (1.Faculty of Environmental Earth Science, Hokkaido University, 2.Lake Biwa Museum, 3.The University of Tokyo, 4.Minerals and Geoscience Department Malaysia, 5.Universiti Malaysia Terengganu, 6.Tropical Peat Research Institute)