1. Department of Environmental Studies, Faculty of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashihiroshima, Hiroshima 739-8521, Japan;
2. Department of Geology, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia;
3. Geology Programme, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia