*Silpa Ammini Sasidharan¹、Madhusoodhan Satish-Kumar²、Naoto Ishikawa³、Krishnan Sajeev⁴ (1.Graduate School of Science and Technology, Niigata University、2.Department of Geology, Faculty of Science, Niigata University、3.Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan、4.Centre for Earth Sciences, Indian Institute of Science, Bangalore, India)