*Pahan Abewardana^1,2、Madhusoodhan Satish-Kumar³、Toshiro Takahashi³、Sajeev Krishnan⁴、Sanjeewa P.K. Malaviarachchi² (1.Graduate School of Science and Technology, Niigata University, Japan、2.Postgraduate Institute of Science, University of Peradeniya, Sri Lanka、3.Department of Geology, Faculty of Science, Niigata University, Japan、4.Centre for Earth Sciences, Indian Institute of Science, Bengaluru, India)