1. Department of Geological Sciences, Brown University, Providence, RI 02912, USA.
2. Environmental Studies, Luther College, 700 College Drive, Decorah, IA 52101, USA.
3. Department of Geology and Environmental Geosciences, Lafayette College, Easton, PA 18042, USA.
4. Department of Earth Sciences, The University of Hong Kong, James Lee Science Building, Pokefulam Road, Hong Kong, People’s Republic of China.