1. Department of Planetology; Kobe University; Kobe 657-8501 Japan
2. Research Center for Inland Seas; Kobe University; Kobe 657-8501 Japan
3. Research Centre for Palaeoclimatology; Ritsumeikan University; Kusatsu 525-8577 Japan
4. Museum of Nature and Human Activities; Hyogo; Sanda 669-1546 Japan
5. Institute of Natural and Environmental Sciences; University of Hyogo; Sanda 669-1546 Japan