1. Department of Earth Sciences, P.O. Box 1773 Dickinson College Carlisle PA 17013‐2896 USA
2. Department of Marine Science University of Otago P.O. Box 56 Dunedin 9054 New Zealand
3. Department of Mathematics and Computer Science, P.O. Box 1773 Dickinson College Carlisle PA 17013‐2896 USA