1. Institute for the Study of Planet Earth and Department of Geosciences; University of Arizona; Tucson; Arizona; 85721; USA
2. Department of Geology; Salem State College; Salem; Massachusetts; 01970; USA
3. Graduate School of Oceanography; University of Rhode Island; Narragansett; Rhode Island; 02882; USA
4. Departments of Plant Biology and Geology; University of Illinois; Urbana; Illinois; 61801; USA
5. Marine Chemistry and Geochemistry; Woods Hole Oceanographic Institution; Woods Hole; Massachusetts; 02543; USA
6. Institute of Arctic and Alpine Research; University of Colorado; Boulder; Colorado; 80303; USA