1. Department of Geological Sciences; Brown University; Providence; Rhode Island; 02912; USA
2. Institute for Rock Magnetism; University of Minnesota-Twin Cities; Minneapolis; Minnesota; 55455; USA
3. Scripps Institution of Oceanography; University of California, San Diego; La Jolla; California; 92093; USA
4. Department of Earth and Environmental Sciences; Rensselaer Polytechnic Institute; Troy; New York; 12180; USA