1. Department of Terrestrial Magnetism; Carnegie Institution of Washington; 5241 Broad Branch Road, NW, Washington D.C. 20015 USA
2. Exponent Environmental Group; 15375 30th Place, Suite 250, Bellevue Washington 98007 USA
3. Department of Geology; University of South Florida; 4202 East Fowler Avenue, Tampa Florida 33620-5201 USA