1. 1Department of Earth and Atmospheric Sciences, University of Houston, Houston, Texas 77204, USA
2. 2Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
3. 3Department of Earth and Environmental Sciences, New Mexico Tech, Socorro, New Mexico 87801, USA
4. 4Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA