1. Department of Earth, Ocean and Atmospheric Sciences, 2020-2207 Main Mall, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
2. Department of Geological and Atmospheric Sciences, 253 Science Hall, Iowa State University, Ames, Iowa, 50011-1027, USA
3. Department of Geological Sciences, Masaryk University, Kotlářska 2, 611 37 Brno, Czech Republic