1. Department of Geosciences, Virginia Tech, 4044 Derring Hall, Blacksburg, Virginia 24061, wqimin86@vt.edu, mcc@vt.edu
2. Now at ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019.
3. ConocoPhillips School of Geology and Geophysics, University of Oklahoma, 100 East Boyd Street, Norman, Oklahoma 73019, xiaowei.chen@ou.edu