Jean M. Self-Trail (a), Marci M. Robinson (a), Debra A. Willard (a), Timothy J. Bralower (b), Lucy E. Edwards (a), David S. Powars (a), Greg A. Wandless (c), Katherine H. Freeman (b) & Elizabeth Denis (b)
(a) U.S. Geological Survey, MS926A, Reston, VA 20192, USA. E-mail: jstrail@usgs.gov
(b) Pennsylvania State University, State College, PA 16801, USA.
(c) U.S. Geological Survey, MS951, Reston, VA 20192, USA.