1 Illinois State Geological Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, 615 E Peabody Drive, Champaign, IL, 61820, USA.
2 Program in Environmental Sciences, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA.
3 Department of Earth and Planetary Sciences, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA.
4 Illinois State Geological Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, 615 E Peabody Drive, Champaign, IL, 61820, USA. ejtheu@illinois.edu.
5 Department of Earth and Environmental Sciences, University of Illinois at Chicago, 845 W Taylor St, Chicago, IL, 60607, USA. ejtheu@illinois.edu.