Geological Survey of Canada, Natural Resources Canada, Ottawa, ON, Canada

Author Contributions: Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, and Validation.

Charles Jefferson served as Guest Editor at the time of manuscript review and acceptance; peer review and editorial decisions regarding this manuscript were handled by Robert Rainbird.

Charles W. Jefferson is now at 133 Sunset Lane, RR#4, Carleton Place, ON K7C 3P2, Canada