1. Department of Geology, University of Johannesburg, P.O. Box 524, Auckland Park, 2006, South Africa e-mail: mdekock@uj.ac.za; ingrit.malatji@gmail.com; hwabo@uj.ac.za
2. Council for Geoscience, Private Bag X112, Pretoria 0001, South Africa e-mail: leoniem@geoscience.org.za