1. Cooperative Research Centre for Landscape Environments and Mineral Exploration, Post Office Box 1130, Bentley, Western Australia 6102, Australia.
2. Department of Earth and Marine Sciences, Australian National University, Acton, ACT 0200, Australia.
3. Research School of Biological Sciences, Electron Microscopy Unit, Australian National University, Acton, ACT 0200, Australia.
4. Commonwealth Scientific and Industrial Research Organisation (CSIRO) Land and Water, PMB2, Glen Osmond, South Australia 5064, Australia.