The "Re-Os" bit indicates that it was Rhenium-Osmium dating of black shale (a sedimentary rock commonly found on paleo-coastlines) in the formation. One of the

The "Re-Os" bit indicates that it was Rhenium-Osmium dating of black shale (a sedimentary rock commonly found on paleo-coastlines) in the formation. One of the major differences between the paleontologists and archaeologists is their opinion of shale and other mudstones. Paleontologists love the stuff, archaeologists hate it.