Coal Dating

Two University of Alaska professors have found a new way to help better define Alaska's huge coal reserves. Their idea depends upon the fact that coal is formed on land in extensive sheet deposits. As the years go by, movements of the earth's crust and erosion deform and break up these sheets. Some portions of the coal seams remain buried and others may outcrop here and there. Mapping of those portions not exposed would be helped if it was possible to identify a particular coal seam regardless of where it outcrops.

Professors Don Triplehorn and Don Turner have found that they can use the University's rock dating laboratory to date the coal seams. The coal itself cannot be dated, but volcanic ash deposited in layers within the coal seams can. Called ash partings, these layers contain minerals which can be accurately dated using the potassium-argon and fission-track techniques. It appears that there have been frequent enough ash depositing volcanic eruptions in Alaska's past to make the dating of ash partings a useful tool.