New K-Ar and fission-track ages from volcanic ash partings in coal beds on the Kenai Peninsula, Alaska, substantiate an 8-m.y. age for the paleobotanical Homerian-Clamgulchian Stage boundary. An age estimate for the Seldovian-Homerian Stage boundary indicates that the Clamgulchian Stage spans an interval of at least 3.3 m.y. Direct radiometric correlations can now be made between these paleobotanical stages and radiometrically dated time-stratigraphic units in other parts of the world.
Ash partings in coals can provide radiometric age control for stratigraphic correlations in terrestrial sections that may otherwise be difficult, if not impossible, to date or correlate by other means. The possibility of detrital contamination in ash-parting samples for dating purposes exists, but careful use of this coal-bed correlation technique can aid in the assessment of coal and petroleum resources in coal-bearing, terrestrial sedimentary sequences.