https://www.usgs.gov/publications/depositional-history-fire-clay-coal-bed-late-duckmantian-eastern-kentucky-usa
Depositional history of the Fire Clay coal bed (Late Duckmantian), Eastern Kentucky, USA | U.S....
More than 3800 coal thickness measurements, proximate analyses from 97 localities, and stratigraphic and sedimentological analyses from more than 300 outcrops...