Urantia Book perspective
The Urantia Book says:
(59:2.5) 330,000,000 years ago marks the beginning of a time sector of comparative quiet all over the world, with much land again above water. The only exception to this reign of terrestrial quiet was the eruption of the great North American volcano of eastern Kentucky, one of the greatest single volcanic activities the world has ever known. The ashes of this volcano covered five hundred square miles to a depth of from fifteen to twenty feet.
Urantia Book dates tend to run parallel with radiometric dating back through the mammalian period, about 35 million years ago. Prior to that there is a divergence, which is analyzed in a short piece written by Chris Halvorson, PhD titled History of Life. Based on his study, 330 million years ago would track with scientific estimates in the range of 500 million years ago. Interestingly, with this topic there seems to be some alignment without making such adjustments suggested by a broad survey of the dating issue.
Related research
This 1985 research by Donald Chestnut of the Kentucky Geological Survey, University of Kentucky, shows that the issue of whether a volcano was responsible for regional coal deposits was controversial at that time.
This research from 2016 published in the International Journal of Coal Geology shows that it is now generally accepted by the scientific community that a volcano was responsible for coal deposits in Kentucky and the surrounding area.
A 1999 West Virginia Geological and Economic Survey publication states:
About 300 to 310 million years ago, during the Middle Pennsylvanian epoch when vast peat swamps were forming in southern West Virginia, a similar but much larger volcanic explosion occurred along what is now the east coast of the United States. The prehistoric eruption generated huge quantities of volcanic ash which fell on southern West Virginia and several bordering states.
A U. of Cincinnati article offers some support to what is said about the volcanic eruption in Kentucky.