SOURCE OF THE VOLCANIC ASH DEPOSIT (FLINT CLAY) IN THE 
FIRE CLAY COAL OF THE APPALACHIAN BASIN 
CHESNUT, Donald R., Kentucky Geological Survey, University of
Kentucky, Lexington, KY 40506

A flint-clay parting in the Fire Clay coal of the Breathitt Formation
(Middle Pennsylvanian, Westphalian B) occurs throughout most of eastern
Kentuckyand in parts of Tennessee, Virginia, and West Virginia. Two
origins for this flint clay have been suggested in the past: detrital
and volcanic. The detrital-origin theory holds that the flint clay was
formed by alteration, in a peat swamp, of a transported heavily weathered 
soil. The volcanic-origin theory suggests that this flint clay re-
sulted from alteration of a volcanic-ash deposit in a peat swamp. Arguments 
for both theories are presented, but volcanic origin is preferred.
	Examination of Westphalain continental reconstructions, trade wind
patterns, and a present-day, ash-fall distribution indicate that the
location of the volcanic source for this flint clay was along a line
from Kentucky to North Carolina (approximately due east). The intersection 
of this line with a palinspastically replaced, known Hercynian
magmatic arc occurs in extreme eastern North Carolina. This is the
approximate location of the volcanic source for the ash.
	This magmatic arc is considered to be related to a Hercynian 
subduction zone. The occurrence of a volcanic ash from this subduction arc in
a Westphalian-B coal indicates active subduction during Westphalian time.