SOURCE OF THE VOLCANIC ASH DEPOSIT (FLINT CLAY) IN A COAL
OF THE APPALACHIAN BASIN
CHESNUT, Donald R.
Kentucky Geological Survey, University of Kentucky,
311 Breckinridge Hall, Lexington, KY 40506-0056, U.S.A.

A widespread flint-clay parting in the Fire Clay coal of the
Breathitt Formation (Westphalian B) in eastern Kentucky and
adjacent areas of the Appalachian Basin is interpreted as a
volcanic-ash deposit. Maximum thickness of the parting is
about 30 cm. An isopach map of the flint-clay parting
indicates a thickening to the south.
	Data from the recent Mount St. Helens eruption show that the
thickness of the ash fall and its geometry are related to the
direction of the wind at the time of eruption. Therefore, the
distribution and thickness of the flint clay and the prevailing
wind direction at the time it was deposited should provide clues
to the location of its volcanic source.
	Paleogeographic reconstructions for Westphalian time, including
prevailing wind patterns, were used to interpret ash-deposit
geometry. The reconstructed ash deposit suggests a source area
in the southern part of the central Appalachians, coinciding
with the Hercynian magmatic arc. Volcanoes emanating from this
arc arc interpreted to be the source of the flint clay.