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An Appalachian isochron: a kaolinized Carboniferous air-fall volcanic-ash deposit (tonstein)

Geological Society of America Bulletin
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Abstract

The Fire Clay tonstein is a kaolinized, airfall volcanic ash bed that was deposited in a widespread late Carboniferous peat-forming mire. Eleven samples from Kentucky and West Virginia, spanning a distance of 200km, and two samples from Tennessee and Virginia indicate a characteristic mineralogical signature. A high-silica alkalic rhyolitic source is suggested by the geochemistry of immobile elements and by electron-probe analyses of glass inclusions. 40Ar/39Ar sanidine plateau dating indicates an age of 312??1 Ma for the Fire Clay tonstein, which is consistent with previous 40Ar/39Ar dates for this tonstein. A new isopachous map of the Fire Clay ash-fall deposit indicates an area of 37 000km2 and a probable source to the present-day southwest. -from Authors

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title An Appalachian isochron: a kaolinized Carboniferous air-fall volcanic-ash deposit (tonstein)
Series title Geological Society of America Bulletin
Volume 104
Issue 11
Year Published 1992
Language English
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Geological Society of America Bulletin
First page 1515
Last page 1527