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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
Number of Pages:
13