The Pennsylvanian Fire Clay tonstein of the Appalachian basin—Its distribution, biostratigraphy, and mineralogy
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Abstract
The Middle Pennsylvanian Fire Clay tonstein, mostly kaolinite and minor accessory minerals, is an altered and lithified volcanic ash preserved as a thin, isochronous layer associated with the Fire Clay coal bed. Seven samples of the tonstein, taken along a 300-km traverse of the central Appalachian basin, contain cogenetic phenocrysts and trapped silicate-melt inclusions of a rhyolitic magma. The phenocrysts include beta-form quartz, apatite, zircon, sanidine, pyroxene, amphibole, monazite, garnet, biotite, and various sulfides. An inherited component of the zircons (determined from U-Pb isotope analyses) provides evidence that the source of the Fire Clay ash was Middle Proterozoic (Grenvillian) continental crust inboard of the active North American margin. 40Ar/39Ar plateau ages of seven sanidine samples from the tonstein have a mean age of 310.9 ± 0.8 Ma, which suggests that it is the product of a single, large-volume, high-silica, rhyolitic eruption possibly associated with one of the Hercynian granitic plutons in the Piedmont. Biostratigraphic analyses correlate the Fire Clay coal bed with a position just below the top of the Trace Creek Member of the Atoka Formation in the North American Midcontinent and near the Westphalian B-C boundary in western Europe.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | The Pennsylvanian Fire Clay tonstein of the Appalachian basin—Its distribution, biostratigraphy, and mineralogy |
| Series title | GSA Special Papers |
| DOI | 10.1130/SPE294-p87 |
| Volume | 294 |
| Year Published | 1994 |
| Language | English |
| Publisher | GSA |
| Contributing office(s) | Eastern Energy Resources Science Center, Eastern Geology and Paleoclimate Science Center |
| Description | 18 p. |
| First page | 87 |
| Last page | 104 |
| Country | United States |
| State | Kentucky, Tennessee, Virginia, West Virginia |
| Other Geospatial | Appalachian Basin |
| Google Analytic Metrics | Metrics page |