The ash-fall pattern of the Fire Clay tonstein, central Appalachian basin: Paleogeographic and plate tectonic implications

Journal Article · Thu Aug 01 00:00:00 EDT 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5695943

Outerbridge, W F; Lyons, P C ^[1]; Keiser, A F ^[2]

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1. Geological Survey, Reston, VA (United States)
2. West Virginia Geological and Economic Survey, Morgantown (United States)

Thickness data for the Fire Clay tonstein bed (Middle Pennsylvania, Breathitt Formation) of Kentucky and its correlatives in West Virginia, Virginia, and Tennessee show a moderately complex ash-fall pattern across the central Appalachian basin. Within the tonstein bed are four or possibly more distinct graded units, which may represent multiple ash-fall events. The mineralogical and chemical signatures for all tonstein beds are similar and suggest a single magmatic source. The absence of coal or non-ash-fall detrital bands between the individual graded units demonstrates that the events occurred in rapid succession. The ash-fall deposits are elongated and thin generally from southwest to northeast. The longest and thickest part of the deposits lies along the southeastern side of the basin, where the deposit's southwestern end is up to 12 in. thick. The areal distribution indicates ash deposition on unstable surfaces and probably changes in wind patterns. Paleogeographic interpretation suggest that the Fire Clay ash fall or falls were deposited from a western source near the paleoequator. This source is thought to be on the Yucatan block, which was involved in collisional tectonics and eastward-directed subduction during the Middle Pennsylvanian. The block contained a volcanic chain from which the deposits may have originated. This composite ash-fall bed, which became the Fire Clay tonstein, formed the most important isochron in the Middle Pennsylvanian of North America.

• OSTI ID: 5695943
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:8; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
APPALACHIAN BASIN
GEOLOGIC DEPOSITS
SHALES
GEOCHEMISTRY
MINERALOGY
VOLCANIC ROCKS
DEPOSITION
ASHES
BITUMINOUS COAL
CARBONIFEROUS PERIOD
CHEMICAL COMPOSITION
COAL SEAMS
GEOLOGIC HISTORY
KAOLINITE
KENTUCKY
PLATE TECTONICS
TENNESSEE
VIRGINIA
WEST VIRGINIA
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
BLACK COAL
CARBONACEOUS MATERIALS
CHEMISTRY
COAL
COAL DEPOSITS
COMBUSTION PRODUCTS
DEVELOPED COUNTRIES
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOLOGIC AGES
GEOLOGIC STRUCTURES
IGNEOUS ROCKS
MATERIALS
MINERAL RESOURCES
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
PALEOZOIC ERA
RESIDUES
RESOURCES
ROCKS
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
TECTONICS
USA
580000* - Geosciences