Radiometric ages of the Fire Clay tonstein [Pennsylvanian (Upper Carboniferous), Westphalian, Duckmantian]: A comparison of U–Pb zircon single-crystal ages and 40Ar/ 39Ar sanidine single-crystal plateau ages

• Published in: International journal of coal geology Vol. 67; no. 4; pp. 259 - 266
• Main Authors: Lyons, Paul C., Krogh, T.E., Kwok, Y.Y., Davis, Donald W., Outerbridge, William F., Evans, Howard T.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 03.07.2006; Elsevier
• Subjects: 40Ar/ 39Ar sandine ages; Ash fall; Crystalline rocks; Duckmantian; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fire Clay tonstein; Geochronology; Igneous and metamorphic rocks petrology, volcanic processes, magmas; Isotope geochemistry. Geochronology; Middle Pennsylvanian; Paleozoic time scale; Pennsylvanian (Upper Carboniferous); Radiometric dating; U/Pb zircon ages; Westphalian; West Virginia; United States; Central Appalachians; Appalachian Basin; Tennessee; Kentucky; Appalachians; Virginia; Middle Pennsylvanian; Westphalian; 40Ar/ 39Ar sandine ages; Duckmantian; U/Pb zircon ages; Ash fall; Fire Clay tonstein; Pennsylvanian (Upper Carboniferous); Paleozoic time scale; Radiometric dating; U-238/Pb-206; feldspar; sanidine; 40Ar/39Ar sandine ages; sedimentation rates; North America; tonstein; zircon; Upper Carboniferous; silicates; dating; framework silicates; K-feldspar; clastic rocks; volcanic ash; nesosilicates; single crystals; alkali feldspar; Carboniferous; Pennsylvanian; U/Pb; ash falls; Paleozoic; sedimentary rocks; upper Paleozoic; Ar-40/Ar-39
• ISSN: 0166-5162; 1872-7840
• DOI: 10.1016/j.coal.2005.12.002

The Fire Clay tonstein [Pennsylvanian (Upper Carboniferous), Westphalian Series, Duckmantian Stage]–a kaolinized, volcanic-ash deposit occurring in Kentucky, West Virginia, Tennessee, and Virginia–is the most widespread bed in the Middle Pennsylvanian of the central Appalachian basin, USA. A concordant single-crystal U–Pb zircon datum for this tonstein gives a 206Pb/ 238U age of 314.6 ± 0.9 Ma (2 σ). This age is in approximate agreement with a mean sanidine plateau age of 311.5 ± 1.3 Ma (1 σ, n = 11) for the Fire Clay tonstein. The difference between the two ages may be due to bias between the 40K and 238U decay constants and other factors. The age of the Fire Clay tonstein has important implications for Duckmantian Stage (Westphalian Series) sedimentation rates, correlations with the Westphalian Series of Europe, Middle Pennsylvanian volcanic events, and the late Paleozoic time scale.